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PubMed2005

Scale and shape issues in focused cluster power for count data.

BACKGROUND: Interest in the development of statistical methods for disease cluster detection has experienced rapid growth in recent years. Evaluations of statistical power provide important information for the selection of an appropriate statistical method in environmentally-related disease cluster investigations. Published power evaluations have not yet addressed the use of models for focused cluster detection and have not fully investigated the issues of disease cluster scale and shape. As meteorological and other factors can impact the dispersion of environmental toxicants, it follows that environmental exposures and associated diseases can be dispersed in a variety of spatial patterns. This study simulates disease clusters in a variety of shapes and scales around a centrally located single pollution source. We evaluate the power of a range of focused cluster tests and generalized linear models to detect these various cluster shapes and scales for count data. RESULTS: In general, the power of hypothesis tests and models to detect focused clusters improved when the test or model included parameters specific to the shape of cluster being examined (i.e. inclusion of a function for direction improved power of models to detect clustering with an angular effect). However, power to detect clusters where the risk peaked and then declined was limited. CONCLUSION: Findings from this investigation show sizeable changes in power according to the scale and shape of the cluster and the test or model applied. These findings demonstrate the importance of selecting a test or model with functions appropriate to detect the spatial pattern of the disease cluster.

Journal Article↗
PubMed1987

Spatial firing patterns of hippocampal complex-spike cells in a fixed environment.

A TV/computer technique was used to simultaneously track a rat's position in a simple apparatus and record the firing of single hippocampal complex-spike neurons. The primary finding is that many of these neurons behave as "place cells," as first described by O'Keefe and Dostrovsky (1971) and O'Keefe (1976). Each place cell fires rapidly only when the rat is in a delimited portion of the apparatus (the cell's "firing field"). In agreement with O'Keefe (1976) and many other authors, we have seen that the firing of place cells is highly correlated with the animal's position and is remarkably independent of other aspects of the animal's behavioral state. Several properties of firing fields were characterized. Firing fields are stable over long time intervals (days) if the environment is constant. They come in several shapes when the animal is in a cylindrical apparatus; moreover, the set of field shapes is different when the animal is in a rectangular apparatus. It also seems that a single cell may have more than one field in a given apparatus. By collecting a sample of 40 place cells in a fixed environment, it has been possible to describe certain features of the place cell population, including the spatial distribution of fields within the apparatus, the average size of fields, and the "intensity" of fields (as measured by maximum firing rate). We also tested the hypothesis that the firing rate of each place cell signals the animal's distance from a point (the field center) so that a weighted average of the firing of the individual cells encodes the animal's position within the apparatus. The animal's position, calculated according to this "distance hypothesis," is systematically different from the animal's true position; this implies that the hypothesis in its simplest form is wrong.

Action Potentials↗
PubMed1998

Enhanced coronary vasa vasorum neovascularization in experimental hypercholesterolemia.

Coronary arteries contain a network of vasa vasorum in the adventitia. The three-dimensional anatomy of the vasa vasorum in early coronary atherosclerosis is unknown. This study was designed to visualize and quantitate the three-dimensional spatial pattern of vasa vasorum in normal and experimental hypercholesterolemic porcine coronary arteries, using a novel computed tomography technique. Animals were killed after being fed either a high cholesterol diet (n = 4) or a control diet (n = 4) for 12 wk. The proximal left anterior descending coronary artery was removed from the heart, scanned, and reconstructed, and quantitation of vasa vasorum density was performed. Two different types of vasa vasorum were defined: first-order vasa vasorum ran longitudinally parallel to the vessel and second-order originated from first-order vasa circumferentially around the vessel wall. Compared with controls in hypercholesterolemic coronary arteries, there was a significant increase in the area of the vessel wall (3.86+/-0.22 vs. 8.07+/-0.45 mm2, respectively, P < 0.01) and in the density of vasa vasorum (1. 84+/-0.05/mm2 vs. 4.73+/-0.24/mm2; respectively, P = 0.0001). This occurred especially by an increase of second-order vasa vasorum and disorientation of normal vasa vasorum spatial pattern. This study suggests that adventitial neovascularization of vasa vasorum occurs in experimental hypercholesterolemic coronary arteries and may be a part of the early atherosclerotic remodeling process.

Animals↗
PubMed1993

The expression of the regulatory myosin light chain 2 gene during mouse embryogenesis.

The fast skeletal muscle myosin light chain 2 (MLC2) gene is expressed specifically in skeletal muscles of newborn and adult mice, and has no detectable sequence homology with any of the other MLC genes including the slow cardiac MLC2 gene. The expression of the fast skeletal muscle MLC2 gene during early mouse embryogenesis was studied by in situ hybridization. Serial sections of embryos from 8.5 to 12.5 days post coitum (d.p.c.) were hybridized to MLC2 cRNA and to probes for the myogenic regulatory genes MyoD1 and myogenin. The results revealed different temporal and spatial patterns of hybridization for different muscle groups. MLC2 transcripts were first detected 9.5 d.p.c. in the myotomal regions of rostral somites, already expressing myogenin. Surprisingly, at the same stage, a weak MLC2 signal was also detected in the cardiomyocytes. The cardiac expression was transient and could not be detected at later stages while the myotomal signal persisted and spread to the more caudal somites, very similar to the expression of myogenin. Beginning from 10.5 d.p.c., several extramyotomal premuscle cells masses have been demarcated by MyoD1 expression. MLC2 transcripts were detected in only one of these cell masses. Although, transcripts of myogenin were detected in all these cell masses, the number of expressing cells was significantly lower than that observed for MyoD1. By 11.5 d.p.c., all three hybridization signals colocalized in most extramyotomal muscle-forming regions, with the exception of the diaphragm and the hindlimb buds, where only few cells expressed MLC2 and more cells expressed MyoD1 than myogenin. At 12.5 d.p.c., all three studied genes displayed a similar spatial pattern of expression in most muscle-forming regions. However, in some muscles, the MyoD1 signal spread over more cells compared to myogenin or MLC2. Our results are consistent with the suggestion that multiple myogenic programs exist for myoblasts differentiating in the myotome and extramyotomal regions.

Animals↗
PubMed2000

Cell cycle-dependent repetitive Ca(2+ )waves induced by a cytosolic sperm extract in mature ascidian eggs mimic those observed at fertilization.

Sperm-triggered Ca(2+) oscillations occur throughout the animal kingdom. The mechanism sperm use to trigger Ca(2+) oscillations at fertilization has not been resolved in any egg. The temporal, spatial and regulatory characteristics of the Ca(2+) oscillations during fertilization in ascidians offer a unique advantage over other systems for determining the mechanism of fertilization. For example, sperm trigger two phases of Ca(2+) oscillations that are all waves in ascidians. The first of these Ca(2+) waves begins at the point of sperm-egg fusion while a second phase of Ca(2+) waves originates at a vegetal protrusion termed the contraction pole. In addition, cyclin B1-dependent kinase activity provides a form of positive feedback, maintaining the second phase of Ca(2+) waves during meiosis and thereby ensuring meiotic exit. We therefore prepared cytosolic ascidian sperm extracts or MonoQ-fractionated ascidian sperm extracts from this urochordate to investigate if a Ca(2+)-releasing sperm-borne factor was responsible for egg activation. Spatially, ascidian sperm extract induced repetitive Ca(2+) waves that mimicked the spatial pattern displayed during fertilization: all the second-phase Ca(2+) waves originated at a vegetal protrusion termed the contraction pole (thus mimicking fertilisation). We also demonstrated that ascidian sperm extract-induced Ca(2+) oscillations were maintained when CDK activity was elevated and MAP kinase activity was low, as found previously for sperm-triggered Ca(2+) oscillations. As would be predicted, large doses of ascidian sperm extract injected into prophase-stage oocytes, lacking CDK activity, failed to induce any Ca(2+) release even though they responded to microinjection of the Ca(2+)-releasing second messenger inositol 1,4,5-trisphosphate. Finally, since the Ca(2+)-releasing activity from Mono-Q fractionated ascidian sperm extract eluted predominantly as one fraction, this may imply that one factor is responsible for the Ca(2+)-releasing activity. These data support a model of egg activation whereby the sperm introduces a Ca(2+)-releasing cytosolic factor into the egg. We demonstrated that ascidian sperm contain a protein factor(s) that is regulated by the egg CDK activity and can trigger all the Ca(2+ )waves observed at fertilization with a spatial pattern that mimics those initiated by sperm.

Animals↗
PubMed1992

Computer-assisted interpretation of visual fields in glaucoma.

Visual field abnormality is an important diagnostic sign in glaucoma. Therefore, the presence or absence of visual field loss most often strongly influences diagnostic and therapeutic decisions in glaucoma management. Interpretation of visual field results is often difficult, however. Physiological variability of perimetric sensitivity values contributes to these difficulties. It has been our aim to develop improved computer-assisted methods for the recognition of early glaucomatous field loss. Our approach has therefore been to design techniques that are highly sensitive to small but significant departures from normality. We have investigated normal physiological variability in perimetric results and combined the obtained knowledge with pathophysiological models which are sensitive to the spatial patterns of field loss commonly seen in glaucoma. Thus, we have devised probability scores in order to take the complex physiological variability into account, and developed a hemifield analysis and an arcuate cluster analysis based on the normal anatomy of the retinal nerve fibre layer. A fundamental approach in the collection of normative data and the selection of glaucoma cases used in this project has been to select subjects using non-perimetric criteria (except for the removal of large field defects). Our objective here was to reduce bias from pre-conceived ideas of visual fields. This approach was used for (1) empirical studies on physiological variability, (2) development of analysis methods, and (3) evaluation of such methods. Glaucoma patients were selected based on evaluations of optic disc appearance. Normal subjects were never eliminated on the basis of perimetric results alone. The new methods developed in these studies have significantly improved discrimination between normal and glaucomatous field results, as compared with previously available techniques. Our results indicated that the usage of probability scores was the main source of this improvement, and that the location of observed field abnormalities and spatial modelling were other important factors. Candidate methods which did not properly combine spatial and normative analyses resulted in false positive defects in the mid-periphery and/or underestimated paracentral glaucomatous field defects. Similar approaches based on classification of visual field results in terms of significances, and on recognition of specific spatial patterns of field loss could be used for other groups of diseases having visual field abnormality as an important diagnostic sign.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed2006

A framework for assessing the impact of land use policy on community exposure to air toxics.

Our research focuses on the linkage between land use planning policy and the spatial pattern of exposure to air toxics emissions. Our objective is to develop a modeling framework for assessment of the community health risk implications of land use policy. The modeling framework is not intended to be a regulatory tool for small-scale land use decisions, but a long-range planning tool to assess the community health risk implications of alternative land use scenarios at a regional or subregional scale. This paper describes the development and application of an air toxic source model for generating aggregate emission factors for industrial and commercial zoning districts as a function of permitted uses. To address the uncertainty of estimating air toxics emission rates for planned general land use or zoning districts, the source model uses an emissions probability mass function that weights each incremental permitted land use activity by the likelihood of occurrence. We thus reduce the uncertainty involved in planning for development with no prior knowledge of the specific industries that may locate within the land use district. These air toxics emission factors can then be used to estimate pollutant atmospheric mass flux from land use zoning districts, which can then be input to air dispersion and human health risk assessment models to simulate the spatial pattern of air toxics exposure risk. The model database was constructed using the California Air Toxics Inventory, 1997 US Economic Census, and land assessment records from several California counties. The database contains information on more than 200 air toxics at the 2-digit Standard Industrial Classification (SIC) level. We present a case study to illustrate application of the model. LUAIRTOX, the interactive spreadsheet model that applies our methodology to the California data, is available at http://www2.bren.ucsb.edu/~mwillis/LUAIRTOX.htm.

Air Pollutants↗
PubMed1994

Expression of insulin-like growth factor and binding protein genes during nephrogenesis.

To study the role of insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) in human nephrogenesis, we examined the temporal and spatial pattern of expression of these genes using in situ hybridization. The uninduced metanephric blastema (MB) expressed abundant IGF-II mRNA. With induction by the ureteric duct (UD), the aggregated MB additionally expressed IGFBP-2 and IGFBP-4 mRNAs. The mature UD expressed IGFBP-3 mRNA while the ampulla in contact with the MB lacked IGFBP-3 mRNA and expressed IGFBP-2 exclusively. Upon formation of the S-shape nephron, IGFBP-2 mRNA was expressed in the committed glomerular and epithelial cells which also expressed IGF-II and IGFBP-4, and the mesenchyme of the vascular cleft expressed IGFBP-5 mRNA. In the maturing glomerulus, the glomerular epithelial cells expressed IGF-II mRNA together with IGFBP-2 and IGFBP-4 mRNAs, while IGFBP-5 mRNA was localized to the mesangium and supporting mesenchyme. As the proximal tubule was formed the epithelium expressed less of IGFBP-2 mRNA and more of IGFBP-4 mRNA. The renal mesenchyme in the cortex and medulla expressed abundant IGF-II mRNA, and lower levels of IGFBP-4 and -5 mRNAs. The epithelium of the collecting ducts and pelvicalyceal system expressed abundant IGFBP-3. In contrast, IGF-I, IGFBP-1, and IGFBP-6 mRNAs were expressed at low levels. The specific temporal and spatial pattern of expression of IGFBP genes on the background of abundant IGF-II gene expression suggests that the IGFBP peptides, as modulators of IGF action, are expressed locally at specific points of nephrogenesis to interact with IGF-II to regulate mesenchymal induction, renal epithelial cell commitment, differentiation and growth.

Carrier Proteins↗
PubMed2004

Evidence that climate change has caused 'emergence' of tick-borne diseases in Europe?

Even though tick-borne disease systems are highly susceptible to climatic influences, climate change to date is not necessarily the cause of the marked increased incidence of a variety of tick-borne diseases in many parts of Europe over the past two decades. To test for causality, rather than coincidence, we need to examine whether the right sorts of climate change have occurred at the right time and in the right places to account for the observed heterogeneous temporal and spatial patterns of tick-borne disease 'emergence'. Tick-borne encephalitis (TBE) incidence, for example, showed a 3-fold step increase from 1983 to 1986 in Sweden, doubled in 1993 in the Czech Republic, increased even more dramatically in the same year in Lithuania and Poland, but declined markedly in 1997 in Hungary, Croatia and Slovenia. Within each country, TBE incidence has changed to different degrees in different regions. Because other tick-borne diseases, notably Lyme borreliosis, has commonly 'emerged' in parallel with TBE, we should first examine climate variables predicted to have a general effect on tick abundance, which has indeed increased in the past decade. These include temperature and moisture stress, which have seasonally differential impacts. Monthly mean records for 1960-2000 from the UK Climate Research Unit's interpolated global climate surface reveal that mean spring, spring-autumn and winter temperatures have all increased gradually over the past 40 years, but apparently most sharply in the late 1980s, when moisture stress also increased. These climate data do not reveal any obvious differences between sites where TBE did or did not 'emerge', and in Sweden increases in TBE pre-dated the onset of warmer springs and winters. If recorded climate changes cannot yet satisfactorily explain the temporal and spatial patterns of tick-borne disease change in Europe, the impact of biotic factors, such as increases in deer abundance and changing habitat structure, and of socio-political changes following the end of communist rule, demand more detailed quantitative analyses.

Animals↗
PubMed2005

Temporal and spatial expression of hypoxia-inducible factor-1alpha and vascular endothelial growth factor in a rat model of myocardial ischemia with or without reperfusion.

BACKGROUND AND PURPOSE: Although hypoxia-inducible factor-1alpha (HIF-1alpha) plays a major role in the prevention of myocardial ischemia, the temporal and spatial patterns of expression of HIF-1alpha in myocardial ischemia-reperfusion are not well known. This study examined the role of HIF-1alpha and vascular endothelial growth factor (VEGF) in myocardial ischemia-reperfusion. METHODS: Adult Wistar rats were studied after ligation of the left anterior descending coronary artery (LAD) for 30 min and then after reperfusion. HIF-1alpha and VEGF were measured immediately after relief of occlusion and at 30 min, 1, 3, 6, and 24 h after reperfusion. HIF-1alpha and VEGF proteins were also measured 6 h after permanent occlusion of the LAD. RESULTS: HIF-1alpha and VEGF mRNA increased 1.8- and 1.4-fold, respectively, immediately after relief of occlusion and reached a maximum of 4.3- and 2.3-fold, respectively, at 3 h after reperfusion and remained elevated up to 24 h. HIF-1alpha and VEGF proteins increased immediately after relief of ischemia. HIF-1alpha protein significantly increased from 0.5 h to 24 h after reperfusion and VEGF protein significantly increased from 1 h to 6 h after reperfusion compared to the sham control. Administration of HIF-1alpha antisense oligonucleotide before ligation of the LAD significantly inhibited VEGF protein expression induced by ischemia-reperfusion. Immunohistochemical study showed increased immunoreactivity of HIF-1alpha and VEGF in the jeopardized myocardium after ischemia-reperfusion. HIF-1alpha and VEGF proteins were increased at 6 h after permanent occlusion of the LAD. CONCLUSIONS: This study demonstrated that HIF-1alpha and VEGF were co-induced in a temporal and spatial pattern after ischemia-reperfusion in the rat ventricular myocardium.

Animals↗
PubMed2002

C-fos gene expression induced in cells in specific hypothalamic structures by noxious mechanical stimulation and its [correction of it's] modification by exposure of the skin to extremely high frequency irradiation.

OBJECTIVES: The purpose of this study was to determine: 1) The spatial pattern of c-fos gene expression in rat hypothalamic neurons after exposure to NMS and 2) The expression of c-fos gene after combined exposure to NMS and EHF irradiation of the rat skin. METHODS: The experiments were performed on 28 male adult Sprague-Dawley rats. After rats were subjected to noxious mechanical stimulation (NMS) or its combination with EHF irradiation of the skin, cells in various hypothalamic structures were analyzed to determine theirs effects on c-fos gene expression, an accepted marker of the activation of neurons. C-Fos-like protein was revealed by an indirect immunoperoxidase method. RESULTS: This study revealed that NMS stimulates c-fos gene expression in the anterior hypothalamic nucleus (AHN), dorsomedial hypothalamic nucleus (DMH), ventromedial hypothalamic nucleus (VMH), and lateral hypothalamic area (LHA) by 157, 101, 199 and 115% respectively compared to control animals. Combined exposure to NMS and EHF irradiation directed at the skin in the region of the St36 acupuncture point projection site (left side) results in a decrease of the number of neurons that are activated in the AHN, DMH, VMH, and LHA by 33.6, 13.2, 31.0 and 32.9% respectively compared to the number of neurons activated by exposure to NMS by itself. EHF exposure of the skin of rats not subjected to NMS differentially effects the number of c-Fos positive cells expressed in hypothalamic structures: a decrease of 39.7% was observed in the number of activated neurons in the central part of LHA (level 28) compared to sham-irradiated animals, while an increase of 80.95% was noted in the number of c-Fos positive cells in the DMH compared to sham-irradiated animals. CONCLUSIONS: The spatial pattern and degree of activation of c-fos gene expression has been shown in cells of the hypothalamus of rats after exposure to NMS by itself and after NMS combined with EHF irradiation of the skin. The "stress" reaction of cells in specific hypothalamic structures has been shown to be decreased after EHF exposure of the skin.

Animals↗
PubMed2007

Detection of spatial clusters: application to cancer survival as a continuous outcome.

In this article, we develop the first detailed illustration of the use of a cluster detection method using a spatial scan statistic based on an exponential survival model. We use this approach to study the spatial patterns of survival of patients with stage III or stage IV colorectal cancer or with stage I/II, stage III, or stage IV lung cancer in the State of California and the County of Los Angeles (LA) diagnosed during 1988 through 2002. We present the location of the detected clusters of short survival or long survival and compute nonparametric estimates of survival inside and outside of those detected clusters confirming the survival pattern detected by the spatial scan statistic in both areas. In LA County, we investigate the possible relationship between the cluster locations and race, sex, and histology using nonparametric methods, and we compare socioeconomic factors such as education, employment, income, and health insurance inside and outside of the detected clusters. Finally, we evaluate the effect of related covariates on statistically significant long and short survival clusters detected in LA County using logistic regression models. This article illustrates a new way to understand survival patterns that may point to health disparities in terms of diagnosis and treatment patterns.

California↗
PubMed2025

Distinct spatial transcriptomic patterns of substantia Nigra in Parkinson disease and Parkinsonian subtype of multiple system atrophy.

To investigate transcriptomic signatures of Parkinson's disease (PD) and the Parkinsonian subtype of Multiple System Atrophy (MSA-P) in substantia nigra pars compacta (SNpc), we conducted transcriptome analysis using in-situ hybridization on paraffin-embedded SNpc tissues from post-mortem brains. The study included 2 MSA-P patients, 2 PD patients, and 2 healthy controls (HC), with 12 regions of interest (ROIs) selected from the dorsal to ventral and medial to lateral aspects of the SNpc. A total of 72 ROIs from 6 participants were analyzed, and differentially expressed genes (DEGs) were identified by comparing MSA-P, PD and HC groups. The MSA-P group showed 88 upregulated DEGs and 326 downregulated DEGs (adjusted &#x1d45d;<0.05) compared to HC. The downregulated DEGs were significantly enriched in pathways related to ribosomal translation, immune processes, mitochondrial function, and autophagy. Notably, the dorsomedial quadrant was uniquely linked to antigen presentation, while other quadrants showed downregulation of protein synthesis. The PD group exhibited 165 upregulated DEGs and 350 downregulated DEGs (adjusted &#x1d45d;<0.05) compared to HC, with downregulated DEGs associated with ribosomal translation, mitochondrial function, and the ubiquitin-proteasome system. In both MSA-P and PD, the upregulated DEGs were not associated with any pathways or biological process in gene enrichment analysis. In network propagation analysis, amyloid precursor protein was the most significant network hub among DEGs in both MSA-P and PD. Comparing the transcriptomic signatures of SNpc between MSA-P and PD, we found immune/inflammation, mitochondrial function and neural signaling related genes were significantly downregulated in MSA-P compared to PD. Overall, the transcriptomic signature of the SNpc in MSA-P and PD revealed overlapping but distinct features, including alterations in protein synthesis, immune processes, mitochondrial function, and protein degradation systems. Future studies with larger cohorts and functional validation are needed to further elucidate these findings.

Humans↗
PubMed1994

Morphology of developing rat genioglossal motoneurons studied in vitro: changes in length, branching pattern, and spatial distribution of dendrites.

The aim of this study is to describe the postnatal change in dendritic morphology of those motoneurons in the hypoglossal nucleus that innervate the genioglossus muscle. Forty genioglossal (GG) motoneurons from four age groups (1-2, 5-6, 13-15, and 19-30 postnatal days) were labeled by intracellular injection of neurobiotin in an in vitro slice preparation of the rat brainstem and were reconstructed in three-dimensional space. The number of primary dendrites per GG motoneuron was approximately 6 and remained unchanged with age. The development of these motoneurons from birth to 13-15 days was characterized by a simplification of the dendritic tree involving a decrease in the number of terminal endings and dendritic branches. Motoneurons lost their 6th-8th order branches, in parallel with an elongation of their terminal dendritic branches maintaining the same combined dendritic length. The elongation of terminal branches was attributed to both longitudinal growth and the apparent lengthening caused by resorption of distal branches. The elimination of dendritic branches tended to increase the symmetry of the tree, as revealed by topological analysis. Later, between 13-15 days and 19-30 days, there was a reelaboration of the dendritic arborization returning to a configuration similar to that found in the newborn. The length of terminal branches was shorter at 19-30 days, while the length of preterminal branches did not change, suggesting that the proliferation of branches at 19-30 days takes place in the intermediate parts of terminal branches. The three-dimensional distribution of dendrites was analyzed by dividing space into six equal volumes (hexants). This analysis revealed that GG motoneurons have major components of their dendritic tree oriented in the lateral, medial, and dorsal hexants. Further two-dimensional polar analysis (consisting of eight sectors) revealed a reconfiguration of the tree from birth up to 5-6 days involving resorption of dendrites in the dorsal, dorsomedial, and medial sectors and growth in the lateral sector. Later in development (between 13-15 days and 19-30 days), there was growth in all sectors, but of a greater magnitude in the dorsomedial, medial, and dorsolateral sectors.

Animals↗
PubMed2003

Spatial expression patterns of skin-type antifreeze protein in winter flounder (Pseudopleuronectes americanus) epidermis following metamorphosis.

Two isotypes of Type I antifreeze protein (AFP), the liver-type and the skin-type, have been described from adult winter flounder (Pseudopleuronectes americanus). Although the liver-type AFP has been well studied, the skin-type has just begun to be characterized. It appears to have a wide tissue distribution, be expressed constitutively, and the absence of a signal sequence suggests it is active intracellularly. The current study was designed to examine the onset of skin-type AFP expression during the thickening of the epidermis at metamorphosis from both the nucleic acid and protein levels. The epidermis appeared as a thin layer overlying a thickened dermis at metamorphosis and showed a gradual increase in thickness through the first fall and winter. The onset of skin-type antifreeze expression occurred in conjunction with this epidermal thickening. In situ hybridization and immunohistochemistry showed a distribution of mRNA and skin-type AFP specific for the epidermis and epidermal pavement cells. The AFP immunoproduct showed a distribution intimate with the pavement cell membrane and through the interstitial spaces. This distribution suggests that the AFP may be important in slowing ice crystal formation in these interstitial regions and thus reducing cellular damage due to osmotic imbalance.

Animals↗
PubMed2004

Patterns of spatial and temporal visceral arch muscle development in the Mexican axolotl (Ambystoma mexicanum).

Vertebrate head development is a classical topic that has received renewed attention during the last decade. Most reports use one of a few model organisms (chicken, mouse, zebrafish) and have focused on molecular mechanisms and the role of the neural crest, while cranial muscle development has received less attention. Here we describe cranial muscle differentiation and morphogenesis in the Mexican axolotl, Ambystoma mexicanum. To determine the onset of differentiation we use antibodies against desmin and optical sectioning using confocal laser scanning microscopy on whole-mount immunostained embryos. This technique makes it possible to document the cranial muscle in three dimensions while keeping the specimens intact. Desmin expression starts almost simultaneously in the first, second, and third visceral arch muscles (as in other amphibians studied). Muscle anlagen divide up early into the different elements which constitute the larval cranial musculature. We extend and refine earlier findings, e.g., by documenting a clear division between interhyoideus and interhyoideus posterior. The timing of cranial muscle differentiation differs among vertebrate groups, but seems to be constant within each group. This study provides a morphological foundation for further studies of muscle cell fate and early differentiation.

Ambystoma mexicanum↗
PubMed1990

Auxin regulates the promoter of the root-inducing rolB gene of Agrobacterium rhizogenes in transgenic tobacco.

The regulation in tobacco of the rolB and rolC promoters of Agrobacterium rhizogenes pRi 1855 TL-DNA was studied by using the beta-glucuronidase (GUS) reporter system in transgenic plants. A 20- to 100-fold increase of GUS activity was selectively induced by auxin in rolB-GUS transformed mesophyll protoplasts, whereas this auxin-dependent increase was only 5-fold in rolC-GUS protoplasts. Moreover, both gene fusions exhibited similar tissue-specific expression in aerial parts but different patterns in roots. The spatial pattern of rolB-GUS expression could be strongly modified by the addition of exogenous auxin, further suggesting that auxin plays a central role in the regulation of the rolB promoter in tobacco. The tissue-specific and auxin-dependent regulation of the rolB promoter is discussed in relation to the effects of the rolB gene on rhizogenesis and on cellular responses to auxin.

Cloning, Molecular↗
PubMed1975

Pattern of spatial distribution in Drosophila melanogaster.

The effect of temperature and sex on spatial distribution of Drosophila melanogaster adults was studied in a specially designed apparatus. It was observed that individuals tend to aggregate in sections of the sphere independently of sex and temperature. Nevertheless, decrease in temperature increase aggregation. The mobility of both males and females indicates a negative geotactic tendency.

Animals↗