THE ENDOCRINE BASIS OF PAIR-FORMATION BEHAVIOUR IN THE MALE EIDER SOMATERIA MOLLISSIMA

Pair-formation behaviour among the Eiders began after the annual moult, in late September. There was a small peak of display in October and November and a large one in the following April and May. As a result, the female population became paired in two phases, up to 50% in the autumn and the remainder in the following spring. The seasonal cycle of the abundance of Leydig cells was bimodal, with a peak in October and a large one in April-May. That the peaks represent increased androgen production was supported by the cycles of Leydig cell enzyme activity and lipid content and of penis weight. The monthly means of Leydig cell abundance and of the rate of display were statistically correlated. Experiments with sexually quiescent males in eclipse plumage demonstrated that testosterone was capable of inducing pair-formation behaviour. Relatively advanced stages of spermatogenesis were found in autumn, and were maintained through the winter, complete development occurring in the spring. Seasonal changes in the production of pituitary gonadotropin followed a bimodal pattern with peaks in autumn and in the spring. Field evidence is presented which suggests that Follicle Stimulating Hormone and Luteinizing Hormone were produced at different phases of a circadian rhythm of photosensitivity.     

Polyproline binding is an essential function of human profilin in yeast.

Structural analysis of human profilin has revealed two tryptophan residues, W3 and W31, which interact with polyproline. The codons for these residues were mutated to encode phenylalanine and the mutant proteins overexpressed in Eschericia coli. The isolated proteins were diminished in their ability to bind polyproline, whereas phosphatidylinositol 4,5-bisphosphate (PIP2) binding remained unchanged. In many strains of Saccharomyces cerevisiae, disruption of the gene encoding profilin, PFY1, is lethal. It was found that expression of the gene for human profilin is capable of suppressing this lethality. The polyproline-binding mutant alleles of the human gene were cloned into various yeast expression vectors. Each of the mutant genes resulted in suppression of the lethality of pfy1Delta. It was observed that the mutant protein expression levels paralleled the growth rates of the strains. The severity of various morphological abnormalities of the strains was also attenuated with increased protein levels, suggesting that profilin polyproline-binding mutations are deleterious to cell growth unless overexpressed. Both tryptophan mutations were combined to give a third mutant allele that was found both unable to bind polyproline and to suppress the lethality of a pfy1 deletion. Immunoprecipitation experiments suggested that the mutants were unaltered in their affinity for actin and PIP2. These data strongly suggest that polyproline binding is an essential function of profilin.     

Chromosomal locations of the gene coding for the CD3 (T3) γ subunit of the human and mouse CD3/T-cell antigen receptor complexes

The gene coding for the M _r 26000 chain of the human CD3 (T3) antigen/T-cell antigen receptor complex was mapped to chromosome band 11q23 by using a cDNA clone (pJ6T3 -2), by in situ hybridization to metaphase chromosomes and by Southern blot analysis of a panel of human-rodent somatic cell hybrids. The mouse homolog, here termed Cdg-3, was mapped to chromosome 9 using the mouse cDNA clone pB10.AT3 -1 and a panel of mouse-hamster somatic cell hybrids. Similar locations for the CD3 genes have been described previously. Thus, the corporate results indicate that the CD3 and genes have remained together since they duplicated about 200 million years ago.     

The gene coding for the human T-lymphocyte CD2 antigen is located on chromosome 1p

Summary A cDNA clone encoding the human T lymphocyte sheep erythrocyte receptor [the CD2 (T11) antigen] was used as a probe to define the chromosomal location of the gene. The signal, revealed by hybridisation to Southern blots of genomic DNA from somatic cell hybrids, showed a high degree of concordance for human chromosome 1. In particular, the hybrid F4Sc13C19 which contained the short arm only of human chromosome 1 was positive. The location of the CD2 gene to 1p13 was confirmed by in situ hybridisation.     

Characterization of a bombesin receptor on Swiss mouse 3T3 cells by affinity cross-linking

We have previously identified by chemical cross-linking a cell surface protein in Swiss 3T3 cells of apparent Mr 75,000-85,000, which may represent a major component of the receptor for peptides of the bombesin family in these cells. Because bombesin-like peptides may interact with other cell surface molecules, it was important to establish the correlation between receptor binding and functions of this complex and further characterize the Mr 75,000-85,000 cross-linked protein. Detailed time courses carried out at different temperatures demonstrated that the Mr 75,000-85,000 affinity-labelled band was the earliest cross-linked complex detected in Swiss 3T3 cells incubated with 125I-labelled gastrin-releasing peptide (125I-GRP). Furthermore, the ability of various nonradioactive bombesin agonists and antagonists to block the formation of the Mr 75,000-85,000 cross-linked complex correlated extremely well (r = 0.994) with the relative capacity of these peptides to inhibit 125I-GRP specific binding. Pretreatment with unlabelled GRP for up to 6 h caused only a slight decrease in both specific 125I-GRP binding and the affinity labelling of the Mr 75,000-85,000 protein. We also show that the cross-linked complex is a glycoprotein. First, solubilized affinity labelled Mr 75,000-85,000 complex applied to wheat germ lectin-sepharose columns was eluted by addition of 0.3 M N-acetyl-D-glucosamine. Second, treatment with endo-beta-N-acetylglucosaminidase F reduced the apparent molecular weight of the affinity-labelled band from 75,000-85,000 to 43,000, indicating the presence of N-linked oligosaccharide groups.     

Structure and biochemistry of endosperm breakdown in date palm (Phoenix dactylifera L.) seeds

Summary The zone of endosperm breakdown in the germinated date seed (Phoenix dactylifera L.) is a narrow area immediately adjacent to the surface of the enlarging cotyledon, or haustorium. The zone width is correlated with the amount of cell division in the adjacent region of the haustorium. The sequence of endosperm breakdown is: 1. protein bodies vacuolate, 2. storage cell walls become electron-transparent immediately adjacent to the protoplast of each endosperm cell, 3. all remaining cytoplasm and lipid bodies disappear, and 4. the remaining cell walls become electron-transparent and collapse against the haustorium surface. Two cell wall hydrolases are present—endo-mannanase (EC3.2.1.78) and -mannosidase (EC3.2.1.25). -mannosidase is detectable in the endosperm before germination. At germination, the major portion of activity is found in the softened endosperm. -mannanase is only detectable from germination and there is always hundreds of fold greater activity in the softened endosperm than elsewhere. Proteinase is detectable in trace amounts at germination in the softened endosperm but is also found in the haustorium at later stages. Isolated haustoria, incubated in extracted ivory nut (Phytelephas macrocarpa) mannan in buffer, cause no mannan breakdown. Haustoria, incubated in a solution of locust bean galactomannan, cause no decrease in galactomannan viscosity. Our observations suggest that although haustoria probably regulate mannan breakdown in the endosperm, they do not seem to secrete the hydrolytic enzymes concerned.     

Structural features of glutamine substrates for transglutaminases. Role of extended interactions in the specificity of human plasma factor XIIIa and of the guinea pig liver enzyme

Amino acid residues at several locations in close primary vicinity to a substrate glutamine residue have been recognized as important determinants for the specificities of human plasma factor XIIIa and guinea pig liver transglutaminase (Gorman, J. J., and Folk, J. E. (1981) J. Biol. Chem. 256, 2712-2715). The present studies measure the influence on transglutaminase specificity of some changes in amino acid side chains in a small synthetic glutamine peptide amide, Leu-Gly-Leu-Gly-Gln-Gly-Lys-Val-Leu-GlyNH2, which was designed to contain most of the known elements needed for enzyme recognition. The results are in agreement with previous findings and show that full catalytic activity of each enzyme may be retained upon replacement of the lysine residue by certain other amino acid residues. Evidence is provided that serine in place of glycine at one or more positions causes a significant increase in specificity with factor XIIIa, but not with liver enzyme. The effective substrate property for factor XIIIa seen with the model peptide amide is lost upon reversal of the sequence Val-Leu. This is not the case with the liver enzyme even though replacement of either of these amino acids by alanine causes a pronounced loss in activity with this enzyme. These differences and the effects of various other substitutions in the model peptide amide on the enzymes' specificities points up the relatively stringent structural requirements of factor XIIIa and the rather broad requirements for liver transglutaminase.