Silage review: Recent advances and future technologies for whole-plant and fractionated corn silage harvesting.

Over the last 25 years, whole-plant corn silage has become an important and popular feedstuff for dairy production. Copious research has been dedicated to the development and evaluation of alternatives to enhance the nutritive value of whole-plant corn silage. These efforts have been aimed at manipulating the physical and chemical characteristics of whole-plant corn silage in an effort to maximize dairy profitability. Results from this review indicate that optimization of harvest maturity, kernel processing, theoretical length of cut, and cutting height improve or maintain the nutritive value and milk production of lactating dairy cows. Technological advancements have been developed and made available to dairy producers and corn growers desiring to enhance fiber and starch digestibility of whole-plant corn silage. Future research should be directed toward further assessment of new processors available in the market and the development of assessment methods for optimization of crop processor settings, harvest efficiency, and nutritional modeling.

Sewer system design moving into the 21st century--a UK perspective.

Change in external factors, such as environmental legislation and climate change, will mean the future of sewerage systems is likely to be different from the past. Combined sewerage systems comprise the vast majority of existing sewers in countries such as the UK. A study funded by UK Water Industry Research Ltd has reviewed the current state of sewerage within the UK, the likely drivers for change and the consequent future impacts over a 75 year timescale. Potential responses to address the anticipated changes have also been considered. It is concluded that due to the wide extent and value of existing sewer systems, these will continue to be used for the foreseeable future. However, in order to meet the major challenges as a result of changing external factors, these need to be operated more effectively, new ideas need to be explored and moves to develop better and more integrated water management systems need to be started if sewer systems in the UK are to provide the anticipated required levels of service well into the 21st century.

Surviving rat distal tubule bicarbonate reabsorption: effects of chronic AT(1) blockade.

To determine the in vivo effects of chronic ANG II type 1 (AT(1))-receptor blockade by losartan (Los) on enhanced unidirectional bicarbonate reabsorption (J(HCO(3))) of surviving distal tubules, nephrectomized rats drank either water or a solution of Los, 7 days before microperfusion. J(HCO(3)) was suppressed by 50% after Los without further reduction by 5 nM concanamycin A (Conc), suggesting that Los suppresses all Conc-sensitive H(+)-ATPase pumping. Indeed, ultrastructural analysis of A-type intercalated cells revealed a 50% reduction of H(+)-ATPase immunogold labeling of the apical plasma membrane, whereas Western blotting showed that H(+)-ATPase protein levels were also reduced by one-half by Los treatment. To identify other transporters sustaining J(HCO(3)), we perfused three inhibitors simultaneously [5-(N, N-dimethyl) amiloride hydrochloride, Conc, Schering 28080] with or without prior Los treatment: J(HCO(3)) was unchanged despite marked reduction of water reabsorption. We conclude enhanced distal tubule J(HCO(3)) of surviving nephrons is largely mediated by AT(1) receptor-dependent synthesis and insertion of apical H(+)-ATPase pumps in A-type intercalated cells.

K depletion stimulates in vivo HCO3 reabsorption in surviving rat distal tubules.

To evaluate whether K depletion enhances in vivo bicarbonate reabsorption (JtCO2) in surviving distal tubules (DT), we compared DT JtCO2 in five-sixths nephrectomized rats (Nx) with and without dietary K depletion (Nx-K). Furthermore, to identify possible mechanisms of increased JtCO2, we perfused inhibitors of proton secretion in both Nx and Nx-K rats. JtCO2 (102 +/- 8 pmol.min-1.mm-1) was significantly increased in Nx-K vs. Nx rats (65 +/- 7 pmol.min-1.mm-1, P < 0.05) but unaffected by 10(-6) M losartan perfusion (94 +/- 6 pmol.min-1.mm-1, P = not significant). Although 10(-5) M Sch-28080 also had no significant effect, 5 x 10(-9) M concanamycin A perfusion significantly decreased JtCO2 in Nx-K rats to 65 +/- 8 pmol.min-1. mm-1 (P < 0.05). Morphometric evaluation and H(+)-ATPase immunogold labeling of Nx-K A-type intercalated cells revealed cellular hypertrophy, elaborated apical microplicae, and enhanced H(+)-ATPase apical polarization. Accordingly, these combined studies confirm that K depletion enhances JtCO2 in surviving DT by stimulating H(+)-ATPase activity, independent of the AT1 receptor.

ANG II-dependent HCO3- reabsorption in surviving rat distal tubules: expression/activation of H(+)-ATPase.

Distal tubules (DT) from sham or five-sixths nephrectomized (Nx) rats were perfused in vivo to evaluate the hypothesis that, after Nx, endogenous angiotensin II (ANG II) modulates DT in vivo bicarbonate reabsorption (JtCO2) via H(+)-adenosinetriphosphatase (H(+)-ATPase) and Na+/H+ exchange. In Nx rats JtCO2 was increased (65 +/- 7 vs. -24 +/- 21 pmol.min-1.mm-1, P < 0.01). Both luminal and intravenous AT1-receptor blockade by losartan reduced Nx DT JtCO2 (41 +/- 6 and 34 +/- 4 pmol.min-1.min-1, respectively, P < 0.05), whereas neither 10(-9) M nor 10(-11) M ANG II luminal perfusion increased JtCO2, suggesting preexisting high endogenous ANG II levels. The Na+/H+ antiporter inhibitors 5-(N-ethyl-N-isopropyl)-amiloride and 5-(N,N-dimethyl)-amiloride were without effect. Luminal perfusion of 5 nM concanamycin A, a V-type H(+)-ATPase inhibitor, reduced Nx DT JtCO2 (45 +/- 8 pmol.min-1.mm-1, P < 0.05). In Nx A-type intercalated cells, we demonstrated cellular hypertrophy, elaboration of apical microplicae, and enhanced expression/apical polarization of H(+)-ATPase. Thus ANG II is an important determinant in sustaining brisk DT JtCO2 following Nx and is associated with enhanced expression and A-type intercalated cell apical polarization of H(+)-ATPase.

Three clustered origins of replication in a promiscuous-plasmid replicon and their differential use in a PolA+ strain and a delta PolA strain of Escherichia coli K-12.

A 1,197-bp region of the broad-host-range plasmid pCU1 is adequate for its replication. Analysis of replicating molecules containing this region reveals three clustered origins of vegetative replication and replication proceeds bidirectionally from each in a theta mode. In an Escherichia coli polymerase I deletion mutant, utilization of one of these three origins was not detected. The potentiality for origin utilization may therefore be a determinant of replicon host range.

Monoclonal antibodies to Gliocladium roseum, a potential biological control fungus of sap-staining fungi in wood.

Immunological probes were developed to discriminate between a potential biological control fungus and sap-staining fungi present in wood. This paper describes the production of monoclonal antibodies to isolated cell wall fragments of the biological control fungus Gliocladium roseum. Two monoclonals, designated 6A5 and 3F12, were characterized. Their specificity was assessed by ELISA, by immunogold silver staining light microscopy, by immunogold electron microscopy, and by immunoblotting. Monoclonal 6A5 specifically recognized G. roseum and closely related species and did not react with any of 21 sap-staining fungi tested. Monoclonal 3F12 recognized most of the biological control fungi tested and also showed reactivity with two of the 21 sap-staining fungi. Both monoclonals appeared to recognize carbohydrate epitopes of the cell wall in G. roseum. Although the antibodies were produced against the cell wall of fungus grown in liquid culture, they also detected specific fungi in wood and, therefore, can be used for studies of wood colonization by fungi and for investigations of the interactions between different fungi growing on wood.

Interrelationship of mitochondria with cytoplasmic 10 nm filaments in tapetal cells of Hyacinthoides non-scripta (L.) Chouard.

An aggregation of 10 nm filamentous structures in a paracrystalline array associated with stacks of mitochondria in the tapetal cells of Hyacinthoides non-scripta (L.) Chouard is reported. The filaments are around 0.4 micrometer long and form two different types of association with mitochondria. They may be in the form of a single layer between adjacent mitochondria or packed into groups surrounded by mitochondria. The former arrangement is reminiscent of that reported for the intercisternal elements of dictyosomes. Various explanations relating to the function of tapetal cells are discussed.

An ultracytochemical study of nucleolar organization in meristematic plant cells (Allium porrum).

The interphase nucleolus in Allium porrum, as in many of the plant species studied so far, is highly heterogeneous in ultrastructure owing to the presence of coarse, contorted, thread-like structures, or nucleolonemata. Each nucleolonema appears to be sharply twisted and to give rise to a skein within the nucleolar mass. In order to characterize further these nucleolar components, a variety of cytochemical techniques were exploited. For that purpose, specimens were mostly fixed in 4% formaldehyde and stained in the block according to procedures known to reveal the presence of nucleic acids or proteins. Certain specimens were also digested with deoxyribonuclease, ribonuclease or proteinase K before staining. By staining with phosphotungstic acid or bismuth oxynitrate, the presence of a high concentration of proteins can be demonstrated within thin (0.15 micrometer), filamentous structures which are believed to correspond to the outer region of the nucleolonema. Such convoluted formations disappear upon sufficiently long extraction with proteinase K. Using Bernhard's regressive staining technique for chromatin, the distribution of this substance throughout the nucleolar mass was found to match closely that of the nucleolonemata as revealed by several other procedures. As a last test for investigating the cytochemical make-up of the nucleolus, blocks of tissues were stained with 3,3'-diaminobenzidine, a substance known to react specifically with nucleic acids. When such specimens are digested with ribonuclease for 1 h, there persist within the nucleolus, fibrillogranular zones the localization of which is highly reminiscent of that of the nucleolonemata. Combination of ribonuclease hydrolysis with subsequent treatment with proteinase K (30 min) induces the extraction of a large proportion of the nucleolar material, the persisting loose and rather evenly distributed fibrils exhibiting a diamter of 3-5 nm. The possibility is considered that these units may correspond to chromatin fibrils although they have most likely been displaced from their original localization during the extraction procedures. Our cytochemical data suggest that, in Allium porrum, the nucleolonema is approximately 0.3 micrometer in diameter and may consist of a central axis from which chromatin loops project radially. A possible interpretation for the presence of protein-rich, 0.1 micrometer-thick, annular structures throughout the nucleolonemal skein is that the newly synthesized RNP products are accumulated transiently at the extremities of these loops before migrating to the immediately adjacent granular nucleolar zones.

A cytochemical and radioautographic study of the ultrastructural organization of puff-like fibrillar structures in plant interphase nuclei (Allium porrum).

Loose, fibrillar, spherical structures have been observed during recent years in interphase nuclei of both animal and plant cells. These nuclear formations have been referred to as karyosomes, fibrillar bodies, micropuffs and centromeres. In order to gain further information on the nature of these structures, a cytochemical and radioautographic investigation was undertaken using plant meristematic cells (Allium porrum). For that purpose roots were fixed with either formaldehyde or glutaraldehyde in order to carry out cytochemical tests for DNA, RNA and proteins. Certain of the preparations were also first digested with DNase, RNase or proteinase K and then stained according to different procedures. Other specimens were labelled with thymidine for high-resolution radioautographic observations. Staining with diaminobenzidine (DAB) revealed that these nuclear puff-like formations consisted partly of a loose fibrillar meshwork containing nucleic acids. Part of this fine fibrillar reticulum persisted whether the preparations were digested with DNase or RNase before staining with DAB, thus indicating that these nuclear structures contained both DNA and RNA. The fact that these formations incorporate thymidine furnished additional support for the view that they correspond to specific chromosome segments. Staining with ethanolic phosphotungstic acid or digestion of specimens with proteinase K showed that these loose fibrillar structures also consisted of proteins. Judging from their ultrastructure, their association with the chromatin reticulum as well as from their cytochemical characteristics, these nuclear formations most likely correspond to centromeres. In view of the presence of DNA within these structures, it is possible to distinguish them from other equally spherical nuclear formations, observed in certain plant species, that have generally been referred to as karyosomes or micronucleoli and that appear to consist of ribonucleoproteins.

The nucleolus and meiosis during microsporogenesis in Endymion non-scriptus (L.).

Stages of meiosis from the bluebell Endymion non-scriptus (L.) were studied by electron microscopy. The segregated components of the nucleolus at meiotic prophase underwent fragmentation and dissolution at pachytene-diplotene. Nucleoli were absent during both meiotic divisions and reformed on the nucleolus organizer into a fibrillar mass from scattered fibrillar components at the dyad and tetrad stages. Ti is argued that the fibrillar region shows continuity through nuclear division though undergoing structural transformations in the process. Nucleolar reformation occurs on condensed nucleolus organizers. Processing of the ribosomal precursors and the resumption of RNA synthesis is discussed in relation to the dispersal of the nucleolus organizer into the fibrillar region of the reformed nucleolus.

The nucleolus organizer and the synaptonemal complex in Endymion non-scriptus (L.).

Stages of meiosis from the bluebell Endymion non-scriptus (L.) were studied by electron microscopy. The nucleolus went through the process of segregation at the beginning of meiosis with the movement to its surface of a pale-staining region. This region was shown to be the same as that called the 'L zone' or lacunae of nucleoli. Its chromosomal nature was strongly suggested by the presence of the synaptonemal complex within it. This demonstrated that the pale-staining region of nucleoli is the nucleolus organizer and almost certainly the chromosome region containing the ribosomal cistrons, and justifies the use of these terms to describe the structure when seen inside the nucleolus. The relationship between this zone and the heterochromatic knob called the nucleolar organizing body in maize by other workers is discussed.