Faculty Bibliography

Blood vessels deliver oxygen, nutrients, hormones and immunity factors throughout the body. To perform these vital functions, vascular cords branch, lumenize and interconnect. Yet, little is known about the cellular, molecular and physiological mechanisms that control how circulatory networks form and interconnect. Specifically, how circulatory networks merge by interconnecting in parallel along their boundaries remains unexplored. To examine this process we studied the formation and functional maturation of the plexus that forms between the Dorsal Longitudinal Anastomotic Vessels (DLAVs) in the zebrafish. We find that the migration and proliferation of endothelial cells within the DLAVs and their Segmental (Se) vessel precursors drives DLAV plexus formation. Remarkably, the presence of Se vessels containing only endothelial cells of the arterial lineage is sufficient for DLAV plexus morphogenesis, suggesting that endothelial cells from the venous lineage make a dispensable or null contribution to this process. The discovery of a circuit that integrates the inputs of circulatory flow and Vascular Endothelial Growth Factor (VEGF) signaling to modulate aortic arch angiogenesis, together with the expression of components of this circuit in the trunk vasculature, prompted us to interrogate the role of these inputs and their relationship during DLAV plexus formation. We find that circulatory flow and VEGF signaling make additive contributions to DLAV plexus morphogenesis, rather than acting as essential inputs with equivalent contributions as they do during aortic arch angiogenesis. Our observations underscore the existence of context-dependent differences in the integration of physiological stimuli and signaling cascades during vascular development.

ML-IAP [melanoma IAP (inhibitor of apoptosis)] is an anti-apoptotic protein that is expressed highly in melanomas where it contributes to resistance to apoptotic stimuli. The anti-apoptotic activity and elevated expression of IAP family proteins in many human cancers makes IAP proteins attractive targets for inhibition by cancer therapeutics. Small-molecule IAP antagonists that bind with high affinities to select BIR (baculovirus IAP repeat) domains have been shown to stimulate auto-ubiquitination and rapid proteasomal degradation of c-IAP1 (cellular IAP1) and c-IAP2 (cellular IAP2). In the present paper, we report ML-IAP proteasomal degradation in response to bivalent, but not monovalent, IAP antagonists. This degradation required ML-IAP ubiquitin ligase activity and was independent of c-IAP1 or c-IAP2. Although ML-IAP is best characterized in melanoma cells, we show that ML-IAP expression in normal mammalian tissues is restricted largely to the eye, being most abundant in ciliary body epithelium and retinal pigment epithelium. Surprisingly, given this pattern of expression, gene-targeted mice lacking ML-IAP exhibited normal intraocular pressure as well as normal retinal structure and function. The results of the present study indicate that ML-IAP is dispensable for both normal mouse development and ocular homoeostasis.

OBJECTIVES: The aims of this work were to study the epidemiological profiles, differences in echinocandin susceptibilities and clinical relevance of the Candida parapsilosis sensu lato species isolated from proven fungaemia cases at La Fe University Hospital of Valencia (Spain) from 1995 to 2007. RESULTS: The prevalence of these species was: C. parapsilosis sensu stricto, 74.4%; Candida orthopsilosis, 23.54%; and Candida metapsilosis, 2.05%. The incidence of the species complex as agents of fungaemia remained stationary until 2005 and doubled in 2006. The incidence of C. orthopsilosis showed an increasing trend during the study period, while C. parapsilosis sensu stricto incidence diminished. Also, an important epidemiological change was observed starting in 2004, when 86.5% of the C. parapsilosis sensu lato strains were found in adult patients, while before that year only 13.5% of the isolates were found in this population. CONCLUSIONS: Echinocandin drug susceptibility testing using the CLSI M27-A3 document showed a wide range of MIC values (0.015-4 mg/L), with micafungin being the most potent in vitro inhibitor followed by anidulafungin and caspofungin (MIC geometric mean of 0.68, 0.74 and 0.87 mg/L, respectively). C. metapsilosis was the most susceptible species of the complex to anidulafungin and micafungin in vitro (MIC(50) for anidulafungin and micafungin: 0.06 mg/L), while there were no differences between C. parapsilosis sensu lato species when caspofungin MIC(50)s were compared (MIC(50) 1.00 mg/L). Differences in caspofungin in vitro susceptibility were observed between the different clinical service departments of La Fe Hospital.

OBJECTIVE To investigate the frequency, epidemiology, clinical features, and prognostic significance of inflamed molluscum contagiosum (MC) lesions, molluscum dermatitis, reactive papular eruptions resembling Gianotti-Crosti syndrome, and atopic dermatitis in patients with MC. DESIGN Retrospective medical chart review. SETTING University-based pediatric dermatology practice. PATIENTS A total of 696 patients (mean age, 5.5 years) with molluscum. MAIN OUTCOME MEASURES Frequencies, characteristics, and associated features of inflammatory reactions to MC in patients with and without atopic dermatitis. RESULTS Molluscum dermatitis, inflamed MC lesions, and Gianotti-Crosti syndrome-like reactions (GCLRs) occurred in 270 (38.8%), 155 (22.3%), and 34 (4.9%) of the patients, respectively. A total of 259 patients (37.2%) had a history of atopic dermatitis. Individuals with atopic dermatitis had higher numbers of MC lesions (P < .001) and an increased likelihood of molluscum dermatitis (50.6% vs 31.8%; P < .001). In patients with molluscum dermatitis, numbers of MC lesions increased during the next 3 months in 23.4% of those treated with a topical corticosteroid and 33.3% of those not treated with a topical corticosteroid, compared with 16.8% of patients without dermatitis. Patients with inflamed MC lesions were less likely to have an increased number of MC lesions over the next 3 months than patients without inflamed MC lesions or dermatitis (5.2% vs 18.4%; P < .03). The GCLRs were associated with inflamed MC lesion (P < .001), favored the elbows and knees, tended to be pruritic, and often heralded resolution of MC. Two patients developed unilateral laterothoracic exanthem-like eruptions. CONCLUSIONS Inflammatory reactions to MC, including the previously underrecognized GCLR, are common. Treatment of molluscum dermatitis can reduce spread of MC via autoinoculation from scratching, whereas inflamed MC lesions and GCLRs reflect cell-mediated immune responses that may lead to viral clearance.

There are many examples of problems in pattern analysis for which it is often possible to obtain systematic characterizations, if in addition a small number of useful features or parameters of the image are known a priori or can be estimated reasonably well. Often the relevant features of a particular pattern analysis problem are easy to enumerate, as when statistical structures of the patterns are well understood from the knowledge of the domain. We study a problem from molecular image analysis, where such a domain-dependent understanding may be lacking to some degree and the features must be inferred via machine-learning techniques. In this paper, we propose a rigorous, fully-automated technique for this problem. We are motivated by an application of atomic force microscopy (AFM) image processing needed to solve a central problem in molecular biology, aimed at obtaining the complete transcription profile of a single cell, a snapshot that shows which genes are being expressed and to what degree. Reed et al (Single molecule transcription profiling with AFM, Nanotechnology, 18:4, 2007) showed the transcription profiling problem reduces to making high-precision measurements of biomolecule backbone lengths, correct to within 20-25 bp (6-7.5 nm). Here we present an image processing and length estimation pipeline using AFM that comes close to achieving these measurement tolerances. In particular, we develop a biased length estimator on trained coefficients of a simple linear regression model, biweighted by a Beaton-Tukey function, whose feature universe is constrained by James-Stein shrinkage to avoid overfitting. In terms of extensibility and addressing the model selection problem, this formulation subsumes the models we studied.

A quantitative understanding of tissue morphogenesis requires description of the movements of individual cells in space and over time. In transparent embryos, such as C. elegans, fluorescently labeled nuclei can be imaged in three-dimensional time-lapse (4D) movies and automatically tracked through early cleavage divisions up to ~350 nuclei. A similar analysis of later stages of C. elegans development has been challenging owing to the increased error rates of automated tracking of large numbers of densely packed nuclei. We present Nucleitracker4D, a freely available software solution for tracking nuclei in complex embryos that integrates automated tracking of nuclei in local searches with manual curation. Using these methods, we have been able to track >99% of all nuclei generated in the C. elegans embryo. Our analysis reveals that ventral enclosure of the epidermis is accompanied by complex coordinated migration of the neuronal substrate. We can efficiently track large numbers of migrating nuclei in 4D movies of zebrafish cardiac morphogenesis, suggesting that this approach is generally useful in situations in which the number, packing or dynamics of nuclei present challenges for automated tracking.

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

The validation of human biological models for inhaled radionuclides is nearly impossible. Requirements for validation are: (1) the measurement of the relevant human tissue data and (2) valid exposure measurements over the interval known to apply to tissue uptake. Two lung models, ICRP 30(( 1)) and ICRP 66(( 2)), are widely used to estimate lung doses following acute occupational or environmental exposure. Both ICRP 30 and 66 lung models are structured to estimate acute rather than chronic exposure. Two sets of human tissue measurements are available: (210)Po accumulated in tissue from inhaled cigarettes and ingested in diet and airborne global fallout (239,240)Pu accumulated in the lungs from inhalation. The human tissue measurements include pulmonary and bronchial tissue in smokers, ex-smokers and non-smokers analysed radiochemically for (210)Po, and pulmonary, bronchial and lymph nodes analysed for (239,240)Pu in lung tissue collected by the New York City Medical Examiner from 1972 to 1974. Both ICRP 30 and 66 models were included in a programme to accommodate chronic uptake. Neither lung model accurately described the estimated tissue concentrations but was within a factor of 2 from measurements. ICRP 66 was the exception and consistently overestimated the bronchial concentrations probably because of its assumption of an overly long 23-d clearance half-time in the bronchi and bronchioles.

While the renin-angiotensin system is important for adrenomedullary responses to stress, the involvement of specific angiotensin II (Ang II) receptor subtypes is unclear. We examined gene expression changes of angiotensin II type 1A (AT(1A)) and type 2 (AT(2)) receptors in rat adrenal medulla in response to immobilization stress (IMO). AT(2) receptor mRNA levels decreased immediately after a single 2-h IMO. Repeated IMO also decreased AT(2) receptor mRNA levels, but the decline was more transient. AT(1A) receptor mRNA levels were unaltered with either single or repeated IMO, although binding was increased following repeated IMO. These effects of stress on Ang II receptor expression may alter catecholamine biosynthesis, as tyrosine hydroxylase and dopamine beta-hydroxylase mRNA levels in PC12 cells are decreased with Ang II treatment in the presence of ZD7155 (AT(1) receptor antagonist) or with CGP42112 (AT(2) receptor agonist) treatment. Involvement of stress-triggered activation of the hypothalamic-pituitary-adrenocortical or sympathoadrenal axis in AT(2) receptor downregulation was examined. Cultured cells treated with the synthetic glucocorticoid dexamethasone displayed a transcriptionally mediated decrease in AT(2) receptor mRNA levels. However, glucocorticoids are not required for the immediate stress-triggered decrease in AT(2) receptor gene expression, as demonstrated in corticotropin-releasing hormone knockout (Crh KO) mice and hypophysectomized rats, although they can regulate basal gene expression. cAMP and pituitary adenylate cyclase-activating polypeptide also reduced AT(2) receptor gene expression and may mediate this response. Overall, the effects of stress on adrenomedullary AT(1A) and AT(2) receptor expression may contribute to allostatic changes, such as regulation of catecholamine biosynthesis.

Environmental factors such as diets rich in saturated fats contribute to dysfunction and death of pancreatic beta-cells in diabetes. Endoplasmic reticulum (ER) stress is elicited in beta-cells by saturated fatty acids. Here we show that palmitate-induced beta-cell apoptosis is mediated by the intrinsic mitochondrial pathway. By microarray analysis, we identified a palmitate-triggered ER stress gene expression signature and the induction of the BH3-only proteins death protein 5 (DP5) and p53-upregulated modulator of apoptosis (PUMA). Knockdown of either protein reduced cytochrome c release, caspase-3 activation, and apoptosis in rat and human beta-cells. DP5 induction depends on inositol-requiring enzyme 1 (IRE1)-dependent c-Jun NH(2)-terminal kinase and PKR-like ER kinase (PERK)-induced activating transcription factor (ATF3) binding to its promoter. PUMA expression is also PERK/ATF3-dependent, through tribbles 3 (TRB3)-regulated AKT inhibition and FoxO3a activation. DP5(-/-) mice are protected from high fat diet-induced loss of glucose tolerance and have twofold greater pancreatic beta-cell mass. This study elucidates the crosstalk between lipotoxic ER stress and the mitochondrial pathway of apoptosis that causes beta-cell death in diabetes.