Factors associated with multiple-pass procedures during chorionic villus sampling: A video analysis

Multiple placental passes during chorionic villus sampling (CVS) increase the risk of fetal loss; however, specific factors that predispose to repeat aspiration have not been delineated. To identify anatomic and technical variables associated with multiple-pass procedures, a detailed review of 205 videotaped CVS procedures (single pass = 163; multiple pass = 42) was performed, blinded to pregnancy outcome. The route of sampling did not influence the need for multiple aspiration attempts (transabdominal—30/ 135; transcervical—12/70), nor was placental location alone discriminatory. However, the combination of a posterior placenta and uterine retroversion was observed more frequently in the multiple-pass cohort (8/42 vs. 9/163; p<0.05). In transabdominal cases, suboptimal needle placement (e.g., perpendicular to the placental long axis) was more common in the initial aspiration of a multiple-pass procedure (21/30 vs. 38/105;p<0.01), while limited penetration of the catheter tip (e.g., just inside the placental edge) characterized a majority of multiple-pass cases in the transcervical subset (7/12 vs. 3/58; p<0.0001). A case-control cohort was constructed to evaluate the impact of these technical variables on sampling efficacy, independent of the influence of uterine position and placental site. In that analysis, suboptimal location and/or orientation of the sampling device remained characteristic of multiple-pass cases. We conclude that further reduction in the frequency of multiple-pass procedures might be achieved by consistent placement of the device tip in the central placental mass. Unlike amniocentesis, where any point of amnion entry will suffice, this technical nuance should be emphasized with CVS to maximize the single-pass success rate.     

Replacement and aging of chloroplasts inStrombidium capitatum (Ciliophora: Oligotrichida)

The planktonic ciliateStrombidium capitatum (Leegaard, 1915) Kahl, 1932 retains functional chloroplasts derived from ingested algal cells. Chloroplast replacement and aging were experimentally investigated in cultured ciliates provided with a cryptophyte (Pyrenomonas salina), a prymnesiophyte (Isochrysis galbana) and a prasinophyte (Pyramimonas sp.) as sources of plastids. All three algae were ingested and chloroplasts from all were retained by the ciliate. Within 15 min of exposure to the cryptophyte, this alga was taken up by the ciliates. Initially, most of the cryptophyte chloroplasts were in intact algal cells in ciliate vacuoles. By 2 h, cryptophyte plastids were commonly found free in the ciliate cytoplasm. WhenS. capitatum was switched from a diet containing cryptophytes to a non-cryptophyte diet, most cryptophyte chloroplasts were diluted out of the ciliates by cell division and/or replaced by non-cryptophyte chloroplasts within 9 h. When the ciliates are not provided with algae, they decrease in size and number. However, the starving ciliate cells contain some chloroplasts for as long as they live (40 h or more). Under these conditions, cryptophyte chloroplasts persist longer than the other chloroplast types. Our observations suggest that chloroplast retention times inS. capitatum depend on the type of chloroplast as well as the availability of phytoplankton containing suitable new chloroplasts, and probably also on the physiological states of the ingested algae and the ciliates. It is interesting that we were not able to grow this ciliate when we provided it only with prey that lacked chloroplasts.Contribution No. 7241 from Woods Hole Oceanographic Institution. This research was supported by NSF grants OCE-8600765 and OCE-8709961 to D.K.S     

Domoic acid in benthic flatfish on the continental shelf of Monterey Bay,California, USA

Within Monterey Bay, California, USA, the food web transfer of domoic acid (DA), a neurotoxin produced by diatoms of the genus Pseudo-nitzschia, has led to major mortality events of marine mammals and birds. Less visible, and less well known, is whether invertebrates and fish associated with the benthos are also affected by blooms of DA-producing Pseudo-nitzschia spp. This study examines the presence of DA in benthic flatfish offshore of Davenport, California, (37°0′36″N, 122°13′12″W) and within Monterey Bay, California (36°45′0″N, 122°1′48″W), including species that feed primarily in the sediment (benthic-feeding) and species that feed primarily in the water column (benthopelagic-feeding). Flatfish caught between 10 December 2002 and 17 November 2003 at depths of 30–180 m had concentrations of DA in the viscera ranging from 3 to 26 μg DA g⁻¹ of viscera. Although the DA values reported are relatively low, benthic-feeding flatfish were frequently contaminated with DA, especially as compared with the frequency of contamination of flatfish species that feed in the water column. Furthermore, on days in which both benthic-feeding and benthopelagic-feeding flatfish were collected, the former had significantly higher concentrations of DA in the viscera. Curlfin turbot, Pleuronicthys decurrens, the flatfish with both the highest level and frequency of DA contamination, are reported to feed exclusively on polychaetes, suggesting that these invertebrates may be an important vector of the toxin in benthic communities and may pose a risk to other benthic-feeding organisms. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Long-term patterns in tropical reforestation: plant community composition and aboveground biomass accumulation.

Primary tropical forests are renowned for their high biodiversity and carbon storage, and considerable research has documented both species and carbon losses with deforestation and agricultural land uses. Economic drivers are now leading to the abandonment of agricultural lands, and the area in secondary forests is increasing. We know little about how long it takes for these ecosystems to achieve the structural and compositional characteristics of primary forests. In this study, we examine changes in plant species composition and aboveground biomass during eight decades of tropical secondary succession in Puerto Rico, and compare these patterns with primary forests. Using a well-replicated chronosequence approach, we sampled primary forests and secondary forests established 10, 20, 30, 60, and 80 years ago on abandoned pastures. Tree species composition in all secondary forests was different from that of primary forests and could be divided into early (10-, 20-, and 30-year) vs. late (60- and 80-year) successional phases. The highest rates of aboveground biomass accumulation occurred in the first 20 years, with rates of C sequestration peaking at 6.7 +/- 0.5 Mg C x ha(-1) x yr(-1). Reforestation of pastures resulted in an accumulation of 125 Mg C/ha in aboveground standing live biomass over 80 years. The 80 year-old secondary forests had greater biomass than the primary forests, due to the replacement of woody species by palms in the primary forests. Our results show that these new ecosystems have different species composition, but similar species richness, and significant potential for carbon sequestration, compared to remnant primary forests.     

Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests

Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of mechanistic links between microbial responses to N deposition and shifts in soil organic matter (SOM) quality and quantity. We used phospholipid fatty acid (PLFA) analysis and microbial enzyme assays in soils to assess microbial community responses to long-term N additions in two distinct tropical rain forests. We used soil density fractionation and 13C nuclear magnetic resonance (NMR) spectroscopy to measure related changes in SOM pool sizes and chemical quality. Microbial biomass increased in response to N fertilization in both tropical forests and corresponded to declines in pools of low-density SOM. The chemical quality of this soil C pool reflected ecosystem-specific changes in microbial community composition. In the lower-elevation forest, there was an increase in gram-negative bacteria PLFA biomass, and there were significant losses of labile C chemical groups (O-alkyls). In contrast, the upper-elevation tropical forest had an increase in fungal PLFAs with N additions and declines in C groups associated with increased soil C storage (alkyls). The dynamics of microbial enzymatic activities with N addition provided a functional link between changes in microbial community structure and SOM chemistry. Ecosystem-specific changes in microbial community composition are likely to have far-reaching effects on soil carbon storage and cycling. This study indicates that microbial communities in N-rich tropical forests can be sensitive to added N, but we can expect significant variability in how ecosystem structure and function respond to N deposition among tropical forest types.     

Origins and microenvironments of bacteria mediating fecal pellet decomposition in the sea

The fecal pellets of zooplankton are thought to be major carriers of organic matter from surface to deeper waters of the oceans. As the pellets descend, they release soluble components, partially due to breakdown by associated microorganisms. Previous laboratory work of other investigators has suggested that the surface of a fecal pellet rapidly acquires bacteria, which increase in abundance until they and their protozoan consumers disrupt the pellet membrane, spilling contents into the water. In contrast, our field collections of fecal pellets from free-floating particle interceptor traps (from the Vertex project off Central California in 1980 and off Mexico in 1981), suggest that microbial decomposition probably is initiated in the sea from inside the fecal pellets. Transmission and scanning electron microscopy indicate that bacterial populations are most abundant in the interior of fecal pellets obtained from the sea, but that the same pellets will acquire the surface bacterial lawn typically observed in laboratory studies if maintained aboard ship. If the fecal pellets are decomposed from the inside, then the principal agents are enteric bacteria or ingested, digestion-resistant bacteria, or both. Such bacteria may differ metabolically from those that colonize the fecal pellet surfaces. Further-more, the abundance of healthy-appearing bacteria inside the pellets suggests that their metabolic activities may produce microhabitats of reduced oxygen tension that could differ considerably from that of the pellet exteriors. Decomposition in these semi-enclosed microenvironments may proceed in a manner not yet predicted by models that attribute decomposition to well-aerated, surface-dwelling bacterial populations on fecal pellets in the sea.     

Differential feeding and fecal pellet composition of salps and pteropods,and the possible origin of the deep-water flora and olive-green “Cells”

Salps (mainly Salpa fusiformis and, to a lesser extent, Pegea socia) and a web-building pteropod (Corolla spectabilis) were studied in epipelagic waters of the central California Current. Although both kinds of gelatinous zooplankton trap phytoplankton in a mucus net, a fecal pellet analysis indicated that their diet differs significantly when they feed together, probably because of differences both in the pore sizes of their nets and in their feeding methods. Salps have a finemesh filter, on which they can retain even the smallest phytoplankton; thus, when small coccolithophores are abundant, as they were in our study, salp feces contain such cells and the coccoliths derived from them. In contrast, pteropods feeding in the same area produce fecal pellets consisting chiefly of larger phytoplankton, especially diatoms. Since fecal pellets transport most biogenic material to the deep sea, changes in herbivore species composition at a given geographic location can change the chemistry of materials entering deep water; at our study site, the more salps, the greater the calcite flux, and, the more pteropods, the greater the silica flux. In addition, fecal pellets of both salps and pteropods include partially digested residues of phytoplankton that appear as olive-green spheres, having an ultrastructure identical with that of the socalled olive-green cells. Presumably, fecal pellets, after sinking into deep water, ultimately disintegrate. releasing both the viable phytoplankton and the olive-green spheres into aphotic waters. Thus the feces of epipelagic herbivores are likely sources of much of the flora of the deep ocean.     

Tissue distribution and neurotoxic effects of domoic acid in a prominent vector species, the northern anchovy Engraulis mordax

The planktivorous northern anchovy is a prominent vector of the phycotoxin domoic acid (DA) to organisms at higher trophic levels, including fish-eating seabirds and mammals. Although there are abundant data reporting DA-induced excitotoxic symptoms in higher vertebrates, to date there has been no reported evidence of neurotoxic effects in lower vertebrate vectors such as fish. To explain this apparent lack of toxicity, it has been suggested that DA may not reach the brain in anchovies and/or that fish are not as sensitive neurologically to DA. In the present study, intracoelomic (IC) injection of DA, at doses ranging from 1 to 14 μg DA g⁻¹ total fish weight, resulted in severe neurotoxic symptoms such as spinning, disorientation, inability to school, and mortality, indicating that anchovies are neurologically susceptible and that DA crosses the blood–brain barrier in fish. An ED₅₀ of 3.2 μg DA g⁻¹ total body weight was determined via IC injection of DA in 83 anchovies. Comparable intraperitoneal injection studies with mice, rats, and monkeys report similar DA-induced neurotoxic symptoms at doses near 3.2 μg DA g⁻¹, suggesting a similar neurologic sensitivity and mechanism of toxicity between anchovies and mammals. DA tissue distribution measurements from freshly collected field-exposed anchovies and orally gavaged anchovies indicate that DA uptake from the gastrointestinal tract does occur. Levels as high as 1,175 μg DA g⁻¹ were measured in anchovy viscera, while muscle and brain tissue DA levels were 3 orders of magnitude lower, indicating low but measurable DA uptake. Further evidence is needed to confirm that uptake is sufficient during field events to induce symptoms in anchovies. Our work provides the first reported evidence of neurotoxic symptoms in fish and suggests that anchovies may be affected by DA during toxic diatom blooms. If sufficient uptake occurs, DA-induced neurotoxic symptoms and mortality may make fish easier prey targets, thereby selecting for the highest toxin levels transferred, as well as providing a possible pathway for the transfer of DA to benthic communities. Received: 19 May 2000 / Accepted: 29 November 2000     

A comparison of taxon co-occurrence patterns for macro- and microorganisms

We examine co-occurrence patterns of microorganisms to evaluate community assembly "rules". We use methods previously applied to macroorganisms, both to evaluate their applicability to microorganisms and to allow comparison of co-occurrence patterns observed in microorganisms to those found in macroorganisms. We use a null model analysis of 124 incidence matrices from microbial communities, including bacteria, archaea, fungi, and algae, and we compare these results to previously published findings from a meta-analysis of almost 100 macroorganism data sets. We show that assemblages of microorganisms demonstrate nonrandom patterns of co-occurrence that are broadly similar to those found in assemblages of macroorganisms. These results suggest that some taxon co-occurrence patterns may be general characteristics of communities of organisms from all domains of life. We also find that co-occurrence in microbial communities does not vary among taxonomic groups or habitat types. However, we find that the degree of co-occurrence does vary among studies that use different methods to survey microbial communities. Finally, we discuss the potential effects of the undersampling of microbial communities on our results, as well as processes that may contribute to nonrandom patterns of co-occurrence in both macrobial and microbial communities such as competition, habitat filtering, historical effects, and neutral processes.