Rat testis motor proteins associated with spermatid translocation (dynein) and spermatid flagella (kinesin-II)

In this study, we report sites in the seminiferous epithelium of the rat testis that are immunoreactive with antibodies to the intermediate chain of cytoplasmic dynein and kinesin II. The study was done to determine whether or not microtubule-dependent motor proteins are present in Sertoli cell regions involved with spermatid translocation. Sections and epithelial fragments of perfusion-fixed rat testis were probed with an antibody (clone 74.1) to the intermediate chain of cytoplasmic dynein (IC74) and to kinesin-II. Labeling with the antibody to cytoplasmic dynein was dramatically evident in Sertoli cell regions surrounding apical crypts containing attached spermatids and known to contain unique intercellular attachment plaques. The antibody to kinesin II reacted only with spermatid tails. The levels of cytoplasmic dynein visible on immunoblots of supernatants collected from spermatid/junction complexes treated with an actin-severing enzyme (gelsolin) were greater than those of controls, indicating that at least some of the dynein may have been associated with Sertoli cell junction plaques attached to spermatids. Results are consistent with the conclusion that an isoform of cytoplasmic dynein may be responsible for the apical translocation of elongate spermatids that occurs before sperm release. Also, this is the first report of kinesin-II in mammalian spermatid tails.     

Distribution of actin bundles in Bowman's capsule of rat kidney

In this study we define the distribution of actin bundle arrangement in Bowman's capsule of rat renal corpuscles. Parietal cells of Bowman's capsule were examined by conventional light microscopy, electron microscopy and confocal microscopy. Within each parietal cell individual actin bundles are arranged in a parallel fashion running the length of the cell. Computer reconstructions obtained using confocal microscopy clearly show the lengths of actin bundles to be arranged, on a capsule level, end-to-end, at angles and perpendicular to bundles in adjacent cells. The bundles stain positively for non-muscle myosin and vinculin. The presence and arrangement of actin bundles in parietal cells is consistent with a role in reinforcing capsule structure.     

Quivisianthone, an evodulone limonoid from the Madagascan Meliaceae Quivisia papinae

An investigation of the seeds of the Madagascan Meliaceae Quivisia papinae has yielded quivisianthone, a novel evodulone group limonoid, together with the known azadiradione and two novel derivatives: 6 alpha-hydroxyazadiradione and 7-deacetyl-7-angeloyl-6 alpha-hydroxyazadiradione. Quivisianthone is the first reported evodulone group limonoid possessing both a ring A lactone and an azadiradione-type ring D.     

A Cross-System Comparison of Bacterial and Fungal Biomass in Detritus Pools of Headwater Streams

The absolute amount of microbial biomass and relative contribution of fungi and bacteria are expected to vary among types of organic matter (OM) within a stream and will vary among streams because of differences in organic matter quality and quantity. Common types of benthic detritus [leaves, small wood, and fine benthic organic matter (FBOM)] were sampled in 9 small (1st-3rd order) streams selected to represent a range of important controlling factors such as surrounding vegetation, detritus standing stocks, and water chemistry. Direct counts of bacteria and measurements of ergosterol (a fungal sterol) were used to describe variation in bacterial and fungal biomass. There were significant differences in bacterial abundance among types of organic matter with higher densities per unit mass of organic matter on fine particles relative to either leaves or wood surfaces. In contrast, ergosterol concentrations were significantly greater on leaves and wood, confirming the predominance of fungal biomass in these larger size classes. In general, bacterial abundance per unit organic matter was less variable than fungal biomass, suggesting bacteria will be a more predictable component of stream microbial communities. For 7 of the 9 streams, the standing stock of fine benthic organic matter was large enough that habitat-weighted reach-scale bacterial biomass was equal to or greater than fungal biomass. The quantities of leaves and small wood varied among streams such that the relative contribution of reach-scale fungal biomass ranged from 10% to as much as 90% of microbial biomass. Ergosterol concentrations were positively associated with substrate C:N ratio while bacterial abundance was negatively correlated with C:N. Both these relationships are confounded by particle size, i.e., leaves and wood had higher C:N than fine benthic organic matter. There was a weak positive relationship between bacterial abundance and streamwater soluble reactive phosphorus concentration, but no apparent pattern between either bacteria or fungi and streamwater dissolved inorganic nitrogen. The variation in microbial biomass per unit organic matter and the relative abundance of different types of organic matter contributed equally to driving differences in total microbial biomass at the reach scale.     

Ectopic expression of a tomato 9-cis-epoxycarotenoid dioxygenase gene causes over-production of abscisic acid

The tomato mutant notabilis has a wilty phenotype as a result of abscisic acid (ABA) deficiency. The wild-type allele of notabilis, LeNCED1, encodes a putative 9-cis-epoxycarotenoid dioxygenase (NCED) with a potential regulatory role in ABA biosynthesis. We have created transgenic tobacco plants in which expression of the LeNCED1 coding region is under tetracycline-inducible control. When leaf explants from these plants were treated with tetracycline, NCED mRNA was induced and bulk leaf ABA content increased by up to 10-fold. Transgenic tomato plants were also produced containing the LeNCED1 coding region under the control of one of two strong constitutive promoters, either the doubly enhanced CaMV 35S promoter or the chimaeric 'Super-Promoter'. Many of these plants were wilty, suggesting co-suppression of endogenous gene activity; however three transformants displayed a common, heritable phenotype that could be due to enhanced ABA biosynthesis, showing increased guttation and seed dormancy. Progeny from two of these transformants were further characterized, and it was shown that they also exhibited reduced stomatal conductance, increased NCED mRNA and elevated seed ABA content. Progeny of one transformant had significantly higher bulk leaf ABA content compared to the wild type. The increased seed dormancy was reversed by addition of the carotenoid biosynthesis inhibitor norflurazon. These data provide strong evidence that NCED is indeed a key regulatory enzyme in ABA biosynthesis in leaves, and demonstrate for the first time that plant ABA content can be increased through manipulating NCED.     

Limonoid derivatives from Astrotrichilia voamatata

The stem bark of Astrotrichilia voamatata (Meliaceae) has yielded the novel limonoids voamatins C and D. These compounds represent a new type of pentanortriterpenoid and are unique in containing a ring A cyclic ether.     

Sesquiterpene lactone and friedelane derivative from drypetes molunduana

A new sesquiterpene lactone, drypemolundein A and a new friedelane derivative, drypemolundein B, along with seven known compounds have been isolated from the whole stems of Drypetes molunduana Pax and Hoffm. Their structures were established on the basis of one- and two-dimensional NMR, homo- and hetero-nuclear spectroscopic evidence.     

Carbon Dioxide Variation in a Hardwood Forest Stream: An Integrative Measure of Whole Catchment Soil Respiration

The concentration of CO₂ in stream water is a product of not only instream metabolism but also upland, riparian, and groundwater processes and as such can provide an integrative measure of whole catchment soil respiration. Using a 5-year dataset of pH, alkalinity, Ca²⁺, and Mg²⁺ in surface water of the West Fork of Walker Branch in eastern Tennessee in conjunction with a hydrological flowpath chemistry model, we investigated how CO₂ concentrations and respiration rates in stream, bedrock, and soil environments vary seasonally and interannually. Dissolved inorganic carbon concentration was highest in summer and autumn (P < 0.05) although the proportion as free CO₂ (pCO₂) did not vary seasonally (P > 0.05). Over the 5 years, pCO₂ was always supersaturated with respect to the atmosphere ranging from 374 to 3626 ppmv (1.0- to 10.1-fold greater than atmospheric equilibrium), and CO₂ evasion from the stream to the atmosphere ranged from 146 to 353 mmol m⁻² d⁻¹. Whereas pCO₂ in surface water exhibited little intra-annual or interannual variation, distinct seasonal patterns in soil and bedrock pCO₂ were revealed by the catchment CO₂ model. Seasonally, soil pCO₂ increased from a winter low of 8167 ppmv to a summer high of 27,068 ppmv. Driven by the seasonal variation in gas levels, evasion of CO₂ from soils to the atmosphere ranged from 83 mmol m⁻² d⁻¹ in winter to 287 mmol m⁻² d⁻¹ in summer. The seasonal variation in soil CO₂ tracked soil temperature (r ²= 0.46, P < 0.001) and model-derived estimates of CO₂ evasion rate from soils agreed with previously reported fluxes measured using chambers (Pearson correlation coefficient = 0.62, P < 0.05) supporting the model assumptions. Although rates of CO₂ evasion were similar between the stream and soils, the overall rate of evasion from the channel was only 0.4% of the 70,752 mol/d that evaded from soils due to the vastly different areas of the two subsystems. Our model provides a means to assess whole catchment CO₂ dynamics from easily collected and measured stream-water samples and an approach to study catchment scale variation in soil ecosystem respiration. Received 24 July 1997; accepted 14 November 1997.