The partial replacement of the serum growth factor requirement of SV3T3 cells by lactalbumin hydrolyzate.

Lactalbumin hydrolyzate (LH), a commercially prepared, enzymatic digest of a milk protein fraction, can partially replace the serum requirement of SV3T3 cells. In a low, but obligatory, background of calf serum (0.15% v/v), LH carses a large increase in the final cell density (5-10 x over the control) while modestly steimulating the actual growth rate. Lactalbumin hydrolyzate does not contain survival activity for SV3T3 cells and does not affect the growth of 3T3 cells. Since even prolonged exposure to pH 4 or 2 results in complete abolishment of the growth-rate stimulatory capability without affecting the capacity to increase the final cell density, it is possible that the LH growth activity may consist of two dissociable components. All of LH growth activity is water soluble, autoclavable, and resists proteolytic treatment. On Sephadex G15 growth activity appears as a single peak at the void volume but on G25 it is retained beyond the void volume as a broad, skewed peak. The relevant molecular weight range lies between 1,500 and 4,000. The putative low pH resistant material is strongly adsorbed to Dowex 1 x 2 and can be displaced from the column by a reduction in the pH. A comparison of the properties of the LH factors with those of known growth promoting agents isolated from serum and various enzymatic digests indicates that these new factors do not correspond to any of these agents.     

Degradation of feather keratin by culture filtrates of Streptomyces fradiae.

Treatment of milled defatted capon feathers with filtrates of Steptomyces fradiae ATCC 10745 that had been concentrated 20 times showed that the most keratin degradation in 0.5h occurred at pH 8.0 and 60degrees C. If assay time was extended, however, adecrease in reaction rate occurred and appeared to result from keratinase instability at elevated temperatures. Exposure of commercial feather meal to unconcentrated culturefiltrates for 15 h produced greatest degradation at 50 degrees C.     

Seasonal and diurnal changes in the water temperature of a temperate pond (England) and a tropical pond (Kenya)

Seasonal changes in water temperatures, embracing periods of low, rising, high and declining temperatures, were recorded in both a temperate and a tropical pond. In the course of a year, the range between the lowest and highest average weekly temperatures was greater in the temperate pond. The spans between the average minimum and the average maximum weekly water temperatures in the warmest months of the year in the tropical pond were greater than those found at any time of the year in the temperate pond. The average weekly air and water temperatures showed the same pattern of seasonal fluctuations; in the tropical pond the average weekly air temperatures were always less than the average minimum weekly water temperatures, whereas they were below, within or above the spans between the average minimum and average maximum weekly aquatic temperatures, according to the time of year, in the temperate pond.In both ponds, diurnal fluctuations were absent during the cooler months; the amplitudes of the fluctuations in the warmer months varied according to the time of year, and were greater, during the warmest months, in the tropical pond. In both ponds lowest temperatures were recorded sometime between 0200 and 1000 hours and highest between 1200 and 2000 hours.The influence of temperature on the life-cycles of invertebrates in both ponds is discussed briefly.

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Zusammenfassung Jahreszeitlich bedingte Schwankungen in der Wassertemperatur, welche Perioden mit niedriger, ansteigender, hoher und abfallender Temperatur einschlossen, wurden in einem gemäßigten und in einem tropischen Teich festgestellt. Im Laufe eines Jahres war der Unterschied zwischen den tiefsten und höchsten wöchentlichen Durchschnittstemperaturen im gemäßigten Teich größer. Hingegen war der Abstand zwischen Mindest- and Höchsttemperatur des Wassers im Wochendurchschnitt während der warmsten Monate des Jahres im tropischen Teich größer als zu irgendeiner Jahreszeit im gemäßigten Teich. Der Wochendurchschnitt der Luft- und Wassertemperaturen wies das gleiche jahreszeitlich bedingte Schwankungsmuster auf. In dem tropischen Teich war die wöchentliche Durchschnittstemperatur der Luft stets niedriger als die Mindestdurchschnittstemperatur des Wassers in einer Woche. Jedoch lag sie — je nach Jahreszeit — unterhalb, auf gleicher Höhe oder oberhalb der Spannweite der niedrigsten and der höchsten wöchentlichen Dutchschnittstemperaturen des Wassers im gemäßigten Teich.In beiden Teichen traten die taglichen Schwankungen während der kÜhleren Monate nicht auf. Der Umfang der Schwankungen in den wärmeren Monaten variierte je nach Jahreszeit and war in den wärmsten Monaten in dem tropischen Teich größer. In beiden Teichen wurden die tiefsten Temperaturen zwischen 2.00 and 10.00 Uhr and die höchsten zwischen 12.00 and 20.00 Uhr gemessen.

     

Proton magnetic relaxation studies of the interaction of D-xylose and xylitol with D-xylose isomerase. Characterization of metal-enzyme-substrate interactions.

The interaction of D-xylose isomerase purified from two sources with Mn2+ and D-xylose or the competitive inhibitor xylitol has been examined by nuclear magnetic resonance. A greater paramagnetic effect of enzyme-bound Mn2+ on the alpha anomer of D-xylose than on the beta anomer was observed, providing independent evidence for the specificity of D-xylose isomerase for the alpha anomeric form of D-xylose. The exchange rate of alpha-D-xylose into the ternary complex, determined from the normalized paramagnetic contribution to the transverse relaxation rate (1/fT2p) of the carbon 1 proton of alpha-D-xylose, exceeds Vmax for the enzymatic reaction by 3 orders of magnitude. The amount of xylitol necessary to displace alpha-D-xylose from the substrate-enzyme-Mn2+ complex is consistent with the Km value for alpha-D-xylose and the inhibitor constant Ki for xylitol previously determined by the methods of enzyme kinetics. These results suggest that the NMR experiments observe complexes of D-xylose isomerase which are kinetically and thermodynamically competent to participate in catalysis. From the frequency dependence of the paramagnetic contribution to the longitudinal relaxation rate (1/T1p) of the carbon 1 proton of alpha-D-xylose, the correlation time (tauc) which modulates the dipolar interaction between enzyme-bound Mn2+ and alpha-D-xylose has been determined (5.1 x 1o(-10) s). From these observations a range of calculated distances between enzyme-bound Mn2+ and the carbon 1 proton of alpha-D-xylose (9.1 +/- 0.7 A) has been found. The enzyme-bound Mn2+ has comparable effects on the carbon 1, carbon 2, and carbon 5 protons of alpha-D-xylose, suggesting that these protons of the enzyme-bound substrate are equidistant from the bound Mn2+. A similar distance (9.4 +/- 0.7 A) between the enzyme-bound Mn2+ and the terminal methylene protons of xylitol, an analog of the open chain intermediate in the reaction, has been determined. The results of the present substrate relaxation and previous water relaxation studies suggest that two small ligands such as water molecules or a large portion of the protein intervene between the bound metal ion and the bound substrate in the active ternary complex.     

Action of Interferon in Enucleated Cells

Interferon induces protection of enucleated BSC-1 cells against infectious vesicular stomatitis virus production if cells are treated before, but not after, enucleation.     

Exercise increases the release of NAMPT in extracellular vesicles and alters NAD + activity in recipient cells

Aging is associated with a loss of metabolic homeostasis, with cofactors such as nicotinamide adenine dinucleotide (NAD⁺) declining over time. The decrease in NAD⁺ production has been linked to the age‐related loss of circulating extracellular nicotinamide phosphoribosyltransferase (eNAMPT), the rate‐limiting enzyme in the NAD⁺ biosynthetic pathway. eNAMPT is found almost exclusively in extracellular vesicles (EVs), providing a mechanism for the distribution of the enzyme in different tissues. Currently, the physiological cause for the release of eNAMPT is unknown, and how it may be affected by age and physical exercise. Here, we show that release of small EVs into the bloodstream is stimulated following moderate intensity exercise in humans. Exercise also increased the eNAMPT content in EVs, most prominently in young individuals with higher aerobic fitness. Both mature fit and young unfit individuals exhibited a limited increase in EV‐eNAMPT release following exercise, indicating that this mechanism is related to both the age and physical fitness of a person. Notably, unfit mature individuals were unable to increase the release of eNAMPT in EVs after exercise, suggesting that lower fitness levels and aging attenuate this important signalling mechanism in the body. EVs isolated from exercising humans containing eNAMPT were able to alter the abundance of NAD⁺ and SIRT1 activity in recipient cells compared to pre‐exercise EVs, indicating a pathway for inter‐tissue signalling promoted through exercise. Our results suggest a mechanism to limit age‐related NAD⁺ decline, through the systemic delivery of eNAMPT via EVs released during exercise.