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Determines the combined effects of chronic ozone and elevated carbon dioxide on ribulose 1,5 bisphosphate carboxylase oxygenase (Rubisco) activity and leaf components in soybean, Glycine max. Interaction between ozone and carbon dioxide; Acceleration of leaf senescence in ozone-fumigated leaves; Deactivation of Rubisco by elevated carbon dioxide levels; Interaction between carbon dioxide and ozone in response to starch and sucrose metabolism.

Investigates the major limitations to carbon dioxide assimilation of soybean under conditions of elevated atmospheric carbon dioxide and tropospheric ozone. Assimilation, rubisco carboxylation and chlorophyll content of soybean over one growing season; Limitations of soybean to the potential assimilation rate; Effects of carbon dioxide, tropospheric ozone and ontogeny on the limits of photosynthesis.

The fundamental trade-off between current and future reproduction has long been considered to result in a tendency for species that can grow large to begin reproduction at a larger size. Due to the prolonged time required to reach maturity, estimates of tree maturation size remain very rare and we lack a global view on the generality and the shape of this trade-off. Using seed production from five continents, we estimate tree maturation sizes for 486 tree species spanning tropical to boreal climates. Results show that a species' maturation size increases with maximum size, but in a non-proportional way: the largest species begin reproduction at smaller sizes than would be expected if maturation were simply proportional to maximum size. Furthermore, the decrease in relative maturation size is steepest in cold climates. These findings on maturation size drivers are key to accurately represent forests' responses to disturbance and climate change., (© 2024 John Wiley & Sons Ltd.)

The benefits of masting (volatile, quasi-synchronous seed production at lagged intervals) include satiation of seed predators, but these benefits come with a cost to mutualist pollen and seed dispersers. If the evolution of masting represents a balance between these benefits and costs, we expect mast avoidance in species that are heavily reliant on mutualist dispersers. These effects play out in the context of variable climate and site fertility among species that vary widely in nutrient demand. Meta-analyses of published data have focused on variation at the population scale, thus omitting periodicity within trees and synchronicity between trees. From raw data on 12 million tree-years worldwide, we quantified three components of masting that have not previously been analysed together: (i) volatility, defined as the frequency-weighted year-to-year variation; (ii) periodicity, representing the lag between high-seed years; and (iii) synchronicity, indicating the tree-to-tree correlation. Results show that mast avoidance (low volatility and low synchronicity) by species dependent on mutualist dispersers explains more variation than any other effect. Nutrient-demanding species have low volatility, and species that are most common on nutrient-rich and warm/wet sites exhibit short periods. The prevalence of masting in cold/dry sites coincides with climatic conditions where dependence on vertebrate dispersers is less common than in the wet tropics. Mutualist dispersers neutralize the benefits of masting for predator satiation, further balancing the effects of climate, site fertility and nutrient demands., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential., (© 2022. The Author(s).)

Tree fecundity and recruitment have not yet been quantified at scales needed to anticipate biogeographic shifts in response to climate change. By separating their responses, this study shows coherence across species and communities, offering the strongest support to date that migration is in progress with regional limitations on rates. The southeastern continent emerges as a fecundity hotspot, but it is situated south of population centers where high seed production could contribute to poleward population spread. By contrast, seedling success is highest in the West and North, serving to partially offset limited seed production near poleward frontiers. The evidence of fecundity and recruitment control on tree migration can inform conservation planning for the expected long-term disequilibrium between climate and forest distribution., Competing Interests: Competing interest statement: M.B., W.D.K., and I.S.P. are collaborators on a 2020 review with T.W., (Copyright © 2021 the Author(s). Published by PNAS.)

Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current estimates are dominated by overrepresentation of small trees in regression models. We combined global fecundity data, including a substantial representation of large trees. We compared size-fecundity relationships against traditional allometric scaling with diameter and two models based on crown architecture. All allometric models fail to describe the declining rate of increase in fecundity with diameter found for 80% of 597 species in our analysis. The strong evidence of declining fecundity, beyond what can be explained by crown architectural change, is consistent with physiological decline. A downward revision of projected fecundity of large trees can improve the next generation of forest dynamic models., Competing Interests: Competing interest statement: C.J.C. and J.C. are coauthors on a 2020 article; S.J.W. and J.C. are coauthors on a 2019 article; J.R.P. and J.C. are coauthors on a 2020 article; M.U., J.K.Z., and J.C. are coauthors on two 2019 articles; and M. Silman, W.F.R., and J.C. are coauthors on 2018, 2019, and 2020 articles.

Indirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here we find from a synthesis of tree species in North America that climate-condition interactions dominate responses through two pathways, i) effects of growth that depend on climate, and ii) effects of climate that depend on tree size. Because tree fecundity first increases and then declines with size, climate change that stimulates growth promotes a shift of small trees to more fecund sizes, but the opposite can be true for large sizes. Change the depresses growth also affects fecundity. We find a biogeographic divide, with these interactions reducing fecundity in the West and increasing it in the East. Continental-scale responses of these forests are thus driven largely by indirect effects, recommending management for climate change that considers multiple demographic rates.

The Additional sex combs-like (ASXL1-3) genes are linked to human neurodevelopmental disorders. The de novo truncating variants in ASXL1-3 proteins serve as the genetic basis for severe neurodevelopmental diseases such as Bohring-Opitz, Shashi-Pena, and Bainbridge-Ropers syndromes, respectively. The phenotypes of these syndromes are similar but not identical, and include dramatic craniofacial defects, microcephaly, developmental delay, and severe intellectual disability, with a loss of speech and language. Bainbridge-Ropers syndrome resulting from ASXL3 gene mutations also includes features of autism spectrum disorder. Human genomic studies also identified missense ASXL3 variants associated with autism spectrum disorder, but lacking more severe Bainbridge-Ropers syndromic features. While these findings strongly implicate ASXL3 in mammalian brain development, its functions are not clearly understood. ASXL3 protein is a component of the polycomb deubiquitinase complex that removes mono-ubiquitin from Histone H2A. Dynamic chromatin modifications play important roles in the specification of cell fates during early neural patterning and development. In this study, we utilize the frog, Xenopus laevis as a simpler and more accessible vertebrate neurodevelopmental model system to understand the embryological cause of Bainbridge-Ropers syndrome. We have found that ASXL3 protein knockdown during early embryo development highly perturbs neural cell fate specification, potentially resembling the Bainbridge-Ropers syndrome phenotype in humans. Thus, the frog embryo is a powerful tool for understanding the etiology of Bainbridge-Ropers syndrome in humans., (Copyright © 2020 Lichtig, Artamonov, Polevoy, Reid, Bielas and Frank.)

Cold-stress syndrome (CSS) is one of the leading natural threats to free-ranging Florida manatees ( Trichechus manatus latirostris ). Cold water exposure below the species' acceptable physiologic range is a frequent occurrence for manatees during cold weather months causing CSS-induced systemic illness and significant annual mortality. Although CSS is a commonly presented condition at manatee rehabilitation facilities, the core body temperatures in CSS manatees are currently unknown due to the lack of clinically applicable and accurate temperature measurement methodologies. Our objective was to establish a clinically applicable measurement methodology of core body temperature in manatees. A novel, minimally invasive temperature technique to obtain esophageal temperature by placing a temperature sensor through an oro-gastric tube was compared to current oral and nasal methods in 20 clinically healthy manatees. Results identified the esophageal measurement as the best performing and most precise temperature methodology. The superior performance of esophageal temperature measurements differed significantly from both nasal and oral measurements, while nasal and oral measurements did not differ when compared with each other. The esophageal measurements were consistent with manatee core body temperature, facilitating generation of a reference interval for core body temperature in healthy manatees (35.0-35.8 C). Four CSS medical cases were evaluated with the newly validated esophageal temperature method, facilitating diagnosis of hypothermia. The application of this temperature measurement technique to CSS manatees in field or rehabilitation settings will help in understanding CSS pathophysiology, improve medical assessments during rehabilitation, and contribute to conservation efforts.

Aquatic species live most or all their lives in water; therefore, the health of the environment is intimately connected to their health and medical care. Understanding and maintaining appropriate husbandry and nutrition for the housed aquarium species are essential to sustain health. Most diseases of fish are secondary opportunistic infections; prevention and early diagnosis are recommended. Treatments involve environmental and/or nutritional management first, followed by targeted pharmacologic treatment to control a specific pathogen. Pharmacokinetic research evaluating the effects and safety of medications in fish are greatly needed in the peer-reviewed literature., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. The incidence is estimated to be between 300,000 and 400,000 neonates globally each year, the majority in sub-Saharan Africa. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

Pulmonary disease has been well documented in wild and managed dolphin populations. The marginal lymph nodes of the dolphin thorax provide lymphatic drainage to the lungs and can indicate pulmonary disease. This study standardized a technique for rapid, efficient, and thorough ultrasonographic evaluation of the marginal lymph nodes in bottlenose dolphins ( Tursiops truncatus). Thoracic ultrasonography was performed on 29 clinically healthy adult bottlenose dolphins. Reference intervals for lymph node dimensions and ultrasonographic characteristics of marginal lymph nodes were determined from four transducer orientations: longitudinal, transverse, oblique, and an orientation optimized to the ultrasonographer's eye. The relationship between lymph node dimensions and dolphin age, sex, length, weight, origin, and management setting (pool versus ocean enclosure) were also evaluated. The mean marginal lymph nodes measured 5.26 cm in length (SD = 1.10 cm, minimum = 3.04 cm, maximum = 7.61 cm, reference interval [10th to 90th percentiles per node dimension] 3.78-6.55 cm) and 3.72 cm in depth (SD = 0.59 cm, minimum = 2.64, maximum = 5.38 cm, reference interval 2.98-4.50 cm). Sex, dolphin length, weight, and management setting had no effect on lymph node dimensions. Dolphins >30 yr of age had longer node lengths than dolphins 5-10 yr old. Node dimensions did differ between dolphins from various origins. Most commonly, the lymph node was found to be hyperechoic relative to surrounding soft tissues (98%) and to have irregular caudal borders (84%), ill-defined deep borders (83%), flat superficial border (67%), triangular or rounded triangle shape (59%), irregular cranial border (55%), and moderate heterogeneity (34%). The data reported in this study serve as a baseline reference that may contribute to earlier detection of pleural and pulmonary disease of managed and wild cetacean populations.

The Xenopus community has embraced recent advances in sequencing technology, resulting in the accumulation of numerous RNA-Seq and ChIP-Seq datasets. However, easily accessing and comparing datasets generated by multiple laboratories is challenging. Thus, we have created a central space to view, search and analyze data, providing essential information on gene expression changes and regulatory elements present in the genome. XenMine (www.xenmine.org) is a user-friendly website containing published genomic datasets from both Xenopus tropicalis and Xenopus laevis. We have established an analysis pipeline where all published datasets are uniformly processed with the latest genome releases. Information from these datasets can be extracted and compared using an array of pre-built or custom templates. With these search tools, users can easily extract sequences for all putative regulatory domains surrounding a gene of interest, identify the expression values of a gene of interest over developmental time, and analyze lists of genes for gene ontology terms and publications. Additionally, XenMine hosts an in-house genome browser that allows users to visualize all available ChIP-Seq data, extract specifically marked sequences, and aid in identifying important regulatory elements within the genome. Altogether, XenMine is an excellent tool for visualizing, accessing and querying analyzed datasets rapidly and efficiently., (Copyright © 2016 Elsevier Inc. All rights reserved.)

A female, captive bred, juvenile swell shark ( Cephaloscyllium ventriosum ) was observed swimming in tight circles and rolling. Radiographs and computed tomography of this individual revealed extensive cartilage mineralization of the skull and cranial cervical vertebrae compared with diagnostic images of clinically healthy conspecifics. Gross necropsy and histopathologic examination revealed ossification and fibrosis of the cartilaginous matrix of the skull and cervical vertebrae with deep invasion by a pigmented hyphal fungus. There was no growth on fungal culture, but fungal polymerase chain reaction identified a DNA sequence compatible with Exophiala sp. (99%). Radiographs and computed tomography were helpful to determine a prognosis and course of action for this individual. This case emphasizes the need to include fungal infections as a differential diagnosis when evaluating elasmobranchs with abnormal swimming behaviors and mineralization of the skeletal structures.

In the vertebrate blastula and gastrula the Nodal pathway is essential for formation of the primary germ layers and the organizer. Nodal autoregulatory feedback potentiates signaling activity, but mechanisms limiting embryonic Nodal ligand transcription are poorly understood. Here we describe a transcriptional switch mechanism mediated by FoxH1, the principle effector of Nodal autoregulation. FoxH1 contains a conserved engrailed homology (EH1) motif that mediates direct binding of groucho-related gene 4 (Grg4), a Groucho family corepressor. Nodal-dependent gene expression is suppressed by FoxH1, but enhanced by a FoxH1 EH1 mutant, indicating that the EH1 motif is necessary for repression. Grg4 blocks Nodal-induced mesodermal gene expression and Nodal autoregulation, suggesting that Grg4 limits Nodal pathway activity. Conversely, blocking Grg4 function in the ectoderm results in ectopic expression of Nodal target genes. FoxH1 and Grg4 occupy the Xnr1 enhancer, and Grg4 occupancy is dependent on the FoxH1 EH1 motif. Grg4 occupancy at the Xnr1 enhancer significantly decreases with Nodal activation or Smad2 overexpression, while FoxH1 occupancy is unaffected. These results suggest that Nodal-activated Smad2 physically displaces Grg4 from FoxH1, an essential feature of the transcriptional switch mechanism. In support of this model, when FoxH1 is unable to bind Smad2, Grg4 occupancy is maintained at the Xnr1 enhancer, even in the presence of Nodal signaling. Our findings reveal that FoxH1 mediates both activation and repression of Nodal gene expression. We propose that this transcriptional switch is essential to delimit Nodal pathway activity in vertebrate germ layer formation., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Intestinal or cloacal strictures that resulted in intestinal obstruction were diagnosed in six green sea turtles (Chelonia mydas) from three rehabilitation facilities and two zoologic parks. The etiologies of the strictures were unknown in these cases. It is likely that anatomic adaptations of the gastrointestinal tract unique to the green sea turtle's herbivorous diet, paired with causes of reduced intestinal motility, may predispose the species to intestinal damage and subsequent obstructive intestinal disease. In aquarium-maintained green sea turtles, obesity, diet, reduced physical activity, chronic intestinal disease, and inappropriate or inadequate antibiotics might also be potential contributing factors. Clinical, radiographic, and hematologic abnormalities common among most of these sea turtles include the following: positive buoyancy; lethargy; inappetence; regurgitation; obstipation; dilated bowel and accumulation of oral contrast material; anemia; hypoglycemia; hypoalbuminemia; hypocalcemia; and elevated creatine kinase, aspartate aminotransferase, and blood urea nitrogen. Although these abnormalities are nonspecific with many possible contributing factors, intestinal disease, including strictures, should be considered a differential in green sea turtles that demonstrate all or a combination of these clinical findings. Although diagnostic imaging, including radiographs, computed tomography, or magnetic resonance imaging, are important in determining a cause for suspected gastrointestinal disease and identifying an anatomic location of obstruction, intestinal strictures were not successfully identified when using these imaging modalities. Lower gastrointestinal contrast radiography, paired with the use of oral contrast, was useful in identifying the suspected site of intestinal obstruction in two cases. Colonoscopy was instrumental in visually diagnosing intestinal stricture in one case. Therefore, lower gastrointestinal contrast radiography and colonoscopy should be considered in green turtles when gastrointestinal obstructions are suspected. Although partial strictures of the cloacal opening may be identified on gross examination and might be managed with appropriate medical treatment, surgical intervention or humane euthanasia are likely the only options for sea turtles once small or large intestinal strictures have formed.

Signaling inputs from multiple pathways are essential for the establishment of distinct cell and tissue types in the embryo. Therefore, multiple signals must be integrated to activate gene expression and confer cell fate, but little is known about how this occurs at the level of target gene promoters. During early embryogenesis, Wnt and Nodal signals are required for formation of the Spemann organizer, which is essential for germ layer patterning and axis formation. Signaling by both Wnt and Nodal pathways is required for the expression of multiple organizer genes, suggesting that integration of these signals is required for organizer formation. Here, we demonstrate transcriptional cooperation between the Wnt and Nodal pathways in the activation of the organizer genes Goosecoid (Gsc), Cerberus (Cer), and Chordin (Chd). Combined Wnt and Nodal signaling synergistically activates transcription of these organizer genes. Effectors of both pathways occupy the Gsc, Cer and Chd promoters and effector occupancy is enhanced with active Wnt and Nodal signaling. This suggests that, at organizer gene promoters, a stable transcriptional complex containing effectors of both pathways forms in response to combined Wnt and Nodal signaling. Consistent with this idea, the histone acetyltransferase p300 is recruited to organizer promoters in a Wnt and Nodal effector-dependent manner. Taken together, these results offer a mechanism for spatial and temporal restriction of organizer gene transcription by the integration of two major signaling pathways, thus establishing the Spemann organizer domain., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Several positron emitting radioisotopes such as (11)C and (13)N can be used in plant biology research. The (11)CO(2) tracer is used to facilitate plant biology research toward optimization of plant productivity, biofuel development and carbon sequestration in biomass. Positron emission tomography (PET) imaging has been used to study carbon transport in live plants using (11)CO(2). Because plants typically have very thin leaves, little medium is present for the emitted positrons to undergo an annihilation event. The emitted positrons from (11)C (maximum energy 960 keV) could require up to approximately 4 mm of water equivalent material for positron annihilation. Thus many of the positrons do not annihilate inside the leaf, resulting in limited sensitivity for PET imaging. To address this problem we have developed a compact beta-positive, beta-minus particle imager (PhytoBeta imager) for (11)CO(2) leaf imaging. The detector is based on a Hamamatsu H8500 position sensitive photomultiplier tube optically coupled via optical grease to a 0.5 mm thick Eljen EJ-212 plastic scintillator. The detector is equipped with a flexible arm to allow its placement and orientation over or under the leaf to be studied while maintaining the leaf's original orientation. To test the utility of the system the detector was used to measure carbon translocation in a leaf of the spicebush (Lindera benzoin) under two transient light conditions.

The Spemann organizer is an essential signaling center in Xenopus germ layer patterning and axis formation. Organizer formation occurs in dorsal blastomeres receiving both maternal Wnt and zygotic Nodal signals. In response to stabilized βcatenin, dorsal blastomeres express the closely related transcriptional activators, Siamois (Sia) and Twin (Twn), members of the paired homeobox family. Sia and Twn induce organizer formation and expression of organizer-specific genes, including Goosecoid (Gsc). In spite of the similarity of Sia and Twn sequence and expression pattern, it is unclear whether these factors function equivalently in promoter binding and subsequent transcriptional activation, or if Sia and Twn are required for all aspects of organizer function. Here we report that Sia and Twn activate Gsc transcription by directly binding to a conserved P3 site within the Wnt-responsive proximal element of the Gsc promoter. Sia and Twn form homodimers and heterodimers by direct homeodomain interaction and dimer forms are indistinguishable in both DNA-binding and activation functions. Sequential chromatin immunoprecipitation reveals that the endogenous Gsc promoter can be occupied by either Sia or Twn homodimers or Sia-Twn heterodimers. Knockdown of Sia and Twn together, but not individually, results in a failure of organizer gene expression and a disruption of axis formation, consistent with a redundant role for Sia and Twn in organizer formation. Furthermore, simultaneous knockdown of Sia and Twn blocks axis induction in response to ectopic Wnt signaling, demonstrating an essential role for Sia and Twn in mediating the transcriptional response to the maternal Wnt pathway. The results demonstrate the functional redundancy of Sia and Twn and their essential role in direct transcriptional responses necessary for Spemann organizer formation., (Copyright © 2011 Elsevier Inc. All rights reserved.)

A post-traumatic cyst is a rare complication of significant soft tissue trauma. It occurs at the junction between the subcutaneous fat and underlying fascia, when a large, subcutaneous haematoma fails to resolve, developing into a chronic, fluid-filled cyst, lined with fibrous tissue. This results in a swelling that persists for years, gradually increasing in size, often without causing significant discomfort to the patient. Clinically and radiologically these swellings may be mistaken for neoplastic lesions. They can be difficult to treat, are refractory to conservative management and have a high rate of recurrence following surgical excision. Careful monitoring and early treatment of persistent postoperative seroma is advocated.

Chromatin immunoprecipitation (ChIP) is a powerful method for analyzing the interaction of regulatory proteins with genomic loci, but has been difficult to apply to studies on early embryos due to the limiting amount of genomic material in these samples. Here, we present a comprehensive technique for performing ChIP on blastula and gastrula stage Xenopus embryos. We also describe methods for optimizing crosslinking and chromatin shearing, verifying antibody specificity, maximizing PCR sensitivity, and quantifying PCR results, allowing for the use of as few as 50 early blastula stage embryos (approximately 5x10(4) cells) per experimental condition. Finally, we demonstrate the predicted binding of endogenous beta-catenin to the nodal-related 6 promoter, binding of tagged Fast-1/FoxH1 to the goosecoid promoter, and binding of tagged Tcf3 to the siamois and nodal-related 6 promoters as examples of the potential application of ChIP to embryological investigations. Developmental Dynamics 238:1422-1432, 2009. (c) 2009 Wiley-Liss, Inc.

Short-lived positron-emitting radiotracer techniques provide time-dependent data that are critical for developing models of metabolite transport and resource distribution in plants and their microenvironments. Until recently these techniques were applied to measure radiotracer accumulation in coarse regions along transport pathways. The recent application of positron emission tomography (PET) techniques to plant research allows for detailed quantification of real-time metabolite dynamics on previously unexplored spatial scales. PET provides dynamic information with millimeter-scale resolution on labeled carbon, nitrogen, and water transport over a small plant-size field of view. Because details at the millimeter scale may not be required for all regions of interest, hybrid detection systems that combine high-resolution imaging with other radiotracer counting technologies offer the versatility needed to pursue wide-ranging plant physiological and ecological research. In this perspective we describe a recently developed hybrid detection system at Duke University that provides researchers with the flexibility required to carry out measurements of the dynamic responses of whole plants to environmental change using short-lived radiotracers. Following a brief historical development of radiotracer applications to plant research, the role of radiotracers is presented in the context of various applications at the leaf to the whole-plant level that integrates cellular and subcellular signals andor controls.

The model of Farquhar, von Caemmerer and Berry is the standard in relating photosynthetic carbon assimilation and concentration of intercellular CO(2). The techniques used in collecting the data from which its parameters are estimated have been the object of extensive optimization, but the statistical aspects of estimation have not received the same attention. The model segments assimilation into three regions, each modeled by a distinct function. Three parameters of the model, namely the maximum rate of Rubisco carboxylation (V(c max)), the rate of electron transport (J), and nonphotorespiratory CO(2) evolution (R(d)), are customarily estimated from gas exchange data through separate fitting of the component functions corresponding to the first two segments. This disjunct approach is problematic in requiring preliminary arbitrary subsetting of data into sets believed to correspond to each region. It is shown how multiple segments can be estimated simultaneously, using the entire data set, without predetermination of transitions by the investigator. Investigation of the number of parameters that can be estimated in the two-segment model suggests that, under some conditions, it is possible to estimate four or even five parameters, but that only V(c max), J, and R(d), have good statistical properties. Practical difficulties and their solutions are reviewed, and software programs are provided.

We present a case of multiple primary malignant melanomata occurring over a six year period in a 63-year-old Caucasian man with neurofibromatosis type 1. There is doubt regarding a definite association between these two diseases despite a number of case reports and clear, potential pathological mechanisms. This case not only strengthens support for an association but also highlights the great difficulties that arise in the management of cutaneous melanomata in patients with neurofibromatosis.

This report concerns congenitally Na(+)-K(+) leaky red cells of the 'hereditary stomatocytosis' class. Three new isolated cases and one new pedigree are described, and one previously reported case is expanded. In all cases, Western blotting of red cell membranes revealed a deficiency in the 32 kDa membrane protein, stomatin. All showed pronounced cation leaks at 37 degrees C with markedly abnormal intracellular Na(+) and K(+) concentrations, like all other such stomatin-deficient cases. Consistent with recent findings in two previously described British pedigrees, immunocytochemistry demonstrated that the deficiency of stomatin was not complete. On typical blood films, some red cells showed positive stomatin immunoreactivity, while most were negative, although in one case only a minority were negative. All platelets and neutrophils were stomatin positive. The cases differed markedly between themselves with regard to the temperature dependence of the passive leak to K(+). Three showed a simple monotonic temperature dependence, while two showed a minimum at around 20-25 degrees C, such that the cells were extremely leaky at 0 degrees C, giving the phenotype known as 'cryohydrocytosis'. These patients are the only two known cases of stomatin-deficient cryohydrocytosis. Both showed a congenital syndrome of mental retardation, seizures, cataracts and massive hepatosplenomegaly, probably defining a new haemato-neurological syndrome.

A simple assay was developed to assess the potential of patients with acute myelogenous leukaemia (AML) to respond to immunotherapy. Lymphocytes, monocytes and leukaemic blasts with their corresponding intracellular cytokine profiles were evaluated by four-colour flow cytometry. In 50 microl samples of whole blood, surface labelling for CD45, CD8 and CD3 was used for cell identification prior to intracellular staining for interleukin (IL)-4, IL-10, IL-12 and interferon (IFN)-gamma. Absolute numbers of CD8(+) and CD8(-) (putative CD4(+)) T-cells, NK cells (CD8(+)/CD3(-)) and monocytes were determined by reference to a fixed number of added fluorescent beads. The absolute numbers of CD8(-) and CD8(+) T-cells in the blood of patients with AML were similar to those of normal controls. More of the lymphocytes in the blood of leukaemic patients spontaneously produced cytokines compared with those of controls. Furthermore, primary AML blasts secreted predominantly IFN-gamma. After recovery from chemotherapy, lymphocyte counts tended to be lower than in normals and reduction of NK cells reached significance after the second chemotherapy (P=0.01). A prominent CD8(lo)/CD3(lo-int) lymphocyte subset appeared after recovery in some patients. This laboratory application of the study of cell subsets and intracellular cytokines in patients undergoing treatment may be helpful in monitoring immunological responses in AML.

A multicenter, prospective study ( = 103) examined the psychological implications of women's decisions for or against breast reconstruction. Recognized measures of anxiety, depression, body image, and quality of life were completed before the operation, and 6 and 12 months later. A reduction in psychological distress over the year following the operation was evident in each surgical group (mastectomy alone or immediate or delayed reconstruction), indicating that reconstructive surgery can offer psychological benefits to some women; however, others report improved psychological functioning without this surgical procedure. In contrast to existing retrospective research, the prospective design enabled the process of adjustment during the first year after the operation to be examined. The results indicate that breast reconstruction is not a universal panacea for the emotional and psychological consequences of mastectomy. Women still reported feeling conscious of altered body image 1 year postoperatively, regardless of whether or not they had elected breast reconstruction. Health professionals should be careful of assuming that breast reconstruction necessarily confers psychological benefits compared with mastectomy alone.

Efavirenz and a series of related quinazolinone nonnucleoside inhibitors of the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) were evaluated in a series of two-drug combinations with several nucleoside RT inhibitors (NRTIs), nonnucleoside RT inhibitors (NNRTIs), and protease inhibitors (PIs). These combinations were tested in an established HIV-1 RT enzyme assay and a cell-based yield reduction assay with HIV-1 (replicative form [RF])-infected MT-2 cells. Synergy, additivity, and antagonism were determined in the two different assay systems by the method of Chou and Talalay (T.-C. Chou and P. Talalay, Adv. Enzyme Reg. 22:27-55, 1984). Efavirenz, DPC082, DPC083, DPC961, and DPC963 used in combination with the NRTIs zidovudine and lamivudine acted synergistically to inhibit RT activity in the HIV-1 RT enzyme assay and additively to slightly synergistically to inhibit HIV-1 (RF) replication in the yield reduction assay. The five NNRTIs in combination with the PI nelfinavir acted additively in the yield reduction assay to inhibit HIV-1 replication. Interestingly, efavirenz in combination with a second NNRTI acted additively to inhibit HIV-1 RT function in the enzyme assay, while it acted antagonistically to inhibit HIV-1 (RF) replication in the yield reduction assay. These data suggest that antiretroviral combination regimens containing multiple NNTRIs should be given thorough consideration before being used.

Recently there has been an increased awareness of a possible link between the use of purine nucleoside analogues and myelodysplasia. We report the case of a patient who developed myelodysplasia with complex cytogenetic changes after receiving fludarabine. We review the literature, discuss the possible links between myelodysplasia and nucleoside analogues and putative mechanisms for secondary neoplasia.

Juvenile xanthogranuloma is a relatively rare cutaneous lesion. In order to make an early diagnosis and be alert to the possibility of visceral complications and associated medical conditions, plastic surgeons should be aware of the entity. The classic presentation is that of successive eruptions in the head, neck and upper trunk of initially red papules or nodules which later become yellow and finally brown flattened plaques or macules. This report is of an unusual variant with atypical histology including frequent mitoses and a lack of Touton giant cells., (Copyright 1999 The British Association of Plastic Surgeons.)

Human peripheral blood contains two populations of dendritic cells (DC) but their developmental relationship has not been established. Freshly isolated CD11c- DC possessed a lymphoid morphology, lacked myeloid markers but expressed lymphoid markers (CD4+ CD10+) whilst the CD11c+ DC were monocytoid in appearance and expressed myeloid markers. Although both populations were allostimulatory, only the CD11c+ DC were able to take up antigen. Irrespective of the culture conditions the CD11c- cells developed into CD11c- CD13- CD33- CD4+ CD1a- CD83+/- DC. In contrast, cultured CD11c+ cells developed the phenotype CD11c+ CD13+ CD33+/- CD4- CD1a+ CD83+ CD9+. Only the CD11c+ DC expressed macrophage colony-stimulating factor (M-CSF) receptor and gave rise to CD14+, esterase+, phagocytic macrophages when cultured in M-CSF. These data suggest that these two populations of DC represent distinct lineages of antigen-presenting DC.

Objectives: To study the susceptibility to infection by different strains of HIV-1 viruses and the roles of chemokines (macrophage inflammatory protein-1alpha [MIP-1alpha], MIP-1beta, and regulated-on-activation-T-expressed-and-secreted [RANTES]) in CD34+ stem cells maturing into dendritic cells (DC)., Design: It has been controversial whether CD34+ stem cells are susceptible to HIV-1 infection and whether high levels of beta-chemokines are beneficial for suppressing HIV-1 infection during DC maturation. These questions were addressed using different strains of HIV-1 and CD34+ stem cells taken from cord blood and cultured with granulocyte-macrophage colony stimulating factor (GM-CSF) and tumor necrosis factor-alpha (TNF-alpha) to generate mature DC., Methods: CD34+ stem cells were exposed with M-tropic virus Ba-L or T-tropic viruses IIIB or Rut at day 1. Beta-chemokines were added to some cells before the virus and kept throughout the culture. Virus replication was measured throughout the maturation of these cells into CD1a+ DC and CD1a- CD14+ cells using enzyme-linked immunosorbent assay (ELISA) for p24, nested polymerase chain reaction (PCR) for env and intracellular p24 detection by flow cytometry., Results: First, CD34+ stem cells acquired or were infected by live virus because maturing cells showed infection by both M- and T-tropic viruses. Second, the viruses replicated actively during the maturation of CD34+ stem cells toward CD1a+ DC and CD1a- CD14+ cells. Third, beta-chemokines suppressed infection by M-tropic virus Ba-L. And finally, beta-chemokines enhanced infection by T-tropic viruses IIIB and Rut., Conclusions: In addition to the initial anti-M-tropic virus effect by beta-chemokines, selective pressure on viruses may also result because of an increase in susceptibility to T-tropic virus. Caution should be taken when evaluating the effect of beta-chemokine receptor agonists in AIDS therapy.

Recently there has been an increased awareness of a possible link between the use of purine nucleoside analogues and myelodysplasia. We report the case of a patient who developed myelodysplasia with complex cytogenetic changes after receiving fludarabine. We review the literature, discuss the possible links between myelodysplasia and nucleoside analogues and putative mechanisms for secondary neoplasia.

Dendritic cells (DC) are potent antigen-presenting cells responsible for the initiation of primary antigen-specific immune responses. In chronic myeloid leukaemia DC have been generated from Ph+ cells and these Ph+ DC are capable of stimulating cytolytic T-cell responses against the parent leukaemia cells. The prevalence of this phenomenon in acute leukaemia (AL) is unknown and we have therefore studied a variety of acute leukaemias to determine their potential for DC development. Peripheral blood mononuclear cells (PBMC) from 21 cases of AL were cultured in GM-CSF + TNF alpha. Of these cases, 15 were viable in culture and cells with typical DC morphology were observed in 12 of these 15 cases. DC growing in culture expressed either CDla and/or CD83 and were HLA-DR+ CD40+ CD80+ CD86+ typical of mature DC. In 9/12 cases the cultured cells possessed potent antigen-presenting capacity as measured in the allo-MLR. The malignant origin of the cultured DC was confirmed by FISH analysis in two cases (one 5q- and one Ph+ AL) and by persistent aberrant expression of CD19 in two cases of biphenotypic leukaemia. Functional DC may be derived from AL blasts in a significant number of patients and such DC may be capable of inducing leukaemia-specific immune responses with potential for clinically beneficial effects.

Dendritic cells (DC) have an essential role in the induction of immune responses to antigen by naive T cells. As 'professional' antigen-presenting cells they are specialized to take up, process and present soluble antigens in complexes with either class I or class II MHC molecules. They are present in only trace numbers in most tissues and in a relatively immature state but, in the presence of inflammatory signals, they rapidly take up foreign antigens and undergo maturation into potent antigen-presenting cells that migrate to secondary lymphoid tissue where they initiate an immune response. It is now possible to expand populations of DC in vitro both from primitive haemopoietic progenitors as well as from more mature peripheral blood mononuclear cells. This has shed light on many developmental aspects of DC biology and furthered our knowledge of the mechanisms of antigen processing and presentation. It is clear that there is more than one pathway of DC differentiation and that some DC may actually induce immunological unresponsiveness--a possible mechanism for tolerance to self-antigens. For clinicians the most exciting prospect is of their use as cellular adjuvants to generate beneficial responses to antigens of low immunogenicity such as tumour antigens. This review outlines aspects of human DC development and the way in which a greater understanding of their biology may lead to promising clinical applications.