Gastric myoelectrical activity in a population of healthy Croatian subjects

Myoelectrical activity of the stomach was estimated in healthy Croatian subjects using the latest multi-channel percutaneous electrogastrograph. The aim of the study was to determine normal values of gastric myoelectrical activity for the population of Croatia. The study included 120 healthy subjects of both sexes, various age groups, body mass index values, and mode of lead placement. The measurement was performed 60 min before and 60 min after test meal. The following parameters of gastric myoelectrical activity were analyzed: dominant frequency (DF, c/min); dominant frequency within normal range (DFNR, %); coefficient of variation for dominant frequency (CVDF); dominant strength (DS, mV); postprandial increase intensity in dominant strength (PPIIDS; %); bradygastria (c/min, %); tachygastria (c/min, %); and arrhythmia. DF for the study group as a whole was around 3 cpm, at the normal range midpoint, and all other parameters were within the normal limits. On postprandial measurement, the rate of arrhythmias showed a significant decline. Age was found to influence DF, CVDF and arrhythmia in preprandial but not in postprandial period, whereas sex influenced DF, DS and bradygastria in preprandial period, and DF, CVDF, PPIIDS and tachygastria in postprandial period. The mode of lead placement had no impact on the electrogastrographic parameters observed. The values of gastric myoelectrical activity recorded in healthy Croatian subjects were within the normal range of the values defined by previous studies across Europe.     

Substrate-induced conformational changes in human UMP/CMP kinase

Human UMP/CMP kinase plays a crucial role in supplying precursors for nucleic acid synthesis by catalyzing the conversion of UMP, CMP, and dCMP into their diphosphate form. In addition, this kinase is an essential component of the activation cascade of medicinally relevant nucleoside analog prodrugs such as AraC, gemcitabine, and ddC. During the catalytic cycle the enzyme undergoes large conformational changes from open in the absence of substrates to closed in the presence of both phosphoryl donor and phosphoryl acceptor. Here we report the crystal structure of the substrate-free, open form of human UMP/CMP kinase. Comparison of the open structure with the closed state previously reported for the similar Dictyostelium discoideum UMP/CMP kinase reveals the conformational changes that occur upon substrate binding. We observe a classic example of induced fit where substrate-induced conformational changes in hinge residues result in rigid body movements of functional domains to form the catalytically competent state. In addition, a homology model of the human enzyme in the closed state based on the structure of D. discoideum UMP/CMP kinase aids to rationalize the substrate specificity of the human enzyme.     

A novel alpha-helix in the first fibronectin type III repeat of the neural cell adhesion molecule is critical for N-glycan polysialylation

Polysialic acid is a developmentally regulated, anti-adhesive glycan that is added to the neural cell adhesion molecule, NCAM. Polysialylated NCAM is critical for brain development and plays roles in synaptic plasticity, axon guidance, and cell migration. The first fibronectin type III repeat of NCAM, FN1, is necessary for the polysialylation of N-glycans on the adjacent immunoglobulin domain. This repeat cannot be replaced by other fibronectin type III repeats. We solved the crystal structure of human NCAM FN1 and found that, in addition to a unique acidic surface patch, it possesses a novel alpha-helix that links strands 4 and 5 of its beta-sandwich structure. Replacement of the alpha-helix did not eliminate polysialyltransferase recognition, but shifted the addition of polysialic acid from the N-glycans modifying the adjacent immunoglobulin domain to O-glycans modifying FN1. Other experiments demonstrated that replacement of residues in the acidic surface patch alter the polysialylation of both N- and O-glycans in the same way, while the alpha-helix is only required for the polysialylation of N-glycans. Our data are consistent with a model in which the FN1 alpha-helix is involved in an Ig5-FN1 interaction that is critical for the correct positioning of Ig5 N-glycans for polysialylation.     

Extracellular polymer substance synthesized by a halophilic bacterium Chromohalobacter canadensis 28

Applied Microbiology and Biotechnology - Halophilic microorganisms are producers of a lot of new compounds whose properties suggest promising perspectives for their biotechnological exploration....     

Developmental neurotoxicity of cadmium on enzyme activities of crucial offspring rat brain regions

Cadmium (Cd) is an environmental contaminant known to exert significant neurotoxic effects on both humans and experimental animals. The aim of this study was to shed more light on the effects of gestational (in utero) and lactational maternal exposure to Cd (50 ppm of Cd as Cd-chloride in the drinking water) on crucial brain enzyme activities in important rat offspring brain regions (frontal cortex, hippocampus, hypothalamus, pons and cerebellum). Our study provides a brain region-specific view of the changes in the activities of three crucial brain enzymes as a result of the developmental neurotoxicity of Cd. Maternal exposure to Cd during both gestation and lactation results into significant changes in the activities of acetylcholinesterase and Na⁺,K⁺-ATPase in the frontal cortex and the cerebellum of the offspring rats, as well as in a significant increase in the hippocampal Mg²⁺-ATPase activity. These brain-region-specific findings underline the need for further research in the field of Cd-induced developmental neurotoxicity. Deeper understanding of the mechanisms underlying the neurodevelopmental deficits taking place due to in utero and early age exposure to Cd could shed more light on the causes of its well-established cognitive implications.     

Renal distribution of ganglioside GM3 in rat models of types 1 and 2 diabetes

Ganglioside GM3 is particularly abundant in the kidney tissue and is thought to play an important role in the maintenance of the charge-selective filtration barrier of glomeruli. Altered expression of ganglioside GM3 was pathologically related with glomerular hypertrophy occurring in diabetic human and rat kidneys. Considering the role of GM3 ganglioside in kidney function, the aim of this study was to determine the difference in expression of GM3 ganglioside in glomeruli and tubules using immunofluorescence microscopy both in rat models of types 1 and 2 diabetes mellitus. Diabetes was induced with streptozotocin (55 mg/kg for type 1 diabetes and 35 mg/kg for type 2 diabetes) injection to male Sprague–Dawley rats which were fed with normal pellet diet (type 1 diabetes) or high-fat diet (type 2 diabetes). Rats were sacrificed 2 weeks after diabetes induction, frozen renal sections were stained with primary antibody GM3(Neu5Ac) and visualized by secondary antibody coupled with Texas red. In addition, renal gangliosides GM3 were analyzed by high-performance thin-layer chromatography followed by GM3 immunostaining. Immunofluorescent microscopy detected 1.7-fold higher GM3 expression in tubules and 1.25-fold higher GM3 in glomeruli of type 1 diabetes mellitus compared with control group. Type 2 diabetes mellitus rats showed slight GM3 increase in whole kidney, unchanged GM3 in glomeruli, but significant higher GM3 expression in tubules, compared with control animals. Taking into consideration increased tubular GM3 content in both types of diabetes, we could hypothesize the role of GM3 in early pathogenesis of diabetic nephropathy.     

Catabolism of terbuthylazine by mixed bacterial culture originating from s-triazine-contaminated soil

The s-triazine herbicide terbuthylazine (TERB) has been used as the main substitute of atrazine in many EU countries for more than 10 years. However, the ecological consequences of this substitution are still not fully understood. Since the fate of triazine herbicides is primarily dependent on microbial degradation, in this paper, we investigated the ability of a mixed bacterial culture, M3-T, originating from s-triazine-contaminated soil, to degrade TERB in liquid culture and soil microcosms. The M3-T culture grown in mineral medium with TERB as the N source and citrate as the C source degraded 50 mg L^?1 of TERB within 3 days of incubation. The culture was capable of degrading TERB as the sole C and N source, though at slower degradation kinetics. A thorough LC-MS analysis of the biodegradation media showed the formation of hydroxyterbuthylazine (TERB-OH) and N-t-butylammelide (TBA) as major metabolites, and desethylterbuthylazine (DET), hydroxydesethylterbuthylazine (DET-OH) and cyanuric acid (CA) as minor metabolites in the TERB degradation pathway. TBA was identified as a bottleneck in the catabolic pathway leading to its transient accumulation in culture media. The supplementation of glucose as the exogenous C source had no effect on TBA degradation, whereas citrate inhibited its disappearance. The addition of M3-T to sterile soil artificially contaminated with TERB at 3 mg kg^?1 of soil resulted in an accelerated TERB degradation with t _1/2 value being about 40 times shorter than that achieved by the native microbial community. Catabolic versatility of M3-T culture makes it a promising seed culture for accelerating biotransformation processes in s-triazine-contaminated environment.     

Multispectral optoacoustic tomography of muscle perfusion and oxygenation under arterial and venous occlusion: A human pilot study

Perfusion and oxygenation are critical parameters of muscle metabolism in health and disease. They have been both the target of many studies, in particular using near‐infrared spectroscopy (NIRS). However, difficulties with quantifying NIRS signals have limited a wide dissemination of the method to the clinics. Our aim was to investigate whether clinical multispectral optoacoustic tomography (MSOT) could enable the label‐free imaging of muscle perfusion and oxygenation under clinically relevant challenges: the arterial and venous occlusion. We employed a hybrid clinical MSOT/ultrasound system equipped with a hand‐held scanning probe to visualize hemodynamic and oxygenation changes in skeletal muscle under arterial and venous occlusions. Four (N = 4) healthy volunteers were scanned over the forearm for both 3‐minute occlusion challenges. MSOT‐recorded pathophysiologically expected results during tests of disturbed blood flow with high resolution and without the need for contrast agents. During arterial occlusion, MSOT‐extracted Hb‐values showed an increase, while HbO₂‐ and total blood volume (TBV)‐values remained roughly steady, followed by a discrete increase during the hyperemic period after cuff deflation. During venous occlusion, results showed a clear increase in intramuscular HbO₂, Hb and TBV within the segmented muscle area. MSOT was found to be capable of label‐free non‐invasive imaging of muscle hemodynamics and oxygenation under arterial and venous occlusion. We introduce herein MSOT as a novel modality for the assessment of vascular disorders characterized by disturbed blood flow, such as acute limb ischemia and venous thrombosis.     

Sunflower Seed Aminopeptidase-Catalyzed Hydrolysis of Phe-Xaa Dipeptides — Exploring the S1′ Specificity of the Enzyme

The S₁′ substrate specificity of the sunflower seed major aminopeptidase was studied with a series of dipeptide substrates with phenylalanine at P₁ and a hydrophobic amino acid at P₁′ position. The kinetic parameters of hydrolysis are significantly affected by the structure, side chain hydrophobicity and configuration of the P₁′ moiety. Its binding during enzyme-substrate complex formation takes place at a hydrophobic site of limited size following an extraction mechanism as seen from the applied structure-activity correlation. Attempts to establish such dependencies for the catalytic step of the reaction reveal the presence of additional S₁′-P₁′ enzyme-substrate interactions of greater complexity.