Biocatalyzed approach for the surface functionalization of poly(L‐lactic acid) films using hydrolytic enzymes

Poly(lactic acid) as a biodegradable thermoplastic polyester has received increasing attention. This renewable polyester has found applications in a wide range of products such as food packaging, textiles and biomedical devices. Its major drawbacks are poor toughness, slow degradation rate and lack of reactive side‐chain groups. An enzymatic process for the grafting of carboxylic acids onto the surface of poly(L‐lactic acid) (PLLA) films was developed using Candida antarctica lipase B as a catalyst. Enzymatic hydrolysis of the PLLA film using Humicola insolens cutinase in order to increase the number of hydroxyl and carboxylic groups on the outer polymer chains for grafting was also assessed and showed a change of water contact angle from 74.6 to 33.1° while the roughness and waviness were an order of magnitude higher in comparison to the blank. Surface functionalization was demonstrated using two different techniques, ¹⁴C‐radiochemical analysis and X‐ray photoelectron spectroscopy (XPS) using ¹⁴C‐butyric acid sodium salt and 4,4,4‐trifluorobutyric acid as model molecules, respectively. XPS analysis showed that 4,4,4‐trifluorobutyric acid was enzymatically coupled based on an increase of the fluor content from 0.19 to 0.40%. The presented ¹⁴C‐radiochemical analyses are consistent with the XPS data indicating the potential of enzymatic functionalization in different reaction conditions.     

DNS-Gehalt und Chromosomenstruktur bei Amphibien

Comparative karyotype analysis and cytophotometric DNA measurements on further amphibian species (Hyla arborea, Bombina variegata, B. bombina, Triturus vulgaris, T. alpestris, and Salamandra salamandra) were carried out. The relative DNA values of the genomes determined for these species and other amphibians investigated earlier (Ullerich, 1966, 1967), already do nearly exclude the hypothesis that the interspecific differences in DNA content in frogs, toads, and salamanders are caused by differential polynemy of their chromosomes. Electron microscopic investigations on the DNA axes of lampbrush chromosomes of Bufo calamita, B. viridis, B. bufo, Rana esculenta, Bombina variegata, and Triturus alpestris treated with trypsin and ribonuclease confirm that the chromosomes of these species are not polynemic; in all species analysed the lampbrush chromosomes consist of the same number of DNA strands. The double-strandedness observed regularly in several segments of the chromatid axes in the loops as well as in the interchromomeric regions of all species suggest that the chromatids possibly are divided into half-chromatids. The minimum diameter of these two deoxyribonuclease-sensitive fibrills is 20–35 Å, whereas the chromatid axes in those segments which do not show double-strandedness mostly measure 40–65 Å. The high DNA amounts and interspecific differences in DNA content in the amphibian species analysed, probably in all amphibians, therefore must be caused during evolutionary processes by local increase (perhaps in a smaller extent also by-local decrease) in DNA in the chromosomes.     

Die genetische Grundlage der Monogenie bei der Schmei?fliege Chrysomya rufifacies (Calliphoridae, Diptera)

Summary Recently in our wild stock of the monogenic blowfly Chrysomya rufifacies a recessive mutation white (w) causing white instead of red-brown eyes spontaneously appeared (Fig. 1). This marker gene enabled us to clarify the genetic basis of monogeny in this species. F₁ offspring produced by reciprocal crossings between normal (+/+) and white-eyed (w/w) flies were phenotypically wildtype (Table 1). In F₂ offspring of female-producing (thelygenic) and male-producing (arrhenogenic) F₁ females wildtype and white-eyed flies appeared in the expected 3:1 ratio; in several crossings a slight deviation of this ratio indicated a reduced viability of the w/w individuals (Table 2). Examination of F₂ progeny of thelygenic F₁+/w females, which had received the w allele from their father, showed that most of the F₂+/+ females were thelygenic, whereas most of the F₂ w/w females were arrhenogenic; among F₂+/w females thelygenic and arrhenogenic individuals occurred in almost equal numbers (Table 3). On the other hand, when F₂ offspring of thelygenic F₁+/w females which had inherited the w allele from their mother were tested, most of the F₂+/+ females turned out to be arrhenogenic and most of the F₂ w/w females thelygenic; among F₂+/w females thelygenic and arrhenogenic flies also were found in almost equal frequencies (Table 4). the sex-linked inheritance of the factor w following from these results was also confirmed by an analysis of the progeny of thelygenic F₁+/w females backcrossed with w/w males. Among the R₁ offspring of F₁+/w females, which had received the w allele from their father, the +/w females were predominantly thelygenic compared to their predominantly arrhenogenic w/w sisters (Table 5). Analysis of R₁ progeny of F₁+/w females, which had inherited the w allele from their mother, yielded reciprocal results (Table 6).This mode of incomplete sex-linkage of the mutation white observed in C. rufifacies (Figs. 2–5) supports the hypothesis that thelygenic females are heterozygous for a dominant female sex realizer (F') with predetermined sex-determining properties, and that arrhenogenic females as well as the males are homozygous for the recessive allele f (Fig. 6). The recombination frequency between F'/f and the w-Locus was calculated to be 12.72±0.72 per cent.

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Mit Unterstützung durch die Deutsche forschungsgemeinschaft.     

Analysis of a recessive mutation on the Y chromosome of the fly Caliphora erythrocephala

Summary In a strain of the mutantw (yellow eye colour, sex-linked and sex-limited to the females) ofCalliphora erythrocephala yellow-eyed males have been found. In connexion with the mechanism of sex-determination in this fly, their origin is explained by an alteration on the Y-chromosome (one of the III^rd large chromosomes) in form of either a pre-meiotic cross-over or a spontaneous mutation on thew ⁺-locus. For being recessive, it can become manifest only in thew strain.     

The day after: effects of vocal interactions on territory defence in nightingales

1. Models on territory acquisition and tenure predict that territorial animals benefit by adjusting territorial defence behaviour to previous challenges they had experienced within the socially complex environment of communication networks. 2. Here, we addressed such issues of social cognition by investigating persisting effects of vocal contests on territory defence behaviour in nightingales Luscinia megarhynchos (Brehm). 3. Using interactive playback during nocturnal song of subjects, a rival was simulated to countersing either aggressively (by song overlapping) or moderately (by song alternating) from outside the subjects' territory. Thereby, the time-specific singing strategy provided an experimentally controlled source of information on the motivation of an unfamiliar rival. 4. Expecting that nightingales integrate information with time, the same rival was simulated to return as a moderately singing intruder on the following morning. 5. The results show that the vigour with which male nightingales responded to the simulated intrusion of an opponent during the day depended on the nature of the nocturnal vocal interaction experienced several hours before. 6. Males that had received the song overlapping playback the preceding night approached the simulated intruder more quickly and closer and sang more songs near the loudspeaker than did males that had received a song alternating playback. 7. This adjustment of territory defence strategies depending on information from prior signalling experience suggests that integrating information with time plays an important part in territory defence by affecting a male's decision making in a communication network.     

Sex differences in responsiveness to begging in a cooperative mammal

In species where young are provisioned by both parents, males commonly contribute less to parental care than females, and are less responsive to variation in begging rates. Similar differences in the care of young occur among adults in cooperative breeders, but fewer studies have investigated whether these are associated with differences in responsiveness. Here, we present results from a playback experiment investigating responsiveness to begging in the meerkat (Suricata suricatta), a cooperatively breeding mammal. Although increased begging rate raised the feeding rate of adults of both sexes, there was no consistent tendency for females to be more responsive than males. However, when we examined changes in the proportion of food items found that were fed to pups (generosity), we found that females were more responsive than males to increased begging rate. These results can be explained in terms of sex differences in dispersal: in meerkats, females are philopatric and receive considerable benefits from investing in young, both directly, by increasing group size, and indirectly, by recruiting helpers if they inherit the breeding position. In addition, they emphasize that generosity provides a more sensitive measure of responsiveness to begging than feeding rate, as it accounts for variation in foraging success.