Development and testing of a filter system for isolation of Giardia lamblia cysts from water.

An inexpensive, practical, and reliable method for isolation of Giardia lamblia cysts from potable and environmental water has been developed from commercially available components. This system was successfully used to isolate cysts from well water associated with a family outbreak of giardiasis.     

Social organization and reproductive behavior of ostraciid fishes from Japan and the Western Atlantic Ocean

Social organization and reproductive behavior were studied in 4 species of ostraciid fishes.Lactoria fornasini andLactoria diaphana from Japan andAcanthostracion polygonius from the western Atlsnyiv were usually found in single male, haremic social groups, although the latter 2 species usually included only 2 females per harem, and individuals in all 3 species foraged solitarily. Elements of both “resource defense” and “female defense” (Emlen & Oring 1977) were evident in the 2Lactoria species, and female defense appeared particularly intense inL. diaphana. Resource defense was apparent inA. polygonius. Lactophrys triquetor occurred in lek-like breeding assemblages at Curacao (Netherlands Antilles) and on the Atlantic coast of Panama. These variations in social organization are discussed and a relationship with feeding habits is suggested. All 4 species appear to be gonochores (demonstrated inLactoria by Moyer 1979). The 2Lactoria spp. showed operational sex ratios (OSR: Emlen & Oring 1977) approaching 1∶1 and a high degree of female spawning synchrony. The occurrence of polygyny in species with 1∶1 OSRs and female spawning synchrony is discussed with reference to the Knowlton (1979) model which predicts monogamy to occur in such situations.     

An orthopoxvirus serpinlike gene controls the ability of infected cells to fuse.

Most orthopoxviruses encode a functional hemagglutinin (HA), which is nonessential for virus growth in cell culture. However, inactivation of the HA gene leads to the formation of polykaryocytes (syncytia) by fusion of infected cells at neutral pH. Fusion is not observed when a functional HA gene is present. Deletion of open reading frames (ORFs) K2, K3, and K4 within the HindIII K fragment of the HA-positive (HA+) vaccinia virus strain WR also led to fusion of cells upon infection at neutral pH. A novel ORF inactivation procedure utilizing the polymerase chain reaction was used to specifically implicate the K2 ORF in this phenomenon. The K2 ORF (the viral SPI-3 gene) encodes a protein resembling serine protease inhibitors (serpins). Inactivation of the SPI-3 gene in any of the HA+ orthopoxviruses tested caused infected cells to fuse in a manner which appeared identical to that seen for HA- mutants, although fusion was most pronounced with cowpox virus. SPI-3-negative strains fused despite the fact that the HA was expressed and processed normally, i.e., cells infected with SPI-3 mutants remained functionally hemadsorption positive, and analysis of the HA protein by Western immunoblot suggested that posttranslational modifications of the HA protein appeared normal. Fusion triggered by SPI-3 mutants, like that for HA- mutants, was inhibited by the monoclonal antibody C3 directed against the vaccinia virus 14-kDa envelope protein. Therefore SPI-3- and HA-mediated fusion share a requirement for the 14-kDa protein, suggesting linkage of the seemingly disparate SPI-3 and HA genes through a common pathway which normally acts to prevent fusion of cells infected with wild-type virus.     

Sulfate reduction and S-oxidation in a moorland pool sediment

In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO₄ ^2– reduction rates in the sediment, (2) depletion of SO₄ ^2– in the overlying water column and (3) release of³⁵S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO₄ ^2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core³⁵SO₄ ^2– injection. Rates of SO₄ ^2– consumption in the overlying water were estimated by changes in SO₄ ^2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m^–2 d^–1. Rates of SO₄ ^2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m^–2 d^–1 (November) to 0.43–1.81 mmol m^–2 d^–1 (July, August and April). Maximum rates of oxidation to SO₄ ^2– in July 1990 estimated by combination of SO₄ ^2– reduction rates and rates of in situ SO₄ ^2– uptake in the enclosed water column were 10.3 and 10.5 mmol m^–2 d^–1 at an organic rich and at a sandy site respectively.Experiments with³⁵S^2– and³⁵SO₄ ^2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO₄ ^2– and (2) the presence of mainly non SO₄ ^2–-S derived from reduced S transported from the sediment into the overlying water. A³⁵S^2– tracer experiment showed that about 7% of³⁵S^2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author     

Complexes of Sendai virus NP-P and P-L proteins are required for defective interfering particle genome replication in vitro.

We present evidence that the formation of NP-P and P-L protein complexes is essential for replication of the genome of Sendai defective interfering (DI-H) virus in vitro, using extracts of cells expressing these viral proteins from plasmids. Optimal replication of DI-H nucleocapsid RNA required extracts of cells transfected with critical amounts and ratios of each of the plasmids and was three- to fivefold better than replication with a control extract prepared from a natural virus infection. Extracts in which NP and P proteins were coexpressed supported replication of the genome of purified DI-H virus which contained endogenous polymerase proteins, but extracts in which NP and P were expressed separately and then mixed were inactive. Similarly, the P and L proteins must be coexpressed for biological activity. The replication data thus suggest that two protein complexes, NP-P and P-L, are required for nucleocapsid RNA replication and that these complexes must form during or soon after synthesis of the proteins. Biochemical evidence in support of the formation of each complex includes coimmunoprecipitation of both proteins of each complex with an antibody specific for one component and cosedimentation of the subunits of each complex. We propose that the P-L complex serves as the RNA polymerase and NP-P is required for encapsidation of newly synthesized RNA.     

Structural changes in the murine yolk sac during gestation: cytochemical and electron microscope observations

Specimens of murine yolk sac prepared for light and electron microscopy at 8, 12, and 18 days of gestational age revealed a changing morphology of the endodermal cells in the visceral layer as gestation progressed. Basophilia increased between 8 and 12 days and decreased slightly between 12 and 18 days. These changes corresponded to the development of a highly organized rough-surfaced endoplasmic reticulum by 12 days and its partial replacement by smooth-surfaced elements by 18 days. Staining of frozen sections with tetrazolium dyes revealed a substrate dependent localization of the staining reaction within the cells and suggested an underlying compartmentalization of metabolic activities. Two types of apical granules were observed on the basis of both cytochemistry and electron microscopy. These granules were most numerous at 12 days of gestational age. The observations suggest that although synthesis and absorption doubtless occur simultaneously throughout gestation, the emphasis is on synthesis during the first half of the period and absorption during the second half. It is suggested that the change in fine structure may be due to the rupture of Reichert's membrane and the subsequent establishment of direct contact between the endodermal cells and the uterine wall.     

The Active and the Inactive Form of the hAT1 Receptor Have an Identical Ligand-Binding Environment: An MPA Study on a Constitutively Active Angiotensin II Receptor Mutant

Several models of activation mechanisms were proposed for G protein-coupled receptors (GPCRs), yet no direct methods exist for their elucidation. The availability of constitutively active mutants has given an opportunity to study active receptor conformations within acceptable limits using models such as the angiotensin II type 1 (AT₁)¹ receptor mutant N111G-hAT₁ which displays an important constitutive activity. Recently, by using methionine proximity assay, we showed for the hAT₁ receptor that TMD III, VI, and VII form the ligand-binding pocket of the C-terminal amino acid of an antagonistic AngII analogue. In the present contribution, we investigated whether the same residues would also constitute the ligand-binding contacts in constitutively activated mutant (CAM) receptors. For this purpose, the same Met mutagenesis strategy was carried out on the N111G double mutants. Analysis of 43 receptors mutants in the N111G-hAT₁ series, photolabeled and CNBr digested, showed that there were only subtle structural changes between the wt-receptor and its constitutively active form.     

Why Are Babies Dying in the First Month after Birth? A 7-Year Study of Neonatal Mortality in Northern Ghana

Objectives

To determine the neonatal mortality rate in the Kassena-Nankana District (KND) of northern Ghana, and to identify the leading causes and timing of neonatal deaths.

Methods

The KND falls within the Navrongo Health Research Centre’s Health and Demographic Surveillance System (HDSS), which uses trained field workers to gather and update health and demographic information from community members every four months. We utilized HDSS data from 2003–2009 to examine patterns of neonatal mortality.

Results

A total of 17,751 live births between January 2003 and December 2009 were recorded, including 424 neonatal deaths 64.8%(275) of neonatal deaths occurred in the first week of life. The overall neonatal mortality rate was 24 per 1000 live births (95%CI 22 to 26) and early neonatal mortality rate was 16 per 1000 live births (95% CI 14 to 17). Neonatal mortality rates decreased over the period from 26 per 1000 live births in 2003 to 19 per 1000 live births in 2009. In all, 32%(137) of the neonatal deaths were from infections, 21%(88) from birth injury and asphyxia and 18%(76) from prematurity, making these three the leading causes of neonatal deaths in the area. Birth injury and asphyxia (31%) and prematurity (26%) were the leading causes of early neonatal deaths, while infection accounted for 59% of late neonatal deaths. Nearly 46% of all neonatal deaths occurred during the first three postnatal days. In multivariate analysis, multiple births, gestational age <32 weeks and first pregnancies conferred the highest odds of neonatal deaths.

Conclusions

Neonatal mortality rates are declining in rural northern Ghana, with majority of deaths occurring within the first week of life. This has major policy, programmatic and research implications. Further research is needed to better understand the social, cultural, and logistical factors that drive high mortality in the early days following delivery.