Temporal shifts in physical habitat of the crayfish,Orconectes neglectus (Faxon)

A total of 300 samples was collected from February 1985 to August 1986 in a medium order Ozark Mountain stream. Physical habitat measurements of temperature, mean water column velocity, depth, and substrate character were recorded for each of the 25 monthly samples along with length and sex of all individuals of Orconectes neglectus (Faxon). Analysis of habitat utilization and suitability (or preference) was conducted using exponential polynomial models of hydraulic stress models. There appeared to be equal preference for depth over the range measured. Both substrate and velocity preference curves were bimodal with each mode designating certain crayfish size classes. Young-of-the-year were found primarily in cobbled, high velocity areas while adults were found in low velocity, macrophyte beds. Utilization curves for laminar sublayer thichness also reflected size-dependent phenomena where young-of-the-year were found in thin sublayer areas and adults were found primarily in thick sublayers. When separated by time and size, adults were found to occupy higher velocity, cobbled habitats during at least two months. This time period corresponded with the time of egg-bearing and further analysis yielded a time-dependent habitat suitability surface which accounted for this movement pattern. We suggest that the application of these suitability surfaces, which reflect habitat changes during the annual life cycle, will produce more accurate predictions of density and will allow better habitat management decisions under various regulated flow scenarios.     

Molecular characterization of cell types in the developing,mature, and regenerating fish retina

The fish retina has become a powerful model system for the study of different aspects of development and regeneration. An important aspect in understanding retinal anatomy and function is to trace the development of various cell types during embryonic stages. Several markers that detect the cessation of proliferative activity have been used in studies of cellular birth days, in order to follow the temporal progression of retinogenesis. Moreover, by using cell type-specific markers, the onset of differentiation can be determined by identifying the earliest time points for which immunolabeling is observed. Additionally, fish retinal regeneration research holds the potential of providing new avenues for the treatment of degenerative diseases of the retina. Retinal markers constitute powerful tools in studies of retinal regeneration, because they allow characterization of the cell types involved in nerve tissue regeneration, providing insights into different aspects of this process. In this review, after presenting several structural and histological aspects of the mature and developing fish visual system, data on the use of various neurochemical markers specifically indicating cell types of the fish neural retina are summarized. This will be done through a review of the pertinent literature, as well as by drawing on our own experience gathered through recent studies on fish retinogenesis.     

Rapid Evaluation of Least-Squares and Minimum-Evolution Criteria on Phylogenetic Trees

We present fast new algorithms for evaluating trees with respectto least squares and minimum evolution (ME), the most commonlyused criteria for inferring phylogenetic trees from distancedata. The new algorithms include an optimal O(N2) time algorithmfor calculating the edge (branch or internode) lengths on atree according to ordinary or unweighted least squares (OLS);an O(N3) time algorithm for edge lengths under weighted leastsquares (WLS) including the Fitch-Margoliash method; and anoptimal O(N4) time algorithm for generalized least-squares (GLS)edge lengths (where N is the number of taxa in the tree). TheME criterion is based on the sum of edge lengths. Consequently,the edge lengths algorithms presented here lead directly toO(N2), O(N3), and O(N4) time algorithms for ME under OLS, WLS,and GLS, respectively. All of these algorithms are as fast asor faster than any of those previously published, and the algorithmsfor OLS and GLS are the fastest possible (with respect to orderof computational complexity). A major advantage of our new methodsis that they are as well adapted to multifurcating trees asthey are to binary trees. An optimal algorithm for determiningpath lengths from a tree with given edge lengths is also developed.This leads to an optimal O(N2) algorithm for OLS sums of squaresevaluation and corresponding O(N3) and O(N4) time algorithmsfor WLS and GLS sums of squares, respectively. The GLS algorithmis time-optimal if the covariance matrix is already inverted.The speed of each algorithm is assessed analytically—thespeed increases we calculate are confirmed by the dramatic speedincreases resulting from their implementation in PAUP* 4.0.The new algorithms enable far more extensive tree searches andstatistical evaluations (e.g., bootstrap, parametric bootstrap,or jackknife) in the same amount of time. Hopefully, the fastalgorithms for WLS and GLS will encourage the use of these criteriafor evaluating trees and their edge lengths (e.g., for approximatedivergence time estimates), since they should be more statisticallyefficient than OLS.     

Direct effects of vitamin D3 analogues on G-protein mediated signalling systems in rat osteosarcoma cells and rat pituitary adenoma cells

In normal rats treated with 1,25(OH)₂D₃ or 24,25(OH)₂D₃, serum Ca²⁺, ALP, PRL and GH are significantly altered. In order to study the primary effect of vitamin D₃ analogues on target organ function, rat UMR 106 osteosarcoma and GH₃ pituitary adenoma cells in monolayer culture were exposed accordingly.Surprisingly, prolonged exposure of these cell lines to physiological levels of either 1,25(OH)₂D₃ or 24,25(OH)₂D₃ did not significantly affect the secretory parameters (ALP, PRL or GH) tested. However, 1,25(OH)₂D₃ exposure significantly reduced PTH- and Gpp(NH)p-elicited AC as well as Gpp(NH)p-stimulated PLC activities in the UMR 106 cells. These changes were accompanied by an increase and decrease in the membrane contents of the G-protein subunits G₃₆ and G_q/11, respectively. In contrast, 24,25(OH)₂D₃ remained without significant biological effect on these signalling systems despite concomitantly augmented levels of G₃₆. TRH- and Gpp(NH)p-elicited PLC activities in the GH₃ cells were significantly reduced by 1,25(OH)₂D₃ with a concurrent reduction in cellular amounts of G_q/11, however, 24,25(OH)₂D₃ did not significantly alter any signalling systems nor G-proteins analyzed.It is concluded that the osteoblastic and pituitary cell secretion of ALP, PRL and GH remain unaffected by the presence of 1,25(OH)₂D₃ and 24,25(OH)₂D₃, despite distinct alterations in components of G-protein mediated signalling pathways. Hence, other factors like ambient Ca²⁺ may be responsible for the perturbed secretory patterns of ALP and PRL seen in vitamin D₃ treated rats.Abbreviations AC adenylate cyclase - ALP alkaline phosphatase - BGP osteocalcin - BSA bovine serum albumin - DA dopamine - DAG diacylglycerol - GH growth hormone - GHRH growth hormone releasing hormone - Gpp(NH)p guanosine 5-[-imido]triphosphate - G-protein guanine nucleotide-binding regulatory protein - G_s etc. G_s protein -subunit - IP₃ inositol 1,4,5 trisphosphate - OAF osteoclast activating factor - PGE₂ prostaglandin E₂ - PKA & PKC protein kinase A & C - PLC phospholipase C - PRL prolactin - PTH parathyroid hormone - SRIF somatostatin - TRH thyrotropin releasing hormone - VIP vasoactive intestinal peptide - 25(OH)D₃ 25 hydroxy vitamin D₃ - 1,25(OH)₂D₃ 1·25 dihydroxy vitamin D₃ - 24,25(OH)₂D₃ 24,25 dihydroxy vitamin D₃