Mucin histochemistry of submandibular and parotid salivary glands of man: light and electron microscopy

Light-microscopy showed parotid serous acinar cells to contain neutral mucin, serous and mucous acinar cells of submandibular gland and intercalary ductal cells of both glands to contain acid and neutral mucins, and cells of striated ducts and excretory ducts to contain neutral mucin. Mucins were demonstrated ultrastructurally in a portion of the components of secretory granules of acinar cells and intercalary ductal cells, and in secretory granules of striated and excretory ductal cells. The mucins were all stained by techniques that reveal 1,2-glycols. Secretory granules of submandibular mucous and serous acinar cells and intercalary ductal cells were stained variably by the low iron-diamine technique for acid mucin, and those of mucous acinar cells by the high iron-diamine technique for sulphomucins mucin and possibly consisted of protein. The results suggest that one type of cell may be able to produce a range of secretory products and to package them variously into secretory granules.     

Comparative study of automated morphometric and semiquantitative estimations of alcoholic liver steatosis

Needle biopsy of the liver is of great value in appreciating the intensity, type and topography of the steatosis commonly observed during chronic alcoholic diseases. The usual semiquantitative optical analysis is very inaccurate and depends on the subjectivity and training of the pathologist. We therefore performed an automated analysis of liver steatosis using a QTM 720 image analyzer connected to a PDP 11/34 minicomputer. Visual control of the results of the automated analysis showed it to give good results: 94% of the droplets were detected and only 10% of the patterns automatically selected were not droplets. Eight normal biopsies and 37 biopsies showing alcoholic liver steatosis were analyzed. The automated morphometric analysis calculated the mean density (percentage) of steatosis and the size distribution of the droplets. Statistical comparison of these results with those of the semiquantitative optical analysis performed independently by two pathologists showed a significant correlation between their calculations of the density/degree of steatosis but significant differences for their evaluation of the type of steatosis. The pathologists constantly overestimated the ratio of macrodroplets to microdroplets.     

Identification of the most significant amphipathic helix with application to HIV and MHV envelope proteins

Amphipathic helices, which play important roles in protein structure,occur in a wide variety of lengths. Yet existing methods employfixed window lengths. We present a hierarchical procedure thatidentifies the Q most significant amphipathic helices regardlessof length. Since the observed hydrophobicities are not normallydistributed, test statistics usually employed for least-squaresregression are inappropriate for assessing statistical significanceof amphipathic helices. We show that an adjusted F statisticprovides a good test. An application to the envelope proteinof HIV finds an unexpected long amphipathic helix in gp41. Received on July 12, 1989; accepted on February 28, 1990     

Complex ecological models with simple dynamics: From individuals to populations

The aim of this work is to study complex ecological models exhibiting simple dynamics. We consider large scale systems which can be decomposed into weakly coupled subsystems. Perturbation Theory is used in order to get a reduced set of differential equations governing slow time varying global variables. As examples, we study the influence of the individual behaviour of animals in competition and predator-prey models. The animals are assumed to do many activities all day long such as searching for food of different types. The degree of competition as well as the predation pressure are dependent upon these activities. Preys are more vulnerable when doing some activities during which they are very exposed to predators attacks rather than for others during which they are hidden. We study the effect of a change in the average individual behaviour of the animals on interspecific relationships. Computer simulations of the whole sets of equations are compared to simulations of the reduced sets of equations.     

Effects of individual activity sequences on prey-predator models

We study the influence of the individual behaviour of animals on predator-prey models. Populations of preys and predators are divided into sub-populations corresponding to different activity classes. The animals are assumed to do many activities all day long such as searching for food of different types. The preys are more vulnerable when doing some activities during which they are very exposed to predators attacks rather than for others during which they are hidden. We study activity sequences of the animals and also the effect of a change in the average individual behaviour of the animals on Lotka-Volterra prey-predator interactions. Numerical simulations are realized for the whole sets of equations (governing the subpopulations) and are compared to the simulations of the reduced sets of equation (governing the populations). We look for the validity of the method with respect to a scaling factor which measures the differences between the two time scales associated to the fast-varying variables and to the slow-time varying global variables. It is shown that when the two time scales differ of about two orders of magnitude, the approximation is satisfying.     

Solvent history dependence of gramicidin-lipid interactions: a Raman and infrared spectroscopic study.

We have investigated the interactions between gramicidin and a model membrane composed of one phospholipid, dimyristoylphosphatidylcholine, as a function of the cosolubilization solvent and incubation time used in the sample preparation. Three organic solvents have been used; trifluoroethanol, a mixture of methanol/chloroform (1:1 v/v), and ethanol. Using Fourier transform infrared spectroscopy, we have demonstrated that the conformation adopted by gramicidin in the membrane is dependent upon the cosolubilization solvent used, and, only with trifluoroethanol, it is possible to incorporate gramicidin entirely as a beta 6.3-helix. Moreover, Raman spectroscopy results indicate that the orientation of the tryptophan side chains in gramicidin and their interaction with the hydrocarbon chains and the carbonyl groups of the lipids are also dependent on the cosolubilization solvent. On the other hand, the effect of the incorporation of gramicidin on the thermotropism of the lipid bilayer was found to be dependent upon the conformation of gramicidin in the lipid bilayers.     

A tightly associated serine/threonine protein kinase regulates phosphoinositide 3-kinase activity.

We identified a serine/threonine protein kinase that is associated with and phosphorylates phosphoinositide 3-kinase (PtdIns 3-kinase). The serine kinase phosphorylates both the 85- and 110-kDa subunits of PtdIns 3-kinase and purifies with it from rat liver and immunoprecipitates with antibodies raised to the 85-kDa subunit. Tryptic phosphopeptide maps indicate that p85 from polyomavirus middle T-transformed cells is phosphorylated in vivo at three sites phosphorylated in vitro by the associated serine kinase. The 85-kDa subunit of PtdIns 3-kinase is phosphorylated in vitro on serine at a stoichiometry of approximately 1 mol of phosphate per mol of p85. This phosphorylation results in a three- to sevenfold decrease in PtdIns 3-kinase activity. Dephosphorylation with protein phosphatase 2A reverses the inhibition. This suggests that the association of protein phosphatase 2A with middle T antigen may function to activate PtdIns 3-kinase.     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.