The mammalian tail: a review of functions

The mammalian tail, present in all mammalian species, has evolved as a surprisingly multi-purpose and important appendage. The major conservative feature appears to be retention of the tail as a single, unbranched appendage; otherwise, colour, shape, size and mobility vary greatly.
Not all of the adaptations discussed are common to all mammalian orders, and no single mammalian order has all the different adaptations occurring in it. These diverse functions may be useful in interpreting behavioural observations, and function as potential guideposts for further investigation.     

Phylogenetic Relationships Among Anuran Trypanosomes as Revealed by Riboprinting

Twenty trypanosome isolates from Anura (frogs and toads) assigned to several species were characterized by riboprinting–restriction enzyme digestion of polymerase chain reaction amplified small subunit ribosomal RNA genes. Restriction site polymorphisms allowed distinction of all the recognized species and no intraspecific variation in riboprint patterns was detected. Phylogenetic reconstruction using parsimony and distance estimates based on restriction fragment comigration showed Trypanosoma chattoni to be only distantly related to the other species, white T. ranarum and T. fallisi appear to be sister taxa despite showing non-overlapping host specificities.     

Characterisation of ACTH Peptides in Human Skin and Their Activation of the Melanocortin-1 Receptor

α-Melanocyte-stimulating hormone (α-MSH) is a proopiomelanocortin (POMC)-derived peptide, which is produced in the pituitary and at other sites including the skin. It has numerous effects and in the skin has a pigmentary action through the activation of the melanocortin-1 (MC-1) receptor, which is expressed by melanocytes. Recent evidence suggests that the related POMC peptides such as adrenocorticotrophin (ACTH), which is the precursor of α-MSH, is also an agonist at the MC-1 receptor. By using immunocytochemistry, we confirmed the presence of α-MSH in human skin where staining was evident in keratinocytes and especially strong in melanocytes and possibly Langerhans cells. ACTH was also present and tended to show the strongest reaction in differentiated keratinocytes. Immunostaining was also observed for the prohormone convertases, PC1 and PC2, which are involved in the formation of ACTH and its cleavage to α-MSH, respectively. The amounts of immunoreactive ACTH exceeded those of α-MSH. Using HPLC we identified for the first time the presence of ACTH1-39, ACTH1-17, ACTH1-10, acetylated ACTH1-10, α-MSH, and desacetyl α-MSH in epidermis and in cultured keratinocytes. The ability of these peptides to activate the human MC-1 receptor was examined in HEK 293 cells that had been transfected with the receptor. All peptides increased adenylate cyclase in these cells with the following order of potency: ACTH1-17 > α-MSH > ACTH1-39 > desacetyl α-MSH > acetylated ACTH1-10 > ACTH1-10. ACTH1-17 also increased the dendricity and melanin content of cultured human melanocytes indicating that the peptide was able to activate MC-1 receptors when present in their normal location. However, as found with α-MSH, not all cultures were responsive and, as we have previously suggested, we suspect that this was the result of changes at the MC-1 receptor. Nevertheless, it would appear that ACTH peptides can serve as natural ligands of the MC-1 receptor on human melanocytes and their presence in the skin suggests that, together with α-MSH, they may have a role in the regulation of human melanocytes.     

Burkitt''s lymphoma: a pericardial presentation

Described herein is a case of childhood Burkitt's lymphoma initially presenting as a pericardial effusion. A cytological diagnosis was made from a Wright's-Giemsa stained cytospin preparation. Supporting diagnostic evidence was provided by immunological surface marker analysis and electron microscopy. To our knowledge, Burkitt's lymphoma has not hitherto been diagnosed initially from the morphology of cells in pericardial fluid.     

What does optimization theory actually predict about crown profiles of photosynthetic capacity when models incorporate greater realism?

Measured profiles of photosynthetic capacity in plant crowns typically do not match those of average irradiance: the ratio of capacity to irradiance decreases as irradiance increases. This differs from optimal profiles inferred from simple models. To determine whether this could be explained by omission of physiological or physical details from such models, we performed a series of thought experiments using a new model that included more realism than previous models. We used ray‐tracing to simulate irradiance for 8000 leaves in a horizontally uniform canopy. For a subsample of 500 leaves, we simultaneously optimized both nitrogen allocation (among pools representing carboxylation, electron transport and light capture) and stomatal conductance using a transdermally explicit photosynthesis model. Few model features caused the capacity/irradiance ratio to vary systematically with irradiance. However, when leaf absorptance varied as needed to optimize distribution of light‐capture N, the capacity/irradiance ratio increased up through the crown – that is, opposite to the observed pattern. This tendency was counteracted by constraints on stomatal or mesophyll conductance, which caused chloroplastic CO₂ concentration to decline systematically with increasing irradiance. Our results suggest that height‐related constraints on stomatal conductance can help to reconcile observations with the hypothesis that photosynthetic N is allocated optimally.     

The influence of the development rates of immature stages of Eristalis arbustorum (Diptera; Syrphidae) on adult abdominal colour pattern

Abstract. The abdominal colour pattern of Eristalis arbustorum (L.) shows seasonal variation, with animals emerging in spring being darker than those emerging during summer. One of the most important environmental cues influencing the abdominal colour pattern is developmental temperature. An experiment was carried out to establish which period during the immature stages was important in determining final adult colour pattern. The results indicate a good relationship between the length of the pupal period and both the extent of the paler markings on the abdomen and the grey score of these markings. The length of the larval period did not have any effect on adult colour pattern.