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PubMed1994

A comparison of the developing dopamine neuron phenotype in cultures of embryonic rat mesencephalon and hypothalamus.

Development of the dopamine (DA) neuron phenotype was monitored in cultures of embryonic rat mesencephalon (MES) and hypothalamus (HYP) maintained for 1 to 21 days in vitro (DIV) in the absence of glial support cells. Cell counts following immunohistochemistry for tyrosine hydroxylase (TH) demonstrated that the number of DA neurons declined by 85% in MES cultures yet increased 5-fold in cultures of HYP, so that by 21 DIV equal numbers of DA neurons were present in these culture systems. After 21 DIV MES DA neurons exhibited a multipolar morphology, with numerous branching processes. HYP DA neurons were primarily fusiform in shape with fewer processes and process branch points. Double-label immunohistochemistry for TH and microtubule-associated protein 2 identified the majority of TH-positive processes in either culture system as dendrites. Individual MES but not HYP DA neurons were also found to generate axons. Western analysis showed that between 1 and 21 DIV the concentration of TH protein increased 2-fold in MES and 4-fold in HYP cultures. After 21 DIV the concentration of TH protein in MES cultures was twice that found in cultures of HYP. In the period between 1 and 21 DIV levels of tetrahydrobiopterin (BH4) increased by 6-fold in MES and 20-fold in HYP cultures. After 21 DIV BH4 content was 3-fold higher in HYP than in MES cultures. The abundance of the mRNA encoding for GTP cyclohydrolase I, the rate-limiting enzyme in BH4 biosynthesis, was similar in MES and HYP cultures despite this difference in BH4 levels. In contrast, TH mRNA was 4-fold more abundant in MES than in HYP cultures. Treatment of MES cultures with the DA neuron toxin 1-methyl-4-phenylpyridinium decreased DA cell numbers, TH protein content and BH4 levels, demonstrating that BH4 is localized primarily to DA neurons. Similar treatment of HYP cultures did not effect any of these parameters. Steady-state levels of DA and the rate of DA synthesis were both 3-fold higher in MES than in HYP cultures. A 95% decline in BH4 content produced by inhibiting BH4 biosynthesis resulted in 64% and 84% declines in the rate of MES and HYP DA synthesis, respectively. Overall, these observations indicate that, with the exception of the capacity to synthesize DA, DA neurons in MES and HYP cultures share few common properties.

1-Methyl-4-phenylpyridinium↗
PubMedDate not supplied

Light and electron microscopical analysis of nitric oxide synthase-like immunoreactive neurons in the rat retina.

We have investigated the morphology of the NOS-like immunoreactive neurons and their synaptic connectivity in the rat retina by immunocytochemistry using antisera against nitric oxide synthase (NOS). In the present study, several types of amacrine cells were labeled with anti-NOS antisera. Type 1 cells had large somata located in the inner nuclear layer (INL) with long and sparsely branched processes ramifying mainly in stratum 3 of the inner plexiform layer (IPL). Somata of type 2 cells with smaller diameters were also located in the INL. Their fine processes branched mostly in stratum 3 of the IPL. A third population showing NOS-like immunoreactivity was a class of displaced amacrine cells in the ganglion cell layer (GCL). Their soma size was similar to that of the type 1 cells; however, their processes stratified mainly in strata 4 and 5 of the IPL. Labeled neurons were evenly distributed throughout the retina, and the mean densities were 57.0 +/- 9.7 cells/mm2 for the type 1 cells, 239.3 +/- 43.4 cells/mm2 for the type 2 cells and 121.2 +/- 27.5 cells/mm2 cells for the displaced amacrine cells. The synaptic connectivity of NOS-like immunoreactive amacrine cells was identified in the IPL by electron microscopy. NOS-labeled amacrine cell processes received synaptic input from other amacrine cell processes and bipolar cell axon terminals in all strata of the IPL. The most frequent postsynaptic targets of NOS-immunoreactive amacrine cells were other amacrine cell processes. Ganglion cell dendrites were also postsynaptic to NOS-like immunoreactive neurons in both sublaminae of the IPL. Synaptic outputs onto bipolar cells were observed in sublamina b of the IPL. In addition, a few synaptic contacts between labeled cell processes were observed. Our results suggest that NOS immunoreactive cells may be modulated by other amacrine cells and ON cone bipolar cells, and act preferentially on other amacrine cells.

Animals↗
PubMed1995

The effect of mating structure and progeny distribution on heterozygosity versus the number of alleles as measures of variation.

Heterozygosity and the number of alleles are both measures of the genetic variation of a population. They are qualitatively similar if the distribution of the number of progeny is Poisson, but not necessarily for other distributions. In particular, selfing decreases heterozygosity and also decreases the number of alleles when the progeny distribution is Poisson, but decreases heterozygosity and increases the number of alleles when there are two progeny per individual. This is because heterozygosity is closely related to the breeding structure (inbreeding) of the population, whereas the number of alleles is more influenced by the variation of the sampling process. Branching processes are employed to model the dynamics of mutant alleles, with drift and subsequent mutation contributing to extinction. In populations of four individuals, double first cousin mating has greater heterozygosity, but fewer alleles, than half-sib mating.

Alleles↗
PubMed2002

Localization of CD15 immunoreactivity in the rat retina.

Using immunocytochemistry, we have investigated the localization of CD15 in the rat retina. In the present study, two types of amacrine cell in the inner nuclear layer (INL) and some cells in the ganglion cell layer were labeled with anti-CD15 antisera. Type 1 amacrine cells have large somata located in the INL, with long and branched processes ramifying mainly in stratum 3 of the inner plexiform layer (IPL). Type 2 cells have a smaller soma and processes branching in stratum 1 of the IPL. A third population showing CD15 immunoreactivity was a class of displaced amacrine cells in the ganglion cell layer. The densities of type 1 and type 2 amacrine cells were 166/mm(2) and 190/mm(2) in the central retina, respectively. The density of displaced amacrine cells was 195/mm(2). Colocalization experiments demonstrated that these CD15-immunoreactive cells exhibit gamma-aminobutyric acid and neuronal nitric oxide synthase (nNOS) immunoreactivities. Thus, the same cells of the rat retina are labeled by anti-CD15 and anti-nNOS antisera and these cells constitute a subpopulation of GABAergic amacrine cells.

Amacrine Cells↗
PubMed1981

Some aspects of modern population mathematics.

"The purpose of this paper is to survey a number of the technical tools and models that have found use in the study of human and other populations, and to indicate some problems of current interest. These tools and models are varied: integral equations, nonlinear oscillations, differential geometry, dynamical systems, nonlinear operation, bifurcation theory, semigroup theory, martingale theory, Markov processes, diffusion processes, branching processes, ergodic theory, prediction theory and state-space models. A fairly extensive bibliography is provided. Also an Appendix has been added describing the analysis of a classical entomological data set." (summary in FRE)

Demography↗
PubMed1997

Fine three-dimensional structure of pericytes in the vocal fold mucosa.

An investigation was carried out to determine the fine three-dimensional structure of pericytes in excised human vocal fold mucosa, by means of scanning and transmission electron microscopic observation. The results are summarized as follows. 1) There were many pericytes around the true capillaries, arterial capillaries, and venous capillaries in the vocal fold mucosa. 2) Newborns had pericytes around the capillaries in the vocal fold mucosa. 3) The pericytes had bulged fusiform or polygonal cell bodies and branching processes. The branching processes consisted of long and relatively thick longitudinal ones and short circumferential ones. 4) The cell body and processes of the pericytes encircled the capillaries, and the tips of the processes formed intercellular tight junctions with endothelial cells and made a firm connection with them. 5) The pericytes had many cytoplasmic filaments. 6) The pericytes in the vocal fold mucosa appeared to support and protect capillary walls in the vibrating tissue.

Adult↗
PubMed2006

Estimation of the reaction efficiency in polymerase chain reaction.

Polymerase chain reaction (PCR) is largely used in molecular biology for increasing the copy number of a specific DNA fragment. The succession of 20 replication cycles makes it possible to multiply the quantity of the fragment of interest by a factor of 1 million. The PCR technique has revolutionized genomics research. Several quantification methodologies are available to determine the DNA replication efficiency of the reaction which is the probability of replication of a DNA molecule at a replication cycle. We elaborate a quantification procedure based on the exponential phase and the early saturation phase of PCR. The reaction efficiency is supposed to be constant in the exponential phase, and decreasing in the saturation phase. We propose to model the PCR amplification process by a branching process which starts as a Galton-Watson branching process followed by a size-dependent process. Using this stochastic modelling and the conditional least-squares estimation method, we infer the reaction efficiency from a single PCR trajectory.

Animals↗