The carbohydrases of Bacillus stearothermophilus NCIB 11412 and NCIB 10814

Summary Two strains (NCIB 11412 and NCIB 10814) of the thermophilic organism Bacillus stearothermophilus were found to produce complex carbohydrase systems. The enzyme activities in each system include -amylase as the major component, maltase, pullulanase, a minor amylase and cyclodextrinase. The latter three activities are produced in low yield in both strains. A crude enzyme preparation from each strain possessed maltogenic properties on hydrolysis of soluble starch. Following rigorous purification procedures, the purified major -amylase from either strain did not produce maltose as a major end-product of starch hydrolysis. However, a partially purified mixture of pullulanase, minor amylase and cyclodextrinase activities from NCIB 11412 and NCIB 10814 produced 56.4% and 62.0% maltose, respectively, from soluble starch.     

Effect of dehydration on thirst and drinking during immersion in men.

The mechanism for reduced voluntary water intake during water immersion was studied in eight men (19-25 yr of age) immersed to the neck while sitting for 3 h at 34.5 degrees C or in air at 28 degrees C when euhydrated (Eu-H2O and Eu-air, respectively) and hypohydrated (Hypo-H2O and Hypo-air) by 3.6% body weight loss. Thirst sensations (degree of thirst, mouth dryness and taste, drinking desirability, and stomach fullness) were similar at the beginning of Hypo-air and Hypo-H2O test periods. Initial drinking of tap water (15 degrees C) was 216 +/- 30 ml/7 min (P less than 0.05) with Hypo-air, decreased to 108 +/- 28 ml/7 min (P less than 0.05) with Hypo-H2O, and was 10-50 ml/10-30 min thereafter. Intake was less than 10 ml/10-30 min in Eu-air, and there was no drinking in Eu-H2O. Within the first 10 min of immersion, compared with Hypo-air findings, the significant reduction in drinking in the Hypo-H2O experiment was associated with unchanged plasma Na+, plasma osmolality, heart rates, and mean arterial pressures; the different responses were increased cardiac output, plasma volume, and atrial natriuretic peptides and decreased plasma renin activity and arginine vasopressin. Thus the extracellular pathway, as opposed to the osmotic pathway, appears to be the major mechanism for immersion-induced suppression of drinking.     

Biosynthesis of membrane bound Ig and secretion of Ig by chicken lymphoid cells.

The metabolic turnover of membrane proteins of chicken lymphoid cells is studied, using a double isotope labeling technique (i.e., [14C]amino acid pulse and [3H]leucine chase). Compared with other membrane proteins, the metabolic turnover of membrane bound immunoglobulins (M-Ig) is very slow. There was no difference in the turnover between M-Ig and specific antigen binding receptor immunoglobulins. Immunoglobulins appear to be a stable constituent of the lumphocyte membrane. Cellular kinetic experiments show that the rate of biosynthesis of secreted immunoglobulins (S-Ig) is nearly ten times as much as that of M-Ig, suggesting that metabolic pathway leading to M-Ig are distinct from those leading to S-Ig. The difference in 3H/14C ratios between S-Ig and M-Ig reflects the rate of biosynthesis of these immunoglobulins by two types of bursa derived lymphoid cells.     

Physiological responses underlying the timing of vernal activities in insects

Temperate zone insect species have evolved three general strategies for synchronizing the end of hibernation with the return of favorable conditions. Recent eco-physiological studies of insect dormancy and development indicate that the prevailing concepts of the adaptations regulating hibernation and the resumption of spring activity, need revision. In particular, experimental evidence shows that despite implications in the term, dormancy is a dynamic state; the organism, by constantly monitoring the constantly-changing environmental parameters, is kept in phase with the seasons at its particular locality. Furthermore, the insect's ability to respond to environmental factors generally changes as the season progresses. Therefore, the construction of realistic predictive models of insect seasonality should be based on investigations of natural populations undergoing hibernation in the field, combined with ecologically and physiologically meaningful laboratory studies.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

Developmental shifts in computations used to detect environmental controllability

Accurate assessment of environmental controllability enables individuals to adaptively adjust their behavior—exploiting rewards when desirable outcomes are contingent upon their actions and minimizing costly deliberation when their actions are inconsequential. However, it remains unclear how estimation of environmental controllability changes from childhood to adulthood. Ninety participants (ages 8–25) completed a task that covertly alternated between controllable and uncontrollable conditions, requiring them to explore different actions to discover the current degree of environmental controllability. We found that while children were able to distinguish controllable and uncontrollable conditions, accuracy of controllability assessments improved with age. Computational modeling revealed that whereas younger participants’ controllability assessments relied on evidence gleaned through random exploration, older participants more effectively recruited their task structure knowledge to make highly informative interventions. Age-related improvements in working memory mediated this qualitative shift toward increased use of an inferential strategy. Collectively, these findings reveal an age-related shift in the cognitive processes engaged to assess environmental controllability. Improved detection of environmental controllability may foster increasingly adaptive behavior over development by revealing when actions can be leveraged for one’s benefit.     

The PRiMA-linked Cholinesterase Tetramers Are Assembled from Homodimers: HYBRID MOLECULES COMPOSED OF ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE DIMERS ARE UP-REGULATED DURING DEVELOPMENT OF CHICKEN BRAIN*

Acetylcholinesterase (AChE) is anchored onto cell membranes by the transmembrane protein PRiMA (proline-rich membrane anchor) as a tetrameric globular form that is prominently expressed in vertebrate brain. In parallel, the PRiMA-linked tetrameric butyrylcholinesterase (BChE) is also found in the brain. A single type of AChE-BChE hybrid tetramer was formed in cell cultures by co-transfection of cDNAs encoding AChE_T and BChE_T with proline-rich attachment domain-containing proteins, PRiMA I, PRiMA II, or a fragment of ColQ having a C-terminal GPI addition signal (Q_N-GPI). Using AChE and BChE mutants, we showed that AChE-BChE hybrids linked with PRiMA or Q_N-GPI always consist of AChE_T and BChE_T homodimers. The dimer formation of AChE_T and BChE_T depends on the catalytic domains, and the assembly of tetramers with a proline-rich attachment domain-containing protein requires the presence of C-terminal “t-peptides” in cholinesterase subunits. Our results indicate that PRiMA- or ColQ-linked cholinesterase tetramers are assembled from AChE_T or BChE_T homodimers. Moreover, the PRiMA-linked AChE-BChE hybrids occur naturally in chicken brain, and their expression increases during development, suggesting that they might play a role in cholinergic neurotransmission.