Rate Of Reabsorption Research Articles

In Vitro and In Vivo Study of a Novel Porcine Collagen Membrane for Guided Bone Regeneration.

For years, in order to improve bone regeneration and prevent the need of a second stage surgery to remove non-resorbable membranes, biological absorbable membranes have gradually been developed and applied in guided tissue regeneration (GTR). The present study’s main objective was to achieve space maintenance and bone regeneration using a new freeze-dried developed porcine collagen membrane, and compare it with an already commercial collagen membrane, when both were used with a bovine xenograft in prepared alveolar ridge bone defects. Prior to surgery, the membrane’s vitality analysis showed statistically significant higher cell proliferation in the test membrane over the commercial one. In six beagle dogs, commercial bone xenograft was packed in lateral ridge bone defects prepared in the left and right side and then covered with test porcine collagen membrane or commercial collagen membrane. Alveolar height changes were measured. Histomorphometric results, in vitro and in vivo properties indicated that the new porcine collagen membrane is biocompatible, enhances bone xenograft osteoconduction, and reduces the alveolar ridge height reabsorption rate.

Cranioplasty: Review of Materials.

Cranioplasty remains a difficult procedure for all craniofacial surgeons, particularly when concerning the reconstruction of large lacunae in the skull. Considering the significant clinical and economic impact of the procedure, the search for materials and strategies to provide more comfortable and reliable surgical procedures is one of the most important challenges faced by modern craniofacial medicine.The purpose of this study was to compare the available data regarding the safety and clinical efficacy of materials and techniques currently used for the reconstruction of the skull. Accordingly, the scientific databases were searched for the following keywords autologous bone, biomaterials, cranial reconstruction, cranioplasty, hydroxyapatite, polyetheretherketone, polymethylmethacrylate, and titanium. This literature review emphasizes the benefits and weaknesses of each considered material commonly used for cranioplasty, especially in terms of infectious complications, fractures, and morphological outcomes.As regards the latter, this appears to be very similar among the different materials when custom three-dimensional modeling is used for implant development, suggesting that this criterion is strongly influenced by implant design. However, the overall infection rate can vary from 0% to 30%, apparently dependent on the type of material used, likely in virtue of the wide variation in their chemico-physical composition. Among the different materials used for cranioplasty implants, synthetics such as polyetheretherketone, polymethylmethacrylate, and titanium show a higher primary tear resistance, whereas hydroxyapatite and autologous bone display good biomimetic properties, although the latter has been ascribed a variable reabsorption rate of between 3% and 50%.In short, all cranioplasty procedures and materials have their advantages and disadvantages, and none of the currently available materials meet the criteria required for an ideal implant. Hence, the choice of cranioplasty materials is still essentially reliant on the surgeon's preference.

Role of the renal sympathetic nerves in renal sodium/potassium handling and renal damage in spontaneously hypertensive rats.

Renal sympathetic nerve activity has an important role in renal disease-associated hypertension and in the modulation of fluid homeostasis. In the present study, changes in renal function and renal sodium/potassium handling were investigated in groups of 12-week-old male, spontaneously hypertensive rats with renal denervation (RDNX group) or sham denervation (sham group). The RDNX group excreted significantly more sodium than the sham group during the 2-week observation period (P<0.05). Following bilateral renal denervation, the fractional lithium excretion was elevated in the RDNX group compared with the sham group, but no significant effect was observed of renal denervation on the fractional distal reabsorption rate of sodium or the fractional excretion of potassium. Furthermore, the glomerular injury score and the wall-to-lumen ratio of the interlobular artery were significantly lower in the RDNX group than in the sham group (P<0.05). In conclusion, the present study indicates an involvement of the renal sympathetic nerves in the regulation of renal tubular sodium reabsorption in spontaneously hypertensive rats and in the renal damage associated with hypertension.

PS 18-16 Renal sodium handling in relation to plasma advanced glycation end products concentration in untreated subjects

Objective: previous experimental study showed that advanced glycation end products (AGEs) might enhance epithelial sodium channel in the renal cortical collecting duct cells. In the present study, we investigated renal sodium handling, as assessed by endogenous lithium clearance indexes, in relation to plasma AGEs concentration in subjects who did not take antihypertensive medication. Design and Method: The study subjects were previously never treated with or stopped antihypertensive medication for at least 2 weeks. We calculated fractional excretion of lithium and fractional distal reabsorption rate of sodium, as markers of proximal and distal sodium handling, respectively. Plasma AGEs concentration was measured by the enzyme-linked immunosorbent assay method and logarithmically transformed for statistical analysis. Results: The 1006 study participants (mean age 51.3 years) included 499 (49.6%) men and 40 (4.0%) diabetic patients. After adjustment for sex, age, body mass index, mean arterial pressure, pulse rate, current smoking and alcohol intake, plasma fasting glucose, serum triglycerides, serum total-to-high-density lipoprotein cholesterol ratio, plasma AGEs concentration (geometric mean [95% confidence interval] 13.4 [12.8 to 14.0] mg/mL) was significantly (P = 0.0007) associated with fractional lithium clearance (mean [±standard deviation] 21.7% ± 12.1%). For each 10-time increase in plasma AGEs concentration, fractional lithium clearance was 4.3% (absolute percentage change) lower. In tertile 3 of sodium urinary excretion, higher plasma AGEs concentration was also associated with lower fractional distal reabsorption rate of sodium (93.3% in tertile 3 vs. 95.1% in tertile 1 of plasma AGEs concentration, P = 0.002). Conclusions: Plasma AGEs concentration was positively associated with sodium renal reabsorption in the proximal tubule, as assessed by fractional lithium clearance. However, on the condition of high sodium intake, it was negatively associated with sodium reabsorption in the distal tubule, probably as a compensation of increased sodium intake and increased sodium reabsorption in the proximal tubule.

Ultrasound characterization of interface oscillation as a proxy for ventriculoperitoneal shunt function.

Hydrocephalus, where cerebrospinal fluid (CSF) production rate is greater than reabsorption rate, leads to impaired neurological function if left untreated. Ventriculoperitoneal shunts (VPS) are implanted in the brain ventricles to route CSF. VPS systems have a high failure rate, and failure symptoms resemble symptoms of common maladies. The current gold standard for shunt diagnosis, surgical intervention, poses high risk and requires an expensive procedure for patients. Current non-invasive methods lack proper insight to assist physicians. We propose a noninvasive method of characterizing the oscillation of the shunt's pressure-relief valve to assist physicians in shunt diagnosis. Brightness-mode and motion-mode ultrasound images can be used to determine fluid flow. Blockage in the system could be detected by observing the phase change of the ultrasound signal in different flow cases with or without perturbation. Future testing and implementation can allow for the use of this method in localizing and identifying the modality of failure.

Nonlinear optimization for a tumor invasion PDE model

In this work, we introduce a methodology to approximate unknown parameters that appear on a non-linear reaction–diffusion model of tumor invasion. These equations consider that tumor-induced alteration of micro-environmental pH furnishes a mechanism for cancer invasion. A coupled system reaction–diffusion explaining this model is given by three partial differential equations for the non-dimensional spatial distribution and temporal evolution of the density of normal tissue, the neoplastic tissue growth and the excess concentration of H $$^+$$ ions. The tumor model parameters have a corresponding biological meaning: the reabsorption rate, the destructive influence of H $$^+$$ ions in the healthy tissue, the growth rate of tumor tissue and the diffusion coefficient. We propose to solve the direct problem using the Finite Element Method (FEM) and minimize an appropriate functional including both the real data (obtained via in-vitro experiments and fluorescence ratio imaging microscopy) and the numerical solution. The gradient of the functional is computed by the adjoint method.

Screening for secondary hyperparathyroidism in preterm infants.

The major cause of osteopathy of prematurity is dietary phosphate deficiency, but secondary hyperparathyroidism caused by calcium deficiency or vitamin D deficiency is also important. Because parathyroid hormone (PTH) mobilizes calcium and phosphate from the bone, hyperparathyroidism worsens osteopathy of prematurity. In order to identify useful markers to screen for and diagnose hyperparathyroidism in preterm infants, we measured serum and urinary biochemical markers. Several biomarkers, including serum intact PTH (iPTH), were measured in urine and serum samples obtained from 95 preterm infants, and the relationship between serum iPTH and the other parameters was analyzed. Mean gestation was 33.2 ± 2.9 weeks, and mean birthweight was 1705 ± 402 g. Samples were collected around postnatal day 17.3 ± 7.4. Fourteen infants (14.7%) had iPTH >65 pg/mL. Cut-offs for serum alkaline phosphatase (ALP) and percent tubular reabsorption rate of phosphate (%TRP) were fixed at 1300 IU/L and 93%, respectively using receiver operating characteristic curves with iPTH cut-off of 65 pg/mL. Serum ALP was proven to be a good marker: ALP had a sensitivity of 78.6% and a specificity of 86.4%, while %TRP itself was not: %TRP had a sensitivity of 64.3% and a specificity of 58.0%. Combined measurement of serum ALP (>1300 IU/L) and %TRP (≤93%), however, had a specificity of 93.8% for detecting elevated iPTH. Measurement of serum ALP (>1300 IU/L) is considered as an effective screening method to detect hyperparathyroidism. In addition, combined assessment of ALP(>1300 IU/L) and %TRP(≤93%) is a good indicator of elevated iPTH in preterm infants.

Efficiency-Gain Product Mechanisms of ZnO-Based Nanorod Ultraviolet Photosensors

In this work, ZnO-based nanorod ultraviolet photosensors with large efficiency-gain product were obtained using the vapor cooling condensation method. To investigate the physical mechanism of the surface potential variation on the sidewall surface of the ZnO nanorods, the reabsorption rate of oxygen molecules, the Poisson equation, and the characteristic of current versus time under various oxygen ambiences were proposed to calculate the resulting surface potential variation. The results verified that both the oxygen reabsorption rate and the electron–hole recombination probability increased with an increasing oxygen concentration, and led to a decrease of the surface potential variation.

Balanço hídrico e excreção renal de metabólitos em ovinos alimentados com palma forrageira (Nopalea cochenillifera Salm Dyck)

Resumo Objetivou-se avaliar balanço hídrico e excreção renal de metabólitos em borregos sem raça definida, alimentados com diferentes quantidades de palma forrageira (Nopalea cochenillifera Salm Dyck), na forma in natura e em farelo. Foram utilizados 20 borregos, com peso vivo médio inicial de 20 Kg e foram distribuídos no delineamento inteiramente casualizado, sendo cinco tratamentos e quatro repetições. As dietas experimentais consistiram em uma dieta controle à base de feno de tífton, farelo de soja, suplemento mineral e calcário, os demais tratamentos visaram testar níveis diferentes de palma forrageira corrigida com ureia em duas formas: in natura e farelada e em dois níveis de substituição (50 e 100%) da matéria seca do feno de tífton. Amostras de sangue e urina foram coletadas para determinação de diferentes metabólitos e minerais e utilização de equações para obtenção dos índices de excreção urinária destes metabólitos, taxa de depuração endógena de creatinina e reabsorção de água livre de eletrólitos, além do registro de ingestão de água e volume de urina. A ingestão voluntária de água sofreu influência das dietas, sendo que os animais submetidos às dietas contendo farelo de palma e feno e farelo de palma foram superiores aos demais tratamentos. A ingestão de água via alimentos também sofreu influência da dieta, sendo maior nos animais que receberam palma in natura e farelo mais palma in natura. Com relação à ingestão total de água foi maior para os animais alimentados com dietas contendo palma in natura em relação aos demais tratamentos. As dietas experimentais influenciaram na excreção renal de metabólitos derivados purínicos e minerais, sem alterar a função renal. A presença da palma forrageira tanto na condição de farelo como in natura proporciona aumento do volume urinário sem alterar a função renal, além de que deve ser considerado como uma excelente estratégia alimentar no semiárido.

Aminoaciduria in the prediction of ifosfamide-induced tubulopathy after childhood cancer: a feasibility study.

BackgroundIfosfamide, an alkylating agent used widely in the treatment of childhood malignancy, can cause many side effects including a proximal tubulopathy. Studies suggest that aminoaciduria is seen most commonly of all the biochemical abnormalities of ifosfamide-induced tubulopathy. A recent systematic review has found a paucity of data regarding the value of early markers indicating clinically significant tubulopathy. We undertook a pilot study to determine the feasibility of examining whether patients can be risk-stratified on the basis of aminoaciduria for the development of future significant ifosfamide-induced tubulopathy, to allow the evolution of appropriate follow-up strategies. We also aimed to define accrual rates, costs and clinical demands for a future larger study.MethodsThis observational study recruited 21 patients from the Leeds Paediatric Oncology service. The medical notes of each patient were reviewed for demographic and clinical data. Simultaneous samples of blood and urine were obtained.ResultsThe investigations in the feasibility study were acceptable to patients and were minimally demanding on both clinical and laboratory staff. Financially, the cost per patient was minimal. This study was not powered to detect significant associations with TmP/GFR (ratio of renal tubular maximum reabsorption rate of phosphate to glomerular filtration rate), growth and electrolyte supplementation. However, all patients with minimal aminoaciduria (≤2 elevated urinary amino acids) had normal TmP/GFR and no need for electrolyte supplementation.ConclusionsThis pilot study has shown that a larger study is feasible and may provide clinically useful data to change current practice. This should aim to establish whether the number of abnormal amino acids or the degree of abnormality is most significant in predicting clinically significant proximal tubulopathy.

HOW TO RESECT A MEDIASTINAL PARATHYROID ADENOMA

A 60 year old woman had a history of fatigue and nephrolithiasis. Her serum calcium and parathyroid hormone levels were 11.45mg/dL (8.6-10.2) and 464,7pg/mL (15-65) respectively. Her tubular phosphate reabsorption rate was 56% while her chloride/phosphate ratio was 69,9. Her neck USG was normal. A parathyroid scintigraphy revealed a mass extending from lower pole of the left thyroid lobe to the mediastinal region with tracer retention. CT scan of neck and thorax verified the mass below the aortic arch, which was nodular, isodense with the thyroid gland and measured approximately 26x27 mm and detected another hypodense nodule within this bigger nodular mass measuring 13x11mm.

Research Highlight: Biomaterials in Otologic Surgery

Scaffolds are routinely used in the middle ear to provide support after tympanic membrane and ossicular chain reconstruction, to provide hemostasis or to promote tissue regeneration. Its permanence within a body cavity will depend upon several factors, such as the scaffold composition and the surgical procedure to be performed. Autologous grafts (i.e. temporalis fascia, cartilage, perichondrium) are considered the gold standard for tympanic membrane repair. Autologous grafts are associated with donor site morbidity, multiple incisions and increased surgical time. Recently, many alternatives to autologous grafts have become available including allografts (Allo Derm™), xenografts and synthetic materials. Scaffolds can also be characterized by their reabsorption rates and host reaction, and these differences can be exploited to serve different purposes during surgery. While some of these materials have been attributed healing enhancement properties, other materials have been associated with adverse effects, mainly aberrant scarring. A descriptive review of the most commonly used scaffolds in otologic surgery, current research highlights and future applications are discussed. //

Determination of the maximum rate of eccrine sweat glands’ ion reabsorption using the galvanic skin conductance to local sweat rate relationship.

The purpose of the present study was to develop and describe a simple method to evaluate the rate of ion reabsorption of eccrine sweat glands in human using the measurement of galvanic skin conductance (GSC) and local sweating rate (SR). This purpose was investigated by comparing the SR threshold for increasing GSC with following two criteria of sweat ion reabsorption in earlier studies such as (1) the SR threshold for increasing sweat ion was at approximately 0.2–0.5 mg/cm2/min and (2) exercise heat acclimation improved the sweat ion reabsorption ability and would increase the criteria 1. Seven healthy non-heat-acclimated male subjects received passive heat treatment both before and after 7 days of cycling in hot conditions (50% maximum oxygen uptake, 60 min/day, ambient temperature 32 °C, and 50% relative humidity). Subjects became partially heat-acclimated, as evidenced by the decreased end-exercise heart rate (p < 0.01), rate of perceived exhaustion (p < 0.01), and oesophageal temperature (p = 0.07), without alterations in whole body sweat loss, from the first to the last day of training. As hypothesized, we confirmed that the SR threshold for increasing GSC was near the predicted SR during passive heating before exercise heat acclimation, and increased significantly after training (0.19 ± 0.09–0.32 ± 0.10 mg/cm2/min, p < 0.05). The reproducibility of sweat ion reabsorption by the eccrine glands in the present study suggests that the relationship between GSC and SR can serve as a new index for assessing the maximum rate of sweat ion reabsorption of eccrine sweat glands in humans.

The rectal complex and Malpighian tubules of the cabbage looper (Trichoplusia ni): regional variations in Na+ and K+ transport and cation reabsorption by secondary cells.

In larvae of most Lepidoptera the distal ends of the Malpighian tubules are closely applied to the rectal epithelia and are ensheathed within the perinephric membrane, thus forming the rectal complex. The cryptonephric Malpighian tubules within the rectal complex are bathed in fluid within a functional compartment, the perinephric space, which is separate from the haemolymph. In this study, the scanning ion-selective electrode technique (SIET) was used to measure transport of Na(+) and K(+) across the rectal complex and across multiple regions of the Malpighian tubules of larvae of the cabbage looper Trichoplusia ni. Measurements were made in an intact preparation in which connections of the tubules upstream to the rectal complex and downstream to the urinary bladder and gut remained intact. SIET measurements revealed reabsorption of Na(+) and K(+) across the intact rectal complex and into the bath (haemolymph), with K(+) fluxes approximately twice as large as those of Na(+). Analyses of fluxes in larvae with empty guts, found in recently moulted larvae, versus those with full guts highlighted differences in the rates of K(+) or Na(+) transport within tubule regions that appeared morphologically homogeneous, such as the rectal lead. The distal rectal lead of larvae with empty guts reabsorbed K(+), whereas the same region secreted K(+) in tubules of larvae with full guts. SIET measurements of the ileac plexus also indicated a novel role for secondary (type II) cells in cation reabsorption. Secondary cells reabsorb K(+), whereas the adjacent principal (type I) cells secrete K(+). Na(+) is reabsorbed by both principal and secondary cells, but the rate of reabsorption by the secondary cells is approximately twice the rate in the adjacent principal cells.

Adjoint method for a tumor invasion PDE-constrained optimization problem in 2D using adaptive finite element method

In this paper we present a method for estimating an unknown parameter that appears in a two dimensional non-linear reaction–diffusion model of cancer invasion. This model considers that tumor-induced alteration of micro-environmental pH provides a mechanism for cancer invasion. A coupled system reaction–diffusion describing this model is given by three partial differential equations for the 2D non-dimensional spatial distribution and temporal evolution of the density of normal tissue, the neoplastic tissue growth and the excess H+ ion concentration. Each of the model parameters has a corresponding biological interpretation, for instance, the growth rate of neoplastic tissue, the diffusion coefficient, the re-absorption rate and the destructive influence of H+ ions in the healthy tissue.The parameter is estimated by solving a minimization problem, in which the objective function is defined in order to compare both the real data and the numerical solution of the cancer invasion model. The real data can be obtained by, for example, fluorescence ratio imaging microscopy.We apply a splitting strategy joint with the adaptive finite element method to numerically solve the model. The minimization problem (the inverse problem) is solved by using a gradient-based optimization method, in which the functional derivative is provided through an adjoint approach.

Changes in Kidney Functions during Middle-distance Triathlon in Male Athletes.

Strenuous exercise induces proteinuria which is related to the intensity of exercise. However, renal responses to each type of exercise during a middle-distance triathlon have not been reported. The present study, carried out on 7 healthy athletes, investigated renal function at rest and after each exercise of a half-triathlon race. Blood and urine samples were collected at rest and after each specific event. Protein excretion and renal clearances were determined on each sample. Compared with resting values, albuminuria was increased by a factor of 30 (p<0.05) after swimming but did not differ from the resting value after cycling and running (p>0.05). Rates of β2-microglobulin and retinol-binding protein excretion did not change throughout the triathlon (p>0.05). Glomerular filtration rate (expressed as creatinine clearance) remained stable after each exercise event, whereas tubular reabsorption rate (expressed as urea clearance) was reduced by 50, 40 and 65% after swimming, cycling and running, respectively, compared to pre-exercise values (p<0.05). Glomerular membrane permeability (expressed as albumin clearance) was significantly increased by the swimming event (13 times, p<0.05). These results suggest that middle-distance triathlon has a noticeable impact on the glomerular membrane permeability (albumin clearance) and elimination of protein waste (urea clearance) depending on exercise type.

Effect of Heat Acclimation on Lactate Excretion Rate and Sodium Ion Reabsorption Rate during Exercise

Sweat production requires two Na+/K+-ATPase energy dependent processes: (i) isoosmotic precursor sweat formation in the secretory coil, and (ii) sodium ion reabsorption along the distal sweat duct. Sweat lactate production has been hypothesized to reflect glycolytic ATP-resynthesis for both processes. Research suggests that heat acclimation does not alter sweat lactate concentration ([Lactate]). This is hard to rationalize considering heat acclimation is reported to increase sweat production and sodium ion reabsorption, which are the energy dependent processes. PURPOSE: (1) To determine the relationships during exercise between sweat rate (SR) and sodium ion reabsorption rate (NaRR), and exercise intensity and lactate excretion rate (LER), and (2) to determine whether heat acclimation affects these relationships. METHODS: Six subjects completed an eight-day heat acclimation protocol comprised of 90-minutes treadmill walking in an environmental chamber set at 39°C and 40% relative humidity. Subjects performed three, 30-minute exercise bouts at 30, 40, and 50% of their previously determined VO2max. Sweat rate was measured volumetrically during each bout on the flexor surface of the proximal half of the forearm. [Lactate] was measured and multiplied by forearm SR to calculate LER. Variables of interest were analyzed using non-parametric Friedman tests. RESULTS: LER, and ratios of LER to NaRR, and [Lactate] to SR were not significantly different between the 30, 40, and 50% workloads or between pre and post-heat acclimation based on 95% confidence intervals. Additionally, these relationships were not significantly different between the three workloads on the first or last day of heat acclimation except for LER to NaRR (p<0.05), which increased from 0.05 ± 0.02 to 0.08 ± 0.02 from 30 to 50% of VO2max. CONCLUSION: These data suggest that sweat gland ATPase activity does not increase as a function of exercise intensity, as demonstrated by LER and NaRR remaining relatively constant. Heat acclimation does not appear to affect these relationships.

Mathematical model of renal hemodynamic and structural consequences of increased proximal sodium reabsorption in early diabetic kidney disease

A mathematical model of integrative renal and cardiovascular function was used to evaluate the potential role of increased sodium reabsorption through sodium glucose cotransporters (SGLT) in the proximal tubule (PT) in driving hemodynamic and structural changes in the kidney in early diabetic kidney disease. First, the effect of glomerular pressure (GP) on adaptive hypertrophy of the glomerulus was modeled based on literature data from subtotal nephrectomy studies. Increased GP following nephrectomy was assumed to drive glomerular hypertrophy, increasing capillary surface area and thus the ultrafiltration coefficient (Kf). As Kf increased, GP returned to close to normal levels, and blood pressure and glomerular filtration rate (GFR) were maintained near pre‐nephrectomy levels. This effect of GP on hypertrophy was assumed to be a general adaptive mechanism, not specific to nephrectomy. Next, increased sodium reabsorption through SGLT resulting from high glucose levels in diabetes was modeled as an increase in the rate of PT sodium reabsorption. This resulted in an initial elevation in both GP and GFR through tubuloglomerular and neurohormonal feedback mechanisms. Over time, Kf increased while GP returned toward baseline. However, maximum hypertrophy occurred before GP completely normalized, indicating that SGLT‐driven PT sodium reabsorption can lead to sustained elevations in GP. This sustained increase in GP, as well as repeated spikes in glucose that elevate GP further, may cause cumulative damage to the glomerular membrane, leading to the progressive decline in GFR that follows the hyperfiltration phase in diabetic kidney disease. An interactive interface to the model is being developed and is available at qsp.engr.uga.edu:3838/CVRmod.

Glucose transporters: cellular links to hyperglycemia in insulin resistance and diabetes.

Abnormal expression and/or function of mammalian hexose transporters contribute to the hallmark hyperglycemia of diabetes. Due to different roles in glucose handling, various organ systems possess specific transporters that may be affected during the diabetic state. Diabetes has been associated with higher rates of intestinal glucose transport, paralleled by increased expression of both active and facilitative transporters and a shift in the location of transporters within the enterocyte, events that occur independent of intestinal hyperplasia and hyperglycemia. Peripheral tissues also exhibit deregulated glucose transport in the diabetic state, most notably defective translocation of transporters to the plasma membrane and reduced capacity to clear glucose from the bloodstream. Expression of renal active and facilitative glucose transporters increases as a result of diabetes, leading to elevated rates of glucose reabsorption. However, this may be a natural response designed to combat elevated blood glucose concentrations and not necessarily a direct effect of insulin deficiency. Functional foods and nutraceuticals, by modulation of glucose transporter activity, represent a potential dietary tool to aid in the management of hyperglycemia and diabetes.

Novel Nanostructured Zn-substituted Monetite Based Biomaterial for Bone Regeneration

A bone regeneration biomaterial must be biocompatible, osteoconductive and osteoinductive, and be gradually replaced by newly formed bone in the shorter time possible. Nanostructured materials, emulating bone composition and morphology, have shown great potential in bone repair because of their higher reactivity, faster reabsorption and improved biological behavior over microstructured materials. This work was aimed at developing a new biomaterial that meets the requirements for effective bone regeneration. Combination of elements with different solubility such as monetite, hydroxyapatite, amorphous calcium phosphate and silica gel, provided with the means to modulate the rate of material reabsorption of this novel biomaterial were Zn was found to be present as a partial substitution of Ca in the monetite lattice. The biomaterial was obtained by a hydraulic cementing reaction and was characterized by XRD, FTIR, NMR, chemical analysis, N2 adsorption porosimetry, Hg porosimetry, picnometry, SEM, TEM and evaluated in vitro and in vivo. Biomaterial showed a nanometric structure with a very high specific surface area (≈80 m2/g), high surface roughness and high intragranular porosity (50%) ranging from macro to nanopores. All of these are key features for a bone regeneration material. Solubility studies demonstrate the different solubility of its components and the release of Ca, P, Si and Zn. In vivo evaluation showed the effectiveness of the material to regenerate and to maintain 89 ± 9% of the volume of a critical size bone defect in sheep at 16 weeks. In the restored volume residual biomaterial was found to occupy 9 ± 5% of the space while newly formed trabeculae occupied 32 ± 6% of the space. The newly formed bone showed abundant vascularization and osteogenic activity. Biomaterial was estimated to have resorbed by 86 ± 7% with a reduction of 67 ± 8% in diameter and clear signs of cell-mediated resorption.