Evidence that the hypothermic response of mice to delta-9-tetrahydrocannabinol is not mediated by changes in thermogenesis in brown adipose tissue.

Delta 9-Tetrahydrocannabinol (20 mg/kg i.p.) and propranolol (20 and 50 mg/kg i.p.) produced marked falls in the rectal temperatures of mice kept at an ambient temperature of 22 degrees C. Propranolol (50 mg/kg i.p.) also decreased the thermogenic activity of brown fat, as measured by a decrease in the level of [3H]GDP binding to mitochondria obtained from mouse interscapular brown adipose tissue. In contrast, delta 9-tetrahydrocannabinol (20 mg/kg i.p.) did not affect mitochondrial GDP binding even though the dose used was one shown previously to depress heat production. GDP binding was also unaffected by this cannabinoid in brown adipose tissue taken from mice that had been kept at 13 degrees C instead of 22 degrees C. In mice kept at 34 degrees C, isoprenaline (0.25 and 1.0 mg/kg s.c.) induced a marked rise in rectal temperature and increased the level of GDP binding to brown fat mitochondria. Propranolol (50 mg/kg i.p.) prevented the hyperthermic response to isoprenaline, the mice becoming hypothermic instead. Delta 9-Tetrahydrocannabinol (20 mg/kg i.p.) had no effect on isoprenaline-induced hyperthermia. We conclude from these data that there is no significant involvement of brown adipose tissue in the hypothermic response of mice to delta 9-tetrahydrocannabinol.     

Catenation and supercoiling in the products of bacteriophage λ integrative recombination in vitro

Catenanes (interlocked circular DNA molecules) are the exclusive products of the bacteriophage λ integrative recombination reaction in vitro when the substrate is a supercoiled DNA molecule containing both the attP and attB sites. It is proposed that the catenation results from the superhelical form of the substrate DNA. We also show that both circular DNA products of a single recombination event can be recovered as superhelical molecules with a superhelical density approximately that of the substrate DNA. The recombination reaction must therefore occur as a coupled process which does not permit free rotation around single-strand breaks at any stage.     

Purification and properties of the Escherichia coli protein factor required for lambda integrative recombination

A purified preparation of the Escherichia coli integration host factor (IHF) displays two polypeptides of apparent molecular weight 11,000 and 9,500 when analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Under nondenaturing conditions, IHF appears to exist as a 1:1 complex of these two polypeptides. Integrative recombination takes place in vitro when purified IHF and purified Int, a product of a bacteriophage lambda gene, are the only proteins added to reaction mixtures. No recombination is detected in the absence of either protein. The characteristics of the recombination reaction carried out by these two purified proteins are described. Purified IHF binds to DNA; in the presence of Int, a ternary complex is formed at one of the specific recombination sites. IHF hs no detectable endonuclease or topoisomerase activity. Several possibilities for the role of IHF in recombination are considered.     

Laboratory observations on the burrowing of the snake blenny, Lumpenus lampretaeformis (Walbaum), in soft sediment

The Lumpenus lampretaeformis used in this study were caught on soft sediments in Irvine Bay and Ardmucknish Bay (West Coast of Scotland). In aquaria the fish is capable of constructing and maintaining its own burrow in soft sediments. The burrow has a'Y'configuration which may be made complex by the construction of additional tunnels as the original system begins to decay. The cross sections of these burrows are distinctive in that they have an oval shape in the main tunnel and a rounded cross section in the subsidiary (side) tunnel. Burrowing can be relatively rapid, a burrow with three entrances being constructed within 12 h.     

Studies on the utilization of dietary thymidine and thymine by Drosophila melanogaster larvae

Deoxycytidine improves tolerance of Drosophila melanogaster to thymidine block, suggesting the presence of deoxycytidine kinase. At appropriate concentrations, a mixture of thymidine and deoxycytidine allows larvae to tolerate a higher concentration of 5-fluoro-2′-deoxyuridine than is tolerated with either thymidine or deoxycytidine alone. Thus, at this high concentration, 5-fluoro-2′-deoxyuridine appears to act primarily upon thymidylate synthetase, as it does at lower concentrations, rather than upon RNA metabolism, as has been suggested previously. Larvae can also be rescued from 5-fluoro-2′-deoxyuridine-induced death by a high concentration of thymine. The effect is enhanced by the presence of deoxyadenosine. Since this compound is known to increase the intracellular concentration of deoxyribose-1-phosphate, the main effect of thymine is probably due to its salvage utilization as a thymidine source, via the anabolic functioning of thymidine phosophorylase.     

Troop fission in free-ranging baboons in the Gombe Stream National Park, Tanzania.

During a 13 month field study of baboons in the Gombe Stream National Park, Tanzania, the troop under observation divided into two groups. One group left the main troop to become ultimately an independent troop with a separate range. The troop fission followed a period of instability in the male status hierarchy. The events prior to and during the troop fission are described in detail and the membership of the group which left is analyzed. Social bonds prior to the fission, including kinship, determined membership in the group which left. Aggression from members of the main troop played a major role in causing the group which left to establish a new range. This fission is compared with troop fissions observed in rhesus and Japances macaques.     

Gene networks in development

A model is presented for the formation of temporal and spatial patterns of cell types during the development of organisms. It is demonstrated that very simple random networks of interactions among genes that affect expression may lead to the autonomous development of patterns of cell types. It is required that the networks contain active feedback loops and that there is limited communication among cells. The only elements of the model, gene interactions, are specified by the DNA nucleotide sequences of the genes. Therefore, the model readily explains how the control of development is specified by the organism's DNA. In the context of this model, the formation of positional information and its interpretation becomes a single process.