The enigmatic invasive Spartina densiflora: a history of hybridizations in a polyploidy context.

The aim of this study was to explore the origin of the invasive Spartina densiflora by analysing samples from the native region (South America) and from a recently colonized area (California). A combination of various molecular data (chloroplast and nuclear sequences, molecular fingerprint) and ploidy level estimations was used to answer the question whether the reticulate phylogenetic pattern previously detected in S. densiflora was restricted to California, or alternatively, whether a more ancient hybrid origin preceded formation of this species in its native area. We found that this species is heptaploid in both its native and introduced range. Identification of nuclear homeologous sequences indicate that this species has a reticulate origin in its native range, involving a lineage related to the hexaploid clade formed by S. alterniflora, S.foliosa, and S. maritima, and another lineage related to the sub-Antarctic endemic S. arundinacea that provided the chloroplast genome. The samples from California displayed similar multilocus patterns to the samples from Chile, supporting the hypothesis that this species originated on the southeast American coast (Argentina), from where it eventually spread to the west coast of South America (Chile) first and to the Northern Hemisphere (California) later.

Evolutionary dynamics of Waxy and the origin of hexaploid Spartina species (Poaceae).

We investigated the evolutionary dynamics of duplicated copies of the granule-bound starch synthase I gene (GBSSI or Waxy) within polyploid Spartina species. Molecular cloning, sequencing, and phylogenetic analyses revealed incongruences between the expected species phylogeny and the inferred gene trees. Some genes within species were more divergent than expected from ploidy level alone, suggesting the existence of paralogous sets of Waxy loci in Spartina. Phylogenetic analyses indicate that this paralogy originated from a duplication that occurred prior to the divergence of Spartina from other Chloridoideae. Gene tree topologies revealed three divergent homoeologous sequences in the hexaploid S. alterniflora that are consistent with the proposal of an allopolyploid origin of the hexaploid clade. Waxy sequences differ in insertion-deletion events in introns, which may be used to diagnose gene copies. Both paralogous and homoeologous coding regions appear to evolving under selective constraints.

Cerebro-splanchnic oxygenation ratio (CSOR) using near infrared spectroscopy may be able to predict splanchnic ischaemia in neonates.

OBJECTIVE: To investigate whether near infrared spectroscopy (NIRS) can detect differences in oxyhaemoglobin signal when applied to the abdomens of neonates with surgically proven splanchnic ischaemia. DESIGN: Prospective, observational cohort study. SETTING: Tertiary neonatal referral centre. PATIENTS: Medical and surgical neonates were studied. Two groups were identified, neonates with acute abdomens referred for surgery and those with normal abdomens admitted for medical reasons. INTERVENTIONS: Tissue oxygenation indexes (TOI) of cerebral and splanchnic regions were measured using near infrared spectroscopy (NIRS) and their relative values expressed as a cerebro-splanchnic oxygenation ratio (CSOR). Measurements were made on admission or immediately prior to surgery and subsequently repeated on a daily basis, whenever possible, until discharge from our unit. The area under the receiver operating characteristic (ROC) curve was evaluated and optimum diagnostic cut-off values determined. RESULTS: Forty neonates were studied: 10 with acute abdomens, including four with necrotising enterocolitis (NEC), 29 controls with normal abdomens and one with cerebral hypoxic ischaemic injury. Median CSOR for the control group was 0.96 (interquartile range 0.83-1.02) whereas the acute abdomen group had a significantly lower median CSOR value of 0.66 (0.45-0.69) (p<0.001). The area under the ROC was 0.91 (95% confidence limits 0.78-1.00) for CSOR. Taking a boundary value of CSOR for the prediction of splanchnic ischaemia as less than 0.75, intestinal ischaemia was identified with a positive predictive value of 0.75 (0.43-0.95) and excluded with a negative predictive value of 0.96 (0.81-1.0). This was a better performance than using abdominal TOI alone. CONCLUSIONS: By comparing the TOI of cerebral and splanchnic regions it may be possible to establish the presence of normal splanchnic perfusion and detect when splanchnic ischaemia develops. CSOR had a 90% (56-100%) sensitivity to detect splanchnic ischaemia in neonates. Further work is necessary to confirm these early findings and establish whether abdominal NIRS has a clinical role in detecting splanchnic ischaemia.

Neonatal encephalopathy with a pungent body odour.

A neonate had transient unexplained bleeding into the gut, severe encephalopathy, and an abnormal pungent body odour. An inherited metabolic defect was excluded. The malodour was due to methanethiol and hydrogen sulphide, identified in urine. These sulphur compounds may have contributed to encephalopathy. Colonic bacteria were the probable source.