The role of pH* and buffer capacity in the recovery of function of smooth muscle cooled to −13 °C in unfrozen media

It has often been suggested that pH changes may be implicated in the injury sustained by biological systems during cooling. This particular mechanism of cryoinjury, however, has received little attention undoubtedly because of the difficulties encountered in making accurate pH measurements at low temperatures.New pH* scales established for some mixtures of dimethyl sulfoxide and water at low temperatures are used in this study to assess the effect of pH* and buffering ability upon the integrity of mammalian smooth muscle stored at −13 °C in a variety of unfrozen solutions containing 30% (w/v) Me₂SO. Smooth muscle, as a component of every organ, is a good model tissue intermediate between cells and organs. Furthermore, its overall function is conveniently tested by measuring isometric contractile responses to the drug histamine. In this way the function of strips of guinea pig taenia coli were examined at 37 °C before and after storage at −13 °C in potassiumrich media containing a variety of zwitterionic buffers. Functional recovery depends markedly on the pH* with a welldefined optimum at the surprisingly high pH*₋₁₃ of 9.2. In medium containing TES buffer, which has a maximum buffer capacity at pH*₋₁₃= 8.6, the cooled muscles recover 50% of their control contractility but in medium containing the buffer Tricine, which has a maximum capacity at the optimum pH* for recovery, the contractile response upon rewarming improves to 70%.These data are the first to quantify the effect of pH in cryopreservation on a sound theoretical basis and some of the possible underlying mechanisms are discussed.     

Relationship between postabsorptive respiratory exchange ratio and plasma free fatty acid concentrations

The relationship between overnight postabsorptive (fasting) respiratory exchange ratio (RER) and plasma FFA concentrations was addressed using data from three separate protocols, each of which involved careful control of the antecedent diet. Protocol 1 examined the relationship between fasting RER and the previous daytime RER. In Protocol 2 fasting, RER and plasma palmitate concentrations were measured in 29 women and 31 men (body mass index <30 kg·m⁻²). Protocol 3 analyzed data from Nielsen et al. (Nielsen, S., Z. K. Guo, J. B. Albu, S. Klein, P. C. O''Brien, M. D. Jensen. 2003. Energy expenditure, sex and endogenous fuel availability in humans. J. Clin. Invest. 111: 981-988.) to understand how fasting RER and palmitate concentrations relate within individuals during four consecutive measurements. The results were as follows: 1) Fasting RER was correlated (r = 0.74, P < 0.001) with the previous day''s average RER, and less so with RER variability. 2) Fasting RER was correlated (r = −0.39, P = 0.007) with fasting plasma palmitate concentrations. 3) The pattern of the RER/palmitate relationship was similar within individuals and between individuals; a negative slope was observed significantly more often than a positive slope (χ² test; P < 0.001). Our findings suggest that, despite a fixed food quotient, the slight departures from energy equilibrium in a controlled General Clinical Research Center environment can effect plasma FFA concentrations. We suggest that including indirect calorimetry as part of FFA metabolism studies may aid in data interpretation.     

Improved assay of coenzyme F420 analogues from methanogenic bacteria

Summary An improved method for separating analogues of coenzyme F₄₂₀ by isocratic reversed-phase high performance liquid chromatography is described. The method offers improved resolution, shorter chromatography runs and requires less complex apparatus.     

Experimental analyses of competition between two species of bumble bees (Hymenoptera: apidae)

Summary Dynamical aspects of flower usage and forager body size in sympatric and experimentally-induced allopatric populations of Bombus flaviforns and Bombus rufocinctus were studied in 10 discrete subalpine meadows and over the last half of one summer. Results indicate that there is a high degree of asymmetry in the competitive effects and that B. flavifrons is the clear competitive and numerical dominant. When occurring alone, B. rufocinctus used the same spectrum of flowers in similar frequencies to that of B. flavifrons whose flower use was invariant over all meadows and treatments. When sympatric with B. flavifrons, B. rufocinctus was relegated to secondary, less preferred flowers. Shifts in flower use by B. rufocinctus were accompanied by changes in forager body-size: body weights were greater in allopatric populations of B. rufocinctus and smaller in those sympatric with B. flavifrons. Competitive dominance may be related to differences in species phenologies. Bombus flavifrons initiated colonies in the spring three weeks before B. rufocinctus and maintained higher densities over the summer; by virtue of greater numbers of foragers, it may control exploitation of the most profitable flowers.     

Fire history of an isolated subalpine mountain range of the Intermountain Region,United States

Fire has historically been an important ecological component of forests in the Intermountain Region of the northwestern United States. This study is set in a small biogeographically disjunct mountain range. Our research objectives were to (1) investigate the historical frequency, severity, size, and spatial pattern of fire; (2) determine if and how fire regimes have changed since Euro-American settlement; and (3) compare how fire regimes of a small isolated range compare to nearby, but considerably larger, mountain agglomerations. Our findings suggest that this mountain range has historically supported fires typified by small size and high frequency, resulting in a high degree of spatial pattern complexity compared to mountain agglomerations. We also found disparity in size and burn severity solely within the study area based on the bisecting Continental Divide. Since the advent of Euro-American settlement in the 1870s, fire frequency and sizes of individual fires in the West Big Hole Range have significantly decreased resulting in an estimated 87% reduction in area burned. We discuss potential relationships of mountain range isolation and fire regimes in the Intermountain Region. Furthermore, we suggest that the relative small size of this mountain range predisposes it to greater anthropogenic effects upon fire occurrence.     

Uteroferrin: A protein in search of a function

Uteroferrin, a purple-colored, iron-containing acid phosphatase, with many of the properties of a lysosomal hydrolase, transports iron from the mother to the conceptus in pregnant pigs. Uteroferrin, however, is but one member of what may be a broad class of iron-containing phosphatases with unusual spectral properties which result from a novel type of di-iron active site. The biological function of uteroferrin is unknown. We argue here that the in vivo function of uteroferrin, despite its undoubted ability to act as a potent acid phosphatase, is that of a transplacental iron transporter.     

Growth of acetotrophic,methane-producing bacteria in a pH auxostat

Three acetotrophicMethanosarcina species, which included marine, nonmarine, and thermophilic strains, were grown on acetate in a 10-liter pH auxostat. Specific growth rates and molar growth yields were constant throughout growth. Cell yields were up to 18-fold greater than previously reported. These properties of the pH auxostat indicate that it is a preferred culture method for the biochemical study of methanogenesis from acetate.     

Reproductive life history of ocelotsLeopardus pardalis in southern Texas

The ocelotLeopardus pardalis Linnaeus, 1758 is an endangered felid in the United States currently restricted to southern Texas. The objectives of our study were to obtain data on ocelot parturition dates, fecundity, sex ratios, den characteristics, and first year survival, all of which are critical in development of population viability models. Sixteen parturition events were recorded ranging from mid-April to late December for 12 wild ocelots. Cumulatively, litters consisted of 1 or 2 kittens (ˉ = 1.2 ± 0.44 SD). Cumulative sex ratio was 1∶2.5 (male:female); however, there was no significant difference between the observed sex ratio and a 1∶1 sex ratio. Ten den sites were in close proximity (≤ 10 m) to dense thornshrub. Adult female ocelots used 2 to 4 den sites for each litter with distance between consecutively occupied dens ranging from 110 to 280 m (ˉ = 158 m ± 93 SD). An estimated annual survival for ocelots 0 to 1 year of age was 0.68. Evidence suggests that ocelots in the wild may breed more frequently than had been previously hypothesized.