The current molecular phylogeny of Eutherian mammals challenges previous interpretations of placental evolution.

Based on histology, the placentae of eutherians are currently grouped in epitheliochorial, endotheliochorial and haemochorial placentae. In a haeckelian sense, the epitheliochorial contact with marked histiotrophic feeding by uterine milk is generally considered as primitive, especially since similar contacts exist in Marsupials. In contrast, the more intimate endotheliochorial and haemochorial contact, facilitating haemotrophic nutrition, is interpreted as a derived state. A cladistic analysis based on the phylogenetic relationships established by molecular analyses reveals that the basic clades are all characterized by an endotheliochorial or haemochorial placenta, and that the epitheliochorial placenta evolved at least three times in a convergent manner. This evolution may be explained by the fact that the epitheliochorial placenta in eutherians is more efficient in nutritional transfer (flow rate by exchange surface). Moreover, this arrangement may confer an advantage to the mother who can probably reduce the degree of manipulation by a genetically imprinted embryo.

Sonication of catheter tips for improved detection of microorganisms on external ventricular drains and ventriculo-peritoneal shunts.

The diagnosis of infections involving internal or external neurosurgical drainage devices is challenging, and to our knowledge no single reliable microbiological test exists. We used sonication to study bacterial colonization in 14 explanted external ventricular drains (EVD) and 13 ventriculo-peritoneal shunt (VPS) devices. This technique dislodges biofilm bacteria from the surface of implanted materials before culture. Removed devices were sonicated in saline (40 kHz, 1 minute, 0.25 W/cm(2)), the resulting fluid was cultured aerobically and anaerobically at 37°C, and bacterial growth was counted. Ventricular cerebrospinal fluid (CSF) was cultured separately. In the EVD group, sonication cultures grew significantly more bacteria (64%, 9/14) than cultures of aspirated ventricular CSF (14%, 2/14). In the VPS group the difference was not significant. Positive sonication cultures of EVD catheters yielded a median of >100 colony forming units (CFU) (range, 60-800). For positive sonication cultures of VPS, the median was 1000 CFU (range, 20-100,000). All patients with bacteria in their CSF also had positive sonication cultures from the removed device. Of the five patients with sterile or presumably contaminated CSF cultures but positive sonication cultures of removed shunts, one became afebrile after removal of the EVD, two developed meningitis and two remained asymptomatic. Sonication culture of EVD appears to improve the microbiological assessment of device-related infection and it corroborates with CSF cultures of revision surgery for VPS. Sonication of the removed EVD tip may raise awareness for the onset of meningitis.

Characterization of a surface metalloprotease from Herpetomonas samuelpessoai and comparison with Leishmania major promastigote surface protease.

The monogenetic kinetoplastid protozoan parasite Herpetomonas samuelpessoai expresses a surface-exposed metalloprotease. Comparable to the Leishmania promastigote surface protease, or PSP, the protease of Herpetomonas is active at the surface of fixed and live organisms, and both enzymes display an identical cleavage specificity toward a nonapeptide substrate. The protease was enriched 440 times by partition into Triton X-114 followed by 2 steps of anion exchange chromatography. The 56-kDa enzyme is inhibited by the metal chelator 1,10-phenanthroline and is susceptible to cleavage by glycosyl-phosphatidylinositol phospholipase C (GPI-PLC). The conservation of an identical surface protease activity in these monogenetic and digenetic trypanosomatids suggests that the enzyme has a physiological function in the promastigote (insect) stage of these parasites.

Determination of radionuclide levels in rainwater using ion exchange resin and gamma-spectrometry.

The evaluation of radioactivity accidentally released into the atmosphere involves determining the radioactivity levels of rainwater samples. Rainwater scavenges atmospheric airborne radioactivity in such a way that surface contamination can be deduced from rainfall rate and rainwater radioactivity content. For this purpose, rainwater is usually collected in large surface collectors and then measured by gamma-spectrometry after such treatments as evaporation or iron hydroxide precipitation. We found that collectors can be adapted to accept large surface (diameter 47mm) cartridges containing a strongly acidic resin (Dowex AG 88) which is able to quantitatively extract radioactivity from rainwater, even during heavy rainfall. The resin can then be measured by gamma-spectrometry. The detection limit is 0.1Bq per sample of resin (80g) for (137)Cs. Natural (7)Be and (210)Pb can also be measured and the activity ratio of both radionuclides is comparable with those obtained through iron hydroxide precipitation and air filter measurements. Occasionally (22)Na has also been measured above the detection limit. A comparison between the evaporation method and the resin method demonstrated that 2/3 of (7)Be can be lost during the evaporation process. The resin method is simple and highly efficient at extracting radioactivity. Because of these great advantages, we anticipate it could replace former rainwater determination methods. Moreover, it does not necessitate the transportation of large rainwater volumes to the laboratory.

Induction of CTL in vivo by major histocompatibility complex class I-peptide complexes covalently associated on the cell surface.

The identification of endogenously produced antigenic peptides presented by MHC class I molecules has opened the way to peptide-based strategies for CTL induction in vivo. Here we demonstrate that the induction in vivo of CTL directed against naturally processed antigens can be triggered by injection of syngeneic cells expressing covalent major histocompatibility complex class I-peptide complexes. In the model system used, the induction of HLA-Cw3 specific cytotoxic T lymphocytes (CTL) in mice by cell surface-associated, covalent H-2Kd (Kd)-Cw3 peptide complexes was investigated. The Kd-restricted Cw3 peptide 170-179 (RYLKNGKETL), which mimics the major natural epitope recognized by Cw3-specific CTL in H-2d mice, was converted to a photoreactive derivative by replacing Arg-170 with N-beta-(4-azidosalicyloyl)-L-2,3-diaminopropionic acid. This peptide derivative was equivalent to the parental Cw3 peptide in terms of binding to Kd molecules and recognition by Cw3-specific CTL clones and could be cross-linked efficiently and selectively to Kd molecules on the surface of Con A-stimulated spleen cells from H-2d mice. Photocross-linking prevented the rapid dissociation of Kd-peptide derivative complexes that takes place under physiological conditions. Cultures of spleen cells or peritoneal exudate cells from mice inoculated i.p. with peptide-pulsed and photocross-linked cells developed a strong CTL response following antigenic stimulation in vitro. The cultured cells efficiently lysed not only target cells sensitized with the Cw3 170-179 peptide but also target cells transfected with the Cw3 gene. Moreover, their TCR preferentially expressed V beta 10 and J alpha pHDS58 segments as well as conserved junctional sequences, as has been observed previously in Cw3-specific CTL responses. In contrast, no Cw3-specific CTL response could be obtained in cultures derived from mice injected with Con A-stimulated spleen cells pulsed with the peptide derivative without photocross-linking.