SPERMATOGENESIS IN COLEOCHAETE PULVINATA (CHAROPHYCEAE): EARLY BLEPHAROPLAST DEVELOPMENT

Transmission electron microscopy of serial thin sections was used to reconstruct several early developmental stages of the blepharoplast in Coleochaete pulvinata spermatids. These were compared to published studies of blepharoplast development in Charales and the closest relatives of charophycean green algae among embryophytes, i.e., hornworts and liverworts. Bicentriolar centrosomes such as occur in bryophytes and fern allies were not observed in Coleochaete. Centriole replication in C. pulvinata was orthogonal as in Charales. The resulting two daughter centrioles were oriented perpendicularly and joined proximally by electron-dense material. Their orthogonal relationship was maintained throughout blepharoplast development by a massive, banded connective which appeared early. In spermatids of hornworts and liverworts, a multilayered structure (MLS) develops in association with two centrioles destined to become flagellar basal bodies. When the MLS of these lower land plants is sectioned at right angles to the long axis of the microtubular layer, the MLS is observed to lie beneath cross sections of both centrioles. In contrast, when developing MLSs of C. pulvinata and Charales are similarly sectioned, they occur beside a cross section of just one of the two centrioles. In C. pulvinata (as in other charophytes), MLS lamellae are oriented at a 90-degree angle to the long axis of the S₁ microtubules from the beginning. This contrasts with the 40–45 degree angle between the MLS lamellae and S₁ microtubules universally reported for archegoniates. In early C. pulvinata spermatids, spline microtubules are closely associated with an anterior mitochondrion having a low stromal density and few cristae. An anterior mitochondrion is typically associated with blepharoplast development in hornworts and liverworts, but has not previously been reported to occur in Coleochaete or any other charophycean alga. In Coleochaete, as in hornworts and liverworts, but unlike Charales, structure of mature blepharoplasts reflects early blepharoplast ontogeny. Very little change in positional relationships among blepharoplast components (flagella, connective, MLS) occurs during development. These character-state differences are of importance in cladistic analyses of charophycean algae and lower land plants.     

Use of two freezing extenders to cool stallion spermatozoa to 5 degrees C with and without seminal plasma

Motion characteristics of cooled stallion spermatozoa in 2 freezing extenders were studied. Ejaculates from 8 stallions were split into treatments and cooled in thermoelectric cooling units at each of 2 rates. Cooling started at 37 degrees C for Experiments 1 and 3 and at 23 degrees C for Experiments 2 and 4, at a rate of -0.7 degrees C/min to 20 degrees C and from 20 to 5 degrees C, at either -0.05 degrees C/min (Rate I) or -0.5 degrees C/min (Rate II). Percentages of motile (MOT) and progressively motile spermatozoa (PMOT) were determined at 6, 24 and 48 h. Treatments in Experiment 1 were modified skim milk extender (SM); SM + 4% egg yolk (EY); SM + 4% glycerol (GL); and SM + 4% egg yolk + 4% glycerol (EY + GL). At 24 and 48 h, MOT and PMOT were lowest (P < 0.05) for spermatozoa extended in SM + EY; spermatozoa in SM + GL had the highest MOT and PMOT. Thus, glycerol partially protected spermatozoa against the effects of cooling after long-term storage. Treatments in Experiment 2 were SM, semen centrifuged and pellet resuspended in SM (SMc), SM + EY, and semen centrifuged and pellet resuspended in SM + EY (EYc). Spermatozoa in SM + EYc had the highest (P < 0.05) PMOT at 24 h and MOT and PMOT at 48 hours. Spermatozoa in SM + EY (not centrifuged) had the lowest MOT and PMOT at 24 and 48 h, respectively. There was a detrimental interaction between egg yolk and seminal plasma. Extenders in Experiment 3 were Colorado extender (CO3), CO3 + 4% egg yolk (EY), CO3 + 4% glycerol (GL), and CO3 + 4% egg yolk + 4% glycerol (EY + GL). Spermatozoa in CO3 + EY had the lowest (P < 0.05) PMOT at 24 and 48 h. CO3 did not protect spermatozoa cooled in the presence of seminal plasma. Therefore, in Experiment 4 we tested CO3 with seminal plasma present (control) and semen centrifuged and pellet resuspended in CO3 (CO3c), CO3 + EY (EYc), CO3 + GL (GLc) and CO3 + EY + GL (EY + GLc). Spermatozoa in CO3 had the lowest (P < 0.05) MOT and PMOT at all time periods, which suggested a detrimental interaction of this extender with seminal plasma.     

Inositol lipid-mediated signalling in response to endothelin and ATP in the mammalian testis

Molecular and Cellular Biochemistry - The testis is a complex organ in which local control is achieved by signalling between its constituent cells. Herein we describe the responses of cultured rat...     

Fatty Acid Methyl Ester Profiles for Characterization of Glomalean Fungi and Their Endomycorrhizae

Arbuscule-forming fungi in the order Glomales form obligate endomycorrhizal associations with plants that make them difficult to quantify, and taxonomy of the group is only beginning to be objectively understood. Fatty acid methyl ester (FAME) profiles were analyzed to assess the diversity and quantity of fatty acids in 53 isolates of 24 glomalean species. Spores and endomycorrhizal roots of sudan grass (Sorghum sudanense) and the citrus rootstock Carrizo citrange (Poncirus trifoliata x Citrus sinensis) were examined. Spores yielded reproducible FAME profiles from replicate spore collections extracted from soil pot cultures despite being grown in association with a host plant and with contaminating microorganisms present. Unweighted pair group analysis revealed relatively tight clusters of groups at the intraspecific, specific, and generic levels; however, lipid profiles at the family level were convergent. Thus, FAME profile comparisons provided a robust measure of similarity below the family level. FAME profiles in sudan grass roots containing vesicles and/or spores of Glomus intraradices were more similar to spore profiles than to profiles from nonmycorrhizal roots. The FAME profiles for Gigaspora species, which do not form vesicles or spores in roots, were less distinct from nonmycorrhizal roots. G. intraradices and G. rosea produced fatty acids in roots that were distinguishable from each other as well as from the host root. Production in citrus roots of the fatty acid 16:1(inf(omega)5) cis by two Glomus species was correlated with the development of mycorrhizal colonization as measured by clearing and staining procedures and by estimates of total incidence and vesicle intensity. FAME analysis of roots not only provided a measure of colonization development but also served as an index of carbon allocated to intraradical fungal growth and lipid storage.