Radiosensitivity of murine hemopoietic colony-forming units assayed in situ in the rib and in other marrow sites

The radiosensitivity of murine hemopoietic colony-forming cells, which produce colonies in situ and which were counted at Day 8 after irradiation in sections of the femur, humerus, sternum, and spleen, is characterized by a D0 value of 91 +/- 9 cGy. The radiosensitivity of such cells in the rib was assessed using a new technique measuring regeneration or ablation of marrow in transverse sections of ribs observed at Day 8 after irradiation. The mean D0 value over a range determined using several different criteria was 108 cGy. These results provide evidence for the common assumptions that radiosensitivity measured using conventional transplantation assays reflects radiosensitivity in situ, and that the radiosensitivity of stem cells in different medullary marrow sites is similar. The techniques could be used with other species where assays for stem cells are not available.     

A spatial open-population capture-recapture model

A spatial open-population capture-recapture model is described that extends both the non-spatial open-population model of Schwarz and Arnason and the spatially explicit closed-population model of Borchers and Efford. The superpopulation of animals available for detection at some time during a study is conceived as a two-dimensional Poisson point process. Individual probabilities of birth and death follow the conventional open-population model. Movement between sampling times may be modeled with a dispersal kernel using a recursive Markovian algorithm. Observations arise from distance-dependent sampling at an array of detectors. As in the closed-population spatial model, the observed data likelihood relies on integration over the unknown animal locations; maximization of this likelihood yields estimates of the birth, death, movement, and detection parameters. The models were fitted to data from a live-trapping study of brushtail possums (Trichosurus vulpecula) in New Zealand. Simulations confirmed that spatial modeling can greatly reduce the bias of capture-recapture survival estimates and that there is a degree of robustness to misspecification of the dispersal kernel. An R package is available that includes various extensions.     

Notes from the New York Botanical Garden Herbarium II. The Herbaria of Charles Warfield Trow and Albert T. Beals

Two private herbaria have been donated to the Garden. The Trow herbarium consists of 87 mounted plants collected in Massachusetts between 1895 and 1900. The Beals herbarium contains 325 mounted plants from New Jersey and Pennsylvania, collected between 1898 and 1901.     

The arginine dihydrolase pathway is present in Giardia intestinalis

Growth of Giardia intestinalis in Diamond's TYI-S-33 medium is characterized by a rapid depletion of the arginine in the medium, and concurrent production of ornithine and ammonia. [Guanidino-14C] arginine was converted to 14CO2 by extracts of G. intestinalis suggesting the presence of the arginine dihydrolase pathway. This was confirmed by the detection of arginine deiminase, catabolic ornithine transcarbamylase, carbamate kinase and ornithine decarboxylase in giardial extracts. The findings demonstrate for the first time the existence of the arginine dihydrolase pathway in Giardia, and suggest that arginine metabolism via this pathway plays a significant role in energy metabolism by providing a site for anaerobic substrate level phosphorylation.     

Effect of metiamide on acid secretion from isolated kitten fundic mucosa.

Isolated kitten fundic mucosa demonstrates low rates of spontaneous acid secretion in vitro when bathed in Krebs-Henseleit solution, and responds consistently to histamine, pentagastrin, and acetylcholine placed in the bath. High rates of spontaneous secretion or secretion in response to histamine and pentagastrin were significantly inhibited by addition of metiamide (5 X 10(-3) M); but mucosa stimulated by constant addition of acetylcholine chloride (10(-4) M) was not inhibited by metiamide at the same concentration.