MATING FREQUENCY AND FECUNDITY IN INSECTS

1. The paper summarizes the published evidence on the relation between mating frequency and fecundity in insects. There is experimental evidence of varying quality for 63 species and non-experimental evidence for about 60.
2. Repeated mating may be universally necessary for full fecundity and fertility in female insects (in species in which the females normally mate more than once).
3. The evidence is remarkably poor. We need more properly designed experiments (and not just observations of natural variation), with sufficient sample sizes and statistics, and measurements of the fecundities and fertilities of singly and multiply mated females, when the multiple matings are separated by many days or weeks. Most of the existing experiments of this sort are defective in some way.
4. In species with greater total fecundity and longevity, multiple mating may be more likely to enhance fertility than in species with small fecundity and short life span.
5. Females in naturally monandrous species do not show increased fecundity or fertility with repeated mating, whereas females of polyandrous species do.
6. There is no obvious connexion between paternal investment, in so far as we know about it, and the increase of fecundity by repeated mating.
7. There is a small tendency for females to breed more quickly and be shorter lived if they mate repeatedly.     

Changes in the heat resistance of Salmonella typhimurium during heating at rising temperatures

The heat resistance of Salmonella typhimurium , measured as survival following a standard heat challenge at 55°C for 25 min, increased progressively as cells were heated up at linearly rising temperatures. The amount by which heat resistance increased depended on the rate of temperature rise; the slower the temperature rise, the greater the increase in resistance.     

Susceptibility of neuroactive peptides to aminopeptidase digestion is related to molecular size.

Peptide fragments derived from the NH₂-terminus of corticotropin were found to exhibit widely differing degrees of stability to degradation by aminopeptidase M. Corticotropin itself was 135 times more stable than its NH₂-terminal pentapeptide, and similar differences in stability were observed with peptides derived from the B-chain of bovine insulin. Enkephalin linked covalently to the A-chain of bovine insulin was at least 100 times more stable than the pentapeptide. The results demonstrate that the molecular size of a peptide is one factor that determines its NH₂-terminal stability.     

Biochemical, biological, and immunological properties of chemically deglycosylated human choriogonadotropin

A chemical method of deglycosylation of human choriogonadotropin (hCG) was used to assess the role of carbohydrate moiety in the maintenance of quaternary structure and functional parameters such as receptor binding, immunological activity, and in vitro biological response. Treatment of purified hCG with anhydrous HF at 0 degrees C for 60 min was effective in removing more than 75% of the carbohydrate moiety. This extent of deglycosylation altered its chromatographic characteristics as revealed by retarded behavior on Sephadex G-100 and failure to be retained on concanavalin A-Sepharose. The electrophoretic heterogeneity present in native hCG was markedly reduced by deglycosylation. The deglycosylated hCG was stable in the lyophilized form and retained its quaternary structure as revealed by the fluorescence probe 8-anilino 1-naphthalene sulfonic acid, receptor binding, and immunological activities. Unlike receptor binding and immunological activities, which were fully retained, the ability of the hormone to stimulate cyclic AMP accumulation in vitro in rat interstitial cells was completely abolished.     

Prolonged alteration in composition of fast transported protein in axons prevented from regenerating after injury

A previous study revealed a characteristic alteration in the ratio of labeling of two fast axonally transported polypeptides identified as S1 (22,000 daltons) and S2 (18,000 daltons) and their ratio (S2/S1) in rat motoneuron axons following axonal injury and subsequent regeneration. In this study the S2/S1 ratio was determined for axons which were resected and ligated proximally and which did not regenerate to reinnervate muscle. While the initial increase in the S2/S1 ratio following section was the same as that following a crush, the S2/S1 ratio did not return towards normal values after 42 days, but remained elevated for at least 98 days after injury. It is concluded that the return of S2/S1 ratio to normal values, like some other manifestations of the cell body reaction, is delayed if the injured axons do not regenerate.