Specific binding of sulphated polymers to ram sperm proacrosin

Sulphated polysaccharides and zona pellucida glycoproteins have been shown to bind non-enzymatically to proacrosin, the protein found within the acrosomal vesicle of mammalian spermatozoa. The mechanism of this interaction has been investigated using ¹²⁵I-fucoidan to probe purified ram sperm proacrosin. Results show that (a) binding of' ¹²⁵I-fucoidan to proacrosin is inhibited only by sulphated polymers and (b) recognition is mediated by poly(sulphate) groups and is largely independent of the composition of the polymer chain. It is suggested that a similar mechanism is responsible for the interaction between proacrosin and zona pellueida glycoproteins during the early stages of fertilization in mammals and this process mediates firm binding of spermatozoa to the egg.     

Cultural transmission and the evolution of cooperative behavior

Sociobiological theory predicts that humans should not cooperate with large groups of unrelated individuals. This prediction is based on genetic models that show that selection acting on variation between large unrelated groups will generally be much weaker than selection acting on variation between individuals. Recently, several authors have presented related models of human evolution that integrate cultural and genetic transmission of behavior. We show that in such models group selection is potentially a strong force. Data on ethnocentrism is examined in the context of these results.     

Physical mapping of the genome and sequence analysis at the inverted terminal repetition of adenovirus type 4 DNA

The genome of adenovirus type 4 (Ad4), the unique member of Ad group E, has been mapped with nine restriction endonucleases. Comparison of the occurrence of restriction endonuclease cleavage sites on Ad2, Ad7, Ad12 and Ad4 indicates that there is very little homology between these serotypes. Sequence analysis at the ITR of Ad4 showed that the "CAT" box which is present in all the ITRs of Ad's so far sequenced is absent in Ad4. The length of 116 bp for the ITR of Ad4 is also different from that of other Ad subgroups.     

Utilization of Citrate, Acetylcarnitine, Acetate, Pyruvate and Glucose for the Synthesis of Acetylcholine in Rat Brain Slices

Slices of rat caudate nuclei were incubated in saline media containing choline, paraoxon, unlabelled glucose, and [1,5-14C] citrate, [1-14C-acetyl]carnitine, [1-14C]acetate, [2-14C]pyruvate, or [U-14C]glucose. The synthesis of acetyl-labelled acetylcholine (ACh) was compared with the total synthesis of ACh. When related to the utilization of unlabelled glucose (responsible for the formation of unlabelled ACh), the utilization of labelled substrates for the synthesis of the acetyl moiety of ACh was found to decrease in the following order: [2-14C]pyruvate greater than [U-14C]glucose greater than [1-14C-acetyl]carnitine greater than [1,5-14C]citrate greater than [1-14C]acetate. The utilization of [1,5-14C]citrate and [1-14C]acetate for the synthesis of [14C]ACh was low, although it was apparent from the formation of 14CO2 and 14C-labelled lipid that the substrates entered the cells and were metabolized. The utilization of [1,5-14C]citrate for the synthesis of [14C]ACh was higher when the incubation was performed in a medium without calcium (with EGTA); that of glucose did not change, whereas the utilization of other substrates for the synthesis of ACh decreased. The results indicate that earlier (indirect) evidence led to an underestimation of acetylcarnitine as a potential source of acetyl groups for the synthesis of ACh in mammalian brian; they do not support (but do not disprove) the view that citrate is the main carrier of acetyl groups from the intramitochondrial acetyl-CoA to the extramitochondrial space in cerebral cholinergic neurons.     

Carbohydrate binding activity of a lectin-like glycoprotein from stems and leaves of Dolichosbiflorus

A glycoprotein from the stems and leaves of the $\text{Dolichos}$$\text{biflorus}$ plant that cross reacts with antibodies to the seed lectin has been found to bind to affinity columns of blood group A + H substance covalently linked to Sepharose. This binding of the cross reactive material to the affinity resin differs from that of the seed lectin in that it is easily dissociated with 0.15 M NaCl. Affinity electrophoresis using entrapped blood group A + H substance shows that the carbohydrate binding activity of the cross reactive material is weakly inhibited with N-acetyl-D

-galactosamine and N-acetyl-D

-glucosamine. Glucose, mannose and galactose gave no inhibition when tested at concentrations of 50 mM. These data indicate that the specificity of the cross reactive material is somewhat different from the N-acetyl-D

-galactosamine specificity of the seed lectin. The significance of these findings is discussed in relation to the structural similarities of the cross reactive material and the seed lectin.