A simple high capacity freeze-drier for histochemical use

Summary A new freeze-drier for histochemical use is described. It uses a refrigerated cooling bath for outer cooling and large amounts of phosphorous pentoxide as water vapor trap.The main features are a very high drying capacity, a simple, reliable easy-to-handle construction and a series of safety devices which, including a rigid stainless steel vacuum chamber which cannot implode, ensures reproducable results.Estimations of relative dryness can be performed during drying. An extra blind flange entrance to the vacuum chamber and the use of standard vacuum connections makes the apparatus versatile. Thus it can be used also for chemical freeze-drying.The apparatus was developed for use with the Falck-Hillarp fluorescence technique for histochemical visualization of monoamines. It gives excellent results with this technique both with peripheral tissues and brain tissue. As many as 20–25 whole brains from adult rats can be processed simultaneously within 3 days.     

Ultrastructural evidence for the biflagellate origin of the uniflagellate fungal zoospore

Summary The morphological similarities between the kinetosome and the second centriole of the zoospores of Phlyctochytrium kniepii and P. punctatum (Chytridiomycetes) suggest that the second centriole in the chytrid zoospore is a vestigial flagellum base. It is suggested that the term vestigial kinetosome may also be used when referring to the structure which is presently termed the second centriole of the chytrid zoospore. Morphological similarities between the chytrid zoospores of P. kniepii and P. punctatum and the zoospores of Rhizidiomyces apophysatus (Hyphochytridiomycetes) are noted. The possible biflagellate origin of fungi with uniflagellate zoospores is discussed. The third fiber (C fiber) of the kinetosome triplet is shown to form as an outgrowth of the B fiber of the kinetosome doublet.     

Adrenergic innervation of the salivary glands in the rat

Summary The adrenergic innervation of the major salivary glands in the rat has been studied by a specific histochemical method for the visualization of the adrenergic transmitter. Adrenergic varicose nerve fibres were found, located in a typical adrenergic ground plexus closely surrounding the serous acini of the submaxillary and parotid glands, but not the acini of the mainly mucous sublingual gland. The ducts were found to be completely devoid of adrenergic innervation. Arterioles and venules in the stroma of all three glands and certain very small vessels, possibly the sphincters of arterio-venous anastomoses, were also richly innervated by adrenergic vasomotor fibres. The relationship of the adrenergic nerve fibres to the different functional units of the gland parenchyma is discussed.The investigation has been supported by a research grant (B 66–257) from the Swedish Medical Research Council and by a Public Health Service Research Grant (NB 05236-01) from the National Institute of Neurological Diseases and Blindness.     

Topographic control of vegetation in a mountain big sagebrush steppe

Mountain big sagebrush steppes in Wyoming have strong spatial patterning associated with topography. We describe the spatial variability of vegetation in a sagebrush steppe, and test the relationship between topography and vegetation using canonical correlation. Results of the analysis suggest that the main control over vegetation distribution in this system is wind exposure. Exposed sites are characterized by cushion plant communities and Artemisia nova, and less exposed sites by the taller sagebrush species Artemisia tridentata ssp. vaseyana. Topographic depressions and leeward slopes are characterized by aspen stands and nivation hollows. Measurements of soil microclimate suggest that a major influence of topographic position on vegetation is snow redistribution and its effect on soil moisture and temperature.Abbreviations ARNO Artemisia nova - ARTRW Artemisia tridentata ssp. wyomingensis - ARTRV Artemisia tridentata ssp. vaseyana - PUTR Purshia tridentata - RIP riparian community - POTR Populus tremuloides - NIV nivation hollow community     

Surface area-independent assessment of lung microvascular permeability with an amphipathic tracer

A combination of an amphipathic-indicator-dilution (ID) diffusing tracer 1,4[14C]butanediol (B) and a hydrophilic tracer ([14C]urea) (U) was hypothesized to provide a capillary surface area- (S) independent assessment of lung microvascular permeability (P). We performed ID studies on isolated perfused dog lungs and administered randomly two interventions, increasing P by alloxan infusion and reduction in S by lobar ligation. The ratio of PS product of U (PSU) to that for butanediol (PSB) was sensitive to changes in P yet insensitive to changes in S. We performed ID studies in which the dependence of PSU and PSB on flow, hematocrit, and plasma protein binding were examined. Measurements of PSU and PSB after flow and hematocrit were changed suggested that these factors have no significant independent effects. From ID and in vitro studies we also found that no significant binding of B to plasma proteins (albumin) occurred. We concluded that ID techniques using B and U provide a consistent measure of P, despite changes in S, hematocrit, plasma protein concentration, and recruitment.     

The reproductive biology of female Père David's deer (Elaphurus davidianus)

Data for this study came from breeding records of 27 Père David's (Elaphurus davidianus) hinds maintained in large pastures and from estrous records of four hand-reared nulliparous hinds. The mean estrous cycle length ranged from 17.5 to 19.6 days. Standing estrus resembled that of other cervids, except that a low, moaning vocalization was given in response to contact, and activity (as measured by pedometers) did not increase. Mean gestation length was 183.38 ± SD 6.11 days (n = 21), and nearly all females conceived in the second and third years. The median interbirth interval was 362 days. The median birth date was April 8, and 80% of the births occurred over a 9.5-week period. Multiparous hinds gave birth an average of 20.5 days earlier in the season than primiparous hinds. There was no dimorphism in birth weight. The results are discussed in light of comparative data for other species.     

The effects of lipid composition on the rate and extent of heme binding to membranes

The effects of membrane composition on heme binding to large unilamellar vesicles were examined using 30 separate phospholipid mixtures. Although there was some variation, most lecithins with Tm values less than or equal to 20 degrees C showed overall equilibrium partition constants equal to approximately 5 x 10(5) and association and dissociation partition rate constants equal to approximately 3 x 10(6) s-1 and 7 s-1, respectively, for CO-heme binding at 30 degrees C. A sharp decrease in the association rate for CO-heme uptake was observed as the lipid vesicles changed from liquid-crystalline to the gel phase. The addition of dicetyl phosphate or dimyristoylphosphatidylglycerol, which are negatively charged at neutral pH, decreased the affinity of the vesicles for CO-heme. The association rate and equilibrium partition constants for CO-heme uptake in unsaturated lecithins were unaffected by cholesterol content at levels up to 40%/mol. The affinity of saturated dimyristoylphosphatidylcholine (DMPC) vesicles for CO-heme decreased with increasing cholesterol content at 30 degrees C. This effect appears to be related to the influence of cholesterol on the DMPC phase transition temperature (Tm) since at low temperatures (less than or equal to 20 degrees C) little CO-heme binds to vesicles composed of DMPC even in the absence of cholesterol.