Search

Current literature shows that predictors of breastfeeding practice vary depending on women's ethnic background. This study examines predictors of planning to breastfeeding and of successful breastfeeding initiation and persistence, including the relationship to maternal depressive symptoms, social support, and mothers' perception of closeness to their infants, in a sample of low-income African American and Hispanic women in the urban Northeast. Detailed interviews were conducted in the early third trimester, at 2 weeks following delivery, and 3 months postpartum. Rates of intention to breastfeed were similar for Hispanic and African American women. Among Hispanics, greater identification with Hispanic culture was associated with increases in the likelihood of planning to breastfeed. A smaller proportion of Hispanic women persisted, especially among those women who supplemented with formula. For all women, we found no relationship between breastfeeding practice and either social support or depressive symptoms. Mothers' perception of closeness to their infants was greater among breastfeeders compared to bottlefeeders. [ABSTRACT FROM AUTHOR]

OBJECTIVE: We evaluated whether adding basal insulin to metformin in adults with early type 2 diabetes mellitus (T2DM) would increase emotional distress relative to other treatments. RESEARCH DESIGN AND METHODS: The Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE) of adults with T2DM of <10 years' duration, HbA1c 6.8–8.5%, and taking metformin monotherapy randomly assigned participants to add insulin glargine U-100, sulfonylurea glimepiride, the glucagon-like peptide-1 receptor agonist liraglutide, or the dipeptidyl peptidase 4 inhibitor sitagliptin. The Emotional Distress Substudy enrolled 1,739 GRADE participants (mean [SD] age 58.0 [10.2] years, 32% female, 56% non-Hispanic White, 18% non-Hispanic Black, 17% Hispanic) and assessed diabetes distress and depressive symptoms every 6 months. Analyses examined differences at 1 year and over the 3-year follow-up. RESULTS: Across treatments, diabetes distress (−0.24, P < 0.0001) and depressive symptoms (−0.67, P < 0.0001) decreased over 1 year. Diabetes distress was lower at 1 year for the glargine group than for the other groups combined (−0.10, P = 0.002). Diabetes distress was also lower for liraglutide than for glimepiride or sitagliptin (−0.10, P = 0.008). Over the 3-year follow-up, there were no significant group differences in total diabetes distress; interpersonal diabetes distress remained lower for those assigned to liraglutide. No significant differences were observed for depressive symptoms. CONCLUSIONS: Contrary to expectations, this randomized trial found no evidence for a deleterious effect of basal insulin on emotional distress. Glargine lowered diabetes distress modestly at 1 year rather than increasing it. Liraglutide also reduced diabetes distress at 1 year. Results can inform treatment decisions for adults with early T2DM. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To describe the individual and joint associations of baseline factors with glycemia, and also with differential effectiveness of medications added to metformin. RESEARCH DESIGN AND METHODS: Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE) participants (with type 2 diabetes diagnosed for <10 years, on metformin, and with HbA1c 6.8–8.5%; N = 5,047) were randomly assigned to a basal insulin (glargine), sulfonylurea (glimepiride), glucagon-like peptide 1 agonist (liraglutide), or dipeptidyl peptidase 4 inhibitor (sitagliptin). The glycemic outcome was HbA1c ≥7.0%, subsequently confirmed. Univariate and multivariate regression and classification and regression tree (CART) analyses were used to assess the association of baseline factors with the glycemic outcome at years 1 and 4. RESULTS: In univariate analyses at baseline, younger age (<58 years), Hispanic ethnicity, higher HbA1c, fasting glucose, and triglyceride levels, lower insulin secretion, and relatively greater insulin resistance were associated with the glycemic outcome at years 1 and/or 4. No factors were associated with differential effectiveness of the medications by year 4. In multivariate analyses, treatment group, younger age, and higher baseline HbA1c and fasting glucose were jointly associated with the glycemic outcome by year 4. The superiority of glargine and liraglutide at year 4 persisted after multiple baseline factors were controlled for. CART analyses indicated that failure to maintain HbA1c <7% by year 4 was more likely for younger participants and those with baseline HbA1c ≥7.4%. CONCLUSIONS: Several baseline factors were associated with the glycemic outcome but not with differential effectiveness of the four medications. Failure to maintain HbA1c <7% was largely driven by younger age and higher HbA1c at baseline. Factors that predict earlier glycemic deterioration could help in targeting patients for more aggressive management. [ABSTRACT FROM AUTHOR]

OBJECTIVE: We examined longitudinal associations between emotional distress (specifically, depressive symptoms and diabetes distress) and medication adherence in Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE), a large randomized controlled trial comparing four glucose-lowering medications added to metformin in adults with relatively recent-onset type 2 diabetes mellitus (T2DM). RESEARCH DESIGN AND METHODS: The Emotional Distress Substudy assessed medication adherence, depressive symptoms, and diabetes distress in 1,739 GRADE participants via self-completed questionnaires administered biannually up to 3 years. We examined baseline depressive symptoms and diabetes distress as predictors of medication adherence over 36 months. Bidirectional visit-to-visit relationships were also examined. Treatment satisfaction, beliefs about medication, diabetes care self-efficacy, and perceived control over diabetes were evaluated as mediators of longitudinal associations. RESULTS: At baseline, mean ± SD age of participants (56% of whom were White, 17% Hispanic/Latino, 18% Black, and 66% male) was 58.0 ± 10.2 years, diabetes duration 4.2 ± 2.8 years, HbA1c 7.5% ± 0.5%, and medication adherence 89.9% ± 11.1%. Higher baseline depressive symptoms and diabetes distress were independently associated with lower adherence over 36 months (P < 0.001). Higher depressive symptoms and diabetes distress at one visit predicted lower adherence at the subsequent 6-month visit (P < 0.0001) but not vice versa. Treatment assignment did not moderate relationships. Patient-reported concerns about diabetes medications mediated the largest percentage (11.9%–15.5%) of the longitudinal link between emotional distress and adherence. CONCLUSIONS: Depressive symptoms and diabetes distress both predict lower adherence to glucose-lowering medications over time among adults with T2DM. Addressing emotional distress and concerns about anticipated negative effects of taking these treatments may be important to support diabetes treatment adherence. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Diabetes is associated with reduced health-related quality of life (HRQoL). Information on the relationship between HRQoL and glucose-lowering medications in recently diagnosed type 2 diabetes (T2D) is limited. We assessed changes in HRQoL in participants with T2D receiving metformin plus one of four glucose-lowering medications in Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE). RESEARCH DESIGN AND METHODS: A total of 5,047 participants, baseline mean age 57 years, with <10 years T2D duration and glycated hemoglobin level 6.8–8.5% and taking metformin monotherapy, were randomly assigned to glargine, glimepiride, liraglutide, or sitagliptin. HRQoL was evaluated at baseline for 4,885 participants, and at years 1, 2, and 3, with use of the self-administered version of the Quality of Well-being Scale (QWB-SA) and SF-36 physical (PCS) and mental (MCS) component summary scales. Linear models were used to analyze changes in HRQoL over time in intention-to-treat analyses. RESULTS: None of the medications worsened HRQoL. There were no differences in QWB-SA or MCS by treatment group at any time point. PCS scores improved with liraglutide versus other groups at year 1 only. Greater weight loss during year 1 explained half the improvement in PCS scores with liraglutide versus glargine and glimepiride. Liraglutide participants in the upper tertile of baseline BMI showed the greatest improvement in PCS scores at year 1. CONCLUSIONS: Adding liraglutide to metformin in participants within 10 years of T2D diagnosis showed improvement in the SF-36 PCS in comparisons with the other medications at 1 year, which was no longer significant at years 2 and 3. Improvement was related to weight loss and baseline BMI. [ABSTRACT FROM AUTHOR]

OBJECTIVE: In Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE) (5,047 participants, mean follow-up 5.0 years), differences in glycemic control were demonstrated over time among four randomized therapies added to metformin. Weight gain and hypoglycemia are also important outcomes for people with type 2 diabetes. We compared the effects of the four randomized GRADE medications on a composite outcome incorporating glycemic deterioration, weight gain, and hypoglycemia. RESEARCH DESIGN AND METHODS: The composite outcome was time to first occurrence of any of the following: HbA1c >7.5%, confirmed; ≥5% weight gain; or severe or recurrent nonsevere hypoglycemia. Secondary analyses included examination of individual components of the composite outcome, subgroup effects and potential mediators, and treatment satisfaction. Cumulative incidence was estimated with the Kaplan-Meier estimator. Cox proportional hazards models were used to assess pairwise group differences in risk of an outcome. RESULTS: Risk of reaching the composite outcome (events per 100 participants per treatment year [PTYs]) was lowest with liraglutide (19 per 100 PTYs) followed by sitagliptin (26 per 100 PTYs), glargine (29 per 100 PTYs), and glimepiride (40 per 100 PTYs); all pairwise comparisons were statistically significant. The order was the same for risk of weight gain and hypoglycemia, but risk of glycemic deterioration was lowest with glargine, followed by liraglutide, glimepiride, and sitagliptin. No significant heterogeneity in risk of composite outcome was detected across prespecified covariates. Participants who reached the composite outcome had modestly but significantly lower treatment satisfaction. CONCLUSIONS: Among participants treated with common second-line drug classes for type 2 diabetes, the liraglutide group had the lowest and glimepiride the highest risk of reaching a composite outcome encompassing glycemic deterioration, weight gain, and hypoglycemia. These findings may inform decision-making regarding type 2 diabetes therapy. [ABSTRACT FROM AUTHOR]

OBJECTIVE: We report mortality outcomes in the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE) among people with type 2 diabetes diagnosed within 10 years and no recent history of cardiovascular events or cancer. RESEARCH DESIGN AND METHODS: Overall mortality rates and major causes of death were assessed over an average of 5 years of follow-up. Cause of death was adjudicated centrally by a committee masked to treatment assignment. We examined baseline covariates and the 10-year Framingham Risk Score for associations. RESULTS: Mortality rate was low (0.59 per 100 participant-years). Participants who died during follow-up were likely to be older, be male, have a history of hypertension, have a history of smoking, and have moderate albuminuria. The two most common underlying causes of death were "cardiovascular-cause" (a composite of underlying causes) (38.6%) and cancer (26.8%). There were no differences by treatment group. CONCLUSIONS: Among people with diabetes of relatively short duration, cause of death was varied. Attention to health risks beyond cardiovascular diseases is warranted. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To compare the long-term effects of glucose-lowering medications (insulin glargine U-100, glimepiride, liraglutide, and sitagliptin) when added to metformin on insulin sensitivity and β-cell function. RESEARCH DESIGN AND METHODS: In the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE) cohort with type 2 diabetes (n = 4,801), HOMA2 was used to estimate insulin sensitivity (HOMA2-%S) and fasting β-cell function (HOMA2-%B) at baseline and 1, 3, and 5 years on treatment. Oral glucose tolerance test β-cell responses (C-peptide index [CPI] and total C-peptide response [incremental C-peptide/incremental glucose over 120 min]) were evaluated at the same time points. These responses adjusted for HOMA2-%S in regression analysis provided estimates of β-cell function. RESULTS: HOMA2-%S increased from baseline to year 1 with glargine and remained stable thereafter, while it did not change from baseline in the other treatment groups. HOMA2-%B and C-peptide responses were increased to variable degrees at year 1 in all groups but then declined progressively over time. At year 5, CPI was similar between liraglutide and sitagliptin, and higher for both than for glargine and glimepiride [0.80, 0.87, 0.74, and 0.64 (nmol/L)/(mg/dL) * 100, respectively; P < 0.001], while the total C-peptide response was greatest with liraglutide, followed in descending order by sitagliptin, glargine, and glimepiride [1.54, 1.25, 1.02, and 0.87 (nmol/L)/(mg/dL) * 100, respectively, P < 0.001]. After adjustment for HOMA2-%S to obtain an estimate of β-cell function, the nature of the change in β-cell responses reflected those in β-cell function. CONCLUSIONS: The differential long-term effects on insulin sensitivity and β-cell function of four different glucose-lowering medications when added to metformin highlight the importance of the loss of β-cell function in the progression of type 2 diabetes. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To compare the effects of insulin sensitivity and β-cell function over time on HbA1c and durability of glycemic control in response to dual therapy. RESEARCH DESIGN AND METHODS: GRADE participants were randomized to glimepiride (n = 1,254), liraglutide (n = 1,262), or sitagliptin (n = 1,268) added to baseline metformin and followed for mean ± SD 5.0 ± 1.3 years, with HbA1c assessed quarterly and oral glucose tolerance tests at baseline, 1, 3, and 5 years. We related time-varying insulin sensitivity (HOMA 2 of insulin sensitivity [HOMA2-%S]) and early (0–30 min) and total (0–120 min) C-peptide (CP) responses to changes in HbA1c and glycemic failure (primary outcome HbA1c ≥7% [53 mmol/mol] and secondary outcome HbA1c >7.5% [58 mmol/mol]) and examined differential treatment responses. RESULTS: Higher HOMA2-%S was associated with greater initial HbA1c lowering (3 months) but not subsequent HbA1c rise. Greater CP responses were associated with a greater initial treatment response and slower subsequent HbA1c rise. Higher HOMA2-%S and CP responses were each associated with lower risk of primary and secondary outcomes. These associations differed by treatment. In the sitagliptin group, HOMA2-%S and CP responses had greater impact on initial HbA1c reduction (test of heterogeneity, P = 0.009 HOMA2-%S, P = 0.018 early CP, P = 0.001 total CP) and risk of primary outcome (P = 0.005 HOMA2-%S, P = 0.11 early CP, P = 0.025 total CP) but lesser impact on HbA1c rise (P = 0.175 HOMA2-%S, P = 0.006 early CP, P < 0.001 total CP) in comparisons with the glimepiride and liraglutide groups. There were no differential treatment effects on secondary outcome. CONCLUSIONS: Insulin sensitivity and β-cell function affected treatment outcomes irrespective of drug assignment, with greater impact in the sitagliptin group on initial (short-term) HbA1c response in comparison with the glimepiride and liraglutide groups. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To describe rescue insulin use and associated factors in the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE). RESEARCH DESIGN AND METHODS: GRADE participants (type 2 diabetes duration <10 years, baseline A1C 6.8%–8.5% on metformin monotherapy, N = 5,047) were randomly assigned to insulin glargine U-100, glimepiride, liraglutide, or sitagliptin and followed quarterly for a mean of 5 years. Rescue insulin (glargine or aspart) was to be started within 6 weeks of A1C >7.5%, confirmed. Reasons for delaying rescue insulin were reported by staff-completed survey. RESULTS: Nearly one-half of GRADE participants (N = 2,387 [47.3%]) met the threshold for rescue insulin. Among participants assigned to glimepiride, liraglutide, or sitagliptin, rescue glargine was added by 69% (39% within 6 weeks). Rescue aspart was added by 44% of glargine-assigned participants (19% within 6 weeks) and by 30% of non-glargine-assigned participants (14% within 6 weeks). Higher A1C values were associated with adding rescue insulin. Intention to change health behaviors (diet/lifestyle, adherence to current treatment) and not wanting to take insulin were among the most common reasons reported for not adding rescue insulin within 6 weeks. CONCLUSIONS: Proportionately, rescue glargine, when required, was more often used than rescue aspart, and higher A1C values were associated with greater rescue insulin use. Wanting to use noninsulin strategies to improve glycemia was commonly reported, although multiple factors likely contributed to not using rescue insulin. These findings highlight the persistent challenge of intensifying type 2 diabetes treatment with insulin, even in a clinical trial. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To evaluate whether baseline levels of depressive symptoms and diabetes-specific distress are associated with glycemic control in Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE), a large randomized controlled trial comparing the metabolic effects of four common glucose-lowering medications when combined with metformin in individuals with type 2 diabetes mellitus (T2DM). RESEARCH DESIGN AND METHODS: The primary and secondary outcomes were defined as an HbA1c value ≥7%, subsequently confirmed, and an HbA1c value >7.5%, subsequently confirmed, respectively. Separate Cox proportional hazards models assessed the association between baseline levels of each exposure of interest (depressive symptoms measured with the eight-item Patient Health Questionnaire and diabetes distress measured with the Diabetes Distress Scale) and the subsequent risk of metabolic outcomes. RESULTS: This substudy included 1,739 participants (56% of whom were non-Hispanic White, 18% non-Hispanic Black, 17% Hispanic, and 68% male; mean [SD] age 58.0 [10.2] years, diabetes duration 4.2 [2.8] years, and HbA1c 7.5% [0.48%]). A total of 1,157 participants reached the primary outcome, with time to event of 2.1 years on average, while 738 participants reached the secondary outcome at 3 years on average. With adjustment for sex, race/ethnicity, treatment group, baseline age, duration of T2DM, BMI, and HbA1c, there were no significant associations between the depressive symptoms or diabetes distress and the subsequent risk of the primary or secondary outcomes. CONCLUSIONS: The current findings suggest that, at least for individuals with diabetes of relatively short duration, baseline levels of emotional distress are not associated with glycemic control over time. [ABSTRACT FROM AUTHOR]

The most prominent structural components in bone are collagen and mineral. However, bone additionally contains a substantial amount of noncollagenous proteins (most notably of the SIBLING protein family), some of which may act as cohesive/adhesive “binders” for the composite hybrid collagen/mineral scaffolding, whether in the bulk phase of bone, or at its interfaces. One such noncollagenous protein – osteopontin (OPN) – appears to be critical to the deformability and fracture toughness of bone. In the present study, we used a reconstructed synthetic mineral-OPN-mineral interface, and a biogenic (natural tooth dentin) mineral/collagen-OPN-mineral/collagen interface, to measure the fracture toughness of OPN on mineralized substrates. We used this system to test the hypothesis that OPN crosslinking by the enzyme tissue transglutaminase 2 (TG2) that is found in bone enhances interfacial adhesion to increase the fracture toughness of bone. For this, we prepared double-cantilever beam substrates of synthetic pure hydroxyapatite mineral, and of narwhal dentin, and directly apposed them to one another under different intervening OPN/crosslinking conditions, and fracture toughness was tested using a miniaturized loading stage. The work-of-fracture of the OPN interface was measured for different OPN formulations (monomer vs. polymer), crosslinking states, and substrate composition. Noncrosslinked OPN provided negligible adhesion on pure hydroxyapatite, whereas OPN crosslinking (by the chemical crosslinker glutaraldehyde, and TG2 enzyme) provided strong interfacial adhesion for both hydroxyapatite and dentin using monomeric and polymeric OPN. Pre-coating of the substrate beams with monomeric OPN further improved the adhesive performance of the samples, likely by allowing effective binding of this nascent OPN form to mineral/matrix components, with this pre-attachment providing a protein layer for additional crosslinking between the substrates. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Differences in type 2 diabetes phenotype by age are described, but it is not known whether these differences are seen in a more uniformly defined adult population at a common early stage of care. We sought to characterize age-related clinical and metabolic characteristics of adults with type 2 diabetes on metformin monotherapy, prior to treatment intensification. RESEARCH DESIGN AND METHODS: In the Glycemia Reduction Approaches in Diabetes: A Comparative Effectiveness Study (GRADE), participants were enrolled who had type 2 diabetes duration <10 years, had HbA1c 6.8–8.5%, and were on metformin monotherapy. Participants were randomly assigned to one of four additional glucose-lowering medications. We compared baseline clinical and metabolic characteristics across age categories (<45, 45 to <55, 55 to <65, and ≥65 years) using ANOVA and Pearson χ2 tests. RESULTS: Within the GRADE cohort (n = 5,047), we observed significant differences by age, with younger adults having greater racial diversity, fewer medications for common comorbidities, lower prevalence of CVD, higher weight and BMI, and more pronounced hyperglycemia and diabetic dyslipidemia and with metabolic profile indicating lower insulin sensitivity (inverse fasting insulin [1/(fasting insulin)], HOMA of steady-state insulin sensitivity, Matsuda index) and inadequate β-cell response (oral disposition index) (P < 0.05 across age categories). CONCLUSIONS: Clinical and metabolic characteristics of type 2 diabetes differ by age within the GRADE cohort. Younger adults exhibit more prominent obesity-related characteristics, including higher obesity levels and lower insulin sensitivity and β-cell compensation. Given the increasing burden of type 2 diabetes and complications, particularly among younger populations, these age-related distinctions may inform risk factor management approaches and treatment priorities. Further study will determine whether age-related differences impact response to therapy. [ABSTRACT FROM AUTHOR]

Abstract: For skeletal mineralization, the avian embryo mobilizes calcium from its calcitic eggshell. This occurs through dissolution of specific interior regions of the shell in a process that also weakens the shell to allow hatching. Here, we have examined eggshell ultrastructure during dissolution occurring between laying of a fertilized egg (with incubation) and hatching of the chick (Gallus gallus). We have focused on changes in shell mammillae where the majority of dissolution takes place. Using scanning electron microscopy, we describe differences in matrix–mineral structure and relationships not observed in unfertilized eggs (unresorbed eggshell). We document changes in the calcium reserve body – an essential sub-compartment of mammillae – consistent with it being an early, primary source of calcium essential for embryonic skeletal growth. Dissolution events occurring in the calcium reserve sac and in the base plate of the calcium reserve body, and similar changes in surrounding bulk mammillae structure, all correlate with advancing skeletal embryonic calcification. The changes in mammillae sub-structures can generally be characterized as mineral dissolutions revealing fine surface topographies on remaining mineral surfaces and the exposure of an extensive, intracrystalline (occluded) organic matrix network. We propose that this mineral-occluded network regulates how shell mineral is dissolved by providing dissolution channels facilitating calcium release for the embryonic skeleton. [Copyright &y& Elsevier]

Abstract: In trabecular bone fracture repair in vivo, osteogenesis occurs through endochondral ossification under hypoxic conditions, or through woven bone deposition in the vicinity of blood vessels. In vitro osteogenesis assays are routinely used to test osteoblastic responses to drugs, hormones, and biomaterials for bone and cartilage repair applications. These cell culture models recapitulate events that occur in woven bone synthesis, and are carried out using primary osteoblasts, osteoblast precursors such as bone marrow-derived mesenchymal stromal cells (BMSCs), or various osteoblast cell lines. With time in culture, cell differentiation is typically assessed by examining levels of alkaline phosphatase activity (an early osteoblast marker) and by evaluating the assembly of a collagen (type I)-containing fibrillar extracellular matrix that mineralizes. In this review, we have made a comparative analysis of published osteogenic assays using calvarial cells, calvaria-derived cell lines, and bone marrow stromal cells. In all of these cell types, alkaline phosphatase activity shows similar progression over time using a variety of osteogenic and mineralizing media conditions; however, levels of alkaline phosphatase activity are not proportional to observed mineralization levels. [Copyright &y& Elsevier]

Bone cell culture systems are essential tools for the study of the molecular mechanisms regulating extracellular matrix mineralization. MC3T3-E1 osteoblast cell cultures are the most commonly used in vitro model of bone matrix mineralization. Despite the widespread use of this cell line to study biomineralization, there is as yet no systematic characterization of the mineral phase produced in these cultures. Here we provide a comprehensive, multi-technique biophysical characterization of this cell culture mineral and extracellular matrix, and compare it to mouse bone and synthetic apatite mineral standards, to determine the suitability of MC3T3-E1 cultures for biomineralization studies. Elemental compositional analysis by energy-dispersive X-ray spectroscopy (EDS) showed calcium and phosphorus, and trace amounts of sodium and magnesium, in both biological samples. X-ray diffraction (XRD) on resin-embedded intact cultures demonstrated that similar to 1-month-old mouse bone, apatite crystals grew with preferential orientations along the (100), (101) and (111) mineral planes indicative of guided biogenic growth as opposed to dystrophic calcification. XRD of crystals isolated from the cultures revealed that the mineral phase was poorly crystalline hydroxyapatite with 10 to 20 nm-sized nanocrystallites. Consistent with the XRD observations, electron diffraction patterns indicated that culture mineral had low crystallinity typical of biological apatites. Fourier-transform infrared spectroscopy (FTIR) confirmed apatitic carbonate and phosphate within the biological samples. With all techniques utilized, cell culture mineral and mouse bone mineral were remarkably similar. Scanning (SEM) and transmission (TEM) electron microscopy showed that the cultures had a dense fibrillar collagen matrix with small, 100 nm-sized, collagen fibril-associated mineralization foci which coalesced to form larger mineral aggregates, and where mineralized sites showed the accumulation of the mineral-binding protein osteopontin. Light microscopy, confocal microscopy and three-dimensional reconstructions showed that some cells had dendritic processes and became embedded within the mineral in an osteocyte-like manner. In conclusion, we have documented characteristics of the mineral and matrix phases of MC3T3-E1 osteoblast cultures, and have determined that the structural and compositional properties of the mineral are highly similar to that of mouse bone. [ABSTRACT FROM AUTHOR]

Abstract: We investigated matrix–mineral relationships in the avian eggshell at the ultrastructural level using scanning and transmission electron microscopy combined with surface-etching techniques to selectively increase topography at the matrix–mineral interface. Moreover, we investigated the distribution of osteopontin (OPN) in the eggshell by colloidal-gold immunolabeling for OPN, and assessed the effects of this protein on calcite crystal growth in vitro. An extensive organic matrix network was observed within the calcitic structure of the eggshell that showed variable, region-specific organization including lamellar sheets of matrix, interconnected fine filamentous threads, thin film-like surface coatings of proteins, granules, vesicles, and isolated proteins residing preferentially on internal {104} crystallographic faces of fractured eggshell calcite. With the exception of the vesicles and granules, these matrix structures all were immunolabeled for OPN, as were occluded proteins on the {104} calcite faces. OPN inhibited calcite growth in vitro at the {104} crystallographic faces producing altered crystal morphology and circular growth step topography at the crystal surface resembling spherical voids in mineral continuity prominent in the palisades region of the eggshell. In conclusion, calcite-occluded and interfacial proteins such as OPN likely regulate eggshell growth by inhibiting calcite growth at specific crystallographic faces and compartmental boundaries to create a biomineralized architecture whose structure provides for the properties and functions of the eggshell. [Copyright &y& Elsevier]

In human voice production (phonation), linear small-amplitude vocal fold oscillation occurs only under restricted conditions. Physiologically, phonation more often involves large-amplitude oscillation associated with tissue stresses and strains beyond their linear viscoelastic limits, particularly in the lamina propria extracellular matrix (ECM). This study reports some preliminary measurements of tissue deformation and failure response of the vocal fold ECM under large-strain shear. The primary goal was to formulate and test a novel constitutive model for vocal fold tissue failure, based on a standard-linear cohesive-zone (SL-CZ) approach. Tissue specimens of the sheep vocal fold mucosa were subjected to torsional deformation in vitro, at constant strain rates corresponding to twist rates of 0.01, 0.1, and 1.0 rad/s. The vocal fold ECM demonstrated nonlinear stress-strain and rate-dependent failure response with a failure strain as low as 0.40 rad. A finiteelement implementation of the SL-CZ model was capable of capturing the rate dependence in these preliminary data, demonstrating the model's potential for describing tissue failure. Further studies with additional tissue specimens and model improvements are needed to better understand vocal fold tissue failure. [ABSTRACT FROM AUTHOR]

Biomineralization is remarkably diverse and provides myriad functions across many organismal systems. Biomineralization processes typically produce hardened, hierarchically organized structures usually having nanostructured mineral assemblies that are formed through inorganic-organic (usually protein) interactions. Calcium‑carbonate biomineral predominates in structures of small invertebrate organisms abundant in marine environments, particularly in shells (remarkably it is also found in the inner ear otoconia of vertebrates), whereas calcium-phosphate biomineral predominates in the skeletons and dentitions of both marine and terrestrial vertebrates, including humans. Reconciliation of the interplay between organic moieties and inorganic crystals in bones and teeth is a cornerstone of biomineralization research. Key molecular determinants of skeletal and dental mineralization have been identified in health and disease, and in pathologic ectopic calcification, ranging from small molecules such as pyrophosphate, to small membrane-bounded matrix vesicles shed from cells, and to noncollagenous extracellular matrix proteins such as osteopontin and their derived bioactive peptides. Beyond partly knowing the regulatory role of the direct actions of inhibitors on vertebrate mineralization, more recently the importance of their enzymatic removal from the extracellular matrix has become increasingly understood. Great progress has been made in deciphering the relationship between mineralization inhibitors and the enzymes that degrade them, and how adverse changes in this physiologic pathway (such as gene mutations causing disease) result in mineralization defects. Two examples of this are rare skeletal diseases having osteomalacia/odontomalacia (soft bones and teeth) – namely hypophosphatasia (HPP) and X-linked hypophosphatemia (XLH) – where inactivating mutations occur in the gene for the enzymes tissue-nonspecific alkaline phosphatase (TNAP, TNSALP, ALPL) and phosphate-regulating endopeptidase homolog X-linked (PHEX), respectively. Here, we review and provide a concept for how existing and new information now comes together to describe the dual nature of regulation of mineralization – through systemic mineral ion homeostasis involving circulating factors, coupled with molecular determinants operating at the local level in the extracellular matrix. For the local mineralization events in the extracellular matrix, we present a focused concept in skeletal mineralization biology called the Stenciling Principle – a principle (building upon seminal work by Neuman and Fleisch) describing how the action of enzymes to remove tissue-resident inhibitors defines with precision the location and progression of mineralization. Unlabelled Image • A review on extracellular matrix mineralization in the skeleton. • Extracellular matrix composition and structure of bone is described. • Mechanisms of mineralization in bone are described. • TNAP enzyme degrades mineralization inhibitor PP i (reference to hypophosphatasia). • PHEX enzyme degrades mineralization inhibitor OPN (reference to X-linked hypophosphatemia). [ABSTRACT FROM AUTHOR]