Organic acids differ in enhancing phosphorus uptake by Triticum aestivum L.—effects of rhizosphere concentration and counterion

Organic acids such as citrate and oxalate have been implicated in enhancing many rhizosphere processes including nutrient acquisition. This study was conducted to determine the importance of organic acid type and concentration on rhizosphere P mobilization and subsequent uptake by wheat (Triticum aestivum L.) roots and its translocation to shoots. A single wheat plant was grown in soil-filled rhizosphere microcosms and allowed to pass through a KH₂PO₄ ³³P-isotopically labeled patch of calcareous soil. Two days after ³³P-injection, citrate and oxalate at concentrations of 1 mM and 10 mM were injected into the microcosms at the same patch every day over a period of 4 days. Oxalate resulted in a several-fold enhancement in plant ³³P accumulation, while citrate had no such effect. In comparison with oxalate, high rates of citrate mineralization were observed suggesting that this reduced its potential to enhance plant ³³P acquisition. This study concludes that organic acids cause an increase in P mobilization and P uptake by wheat but that this response is highly organic acid specific.     

Modeling muscle activity to study the effects of footwear on the impact forces and vibrations of the human body during running

A previously developed mass-spring-damper model of the human body is improved in this paper, taking muscle activity into account. In the improved model, a nonlinear controller mimics the functionality of the Central Nervous System (CNS) in tuning the mechanical properties of the soft-tissue package. Two physiological hypotheses are used to determine the control strategies that are used by the controller. The first hypothesis (constant-force hypothesis) postulates that the CNS uses muscle tuning to keep the ground reaction force (GRF) constant regardless of shoe hardness, wherever possible. It is shown that the constant-force hypothesis can explain the existing contradiction about the effects of shoe hardness on the GRF during running. This contradiction is emerged from the different trends observed in the experiments on actual runners, and experiments in which the leg was fixed and exposed to impact. While the GRF is found to be dependent on shoe hardness in the former set of experiments, no such dependency was observed in the latter. According to the second hypothesis, the CNS keeps the level of the vibrations of the human body constant using muscle tuning. The results of the study show that this second control strategy improves the model such that it can correctly simulate the effects of shoe hardness on the vibrations of the human body during running.     

A GIP Receptor Agonist Exhibits β-Cell Anti-Apoptotic Actions in Rat Models of Diabetes Resulting in Improved β-Cell Function and Glycemic Control

Aims

The gastrointestinal hormone GIP promotes pancreatic islet function and exerts pro-survival actions on cultured β-cells. However, GIP also promotes lipogenesis, thus potentially restricting its therapeutic use. The current studies evaluated the effects of a truncated GIP analog, D-Ala²-GIP_1–30 (D-GIP_1–30), on glucose homeostasis and β-cell mass in rat models of diabetes.

Materials and Methods

The insulinotropic and pro-survival potency of D-GIP_1–30 was evaluated in perfused pancreas preparations and cultured INS-1 β-cells, respectively, and receptor selectivity evaluated using wild type and GIP receptor knockout mice. Effects of D-GIP_1–30 on β-cell function and glucose homeostasis, in vivo, were determined using Lean Zucker rats, obese Vancouver diabetic fatty rats, streptozotocin treated rats, and obese Zucker diabetic fatty rats, with effects on β-cell mass determined in histological studies of pancreatic tissue. Lipogenic effects of D-GIP_1–30 were evaluated on cultured 3T3-L1 adipocytes.

Results

Acutely, D-GIP_1–30 improved glucose tolerance and insulin secretion. Chronic treatment with D-GIP_1–30 reduced levels of islet pro-apoptotic proteins in Vancouver diabetic fatty rats and preserved β-cell mass in streptozotocin treated rats and Zucker diabetic fatty rats, resulting in improved insulin responses and glycemic control in each animal model, with no change in body weight. In in vitro studies, D-GIP_1–30 exhibited equivalent potency to GIP_1–42 on β-cell function and survival, but greatly reduced action on lipoprotein lipase activity in 3T3-L1 adipocytes.

Conclusions

These findings demonstrate that truncated forms of GIP exhibit potent anti-diabetic actions, without pro-obesity effects, and that the C-terminus contributes to the lipogenic actions of GIP.     

The pancreatic beta cell is a key site for mediating the effects of leptin on glucose homeostasis

The hormone leptin plays a crucial role in maintenance of body weight and glucose homeostasis. This occurs through central and peripheral pathways, including regulation of insulin secretion by pancreatic beta cells. To study this further in mice, we disrupted the signaling domain of the leptin receptor gene in beta cells and hypothalamus. These mice develop obesity, fasting hyperinsulinemia, impaired glucose-stimulated insulin release, and glucose intolerance, similar to leptin receptor null mice. However, whereas complete loss of leptin function causes increased food intake, this tissue-specific attenuation of leptin signaling does not alter food intake or satiety responses to leptin. Moreover, unlike other obese models, these mice have reduced fasting blood glucose. These results indicate that leptin regulation of glucose homeostasis extends beyond insulin sensitivity to influence beta cell function, independent of pathways controlling food intake. These data suggest that defects in this adipoinsular axis could contribute to diabetes associated with obesity.     

Mathematical modeling of non-ideal mixing continuous flow reactors for anaerobic digestion of cattle manure

Most conventional digesters used for animal wastewater treatment include continuously stirred-tank reactors. While imperfect mixing patterns are more common than ideal ones in real reactors, anaerobic digestion models often assume complete mixing conditions. Therefore, their applicability appears to be limited. In this study, a mathematical model for anaerobic digestion of cattle manure was developed to describe the dynamic behavior of non-ideal mixing continuous flow reactors. The microbial kinetic model includes an enzymatic hydrolysis step and four microbial growth steps, together with the effects of substrate inhibition, pH and thermodynamic considerations. The biokinetic expressions were linked to a simple two-region liquid mixing model, which considered the reactor volume in two separate sections, the flow-through and the retention regions. Deviations from an ideal completely mixed regime were represented by changing the relative volume of the flow-through region (a) and the ratio of the internal exchange flow rate to the feed flow rate (b). The effects of the hydraulic retention time, the composition of feed, the initial conditions of the reactor and the degree of mixing on process performance can be evaluated by the dynamic model. The simulation results under different conditions showed that deviations from the ideal mixing regime decreased the methane yield and resulted in a reduced performance of the anaerobic reactors. The evaluation of the impact of the characteristic mixing parameters (a) and (b) on the anaerobic digestion of cattle manure showed that both liquid mixing parameters had significant effects on reactor performance.     

Characterization of supernumerary ring marker chromosomes by fluorescence in situ hybridization (FISH).

Five cases with small supernumerary ring chromosomes are characterized at the molecular level. Routine chromosome banding analysis was insufficient for identification of the ring chromosomes, and none of them was DA/DAPI positive. Fluorescence in situ hybridization utilizing repetitive centromeric probes for all chromosomes has determined that one of these five ring chromosomes originates in each of chromosomes 4, 7, 8, 9, and 20. Chromosome painting with chromosome-specific libraries has confirmed this and excluded the involvement of additional chromosomes in the rearrangements.     

Detection of the markers of herpes simplex virus and cytomegalovirus in newborns and infants

A total of 111 children suspected for herpesvirus infection were examined. In blood and urine samples the infectious activity of herpes simplex virus (HSV) and cytomegalovirus (CMV) was detected by the rapid culture method (RCM) and the presence of virus DNA--by the polymerase chain reaction (PCR). HSV and/or CMV were detected by two laboratory methods in 57 examined children (51%). Of these, in 18 children (16.2%) both HSV and CMV were detected. The coincidence of the results of the detection of HSV and CMV by these two methods was observed in 72.4% and 75.2% of cases respectively. The comparative analysis of the detection of anti-CMV IgG and IgM was made with the use of commercial test systems produced bythe following manufacturers: "Vector-Best" and "Bioservice" (Russia), "HUMAN" and "Boehringer" (Germany). The effective detection of both anti-CMV (IgG and IgM) was ensured by the test systems "Boehringer". The test system "Vector-Best" for anti-CMV IgG proved to be not inferior as regards sensitivity and specificity. The German test systems demonstrated the highest specificity in the detection of low-avid antibodies. The data obtained in this study indicate that the detection rate of HSV and CMV markers in newborns and infants suspected for herpesvirus infection was, on the average, 20 - 40%. Reliable diagnostics in newborns and infants is possible only in the presence of the combination of at least 2 serological tests (the determination of antivirus IgM and IgG avidity) and 2 methods for the detection of direct herpesvirus markers (PCR and RCM).     

The verification of the results of screening antibodies to hepatitis C virus in blood donors

6,744 persons were examined for the presence of antibodies to hepatitis C virus (HCV) before blood donation (4,219 persons in Moscow and 2,525 persons in St. Petersburg). The serum samples found to contain antibodies to HCV were additionally studied by the immunoblot techniques. The positive results of antibody screening were registered in 78 persons: 26 persons in Moscow (0.62%) and 52 in St. Petersburg (2.05%). In both cities the positive results of screening were confirmed in 62% of cases. Different occurrence of the profile with the presence of antibodies to all fragments of the virus: 52% in Moscow, 12% in St. Petersburg (chi2 = 12.11; p < 0.001). Considerable differences were also registered in the spread of individual antibodies.