Obesity in Older Adults: Technical Review and Position Statement of the American Society for Nutrition and NAASO,The Obesity Society

Obesity causes serious medical complications and impairs quality of life. Moreover, in older persons, obesity can exacerbate the age‐related decline in physical function and lead to frailty. However, appropriate treatment for obesity in older persons is controversial because of the reduction in relative health risks associated with increasing body mass index and the concern that weight loss could have potential harmful effects in the older population. This joint position statement from the American Society for Nutrition and NAASO, The Obesity Society reviews the clinical issues related to obesity in older persons and provides health professionals with appropriate weight‐management guidelines for obese older patients. The current data show that weight‐loss therapy improves physical function, quality of life, and the medical complications associated with obesity in older persons. Therefore, weight‐loss therapy that minimizes muscle and bone losses is recommended for older persons who are obese and who have functional impairments or medical complications that can benefit from weight loss.     

PHYSIOLOGICAL AND OPTICAL PROPERTIES OF RHIZOSOLENIA FORMOSA (BACILLARIOPHYCEAE) IN THE CONTEXT OF OPEN-OCEAN VERTICAL MIGRATION1

Cultures of Rhizosolenia formosa H. Peragallo were studied to assess whether or not physiological and optical characteristics of this large diatom were consistent with the ability to migrate vertically in the open ocean. Time-course experiments examined changes in chemical composition and buoyancy of R. formosa during nitrate (N)–replete growth, N starvation, and recovery. Cells could maintain unbalanced growth for at least 53 h after depletion of ambient nitrate. Increases in C:N and carbohydrate: protein ratios observed during N starvation reversed within 24 h of reintroduction of nitrate to culture medium. Buoyancy was related to nutrition: Upon N depletion, the percentage of positively buoyant cells decreased to 4% from 11% but reverted to 9% within 12 h of nitrate readdition. Cells took up nitrate in the dark. Nitrogen-specific uptake rates averaged 0.48 d^?1; these rates were higher than N-specific growth rates (0. 15 d^?1), indicating the potential for luxury consumption of nitrate, which can be stored for later use. Measurements of photosynthesis vs. irradiance, chlorophyll-specific absorption (a_ph*(λ)), and pigment composition showed that cells may be adapted for growth under a wide range of irradiances. Values of a_ph*(λ) were lower for N-depleted cells than for N-replete cells, and N-depleted cells had higher ratios of total carotenoids to chlorophyll a. Aggregation of chloroplasts was more pronounced in N-depleted cells. These are possibly photoprotective mechanisms that would be an advantage to N-depleted cells in surface waters. Compounds that absorb in the ultraviolet region were detected in N-replete cells but were absent in N-depleted cultures. Overall, these results have important implications for migrations of Rhizosolenia in nature. Cells may survive fairly long periods in N-depleted surface waters and will continue to take up carbon; then they can resume nitrate uptake and revert to positive buoyancy upon returning to deep, N-rich water. Uncoupled uptake of carbon and nitrogen during migrations of Rhizosolenia is a form of new production that may result in the net removal of carbon from oceanic surface waters.     

Classification of cultivated rices into indica and japonica types by the isozyme,RFLP and two milled-rice methods

Four methods for classifying cultivated rices (Oryza sativa L.) (including IR varieties) into indica and japonica types — waxy gene product in endosperm starch, glutelin ₃ molecular weight in milled rice, RFLP polymorphism at the Wx locus and Glaszmann's isozyme method — were compared. On the basis of the two endosperm traits and the RFLP method Glaszmann's group 1 (indica) was classified as mainly indica and intermediate groups 2, 3 and 4 as exclusively indica. However, the endosperm traits classified Glaszmann's group 5 as mainly indica, while the RFLP method classified it as japonica. The RFLP waxy gene probe was closest to the isozyme method in classifying group 6 as japonicas; the waxy gene product gave mainly indica reaction even in group 6, and the glutelin ₃ method was intermediate. All IR rices were classified as being indica on the basis of Wx gene product and by Glaszmann's method, but a few were classified as japonica by the glutelin ₃ method and by the RFLP waxy gene probe.     

Patterns of sequence variation in the mitochondrial D-loop region of shrews

Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews (genus Sorex) for the region between the tRNA(Pro) and the conserved sequence block-F revealed variable numbers of 79-bp tandem repeats. These repeats were found in all 19 individuals sequenced, representing three subspecies and one closely related species of the masked shrew group (Sorex cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an adjacent 76-bp imperfect copy of the tandem repeats. One individual was heteroplasmic for length variants consisting of five and seven copies of the 79-bp tandem repeat. The sequence of the repeats is conducive to the formation of secondary structure. A termination-associated sequence is present in each of the repeats and in a unique sequence region 5' to the tandem array as well. Mean genetic distance between the masked shrew taxa and the pygmy shrew was calculated separately for the unique sequence region, one of the tandem repeats, the imperfect repeat, and these three regions combined. The unique sequence region evolved more rapidly than the tandem repeats or the imperfect repeat. The small genetic distance between pairs of tandem repeats within an individual is consistent with a model of concerted evolution. Repeats are apparently duplicated and lost at a high rate, which tends to homogenize the tandem array. The rate of D- loop sequence divergence between the masked and pygmy shrews is estimated to be 15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid sequence evolution in shrews may be due either to their high metabolic rate and short generation time or to the presence of variable numbers of tandem repeats.      

Modeling interactions between voltage-gated Ca2+ channels and KCa1.1 channels

High voltage-activated (HVA) Cav channels form complexes with KCa1.1 channels, allowing reliable activation of KCa1.1 current through a nanodomain interaction. We recently found that low voltage-activated Cav3 calcium channels also create KCa1.1-Cav3 complexes. While coimmunoprecipitation studies again supported a nanodomain interaction, the sensitivity to calcium chelating agents was instead consistent with a microdomain interaction. A computational model of the KCa1.1-Cav3 complex suggested that multiple Cav3 channels were necessary to activate KCa1.1 channels, potentially causing the KCa1.1-Cav3 complex to be more susceptible to calcium chelators. Here, we expanded the model and compared it to a KCa1.1-Cav2.2 model to examine the role of Cav channel conductance and kinetics on KCa1.1 activation. As found for direct recordings, the voltage-dependent and kinetic properties of Cav3 channels were reflected in the activation of KCa1.1 current, including transient activation from lower voltages than other KCa1.1-Cav complexes. Substantial activation of KCa1.1 channels required the concerted activity of several Cav3.2 channels. Combined with the effect of EGTA, these results suggest that the Ca²⁺ domains of several KCa1.1-Cav3 complexes need to cooperate to generate sufficient [Ca²⁺]_i, despite the physical association between KCa1.1 and Cav3 channels. By comparison, Cav2.2 channels were twice as effective at activating KCa1.1 channels and a single KCa1.1-Cav2.2 complex would be self-sufficient. However, even though Cav3 channels generate small, transient currents, the regulation of KCa1.1 activity by Cav3 channels is possible if multiple complexes cooperate through microdomain interactions.     

Calcium dynamics during fertilization in C. elegans

Background

Of the animals typically used to study fertilization-induced calcium dynamics, none is as accessible to genetics and molecular biology as the model organism Caenorhabditis elegans. Motivated by the experimental possibilities inherent in using such a well-established model organism, we have characterized fertilization-induced calcium dynamics in C. elegans.

Results

Owing to the transparency of the nematode, we have been able to study the calcium signal in C. elegans fertilization in vivo by monitoring the fluorescence of calcium indicator dyes that we introduce into the cytosol of oocytes. In C. elegans, fertilization induces a single calcium transient that is initiated soon after oocyte entry into the spermatheca, the compartment that contains sperm. Therefore, it is likely that the calcium transient is initiated by contact with sperm. This calcium elevation spreads throughout the oocyte, and decays monotonically after which the cytosolic calcium concentration returns to that preceding fertilization. Only this single calcium transient is observed.

Conclusion

Development of a technique to study fertilization induced calcium transients opens several experimental possibilities, e.g., identification of the signaling events intervening sperm binding and calcium elevation, identifying the possible roles of the calcium elevation such as the completion of meiosis, the formation of the eggshell, and the establishing of the embryo's axis of symmetry.     

Persistent Chlamydiae and chronic arthritis

Urogenital infection with Chlamydia trachomatis can lead to development of an acute inflammatory arthritis, and this acute disease becomes chronic in some individuals. Research indicates that the organism is present in synovial tissue of patients with chronic disease in a persistent, rather than an actively growing, form. Importantly, metabolic and other characteristics of persistent Chlamydia differ from those of actively growing bacteria. Other studies suggest that Chlamydia pneumoniae can be found in a persistent state in the synovium and that it too may be involved in joint pathogenesis. These and other observations suggest a more complex role for the Chlamydiae in joint disease than previously recognized. This realization should engender a realignment of thinking among clinicians and researchers concerning both mechanisms of chlamydial pathogenesis in the synovium and design of new treatments for the disease.     

Effects of mesozooplankton removal and ammonium addition on planktonic trophic structure during a bloom of the Texas 'brown tide': a mesocosm study

A bloom of the alga Aureoumbra lagunensis, known as the Texas‘brown tide’, persisted in the Laguna Madre of Texasfor most of the 1990s. The dominant mesozooplankter in LagunaMadre, Acartia tonsa, does not feed on A. lagunensis, and duringblooms there are few other suitably sized phytoplankton cellsavailable to feed on. We hypothesized that these copepods increasedtheir feeding on microzooplankton, thereby reducing grazingpressure by microzooplankton on A. lagunensis and contributingto the persistence of this bloom. A mesocosm experiment wascarried out to test this hypothesis during the summer of 1999.Twelve fiberglass corral-type mesocosms were deployed in thefield for 16 days, each enclosing 1.2 m³ of Laguna Madre waterand 1.1 m² of natural benthos. Mesozooplankton were removedfrom six mesocosms with a 153 µm mesh dip net every 4days; the other six mesocosms were treated in the same way,except that the contents of the net were returned to the mesocosm.For each zooplankton treatment, half of the mesocosms were dosedwith 40 µm NH₄ at 4 day intervals, and half received noadditions. Phytoplankton populations in these mesocosms at thestart of the experiment were dominated by A. lagunensis andthe cyanobacterium Synechococcus spp. Growth rates of A. lagunensiswere higher in mesocosms without ammonium additions, providingno evidence for nitrogen limitation. Acartia tonsa populationswere reduced by 50% in the zooplankton removal mesocosms, andciliate populations were significantly higher. The increasein ciliate population had no significant impact on A. lagunensispopulation dynamics, however, providing no evidence to supportthe hypothesis that a trophic cascade reducing microzooplanktonpopulations contributed to the persistence of the brown-tidebloom. In contrast, populations of Synechococcus sp. showedevidence of both ‘top–down’ and ‘bottom–up’control; they grew faster in nutrient addition mesocosms andhad lower populations in mesocosms with increased densitiesof ciliate grazers.     

Absence of left ventricular and arterial adaptations to exercise in octogenarians.

Recent evidence suggests that octogenarians exhibit attenuated adaptations to training with a small increase in peak O2 consumption (VO2) that is mediated by a modest improvement in cardiac output without an increase in arteriovenous O2 content difference. This study was designed to determine whether diminished increases in peak VO2 and cardiac output in the octogenarians are associated with absence of left ventricular and arterial adaptations to exercise training. We studied 22 octogenarians (81.9 +/- 3.7 yr, mean +/- SD) randomly assigned a group that exercised at an intensity of 82.5 +/- 5% of peak heart rate for 9 mo and 14 (age 83.1 +/- 4.1) assigned to a control group. Peak VO2 increased 12% in the exercise group but decreased slightly (-7%) in the controls. The exercise group demonstrated significant but small decreases in the heart rate (6%, P = 0.002) and the rate-pressure product (9%, P = 0.004) during submaximal exercise at an absolute work rate. Training induced no significant changes in the left ventricular size, geometry (wall thickness-to-radius ratio), mass, and function assessed with two-dimensional echocardiography or in arterial stiffness evaluated with applanation tonometry. Data suggest that the absence of cardiac and arterial adaptations may in part account for the limited gain in aerobic capacity in response to training in the octogenarians.