Preliminary data on rotifers in the interstitial of the Ninnescah river, Kansas, USA

One-hundred five rotifer species were identified from a sandy, plains river in Kansas, USA (the Ninnescah river). Of those rotifers identified, eighty occurred only in the interstitial sand, fifty-six in only the flow as plankton, and thirty-one from both habitats. Most species can be characterized as being more commonly found in littoral habitats, and not the interstitial or plankton. Lecane inermis (Bryce, 1892) had the highest density in the hygropsammon interstitial with an average 401 ind. 10 cm⁻³ at 1–3 cm depth in September 1993. New records for the US include Encentrum wiszniewski Wulfert (1939), E. longidens Donner (1943) ant E. (Parencentrum) longipes Wulfert (1960). A small form of Lecane levistyla Olofsson (1917) is further examined and discussed.     

Expressed Peromyscus maniculatus (Pema) MHC class I genes: evolutionary implications and the identification of a gene encoding a Qa1-like antigen

To gain insight into the evolution of rodent major histocompatibility complex (MHC) class I genes and identify important (conserved) nonclassical class I (class Ib) gene products and residues in these proteins, sixPeromyscus maniculatus MHC (Pema) class I cDNA clones were isolated and sequenced. FivePema class I cDNAs appeared most similar to mouse and rat classical class I (class Ia) genes. One exhibited highest similarity to anH2 class Ib gene,H2-T23 (encoding the Qa1 antigen). Phylogenetic trees constructed withPema, RT1, andH2 class I sequences suggested that the lineages of some rodent class Ib genes (e.g.,T23 andT24) originated prior toMus andPeromyscus speciation [>50 million years (My) ago]. Sequences of four Qa1-like proteins from three species permitted the identification of ten Qa1-specific amino acids. On the basis of molecular modeling, three residues showed the potential to interact with T-cell receptors and three residues (all corresponding to polymorphic positions among H2 class Ia proteins) were predicted to influence antigen binding. The recognition of mouse Qa1 proteins by a subset of T-cells in influenced by a locus,Qdm, which encodes the H2-D leader peptide. One of thePema class I cDNA clones classified asH2-K, D/L-like (class Ia) is predicted to encode an identical peptide, implying that an antigen binding protein (Qa1) and the antigen to which it binds (the product ofQdm) has been conserved for over 50 My. The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers U12822 (Pm13), U12885 (Pm41), U12886 (Pm52), U12887 (Pm62), U16846 (Pm11), and U16847 (Pm53)     

Characterization of In Vivo Reporter Systems for Gene Expression and Biosensor Applications Based on luxAB Luciferase Genes

Advances in genetic engineering methods have allowed the development of an increasing number of practical and scientific applications for bioluminescence with lux genes cloned from a variety of organisms. Bioluminescence derived from the shortened lux operon (luxAB genes) is a complex process, and applications seem to be proliferating in advance of an understanding of the underlying biochemical processes. In this report, we describe a two-phase kinetic behavior of the light emission which must be properly taken into account in any quantitative measurements of the bioluminescence signal. By using strains of Escherichia coli and Caulobacter crescentus, this behavior was characterized and interpreted in terms of the biochemistry underlying the bacterial luciferase mechanism. We show that the intensity profile of each of the two phases of the luminescence signal is responsive (and exhibits different sensitivities) to the concentration of added decanal and other components of the assay mix, as well as to the order of mixing and incubation times. This study illustrates the importance of appropriate protocol design, and specific recommendations for using the luxAB system as a molecular reporter are presented, along with versatile assay protocols that yield meaningful and reproducible signals.     

Evaluation of Wetland Gain and Loss of Abandoned Agricultural Impoundments in South Louisiana, 1978–1988

At least 43 agriculture fields were built in south Louisiana wetlands between 1900 and 1920 using pumps and levees. All but one project is now abandoned as a result of soil subsidence, financial difficulties, or multiple levee failures. Some are now in flood-protected urban zones, and the remainder are mostly open water. The total area of abandoned agricultural fields in 1990 is large (> 80,000 ha), and their levees continue to deteriorate naturally. Ten failed or abandoned coastal agricultural impoundments (22,680 ha) were examined to determine recent wetland restoration or regression rates from 1978 to 1988. Wetland area and levee length were determined from aerial photography for 1978,1983,1985, and 1988. Average wetland change rates for all areas ranged from ?4.28 to +2.54% per year from 1978 to 1988. One site gained wetland area between 1978 and 1988 (77 ha/yr), and four sites gained wetland area between 1985 and 1988 (range 14–439 ha/yr). Wetland area in the other sites either remained stable or declined during the study period. The results from a multiple regression model indicate that restoration is inversely related to impoundment size and directly related to levee reduction. Results from a multiple regression model indicate that active levee removal will probably enhance wetland restoration rates at a very favorable cost (< $1/ha) and will be sustainable with little additional management.     

Dry Matter Assimilation and Partitioning in Pepper Cultivars Differing in Susceptibility to Stress-induced Bud and Flower Abscission

Stress-induced abscission of buds and flowers is a constraintto the production of peppers (Capsicum annuum L.). Susceptibilityof pepper cultivars to stress-induced abscission may be relatedto assimilate levels and partitioning. Growth analysis experimentswere conducted in the field to determine whether cultivars differingin susceptibility to stress-induced abscission showed correspondingdifferences in growth rates and dry matter partitioning whensubjected to low light stress. With the stress susceptible cultivar'Shamrock', reduction in net assimilation rate (NAR) and relativegrowth rate (RGR) was greater under low light stress than withthe more tolerant cultivar 'Ace'. Compared to 'Ace', 'Shamrock'partitioned a smaller proportion of dry matter into reproductiveorgans and a larger proportion into expanded leaves. Cultivarsdid not differ in the amount of dry matter partitioned to youngleaves or in the extent to which accumulation of dry matterby young leaves was reduced by low light stress. Other experimentsconducted in growth chambers and greenhouse examined the effectof removal of leaves less than 3 cm long on high temperatureand low light stress-induced bud and flower abscission. Forboth 'Ace' and 'Shamrock', abscission was not altered by removalof these leaves. Preferential partitioning of assimilate toyoung leaves does not appear to be involved in stress-inducedabscission in these pepper cultivars.Copyright 1994, 1999 AcademicPress Pepper (Capsicum annuum L.), abscission, low light stress, high temperature stress, assimilate partitioning, assimilation/growth rate, growth analysis, defoliation     

Microatoll microbialites of Lake Clifton,Western Australia: Morphological analogues ofCryptozoön proliferum Hall,the first formally-named stromatolite

Summary The Linnaean nameCryptozo?n proliferum Hall was proposed in 1883 for a previously undescribed life-form preserved in spectacular exposures of Cambrian limestones in New York State, USA. It is now recognised that these are exposures of stromatolitic microbialites, laminated organosedimentary structures formed from interaction between a benthic microbial community (BMC) and the environment. Microbialites are neither fossil organisms nor trace fossils. These complex structures are the products of dissipative, self-organising systems involving a BMC, the external environment and the accreting microbialite. Functionally analogous BMCs of different species compositions may build similar structures in similar environments in quite separate periods. The type exposures ofCryptozo?n proliferum show objects composed of complex, concentric rings, up to a metre in diameter, that have grown laterally without any restriction other than that provided by neighbouring structures. They are not the relicts of domes truncated by penecontemporaneous erosion or Pleistocene glaciation, but depositional forms in which upward growth was restricted. Analogous modern structures occur on a reef platform along the north east shore of hyposaline Lake Clifton, Western Australia. These are tabular thrombolitic microbialites that vary lakeward across the reef platform from low, compound structures to discrete, concentric structures up to 50 cm high. The Lake Clifton forms are, in turn, morphological analogues of microatolls found on coral reef platforms. Coral microatolls are coral colonies with flat, dead tops and living perimeters in which upward growth is constrained by the sea surface. In shallow water they form circular rims of laterally growing coral around a dead centre. In deeper water they form coral heads that develop flat tops on reaching sea level. It is concluded that both the tabular microbialites of Lake Clifton and the type exposures ofCryptozo?n proliferum are analogous to coral microatolls in both form and origin-structures that have been able to grow laterally, but in which upward growth is restricted by subaerial exposure. Similar microatoll microbialites have been described from other modern environments, including Great Salt Lake, Utah, USA and Stocking Island, Exuma Cays, Bahamas. Ancient examples may include some of the “tufa” deposits of the Basal Purbeck Formation in Dorset, UK, as well as the coalesced domal bioherms of the Upper Cambrian Arrinthrunga Formation of the Georgina Basin, Central Australia, and the “washbowl” structures described from the B?tsfjord Formation of the Varanger Peninsula, north Norway. Progress towards a reliable interpretation of ancient microbialites depends on an understanding of modern environments in which analogous structures are forming. This study of microatolls has demonstrated that other sessile life forms may create colonial ecomorphs that, used cautiously, can serve as analogues for understanding the factors controlling the growth and form of microbialites. The surprising lack of pre-Pleistocene examples of microatolls recorded to date has simply been due to their lack of recognition in the geological record. They occur in sequences from the Proterozoic onwards, and provide powerful environmental indicators of ancient reef platforms on which biological growth was adjusted to contemporary sea level.     

Age-Dependent Impairment of Mitochondrial Function in Primate Brain

Abstract: It has been hypothesized that some of the functional impairments associated with aging are the result of increasing oxidative damage to mitochondrial DNA that produces defects in oxidative phosphorylation. To test this hypothesis, we examined the enzymes that catalyze oxidative phosphorylation in crude mitochondrial preparations from frontoparietal cortex of 20 rhesus monkeys (5-34 years old). Samples were assayed for complex I, complex II-III, complex IV, complex V, and citrate synthase activities. When enzyme activities were corrected for citrate synthase activities (to account for variable degrees of mitochondrial enrichment), linear regression analysis demonstrated a significant negative correlation of the activities of complex I (p < 0.002) and complex IV (p < 0.03) with age but no significant change in complex II-III or complex V activities. Relative to animals 6.9 ± 0.9 years old (n = 7), the citrate synthase-corrected activity of complex I was reduced by 17% in animals 22.5 ± 0.9 years old (n = 6) (p < 0.05) and by 22% in animals 30.7 ± 0.9 years old (n = 7) (p < 0.01). Similar age-related reductions in the activities of complexes I and IV were obtained when enzyme activities were corrected for complex II-III activity. These findings show an age-associated progressive impairment of mitochondrial complex I and complex IV activities in cerebral cortices of primates.