Growth,proliferation, and cell death in the ontogeny of transient DRG (Froriep's ganglia) of chick embryos

A striking example of axial patterning in nervous system development is the unusual fate of dorsal root ganglia (DRG) that develop in the most rostral somites, the Froriep's ganglia. In amniotes, the DRG that develop adjacent to the occipital (cranial) and the first cervical segments of the CNS “disappear” early in embryonic development. In contrast, all other DRG are present throughout the animal's life. We here reexamine in greater detail the ontogeny of the longest surviving Froriep's ganglion of the chick embryo, DRG C-2. By 50 h of development (stage, st. 15), an anlagen of a DRG had formed in C-2 that was indistinguishable from those of adjacent “permanent” ganglia. At st. 18 [embryonic day (E) 2.5+], the C-2 DRG had the same shape and volume as permanent ganglia C-5 and C-6. C-2's development first diverged from that of normal DRG at st. 19 (E3−), when C-2 was observed to be half the size and shaped differently from its neighbors, and its peripheral nerve root began to degenerate. Two cellular mechanisms appear to contribute to the reduced size of C-2 compared to normal DRG at st. 20 at this early stage: lower proliferation and higher apoptosis rates. One-third fewer C-2 cells were found to be in the S phase when compared to neighboring ganglia, and apoptotic cells were more than three times more abundant in C-2 than in conventional DRG at this stage. The C-2 DRG continued to grow, but at a slower pace than neighboring ganglia through st. 32 (E7). At the height of the normal programmed DRG cell death in normal cervical DRG at st. 28 (E6), even more massive apoptosis occurred in C-2, which resulted in the absence of this ganglion in 80% of st. 36 (E10) embryos. A recent study demonstrated that the overexpression of a single Hox gene can “rescue” the C-2 DRG in transgenic mice. We speculate that Hox genes may produce the difference in fate between C-2 and normal DRG by modulating proliferation and apoptosis via modified neurotrophic factor and/or receptor expression. © 1996 John Wiley & Sons, Inc.     

Clogging of groundwater recharge basins by cyanobacterial mats

Abstract Cyanobacterial mats, which develop on the surface of groundwater recharge basins in the Dan Region Wastewater Reclamation Project in Israel, tend to reduce the rate of effluent infiltration into the ground. The purpose of this work was to study the cyanobacterial populations found in the basins and to elucidate their contribution to the clogging process.
Three cyanobacterial types were isolated and their clogging capacity was determined in a simulation system. Simulation experiments were also used to study the effects of various flooding regimes on mat development and permeability.
In the recharge basins, clogging events have occurred in the autumn, winter or spring. During these seasons, Phormidium autumnale was found to be one of the dominant cyanobacterial types in the mat. This organism is capable of rapid gliding, forms raft-like structures, produces an extracellular sheath, and secretes copious amounts of mucus. The remarkable clogging capacity of P. autumnale is thought to be related to these features. Another cyanobacterium, which predominates in the mats during the summer, does not express this combination of features and its clogging capacity is much lower.
The recharge basins are normally flooded with effluent for 24 h and dried for 48 h. In a simulation experiment clogging was enhanced when cyanobacterial mats were not allowed to dry thoroughly between floodings. Alteration of the recharge regime to 10 h of flooding during the night only, followed by 38 h of drying, enabled temporal separation of light availability and water availability. Under this regime the development of cyanobacterial mats was significantly retarded. It is concluded that night-flooding can alleviate the operational problems associated with clogging of the recharge basins by cyanobacterial mats.     

Clonality Despite Sex: The Evolution of Host-Associated Sexual Neighborhoods in the Pathogenic Fungus Penicillium marneffei

Molecular genetic approaches typically detect recombination in microbes regardless of assumed asexuality. However, genetic data have shown the AIDS-associated pathogen Penicillium marneffei to have extensive spatial genetic structure at local and regional scales, and although there has been some genetic evidence that a sexual cycle is possible, this haploid fungus is thought to be genetically, as well as morphologically, asexual in nature because of its highly clonal population structure. Here we use comparative genomics, experimental mixed-genotype infections, and population genetic data to elucidate the role of recombination in natural populations of P. marneffei. Genome wide comparisons reveal that all the genes required for meiosis are present in P. marneffei, mating type genes are arranged in a similar manner to that found in other heterothallic fungi, and there is evidence of a putatively meiosis-specific mutational process. Experiments suggest that recombination between isolates of compatible mating types may occur during mammal infection. Population genetic data from 34 isolates from bamboo rats in India, Thailand and Vietnam, and 273 isolates from humans in China, India, Thailand, and Vietnam show that recombination is most likely to occur across spatially and genetically limited distances in natural populations resulting in highly clonal population structure yet sexually reproducing populations. Predicted distributions of three different spatial genetic clusters within P. marneffei overlap with three different bamboo rat host distributions suggesting that recombination within hosts may act to maintain population barriers within P. marneffei.     

Electron Spin Resonance Micro-imaging of Live Species for Oxygen Mapping

This protocol describes an electron spin resonance (ESR) micro-imaging method for three-dimensional mapping of oxygen levels in the immediate environment of live cells with micron-scale resolution¹. Oxygen is one of the most important molecules in the cycle of life. It serves as the terminal electron acceptor of oxidative phosphorylation in the mitochondria and is used in the production of reactive oxygen species. Measurements of oxygen are important for the study of mitochondrial and metabolic functions, signaling pathways, effects of various stimuli, membrane permeability, and disease differentiation. Oxygen consumption is therefore an informative marker of cellular metabolism, which is broadly applicable to various biological systems from mitochondria to cells to whole organisms. Due to its importance, many methods have been developed for the measurements of oxygen in live systems. Current attempts to provide high-resolution oxygen imaging are based mainly on optical fluorescence and phosphorescence methods that fail to provide satisfactory results as they employ probes with high photo-toxicity and low oxygen sensitivity. ESR, which measures the signal from exogenous paramagnetic probes in the sample, is known to provide very accurate measurements of oxygen concentration. In a typical case, ESR measurements map the probe''s lineshape broadening and/or relaxation-time shortening that are linked directly to the local oxygen concentration. (Oxygen is paramagnetic; therefore, when colliding with the exogenous paramagnetic probe, it shortness its relaxation times.) Traditionally, these types of experiments are carried out with low resolution, millimeter-scale ESR for small animals imaging. Here we show how ESR imaging can also be carried out in the micron-scale for the examination of small live samples. ESR micro-imaging is a relatively new methodology that enables the acquisition of spatially-resolved ESR signals with a resolution approaching 1 micron at room temperature². The main aim of this protocol-paper is to show how this new method, along with newly developed oxygen-sensitive probes, can be applied to the mapping of oxygen levels in small live samples. A spatial resolution of ~30 x 30 x 100 μm is demonstrated, with near-micromolar oxygen concentration sensitivity and sub-femtomole absolute oxygen sensitivity per voxel. The use of ESR micro-imaging for oxygen mapping near cells complements the currently available techniques based on micro-electrodes or fluorescence/phosphorescence. Furthermore, with the proper paramagnetic probe, it will also be readily applicable for intracellular oxygen micro-imaging, a capability which other methods find very difficult to achieve.     

Relationship between genetic anomalies of different levels and deviations in dermatoglyphic traits. Part 7: Dermatoglyphic peculiarities of females with cervical and endometrial carcinoma

This study was carried out to evaluate the effects of neoplastic diseases like carcinoma of the cervix and endometrial carcinoma, and was based on dermatoglyphic traits and their indices of intraindividual diversity (Div), fluctuating asymmetry (FIA) and directional asymmetry (DA). The results were compared with control groups of women and men, whose data have been detailed in our previous publications (Kobyliansky et al., 1999 a-d), and with analogous data of additional cancer groups available in the literature, like acute leukemia, bronchial cancer and breast cancer. The general aims of the study were as follows: (a) to obtain a dermatoglyphic characterization of discrete and quantitative traits and their Div, DA, FIA values in cancer patients, compared to healthy control groups, both female and male; (b) to test the hypothesis that in cancer patients there is an increased level of FIA as a result of an impaired developmental homeostasis; (c) to explore the possibility of using DT (dermatoglyphic traits) data of CW (women with cancer) to predict the probability of the appearance of cervical and endometrial carcinoma in apparently healthy females at a young age. The sample consisted of 94 Israeli-Jewish women of various groups, of which 54 had endometrial carcinoma and 40 had cervical carcinoma. The prints were collected in the Tel-Hashomer Hospital. The control group was a sample of 874 healthy subjects, half of them male and the other female, all from Jewish communities of European extractions (50%) as well as from Africa (50%). All controls were adults (over 18 years of age). Interpretation of prints was performed according to Cummins & Midlo (1961) and Penrose (1968) and included identification of patterns, ridge counts and the measurement of distances and angles in the palms, 79 DT for every individual were assessed. Significant differences were found for some of the studied traits between cancer patients and their healthy control groups. We encountered merely a low sexual dimorphism between the CW and the control males as compared to that between control males and females (with significant differences in 18% of the quantitative traits vs 64% in the control). The indices of diversity and asymmetry proved more suitable for discrimination, yielding the highest discrimination level between CW and control females. This finding suggested other data in the present study which points to a similarity between CW and control males.     

Very long-term radiographic and bone scan results of frozen autograft and allograft bone grafting in 17 patients (20 grafts) a 30- to 35-year follow-up

In the early 1950s, 48 patients received bone implants from a bone bank in Tel-Hashomer Hospital that stored frozen autograft and allograft bones at temperatures less than -17 degrees C. Seventeen (35%) of these patients (20 implants), 10 men and 7 women, with a mean age of 52.4 (34-69) years were available for follow-up after a mean period of 32.5 (30-35) years. They underwent clinical examination, radiographs and bone scans to evaluate their surgical results. Fracture healing, non-union, graft resorption, osteoporosis and bone sclerosis were used as radiographic criteria for bone incorporation, and normal, increased and decreased uptake served to assess the bone scan. Based on the above criteria, the results were satisfactory in 17 (85%) and poor in 3 (15%). The three failures were after shelf operation for hip dysplasia that used two allografts and one autograft. Allogenous or a combination of allogenous with autogenous frozen bone grafts proved to be a satisfactory and durable method for filling bone defects.     

PCP4 is highly expressed in ectoderm and particularly in neuroectoderm derivatives during mouse embryogenesis

PCP4 (PEP-19) belongs to a family of proteins involved in calcium transduction signals and binds calmodulin via an IQ motif, in a calcium independent manner. PCP4 gene maps to murine chromosome 16 and in human to chromosome 21. Murine PCP4 expression in the brain has been detected by Northern blot analysis to be mainly post-natal and in the adult to have a neuronal pattern. To investigate if it might have a role earlier in development, we analyzed its expression during mouse embryogenesis by in situ hybridization from E7.5 post-coitum (p.c.) to E17.5 p.c., and in P0 brain. Early, at E7.5, a high expression is restricted to the extra embryonic ectoderm. Embryonic expression starts at E9.5. At E10.5, PCP4 shows a strong signal in the post-mitotic cells of the diencephalon, the metencephalon and the myelencephalon and in the dorsal and cranial ganglia. The floor plate is also densely labelled. At E17.5, PCP4 is expressed in the central nervous system, in the myenteric plexus, and in other ectoderm derivatives, for instance the lens, the hairy cells of the cochlea, the enamel organ and the hair follicles. Thus, during embryogenesis PCP4 is mainly expressed in ectoderm and neuroectoderm comprising neural crest derived cells.     

Chemokine stimulation of lymphocyte alpha 4 integrin avidity but not of leukocyte function-associated antigen-1 avidity to endothelial ligands under shear flow requires cholesterol membrane rafts

VLA-4 and LFA-1 are the major vascular integrins expressed on circulating lymphocytes. Previous studies suggested that intact cholesterol rafts are required for integrin adhesiveness in different leukocytes. We found the alpha(4) integrins VLA-4 and alpha(4)beta(7) as well as the LFA-1 integrin to be excluded from rafts of human peripheral blood lymphocytes. Disruption of cholesterol rafts with the chelator methyl-beta-cyclodextrin did not affect the ability of these lymphocyte integrins to generate high avidity to their respective endothelial ligands and to promote lymphocyte rolling and arrest on inflamed endothelium under shear flow. In contrast, cholesterol extraction abrogated rapid chemokine triggering of alpha(4)-integrin-dependent peripheral blood lymphocytes adhesion, a process tightly regulated by G(i)-protein activation of G protein-coupled chemokine receptors (GPCR). Strikingly, stimulation of LFA-1 avidity to intercellular adhesion molecule 1 (ICAM-1) by the same chemokines, although G(i)-dependent, was insensitive to raft disruption. Our results suggest that alpha(4) but not LFA-1 integrin avidity stimulation by chemokines involves rapid chemokine-induced GPCR rearrangement that takes place at cholesterol raft platforms upstream to G(i) signaling. Our results provide the first evidence that a particular chemokine/GPCR pair can activate different integrins on the same cell using distinct G(i) protein-associated machineries segregated within defined membrane compartments.