Feeding rates of amphipods in boreal lakes: is there a seasonal shift independent of temperature and photoperiod?

In boreal lakes, temperature and photoperiod are important environmental cues affecting reproduction, growth and feeding rates of benthic invertebrates; however, how invertebrates cope with seasonal changes in the availability of their food sources has rarely been addressed. In this study, where temperature and light conditions were controlled, we aimed at assessing whether Hyalella azteca amphipods from the littoral zone of boreal lakes adjust their feeding rates in response to the dynamics of their food sources and their population structure. Using a gravimetric approach, we compared the ingestion and absorption rates of amphipods from a natural population collected periodically during the ice-free season. Amphipods were fed in the laboratory with conditioned leaf detritus. Feeding rates increased regardless of seasonal variations of temperature and photoperiod in the lake. Field data suggest this increase could be linked to seasonal changes in the population structure or in the diet of amphipods. This suggests that H. azteca amphipods adjusted their feeding rates with their energy and nutrient requirements and/or developed a compensatory feeding trade-off to cope with the dynamics of their different food sources in lakes.     

Mutual replacement of species in space in a grassland community: is there an evidence for functional complementarity of replacement groups?

Many plant communities show strong fine‐scale spatiotemporal dynamics due to frequent natality and mortality events. This process is often non‐random, implying that the community can be broken into groups within which species mutually replace each other in time and are distinct from the other such groups. We examined whether such groups fill separate niches and are functionally complementary in a species‐rich mountain grassland. We used cluster analysis of fine‐scale spatial data time series to discern which species were more likely to replace each other in space. Next, a four‐year removal experiment (removing one group in each experimental treatment, or similar amount of biomass across all groups) was used to determine whether simultaneous occurrence of all these groups would maintain a greater total biomass than if an entire group were eliminated. The results do not support the hypothesis that the simultaneous presence of groups of species that replace each other in space is necessary for the community to attain its maximum biomass. However, the experiment showed strong differences among the replacement groups in their capacity for opportunistic behaviour: some groups responded quickly to space made available by removal while others did not. Furthermore, there were strong differences between groups composed primarily of grasses and groups composed primarily of dicots. In spite of the large differences among these groups, they are not functionally complementary. We therefore conclude that replacement processes in this grassland community more closely resemble a neutral process with sets of species differing in the speed at which they fill empty spaces.     

Stem cells: is there a future in plastics?

The concept that ostensibly tissue-specific stem cells can give rise to cells of heterologous lineages has gained support from studies using purified hematopoietic stem cells and sensitive donor-cell tracking methods. The ability to exploit these findings in clinical settings will probably depend on new insights into the mechanisms by which such stem cells or their progeny migrate to sites of organ damage and differentiate to cell types competent to participate in tissue regeneration.     

The impact of new emerging drugs in the treatment of multiple myeloma: is there still a role for PBSC transplantation?

High-dose therapy with the rescue of autologous stem cells represents today the standard approach for multiple myeloma patients aged <65 years. Several studies, in fact, have demonstrated the superiority of high-dose therapy with respect to conventional chemotherapy in younger patients. Peripheral blood stem cells (PBSCs) provide a rapid and effective hematopoietic recovery after the administration of supra maximal chemotherapy and mainly for this reason have become the preferred source of stem cells for autologous transplantation. Recently, however, a number of new drugs have appeared in the armamentarium of the hematologist. Among these, thalidomide has been the first antiangiogenetic drug effectively adopted firstly in refractory-relapsed patients and now also as first line treatment with better results respect to VAD or VAD-like regimens. Inhibitors of proteasome, such as bortezomib, and other immunomodulatory agents, such as lenalidomide, have been also studied more recently in myeloma patients. In particular, bortezomib has shown to be very effective as single agent or in combination with high-dose dexamethasone. In this review, we try to define the potential role of these new drugs, how and when they can be included in the therapeutic program designed for younger and older patients, and mostly if and how these new agents could jeopardize the central role of autologous stem cell transplantation in the treatment of multiple myeloma.     

Activation of development in mammals: is there a role for a sperm cytosolic factor?

In mammalian oocytes, fertilization-associated calcium [Ca2+]i oscillations are responsible for the activation of development. The mechanism(s) by which the sperm triggers the initial [Ca2+]i rise and supports long-lasting oscillations is not resolved. It has been proposed that the sperm may interact with receptors in the oocyte's plasma membrane and engage intracellular signaling pathways that result in Ca2+ release. A different line of investigation suggests that upon sperm-oocyte fusion, a sperm cytosolic factor is released into the oocyte which interacts with unknown cytosolic targets, and generates [Ca2+]i oscillations. We will discuss the most recent evidence for both lines of thought and demonstrate that injections of sperm crude extracts (SF) into mammalian oocytes trigger [Ca2+]i oscillations that support in vitro parthenogenetic development to the blastocyst stage.     

Self-incompatibility in a distylous species of Rubiaceae: is there a single incompatibility response of the morphs?

Heterostyly is a genetically controlled floral polymorphism usually associated with an incompatibility system. This set of features is known to occur in several angiosperm families, but some aspects of its biology has not been well studied. The present study investigates cellular aspects of the pollen–pistil interaction after compatible and incompatible pollinations of Psychotria nuda, to increase our knowledge of heteromorphic self-incompatibility (HetSI). The use of bright field, fluorescence and transmission electron microscopy methods allowed us to demonstrate that pollen tubes behave differently after incompatible and compatible pollinations. Pollen tubes were particularly distinct after incompatible pollinations of L- and S-morph flowers. Relative to compatible pollen tubes, incompatible L-morph tubes had a drastic reduction in cellular contents, but no cell rupture. Incompatible S-morph tubes exhibited dense cytoplasm in apical regions, as well as in other regions, accompanied by a rupture of the apex. These results support the hypothesis that L- and S-morph flowers have different incompatibility mechanisms during HetSI.     

Avian thyroid development in chemically contaminated environments: is there evidence of alterations in thyroid function and development?

Poor reproductive success, developmental abnormalities, and behavioral alterations in fish-eating birds in some Great Lakes areas have led to more than 35 years of toxicological studies and residue monitoring of herring gull (Larus argentatus) populations. Polyhalogenated aromatic hydrocarbons (PHAHs), especially polychlorinated biphenyls (PCBs), are widespread contaminants in the Great Lakes ecosystem. The introduction of regulations and elimination of point sources since the 1970s have resulted in decreased PHAHs in fish-eating bird eggs and tissues. PCB exposure is associated with thyroid disruption (hypothyroidism) in mammals, but much less is known of PCB effects on avian thyroid function. Our 1998-2000 studies of herring gulls from the Great Lakes show that both pipping embryos and prefledglings from highly contaminated sites have marked depletion of thyroid gland hormone stores compared with similarly aged gulls at the reference sites. However, organismal hypothyroidism was not apparent in many embryo and chick collections where severe depletion of thyroid gland hormone was observed. Adults, sampled at two high PCB sites and a low PCB site in the Great Lakes and the maritime reference colony in 2001, showed no differences in organismal thyroid status across sites, but gulls from the high sites had enlarged thyroid glands and depressed thyroid gland hormone stores. Here we discuss the evidence that ecological exposure to PHAHs are responsible for thyroid deficiencies in gulls and that during development these deficiencies lead to developmental abnormalities in young gulls from highly contaminated Great Lakes sites.     

Age structure of annual Nothobranchius fishes in Mozambique: is there a hatching synchrony?

The age structures of populations of African annual Nothobranchius spp. were examined for the first time. Daily increments in sagittal otoliths of Nothobranchius furzeri, Nothobranchius kadleci, Nothobranchius orthonotus and Nothobranchius rachovii from southern and central Mozambique were used for age determination. Four hypotheses were tested: (1) timing of hatching is consistent with the calendar onset of the rainy season, (2) hatching is synchronized within a population in a pool, (3) there is a difference in hatching date between geographical regions differing in mean total annual precipitation and (4) sympatric Nothobranchius spp. hatch at the same time. The results show that daily increment analysis represents an applicable method for age determination in Nothobranchius spp. Despite a significant positive relationship between age and size of fishes, a pronounced variation in fish size at an age precluded the use of fish size as a valid age marker. Timing of hatching was not consistent with the calendar onset of the rainy season. Interpopulation variability was observed in the degree of hatching date synchronization within a population. Hatching dates were relatively uniform in some populations, while there was considerable variability in others. Differences in timing of hatching date were found in only 1 of 2 years within the three regions investigated (Chefu, lower Limpopo and Sofala regions), each of which differed in mean total annual rainfall. The hatching dates of sympatric Nothobranchius spp. were marginally different, but further testing on a larger sample is needed for conclusive results.     

Inflammation in atherosclerosis: a cause or a result of vascular disorders?

Sound data support the concept that in atherosclerosis, inflammation and dyslipidemia intersect each other and that irrespective of the initiator, both participate from the early stages to the ultimate fate of the atheromatous plaque. The two partakers manoeuvre a vicious circle in atheroma formation: dyslipidaemia triggers an inflammatory process and inflammation elicits dyslipidaemia. Independent of the initial cause, the atherosclerotic lesions occur focally, in particular arterial-susceptible sites, by a process that, although continuous, can be arbitrarily divided into a sequence of consecutive stages that lead from fatty streak to the fibro-lipid plaque and ultimately to plaque rupture and thrombosis. In the process, the initial event is a change in endothelial cells (EC) constitutive properties. Then, the molecular alarm signals send by dysfunctional EC are decoded by specific blood immune cells (monocytes, T lymphocytes, neutrophils, mast cells) and by the resident vascular cells, that respond by initiating a robust inflammatory process, in which the cells and the factors they secrete hasten the atheroma development. Direct and indirect crosstalk between the cells housed within the nascent plaque, complemented by the increase in risk factors of atherosclerosis lead to atheroma development and outcome. The initial inflammatory response can be regarded as a defense/protective reaction mechanism, but its further amplification, speeds up atherosclerosis. In this review, we provide an overview on the role of inflammation and dyslipidaemia and their intersection in atherogenesis. The data may add to the foundation of a novel attitude in the diagnosis and treatment of atherosclerosis.     

The chemistry of copper binding to PrP: is there sufficient evidence to elucidate a role for copper in protein function?

There has been an enormous body of literature published in the last 10 years concerning copper and PrP (prion protein). Despite this, there is still no generally accepted role for copper in the function of PrP or any real consensus as to how and to what affinity copper associates with the protein. The present review attempts to look at all the evidence for the chemistry, co-ordination and affinity of copper binding to PrP, and then looks at what effect this has on the protein. We then connect this evidence with possible roles for PrP when bound to copper. No clear conclusions can be made from the available data, but it is clear from the present review what aspects of copper association with PrP need to be re-investigated.     

Hydroxyapatite ceramics in multilevel cervical interbody fusion - is there a role?

The aim of this study is to evaluate the efficacy of hydroxyapatite grafts in multilevel cervical interbody fusion during the one year follow-up. A total of 86 patients with degenerative cervical disc disease underwent all together 224 cervical interbody fusion procedures in which either Smith-Robinson or Cloward type hydroxyapatite grafts were used. The surgeries included radiculopathy in 38 cases, myelopathy in 20 cases and myeloradicuopathy in 28 patients. In 65 out of 86 patients, fusion was followed by an anterior instrumentation (plating). Postoperatively, patients were followed for a mean of 15.64 (range 11-23.3) months. All patients underwent radiography to evaluate fusion and the axis curvature. Excellent clinical results (86%), described as a complete or partial relief of symptoms with full return to preop activity, were obtained in patients with radiculopathy. There were 5 grafts mobilizations and one graft fracture. Two grafts extruded in non-instrumented patients and required repeated surgery. There were other three reoperations due to the hardware problems. One year fusion rate was obtained at 86% for two-level surgery, 80.1% for three-level surgery and 74% for four-level surgery. The mean (SD) hospital stay was 3.8 (0.7) days. A hydroxyapatite cheramic can be a very effective synthetic material for multilevel cervical interbody fusion. It is characterized by a high fusion rate and a small percentage of graft-related complications, especially when fusion procedure is followed by plating.     

Cardiac effects of oxytocin: is there a role for this peptide in cardiovascular homeostasis?

Oxytocin is well known for its role in reproduction. However, evidence has emerged suggesting a role in cardiovascular and hydroelectrolytic homeostasis. Although its renal effects have been characterized, the cardiac ones have not been much studied. Therefore, we aimed to investigate the cardiac effects of oxytocin both in vivo and in vitro. In unanesthetized rats (n=6) intravenous oxytocin (1 mug) decreased dP/dt(max) by 15% (P<0.05) and heart rate by 20% (P<0.001), at the first minute after injection. dP/dt(max) was still lower in OT-treated rats than in controls (n=8) after 15 min (P<0.05), while heart rate returned to control values after 5 min. In isolated hearts, oxytocin was able to promote negative inotropic and chronotropic effects. Perfusion with 10(-5), 10(-6) and 10(-7)M oxytocin resulted in approximately 60% (P<0.01), 25% (P<0.01) and 10% (P<0.05) reduction of left ventricle developed pressure, without effect in lower concentrations (10(-10) to 10(-8) M). Also, dP/dt(max) was reduced by 45 and 20% (10(-5) e 10(-6) M; P<0.01), while diastolic pressure raised and heart rate fell only with 10(-5)M oxytocin (P<0.05). Intravenous oxytocin (1 mug; n=6) increased arterial pressure by 22% at the first minute (+23+/-3 mm Hg; P<0.001), returning to control value thereafter. Thus, oxytocin is able to promote directly negative inotropic and chronotropic effects, but its in vivo effect also involves a reflex mechanism, originated from its pressor effect.     

Intersex in the clam Scrobicularia plana: a sign of endocrine disruption in estuaries?

The phenomenon of endocrine disruption is currently a source of growing concern. Feminization of male fish in UK rivers has been shown to occur extensively and has been linked with exposure to endocrine-disrupting compounds present in the environment. Much less is known of the extent and scale of endocrine disruption in estuarine and marine ecosystems, particularly in invertebrates. We present evidence that intersex, in the form of ovotestis, is occurring in the common estuarine bivalve Scrobicularia plana, which is considered to be inherently gonochoristic. We report varying degrees in the severity of ovotestis in male S. plana, and have adopted and developed a grading method to assess the extent of this intersex condition. These findings indicate that S. plana offers potential for widespread screening and investigation of endocrine disruption, helping to focus remediatory strategy.