IDENTIFICATION OF HYBRID DYNAMICAL SYSTEM IN GLYCEROL FERMENTATION: ESTIMATING THE INHIBITION RANGE OF 3-HPA ONTO TWO KEY ENZYMES BASED ON BIOLOGICAL ROBUSTNESS

As an important intermediate substance in the process of producing 1,3-propanediol (1,3-PD) by bio-dissimilation of glycerol, the concentration of 3-hydroxypropionaldehyde (3-HPA) has inhibitory action on glycerol dehydratase (GDHt) and 1,3-propanediol oxidoreductase (PDOR). Considering the transmission of glycerol and 1,3-PD across cell membrane by both passive diffusion and active transmission as well as the inhibitory action of 3-HPA on the specific rate of growth, this paper aims to establish and discuss a nonlinear hybrid dynamical system model to ascertain the concentration range of 3-HPA where it does exhibit an inhibitory action on GDHt and PDOR. A quantitative definition of biological robustness is presented and an identification model is established based on biological robustness. An algorithm procedure is constructed to solve the identification problem. Numerical results show that only within a proper concentration range 3-HPA can have inhibitory action on the two enzymes mentioned above.

STUDIES ON TUBERCULIN FEVER

Utilizing techniques of passive transfer, we have investigated the factors responsible for production of fever when tuberculin is given intravenously to specifically sensitized rabbits. The ability to develop a febrile response to tuberculin could be passively transferred to normal recipients with viable mononuclear cells from peritoneal exudates, spleen, or lymph nodes of donor rabbits sensitized with BCG. Sensitivity was usually apparent 48 hr after transfer, maximal at 7 to 14 days, and rapidly declined thereafter. Granulocytes and nonviable, sonicated, mononuclear cells from similarly sensitized donors were unable to transfer this form of reactivity. Passive transfer of reactivity was also effected with plasma and serum, suggesting that the reaction of antibody with antigen contained in tuberculin is one of the initial steps by which the host cells are activated to release the endogenous pyrogen (EP) that mediates this form of hypersensitivity fever. An intravenous infusion of granulocytes, as well as of several types of mononuclear cells from sensitized donors, made most recipients responsive to the pyrogenic effect of old tuberculin (OT) given 2 hr later. Some of these passively transferred cells, such as the granulocyte and alveolar macrophage, may be activated in vivo by OT, as they are in vitro. However, in the case of splenic and lymph node cells that cannot be activated by OT to produce EP in vitro, it seems likely that an intravenous injection of OT causes these transferred, sensitized cells to liberate an intermediate substance that either directly, or in association with antigen, activates the host's normal cells to produce EP. In support of previous suggestions that leukocytes of several types, as well as phagocytic cells of the reticuloendothelial system, serve as potential sources of EP in tuberculin-induced fever, evidence was presented that OT also activates both granulocytes and mononuclear cells from sterile exudates of BCG-sensitized donors to produce EP in vitro.

Some Problems in Anaximander

This article deals with four almost classic problems in Anaximander. of these the first is of comparatively minor importance, and the second is important not for what Anaximander thought but for what Aristotle thought he thought. Problem i is: Did Anaximander describe his as ? Problem 2: Did Aristotle mean Anaximander when he referred to people who postulated an intermediate substance ? Problem 3: Did Anaximander think that there were innumerable successive worlds? Problem 4: What is the extent and implication of the extant fragment of Anaximander? Appended is a brief consideration of the nature of Theophrastus' source-material for Anaximander; on one's opinion of this question the assessment of the last two problems will clearly depend.

THE CONVERSION OF PREGNENOLONE TO A MORE ACTIVE PROGESTATIONAL SUBSTANCE BY INCUBATION WITH ENDOCRINE TISSUES IN VITRO

Incubation of pregnenolone with minced beef corpora lutea resulted in conversion of the steroid to a more active progestational substance as shown by biological assay on the endometrium of the spayed rabbit. Control studies with non-incubated pregnenolone and corpus luteum incubated without steroid, injected separately and in combination, all yielded negative results. To exclude bacterial action, experiments were repeated under sterile conditions, but without diminution in conversion activity. Negative results were obtained when pregnenolone was incubated with spleen, liver or ovaries. The incubation of this steroid with beef adrenal and human placenta, however, resulted in active conversion. It is noteworthy that the adrenal appears to be even more active in the conversion of pregnenolone than the corpus luteum. The association exhibited by the adrenal gland of a lower progesterone content and greater conversion activity, as compared with the corpus luteum, points to progesterone as a likely intermediate substance in the synthesis of the adrenal corticoids.

Bacterial Synergism—The Formation byB. typhosusorB. coli anaerogenesfrom Mannitol of an Intermediate Substance from which Morgan's Bacillus produces Gas

In the operations of bacteria under natural conditions it is the general rule to find mixed cultures at work, the variability of the results depending upon many factors. Therefore it has been suggested by Holman (1928) that the general term “bacterial association” be used to cover such processes. When, however, the combined action of two or more micro-organisms effects changes which each by itself is incapable of achieving, the term “synergism” is applied. Synergism appears to be used now in a more restricted sense to describe a particular type of bacterial association, and has been defined by Fiallos (1925) as follows: “two bacilli neither of which causes the production of gas in certain compounds, may do so when artificially mixed together provided one of them is capable of producing acidity (never gas) in these carbon compounds, and the other though inert to these compounds (i.e. produces in them neither acid nor gas) is capable of producing gas from glucose.” In 1911 Penfold observed the production of gas from a glucose medium in whichB. typhosuswas growing along with a variant non-aerogenic strain ofB. coli communis, the latter having been derived from a typical gas-producing culture by selective growth on agar containing sodium monochloracetate. Although this organism had lost the power of gas-fermenting glucose it retained the power of gas-fermenting sodium formate. Castellani (1925, 1926 and 1927) states that he noted the phenomenon, which he calls “symbiotic,” in 1904 when investigating the fermentation reactions of bakers' yeast, which is not a pure culture but consists generally of two or more species of yeasts together with one or more types of Gram-negative bacilli.