STUDIES ON THE DEPLETION AND ACCUMULATION OF MICROVILLI AND CHANGES IN THE TUBULOVESICULAR COMPARTMENT OF MOUSE PARIETAL CELLS IN RELATION TO GASTRIC ACID SECRETION

Gastric parietal cells in mice present a spectrum of microscopic appearances due mainly to variations in the abundance of the tubular and vesicular component of the cytoplasm and in the size and number of microvilli lining the intracellular canaliculi. Differences in the range of forms among parietal cells of fasting versus fed mice were not especially striking, but cells with very numerous tubules and vesicles were more common after fasting. However, in mice treated with drugs or hormones that induce acid secretion, parietal cells were more uniform in appearance. There was a marked reduction of these cytoplasmic membranes and a concomitant increase in both the number and size of microvilli. Measurements of acid secretion in control animals and in animals treated with acid secretagogues indicated hydrogen ion secretion contemporaneous with depletion of the cytoplasmic tubulovesicular membranes and with increase of the microvilli. In mice with inhibited acid secretion, parietal cells showed an accumulation of cytoplasmic tubules and vesicles and reduction in the numbers of microvilli. Stereological methods were used to quantitate 10 different parietal cell compartments. Tracer studies with lanthanum did not reveal continuity between the tubules and the plasma membrane. However, there were regions of close apposition between the tubulovesicular membranes and the cell membrane of the canaliculus, and instances where cytoplasmic tubules extended from the cell into the core of enlarged microvilli.     

Computer monitoring, capture and analysis of gas/liquid chromatograph traces

The work described here is effectively the computerization ofa gas/liquid chromatograph of the pen recorder type using aBBC microcomputer. The output from the g. l. c. can be capturedby the computer in accordance with a series of parameters. Thesampling rate can be altered, as can an averaging facility toreduce noise, and a threshold level to eliminate the storageof irrelevent and space-consuming data. The unprocessed readingsare initially stored on the computer's floppy disk, then laterretrieved and cut into smaller sections to allow maximum resolutionfor on-screen analysis. In the main analysis stage of the systemall processing is shown graphically on the computer monitorat all stages. The principal steps in analysis involve the mathematicalmodelling and elimination of the solvent peak, the fixing ofthe retention time for each subsequent peak and its disentanglingfrom any following peaks, and finally the calculation of thearea under each individual peak. Several alternative methodsare made available for disentangling peaks, which can be triedsuccessively on a single peak then each printed out with commentsfor comparison later. All readings and results in table formand screen dumps of all trace images are available via a dotmatrix printer. Received on October 29, 1985; accepted on June 27, 1986     

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.     

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.