Tooth replacement rates in early chondrichthyans: a qualitative approach

The continuous replacement of teeth throughout their lifetime is a common characteristic of most chondrichthyans. This process was already present in the earliest representatives of the group. It has been well established that different species of extant sharks show rapid tooth replacement rates; however, some authors have suggested that in early chondrichthyans this rate might have been much slower. Here we present a qualitative approach to analyse tooth replacement rates in the Early Devonian shark Leonodus carlsi , the earliest tooth-bearing shark known to date. For this, we have examined 1,103 isolated teeth from Celtiberia, Spain. Our study provides strong evidences of an extremely slow dental replacement in this primitive chondrichthyan based on three independents analyses: (1) statistical analysis of the wear degree, demonstrating that teeth remain functional for a long period of time; (2) analysis of both the histological and the morphological features of the teeth cusps suggests that this chondrichthyan used a maturation process that optimizes its function, thus worn teeth show an efficient working shape that implies their teeth remained functional for a long time after being modelled by use; and (3) estimations of size increments between teeth (Δs) of the same dental family for some recent sharks whose rates of replacement were known prove that Δs is inversely proportional to the rate of replacement ( R ² = 0.8327). The estimated values of tooth replacement rates obtained from Δs for L. carlsi and for some Late Devonian cladoselachian sharks are significatively slower than those observed in current sharks.     

Ligands of boron in Pisum sativum nodules are involved in regulation of oxygen concentration and rhizobial infection

Boron (B) is an essential nutrient for N₂‐fixing legume–rhizobia symbioses, and the capacity of borate ions to bind and stabilize biomolecules is the basis of any B function. We used a borate‐binding‐specific resin and immunostaining techniques to identify B ligands important for the development of Pisum sativum–Rhizobium leguminosarum 3841 symbiotic nodules. arabinogalactan–extensin (AGPE), recognized by MAC 265 antibody, appeared heavily bound to the resin in extracts derived from B‐sufficient, but not from B‐deficient nodules. MAC 265 stained the infection threads and the extracellular matrix of cortical cells involved in the oxygen diffusion barrier. In B‐deprived nodules, immunolocalization of MAC 265 antigens was significantly reduced. Leghaemoglobin (Lb) concentration largely decreased in B‐deficient nodules. The absence of MAC 203 antigens in B‐deficient nodules suggests a high internal oxygen concentration, as this antibody detects an epitope on the lipopolysaccharide (LPS) of bacteroids typically expressed in micro‐aerobically grown R. leguminosarum 3841. However, B‐deprived nodules did not accumulate oxidized lipids and proteins, and revealed a decrease in the activity of the major antioxidant enzyme ascorbate peroxidase (APX). Therefore, B deficiency reduced the stability of nodule macromolecules important for rhizobial infection, and for regulation of oxygen concentration, resulting in non‐functional nodules, but did not appear to induce oxidative damage in low‐B nodules.     

Long-term exposure of Boeckellagibbosa (Copepoda, Calanoida) to in situ levels of solar UVB radiation

1. The freshwater calanoid copepod Boeckella gibbosa is typical of high elevation lakes and ponds in Patagonia (Argentina). Previous studies have shown that this species is highly tolerant to short-term exposure to natural and artificial UVB radiation, and that its tolerance is due to photoreactivation by longer wavelength radiation. In this study, we investigate the potential sublethal effects of solar radiation after prolonged exposure.
2. We incubated B. gibbosa at 1 m depth in oligotrophic Lake Toncek for 24 days. The incubation chambers were 1.2 l acrylic cylinders covered with appropriate filters in order to obtain three radiation treatments: visible radiation only, visible radiation + UVA and visible radiation + UVA + UVB.
3. The three treatments did not differ significantly in variables considered as indicators of survival (number of individuals), reproduction (proportion of ovigerous females, clutch size) and development (instar composition). Although resistance to solar UVB radiation is certainly a requisite to live in transparent high elevation habitats, the fact of being effectively exposed to natural levels of UVB radiation does not seem to have measurable consequences on an already adapted species, such as B. gibbosa     

Bird community composition across an Andean tree‐line ecotone

Few studies have found strong evidence to suggest that ecotones promote species richness and diversity. In this study we examine the responses of a high‐Andean bird community to changes in vegetation and topographical characteristics across an Andean tree‐line ecotone and adjacent cloud forest and puna grassland vegetation in southern Peru. Over a 6‐month period, birds and vegetation were surveyed using a 100 m fixed‐width Distance Sampling point count method. Vegetation analyses revealed that the tree‐line ecotone represented a distinctive high‐Andean vegetation community that was easily differentiated from the adjacent cloud forest and puna grassland based on changes in tree‐size characteristics and vegetation cover. Bird community composition was strongly seasonal and influenced by a pool of bird species from a wider elevational gradient. There were also clear differences in bird community measures between tree‐line vegetation, cloud forest and puna grassland with species turnover (β‐diversity) most pronounced at the tree‐line. Canonical Correspondence Analysis revealed that the majority of the 81 bird species were associated with tree‐line vegetation. Categorizing patterns of relative abundance of the 42 most common species revealed that the tree‐line ecotone was composed primarily of cloud forest specialists and habitat generalists, with very few species from the puna grassland. Only two species, Thlypopsis ruficeps and Anairetes parulus, both widespread Andean species more typical of montane woodland vegetation edges, were categorized as ecotone specialists. However, our findings were influenced by significant differences in species detectability between all three vegetation communities. Our study highlights the importance of examining ecotones at an appropriate spatial and temporal scale. Selecting a suitable distance between sampling points based on the detection probabilities of the target bird species is essential to obtain an unbiased picture of how ecotones influence avian richness and diversity.     

Vanadate enhances insulin-receptor binding in gestational diabetic human placenta

Although vanadium is found abundantly in animal and plant kingdoms its biological effects are not clear. Vanadate compounds have been shown to normalize blood glucose levels in streptozotocin treated rats, enhance glucose oxidation and improve the sensitivity to insulin by enhanced receptor binding in rat adipocytes. The aim of the present study was to investigate the effect of vanadate, at high (0–8 mmol l^?1) and low (0–1·0 mmol l^?1) physiological concentrations, on [¹²⁵I]-insulin binding in the placenta of three groups of pateints, namely from normal (N) controls, gestational diabetics (GDM) and women with risk factors in their medical history for developing diabetes mellitus (RF). Vanadate at low concentrations (0·2–0·6 mmol l^?1) enhanced the maximal binding 2-fold in GDM placenta but only increased (up to 1·2-fold) the binding slightly at high cncentrations (5 mmol l^?1). However with placenta from normal or women at risk, vanadate increased the [¹²⁵I]-insulin binding up to 1·2-fold both at low and high concentrations. Thus it appears that vanadate augements insulin binding in the placenta from women with gestational diabetes mellitus.     

Associations of Spexin and cardiometabolic parameters among women with and without gestational diabetes mellitus

Spexin (SPX) is a novel biomarker abundantly expressed in several animal and human tissues implicated in food intake and glucose control, respectively. As new roles for SPX are emerging, the present study explored for the first time, the associations of SPX to several cardiometabolic indices and inflammatory markers in pregnant women, a demographic not yet investigated with respect to SPX. A total of 117 Saudi women subdivided to those with gestational diabetes mellitus (GDM) (N?=?63) and those without (N?=?54) were included in this cross-sectional study. Anthropometry, glycemic, lipid, vitamin D, adipocytokines and inflammatory markers were measured consecutively at baseline and after the 2nd and 3rd trimesters. Age- and BMI adjusted comparisons revealed that levels of SPX were not significantly different in pregnant women with and without GDM. In all subjects, circulating levels of SPX showed modest associations with glucose (R?=?0.18; p?=?.08) and HOMA β (R?=??0.19; p?=?.09) as well as significant positive associations with total cholesterol (R?=?0.25; p?=?.02), LDL-cholesterol (R?=?0.25; p?=?.02), 25(OH)D (R?=?0.22; p?=?.04), albumin (R?=?0.30; p?<?.01) and IL1β (R?=?0.41; p?<?.01). Stepwise regression analysis also suggested that IL1β, leptin and albumin were the significant predictors of SPX. In summary, SPX levels modestly affect glucose and insulin sensitivity in pregnant women but is not associated with GDM and obesity. The significant association of SPX to ILβ warrants further investigation as to the role of SPX in immune modulation.     

Caffeine: cardiorespiratory effects and tissue protection in animal models

The aim of this review is to analyze the cardiorespiratory and tissue-protective effects of caffeine in animal models. Peer-reviewed literature published between 1975 and 2021 was retrieved from CAB Abstracts, PubMed, ISI Web of Knowledge, and Scopus. Extracted data were analyzed to address the mechanism of action of caffeine on cardiorespiratory parameters (heart rate and rhythm), vasopressor effects, and some indices of respiratory function; we close this review by discussing the current debate on the research carried out on the effects of caffeine on tissue protection. Adenosine acts through specific receptors and is a negative inotropic and chronotropic agent. Blockage of its cardiac receptors can cause tachycardia (with arrhythmogenic potential) due to the intense activity of β1 receptors. In terms of tissue protection, caffeine inhibits hyperoxia-induced pulmonary inflammation by decreasing proinflammatory cytokine expression in animal models. The protection that caffeine provides to tissues is not limited to the CNS, as studies have demonstrated that it generates attenuation of inflammatory effects in pulmonary tissue. It inhibits the effects of some pro-inflammatory cytokines and prevents functional and structural changes.     

Insulin receptor binding from mid-term and full-term placentas of patients with gestational diabetes mellitus and normal pregnant women

Insulin receptor binding was examined in the microvillous membranes of mid-term (20–22 weeks of gestation, MT) and full-term (FT) placentas from patients with gestational diabetes mellitus (GDM) and in normal pregnant control (N). Mid-term placentas were obtained from patients who have had spontaneous abortion. The maximum per cent specific binding (%SB) in MT placenta for GDM was significantly lower (4.8%) compared with the FT placenta (22%, p<0.001), while in the N group the maximum per cent specific binding for MT placenta was 14.1% compared with 26% for the FT placneta (p<0.001). Binding data from FT placenta of well-controlled GDM patients were similar with the FT placenta from N group (22%SB for GDM VS 26% SB for N). Even as there were similarities in the binding characteristics of FT placentas from both groups the placental membrane protein content in the GDM group was lower by 50% compared with the N control (2.5±0.11 VS 4.8±0.15 mg protein/g placenta respectively, p<0.001) suggesting that in the GDM group achieving a tight glycemic control could improve receptor affinities. Data from the competitive binding assay of GDM patients showed that the insulin necessary to achieve 50% inhibition (ID₅₀) was significantly lower in MT compared with the FT placenta (0.9×10^–9 M VS 3.8×10^–9 M, p<0.001) but in the N placenta there was no alteration in the ID₅₀ of MT and FT placentas (3.1×10^–9 M VS 4×10^–9 M, p<0.01, respectively). The present study demonstrated that in GDM the placental insulin receptor binding was significantly lower in spontaneously aborted placenta compared with placentas collected at full-term. Furthermore, these data suggest that the objective to achieve a tight glycemic control in GDM patients could optimize insulin receptor function similar to that of a normal pregnancy. Thus a full term placenta from GDM patients under a well managed glycemic control throughout the entire duration of pregnancy would result in an optimum insulin receptor function.