Physicochemical features of ultra-high viscosity alginates

The physicochemical characteristics of the ultra-high viscosity and highly biocompatible alginates extracted from Lessonia nigrescens (UHV_N) and Lessonia trabeculata (UHV_T) were analyzed. Fluorescence and ¹H NMR spectroscopies, viscometry, and multi-angle light scattering (MALS) were used for elucidation of the chemical structure, molar mass, and coil size. The sequential structures from NMR spectroscopy showed high guluronate content for UHV_T, but low for UHV_N. Intrinsic viscosity [η] measurements exhibited unusual high values (up to 2750 mL/g), whereas [η] of a commercial alginate was only about 970 mL/g. MALS batch measurements of the UHV-alginates yielded ultra-high values of the weight average molar mass (M_w up to 1.1 × 10⁶ g/mol) and of the z-average gyration radius (〈R_G〉_z up to191 nm). The M_w and 〈R_G〉_z distributions of UHV-alginates and of ultrasonically degraded fractions were determined using size exclusion chromatography combined with MALS and asymmetrical flow-field-flow fractionation. The M_w dependency of [η] and 〈R_G〉_z could be described by [η] = 0.059 ×  and 〈R_G〉_z = 0.103 × . (UHV_N: x = 0.52; UHV_T: x = 0.53) indicating that the monomer composition has no effect on coil expansion. Therefore, the equations can be used to calculate M_w and 〈R_G〉_z values of UHV_T- and UHV_N-alginate mixtures as used in immunoisolation. Furthermore, the simple and inexpensive capillary viscometry can be used for real-time validation of the extraction and purification process of the UHV-alginates.     

Behavior of red king crab larvae: Phototaxis,geotaxis and rheotaxis

Zoeae of Paralithodes camtschatica were positively phototactic to white light intensities above 1 × 10¹³ q cm^?2 s^?1. Negative phototaxis occurred at low (1 × 10¹² q cm^?2 s^?1), but not high intensities (2.2 × 10¹⁶q cm^?2 s^?1). Phototactic response was directly related to light intensity. Zoeae also responded to red, green and blue light. Zoeae were negatively geotactic, but geotaxis was dominated by phototaxis. Horizontal swimming speed of stage 1 zoeae <4 d old was 2.4 ± 0.1 (SE) cms^?1 and decreased to 1.7 ± 0.1 cm s^?1 in older zoeae (P <0.01). Horizontal swimming speed of stage 2 zoeae was not significantly different from ≥4 d old stage 1 zoeae. Vertical swimming speed, 1.6 ± 0.1 cm s^?1, and sinking rate, 0.7 ± 0.1 cm s^?1, did not change with ontogeny. King crab zoeae were positively rheotactic and maintained position in horizontal currents less than 1.4 cm s^?1. Starvation reduced swimming and sinking rates and phototactic response.     

Vitamin D deficiency and whole-body and femur bone mass relative to weight in healthy newborns

Background

Vitamin D is required for normal bone growth and mineralization. We sought to determine whether vitamin D deficiency at birth is associated with bone mineral content (BMC) of Canadian infants.

Methods

We measured plasma 25-hydroxyvitamin D [25(OH)D] as an indicator of vitamin D status in 50 healthy mothers and their newborn term infants. In the infants, anthropometry and lumbar, femur and whole-body BMC were measured within 15 days of delivery. Mothers completed a 24-hour recall and 3-day food and supplement record. We categorized the vitamin D status of mothers and infants as deficient or adequate and then compared infant bone mass in these groups using nonpaired t tests. Maternal and infant variables known to be related to bone mass were tested for their relation to BMC using backward stepwise regression analysis.

Results

Twenty-three (46%) of the mothers and 18 (36%) of the infants had a plasma 25(OH)D concentration consistent with deficiency. Infants who were vitamin D deficient were larger at birth and follow-up. Absolute lumbar spine, femur and whole-body BMC were not different between infants with adequate vitamin D and those who were deficient, despite larger body size in the latter group. In the regression analysis, higher whole-body BMC was associated with greater gestational age and weight at birth as well as higher infant plasma 25(OH)D.

Conclusion

A high rate of vitamin D deficiency was observed among women and their newborn infants. Among infants, vitamin D deficiency was associated with greater weight and length but lower bone mass relative to body weight. Whether a return to normal vitamin D status, achieved through supplements or fortified infant formula, can reset the trajectory for acquisition of BMC requires investigation.In northern countries, endogenous synthesis of vitamin D is thought to be limited to the months of April through September.¹ During the winter months, dietary or supplemental vitamin D intake at values similar to the recommended intake of 200 IU/day (5 μg/day) is not enough to prevent vitamin D deficiency in young women.² Vitamin D deficiency is well documented among Canadian women^3,4,5,6,7 and young children^4,8,9,10,11 and has been reported at levels as high as 76% of women and 43% of children (3–24 months) in northern Manitoba⁴ and 48.4%–88.6% of Aboriginal women and 15.1%–63.5% of non-Aboriginal women in the Inuvik zone of the former Northwest Territories.³ Vitamin D dependent rickets in children and osteomalacia in adults are the most commonly reported features of deficiency.¹² We sought to determine whether maternal or infant vitamin D deficiency at birth is associated with BMC of Canadian infants.     

Potential pleiotropic effects of Mpdz on vulnerability to seizures

We previously mapped quantitative trait loci (QTL) responsible for approximately 26% of the genetic variance in acute alcohol and barbiturate (i.e., pentobarbital) withdrawal convulsion liability to a < 1 cM (1.8 Mb) interval of mouse chromosome 4. To date, Mpdz , which encodes the multiple PSD95/DLG/ZO-1 (PDZ) domain protein (MPDZ), is the only gene within the interval shown to have allelic variants that differ in coding sequence and/or expression, making it a strong candidate gene for the QTL. Previous work indicates that Mpdz haplotypes in standard mouse strains encode distinct protein variants (MPDZ1-3), and that MPDZ status is genetically correlated with severity of withdrawal from alcohol and pentobarbital. Here, we report that MPDZ status cosegregates with withdrawal convulsion severity in lines of mice selectively bred for phenotypic differences in severity of acute withdrawal from alcohol [i.e., High Alcohol Withdrawal (HAW) and Low Alcohol Withdrawal (LAW) lines] or pentobarbital [High Pentobarbital Withdrawal (HPW) and Low Pentobarbital Withdrawal (LPW) lines]. These analyses confirm that MPDZ status is associated with severity of alcohol and pentobarbital withdrawal convulsions. Using a panel of standard inbred strains of mice, we assessed the association between MPDZ status with seizures induced by nine chemiconvulsants. Our results show that MPDZ status is genetically correlated with seizure sensitivity to pentylenetetrazol, kainate and other chemiconvulsants. Our results provide evidence that Mpdz may have pleiotropic effects on multiple seizure phenotypes, including seizures associated with withdrawal from two classes of central nervous system (CNS) depressants and sensitivity to specific chemiconvulsants that affect glutaminergic and GABAergic neurotransmission.     

Site specific effects of zoledronic acid during tibial and mandibular fracture repair

Numerous factors can affect skeletal regeneration, including the extent of bone injury, mechanical loading, inflammation and exogenous molecules. Bisphosphonates are anticatabolic agents that have been widely used to treat a variety of metabolic bone diseases. Zoledronate (ZA), a nitrogen-containing bisphosphonate (N-BP), is the most potent bisphosphonate among the clinically approved bisphosphonates. Cases of bisphosphonate-induced osteonecrosis of the jaw have been reported in patients receiving long term N-BP treatment. Yet, osteonecrosis does not occur in long bones. The aim of this study was to compare the effects of zoledronate on long bone and cranial bone regeneration using a previously established model of non-stabilized tibial fractures and a new model of mandibular fracture repair. Contrary to tibial fractures, which heal mainly through endochondral ossification, mandibular fractures healed via endochondral and intramembranous ossification with a lesser degree of endochondral ossification compared to tibial fractures. In the tibia, ZA reduced callus and cartilage formation during the early stages of repair. In parallel, we found a delay in cartilage hypertrophy and a decrease in angiogenesis during the soft callus phase of repair. During later stages of repair, ZA delayed callus, cartilage and bone remodeling. In the mandible, ZA delayed callus, cartilage and bone remodeling in correlation with a decrease in osteoclast number during the soft and hard callus phases of repair. These results reveal a more profound impact of ZA on cartilage and bone remodeling in the mandible compared to the tibia. This may predispose mandible bone to adverse effects of ZA in disease conditions. These results also imply that therapeutic effects of ZA may need to be optimized using time and dose-specific treatments in cranial versus long bones.     

Conformational and functional studies of gomesin analogues by CD, EPR and fluorescence spectroscopies

The aim of this work was to examine the bioactivity and the conformational behavior of some gomesin (Gm) analogues in different environments that mimic the biological membrane/water interface. Thus, manual peptide synthesis was performed by the solid-phase method, antimicrobial activity was evaluated by a liquid growth inhibition assay, and conformational studies were performed making use of several spectroscopic techniques: CD, fluorescence and EPR. [TOAC(1)]-Gm; [TOAC(1), Ser(2,6,11,15)]-Gm; [Trp(7)]-Gm; [Ser(2,6,11,15), Trp(7)]-Gm; [Trp(9)]-Gm; and [Ser(2,6,11,15), Trp(9)]-Gm were synthesized and tested. The results indicated that incorporation of TOAC or Trp caused no significant reduction of antimicrobial activity; the cyclic analogues presented a beta-hairpin conformation similar to that of Gm. All analogues interacted with negatively charged SDS both above and below the detergent's critical micellar concentration (cmc). In contrast, while Gm and [TOAC(1)]-Gm required higher LPC concentrations to bind to micelles of this zwitterionic detergent, the cyclic Trp derivatives and the linear derivatives did not seem to interact with this membrane-mimetic system. These data corroborate previous results that suggest that electrostatic interactions with the lipid bilayer of microorganisms play an important role in the mechanism of action of gomesin. Moreover, the results show that hydrophobic interactions also contribute to membrane binding of this antimicrobial peptide.     

Spatio-temporal modification of collagen scaffolds mediated by triple helical propensity

Functionalized collagen that incorporates exogenous compounds may offer new and improved biomaterials applications, especially in drug-delivery, multifunctional implants, and tissue engineering. To that end, we developed a specific and reversible collagen modification technique utilizing associative chain interactions between synthetic collagen mimetic peptide (CMP) [(ProHypGly) chi; Hyp = hydroxyproline] and type I collagen. Here we show temperature-dependent collagen binding and subsequent release of a series of CMPs with varying chain lengths indicating a triple helical propensity driven binding mechanism. The binding took place when melted, single-strand CMPs were allowed to fold while in contact with reconstituted type I collagens. The binding affinity is highly specific to collagen as labeled CMP bound to nanometer scale periodic positions on type I collagen fibers and could be used to selectively image collagens in ex vivo human liver tissue. When heated to physiological temperature, bound CMPs discharged from the collagen at a sustained rate that correlated with CMP's triple helical propensity, suggesting that sustainability is mediated by dynamic collagen-CMP interactions. We also report on the spatially defined modification of collagen film with linear and multi-arm poly(ethylene glycol)-CMP conjugates; at 37 degrees C, these PEG-CMP conjugates exhibited temporary cell repelling activity lasting up to 9 days. These results demonstrate new opportunities for targeting pathologic collagens for diagnostic or therapeutic applications and for fabricating multifunctional collagen coatings and scaffolds that can temporally and spatially control the behavior of cells associated with the collagen matrices.     

Inability to produce a model of dialysis encephalopathy in the rat by aluminum administration

We attempted to produce a rat model of brain aluminum toxicity in order to explore whether or not aluminum accumulation produces the neurochemical changes observed in brains of patients who die with dialysis encephalopathy. Daily subcutaneous injection of Al(OH)₃ caused marked elevation of serum aluminum concentrations, but did not increase brain aluminum contents, either in rats with normal renal function, or in rats with unilateral or 5/6 nephrectomies. LiCl pretreatment, which has been reported to cause irreversible renal failure, did not impair renal function nor aid in achieving elevated brain aluminum contents. No reductions in brain contents of -aminobutyric acid (GABA) or in glutamic acid decarboxylase (GAD, E.C.4.1.1.15) and choline acetyltransferase (ChAT, E.C.2.3.1.6) activities were observed in aluminum-treated rats. We conclude that the rat is not a suitable laboratory animal to explore the role of aluminum toxicity in causing the GABA and ChAT deficits present in brains of hemodialyzed human patients.     

The Development of Primate Raiding: Implications for Management and Conservation

Ecosystems and habitats are fast becoming human dominated, which means that more species, including primates, are compelled to exploit new human resources to survive and compete. Primate “pests” pose major management and conservation challenges. I here present the results from a unique opportunity to document how well-known individuals and groups respond to the new opportunity to feed on human foods. Data are from a long-term study of a single population in Kenya at Kekopey, near Gilgil, Kenya. Some of the naïve research baboons became raiders while others did not. I compare diet, activity budgets, and home range use of raiders and nonraiders both simultaneously, after the incursion of agriculture, and historically compared to the period before agriculture appeared. I present measures of the relative benefits (female reproduction) and costs (injuries, mortality, and survivorship) of incorporating human food into the diet and discuss why the baboons raid and their variations in raiding tendencies. Guarding and chasing are evaluated as control techniques. I also suggest conflict mitigation strategies by identifying the most likely options in different contexts. I end with a proposal for a rapid field assessment of human wildlife conflict involving primates.     

ANALYSIS OF PETAL VENATION IN RANUNCULUS. I. ANASTOMOSES IN R. REPENS V. PLENIFLORUS

Arnott , Howard J., and Shirley C. Tucker . (Northwestern U., Evanston, Ill.) Analysis of petal venation in Ranunculus. I. Anastomoses in R. repens v. pleniflorus. Amer. Jour. Bot. 50(8): 821–830. Illus. 1963.—The venation patterns of 1218 petals of Ranunculus repens v. pleniflorus were analyzed, with particular attention to the number and position of vein anastomoses. The essentially open dichotomous vascular pattern is complicated by the presence of vein fusions in 69.4% of the petals. The anastomosis ratio (number of anastomoses/number of appendages) is, therefore, high (1.37), compared to a maximal 0.61 for Ginkgo leaves. Of the petals having such fusions, 55.3% have more than 1 anastomosis; the maximal number of fusions found per petal is 8. The presence of anastomoses shows a high degree of correlation with petal size and petal lobing. The types of fusions (types A, B, C, D) are identical with those found in Ginkgo leaves, with the addition of 2 modifications of type C. Curiously, types C and D account for 98.7% of the total anastomoses, while types A and B are rare. An analysis of the location of each type within the petal shows that type C's are disproportionately numerous along the distal periphery, and that type-D fusions are unusually numerous in the central and basal regions. Such evidence suggests that the occurrence of a vein fusion is no “accident,” but rather that it is one manifestation of morphogenetic control.