Isolation of a high molecular weight glycoconjugate derived from the surface of S purpuratus eggs that is implicated in sperm adhesion

Sea urchin sperm–egg adhesion is mediated by bindin, a sperm surface protein that has lectin-like activity. Bindin agglutinates eggs, and this interaction has been shown to be inhibited by glycopeptides released from the egg surface by protease treatment. In this study, we report the purification and properties of such an egg surface glycoconjugate that may be involved in sperm adhesion. The glycoconjugate was partially purified by gel filtration and affinity chromatography on bindin particles. Upon gel filtration on Sepharose CL 4-B, the glycoconjugate elutes near the void volume, suggesting that it has a molecular weight in excess of one million. In addition, we have found that the egg surface glycoconjugate agglutinates bindin particles, indicating that it is multivalent. Carbohydrate analysis indicates that the glycoconjugate is composed primarily of fucosc, xylose, galactose, and glucose. This purified egg surface component is the most potent inhibitor of bindin-mediated egg agglutination yet described.     

The response of serum ceruloplasmin to injections of walker 256 tumor cells or turpentine into rats

The subcutaneous injection of Walker 256 carcinosarcoma cells into a rat was followed by a pronounced increase in plasma ceruloplasmin activity. This lasted only about 3 weeks even though the tumors were still enlarging rapidly. Based upon studies with⁶⁷Cu, the increase in plasma ceruloplasmin seemed to reflect increased production of the enzyme by the livers of rats bearing the tumors. Injections of turpentine also raised plasma ceruloplasmin, but to a significantly lesser extent and normal values were reached within 2 weeks.     

Immune surveillance and neoplasia—1 a minimal mathematical model

A deterministic predator-prey model is presented for describing the dynamics of a solid tumor in the presence of a specifically reactive lymphocyte population which is stimulated by, and antagonistic to, the tumor. The qualitative behavior of the solutions is developed and briefly compared to the results of transplantation experiments. Although the model is primitive, it leads to predictions that are in general agreement with observation and intuitive expectations. In particular, it is found that: (1) very low levels of transplanted tumor will not survive in the recipient. (2) At somewhat higher levels, tumor growth will be uncontrolled in the syngeneic recipient. However, immune intervention if early enough, can lead to control and elimination of the tumor. (3) At still higher levels of transplanted tumor, no amount of immune intervention will be effective in controlling the tumor. (4) If the recipients immune system is suppressed prior to transplantation, or is debilitated for any reason, the chance that the tumor will grow increases. (5) If the recipients immune system is stimulated prior to transplantation, the chance of tumor survival decreases. (6) The survival of the tumor is much more sensitive to changes in tumor parameters (for example, antigenicity) than in lymphocyte parameters. In addition it makes the unintuitive prediction that (7) There areisolated instances under which anincrease in the number of lymphocytes canincrease the chance of tumor survival.     

Some techniques in building and validating stochastic models of human reproduction

Stochastic models of human reproduction are beginning to play significant roles in the evaluation of family planning programs. A class of stochastic processes called absorbing, agedependent, semi-Markov processes frequently arises in the construction of such models. The paper begins with a discussion of some technicalities regarding absorbing, age-dependent, semi-Markov processes. Then, an algorithm due to Littman, which makes possible the computerization of this class of stochastic processes, is presented. Briefly, Littman’s algorithm provides an efficient method for numerically solving systems of renewal type integral equations, provided the system does not contain a large number of equations. After setting down a concrete model for a large clinical trial of intrauterine devices conducted in Taiwan, the paper concludes with a discussion of a method for validating the model based on the data collected in the clinical trial. Presented at the Society for Mathematical Biology Meeting, University of Pennsylvania, Philadelphia, August 19–21, 1976.     

Abscisic acid and the accumulation, biological activity and metabolism of four derivatives of [3H]gibberellin A1 in barley aleurone layers

Tritiated GA₁ and four of its synthetic derivatives were studiedin relation to their biological activity, uptake and metabolismby barley aleurone layers. Incubation was done in the presenceand absence of ABA. Tentative identification of some of themetabolites was made by TLC and GLC radiocounting of the metaboliteand its acid hydrolyzed derivative. Only GA₁ promoted -amylase synthesis. Uptake ranged from 20to 42%, varying with the derivative. ABA enhanced uptake of[³H]GA₁ and [³H]pseudoGA₁ and inhibited uptake of [³H]ketoGA₁the Wagner-Meerwein rearrangement product of [³H]GA₁ Uptakeof [³H]GA₁ methyl ester ([³H]GA₁-Me) and [³H]dihydroGA₁ wasunaffected by ABA. [³H]GA₁ was converted to an amphoteric GA₁ derivative ([³H]amphoGA₁)and [³H]GA₁-glycosyl ester. GA₁-Me was metabolized to four products,all of them GA₁ derivatives, including an apparent amphotericGA₁ derivative. DihydroGA₁ was quite stable; only one metabolitewas produced in sufficient yield to analyze. This product didnot cochromatograph with either of the expected acid hydrolyzedepimers of [³H]dihydroGA₁. [³H]ketoGA₁ was readily metabolizedto one product, probably the glycoside. [³H]pseudoGA₁ remainedessentially unmetabolized. Metabolism of all compounds testedwas not dramatically affected by ABA. Surprisingly, no metabolitesfrom hydroxylation at the 2-position were found. ¹ Present address: Monsanto Agricultural Co., 800 N. LindberghBlvd., St. Louis, MO 63166, U.S.A. (Received January 31, 1977; )     

Habitat choice in natural populations of Drosophila

Summary Mark-release-recapture experiments performed with natural populations of Drosophila at Mather, California show that flies tend to return to their area of original capture or an area ecologically similar to it. Such habitat choice explains the microgeographic genetic differentiation we observed in the population. This behavioral difference between the flies may have a genetic component or may be environmentally induced. Either way, the results help explain how high levels of genetic variation are maintained by natural selection in these species.