Gripping during climbing of arboreal snakes may be safe but not economical

On the steep surfaces that are common in arboreal environments, many types of animals without claws or adhesive structures must use muscular force to generate sufficient normal force to prevent slipping and climb successfully. Unlike many limbed arboreal animals that have discrete gripping regions on the feet, the elongate bodies of snakes allow for considerable modulation of both the size and orientation of the gripping region. We quantified the gripping forces of snakes climbing a vertical cylinder to determine the extent to which their force production favoured economy or safety. Our sample included four boid species and one colubrid. Nearly all of the gripping forces that we observed for each snake exceeded our estimate of the minimum required, and snakes commonly produced more than three times the normal force required to support their body weight. This suggests that a large safety factor to avoid slipping and falling is more important than locomotor economy.     

Msx1 and Msx2 have shared essential functions in neural crest but may be dispensable in epidermis and axis formation in Xenopus

The homeodomain factors Msx1 and Msx2 are expressed in essentially identical patterns in the epidermis and neural crest of Xenopus embryos during neurula stages. Disruption of Msx1 and Msx2 RNA splicing with antisense morpholino oligonucleotides shows that both factors are also required for expression of the neural crest gene Slug. Loss of Msx1 can be compensated by overexpression of Msx2 and vice versa. Loss of Msx factors also leads to alterations in the expression boundaries for neural and epidermal genes, but does not prevent or reduce expression of epidermal keratin in ventrolateral ectoderm, nor is there a detectable effect on dorsal mesodermal marker gene expression. These results indicate that Msx1 and Msx2 are both essential for neural crest development, but that the two genes have the same function in this tissue. If Msx genes have important functions in epidermis or axial mesoderm induction, these functions must be shared with other regulatory proteins.     

psbG is not a photosystem two gene but may be an ndh gene

A gene of the chloroplast genome has been designated the psbG gene on the basis that in maize the gene product is a 24-kDa polypeptide of photosystem two (PS2) (Steinmetz, A. A., Castroviejo, M., Sayre, R. T., and Bogorad, L. (1986) J. Biol. Chem. 261, 2485-2488). We have located and sequenced the equivalent gene in wheat (Triticum aestivum) and have raised specific antibodies to the gene product following its expression in Escherichia coli as a beta-galactosidase fusion protein. Using these antibodies, we have investigated the location of the gene product in various thylakoid membrane fractions of pea (Pisum sativum). The gene product of apparent molecular mass 27-28 kDa is severely depleted in PS2-enriched membrane preparations and its distribution between stromal and granal regions of the membrane is distinct to that of the psbC gene product which is known to be a core polypeptide of PS2. We therefore conclude that psbG does not code for a component of PS2 but instead suggest that it is present in a novel protein complex of the thylakoid membrane. On the basis of 1) the conserved overlap between psbG and ndhC, a chloroplast gene which shows significant homology to a mitochondrial gene that codes for a subunit of the NADH-ubiquinone oxidoreductase of mitochondria, and 2) sequence similarity between the psbG gene product and the ndh gene product of E. coli, which codes for a respiratory NADH dehydrogenase, we propose that this ill-defined complex functions as a NADH or NADPH-plastoquinone oxidoreductase.     

Thallium poisoning. Diagnosis may be elusive but alopecia is the clue.

Thallium is a heavy metal whose salts are used in some rodent poisons and in the manufacture of optical lenses, semiconductors, scintillation counters, low temperature thermometers, and switching devices, green coloured fireworks, and imitation jewelery, and as chemical catalysts. In clinical practice thallium isotopes are used in cardiac scanning, but the use of thallium salts to treat scalp ringworm was abandoned earlier this century because of their toxicity. The sale of thallium in Britain is strictly licensed because of its toxicity and potential for use in murder, which is helped by the fact that thallous salts are colourless, tasteless, and odorless. The more water soluble salts (such as thallium sulphate, acetate, or carbonate) have higher toxicity, and although the toxic dose is variable most deaths occur after the ingestion of 10-15 mg/kg of soluble salt. Most cases of thallium toxicity occur after oral ingestion but severe toxicity has been reported after inhalation of contaminated dust from pyrite burners, in zinc and lead smelting, and in the manufacture of cadmium, after dermal absorption through protective rubber gloves, and after snorting what was thought to be cocaine. The elimination half time of thallium is between 1.7 and 30 days depending on the time since, and chronicity of, ingestion. The elimination time phases are apparent and because of the long terminal elimination half time thallium may act as a cumulative poison. We present two cases of thallium poisoning with intent to kill.     

Bioactive deoxypreussomerins and dimeric naphthoquinones from Diospyros ehretioides fruits: deoxypreussomerins may not be plant metabolites but may be from fungal epiphytes or endophytes

Deoxypreussomerin derivatives, palmarumycins JC1 (1) and JC2 (2), and two dimeric naphthoquinones, isodiospyrin (3) and its new derivative isodiospyrol A (4), were isolated from dried fruits of Diospyros ehretioides. Structures of the isolated compounds were elucidated by spectroscopic analyses. Palmarumycins were not found in the extract of freshly collected fruits; however, they were present in dried fruit extract. The absence of palmarumycins in fresh fruits of D. ehretioides, together with the chemotaxonomic point of view, we proposed that palmarumycins JC1 (1) and JC2 (2) are more likely to be fungal metabolites, i.e., endophytes or epiphytes. The isolation of palmarumycins 1 and 2 from dried D. ehretioides fruits could be reproducible; both plant samples collected in the years 2002 and 2004 provided the same result, and, therefore, symbiont fungal strains should be specific to the plant host, D. ehretioides, and they can grow on the fruits during drying the sample. Palmarumycin JC1 (1) did not exhibit antimalarial, antifungal, antimycobacterial, and cytotoxic activities. Palmarumycin JC2 (2) exhibited antimalarial (IC50 4.5 microg/ml), antifungal (IC50 12.5 microg/ml), antimycobacterial (MIC 6.25 microg/ml), and cytotoxic (IC50 11.0 microg/ml for NCI-H187 cell line) activities. In our bioassay systems, isodiospyrin (3) did not exhibit antimycobacterial, antifungal, antimalarial, and cytotoxic activities. Isodiospyrol A (4) exhibited antimalarial (IC50 2.7 microg/ml) and antimycobacterial (MIC 50 microg/ml) activities, but was inactive towards Candida albicans. Compound 4 also exhibited cytotoxicity against BC cells (IC50 12.3 microg/ml), but not towards KB and Vero cell lines.     

A recipe for postfledging survival in great tits Parus major: be large and be early (but not too much)

Survival of juveniles during the postfledging period can be markedly low, which may have major consequences on avian population dynamics. Knowing which factors operating during the nesting phase affect postfledging survival is crucial to understand avian breeding strategies. We aimed to obtain a robust set of predictors of postfledging local survival using the great tit (Parus major) as a model species. We used mark–recapture models to analyze the effect of hatching date, temperatures experienced during the nestling period, fledging size and body mass on first‐year postfledging survival probability of great tit juveniles. We used data from 5192 nestlings of first clutches ringed between 1993 and 2010. Mean first‐year postfledging survival probability was 15.2%, and it was lower for smaller individuals, as well as for those born in either very early or late broods. Our results stress the importance of choosing an optimum hatching period, and raising large chicks to increase first‐year local survival probability in the studied population.