Automated extraction of bank angles from bird‐borne video footage using open‐source software

The use of miniaturized video cameras to study the at‐sea behavior of flying seabirds has increased in recent years. These cameras allow researchers to record several behaviors that were not previously possible to observe. However, video recorders produce large amounts of data and videos can often be time‐consuming to analyze. We present a new technique using open‐source software to extract bank angles from bird‐borne video footage. Bank angle is a key facet of dynamic soaring, which allows albatrosses and petrels to efficiently search vast areas of ocean for food. Miniaturized video cameras were deployed on 28 Wandering Albatrosses (Diomedea exulans) on Marion Island (one of the two Prince Edward Islands) from 2016 to 2018. The OpenCV library for the Python programming language was used to extract the angle of the horizon relative to the bird’s body (= bank angle) from footage when the birds were flying using a series of steps focused on edge detection. The extracted angles were not significantly different from angles measured manually by three independent observers, thus being a valid method to measure bank angles. Image quality, high wind speeds, and sunlight all influenced the accuracy of angle estimates, but post‐processing eliminated most of these errors. Birds flew most often with cross‐winds (58%) and tailwinds (39%), resulting in skewed distributions of bank angles when birds turned into the wind more often. Higher wind speeds resulted in extreme bank angles (maximum observed was 94°). We present a novel method for measuring postural data from seabirds that can be used to describe the fine‐scale movements of the dynamic‐soaring cycle. Birds appeared to alter their bank angle in response to varying wind conditions to counter wind drift associated with the prevailing westerly winds in the Southern Ocean. These data, in combination with fine‐scale positional data, may lead to new insights into dynamic‐soaring flight.     

The uptake of liposome-entraped 125I-labelled poly(vinylpyrrolidone) by rat jejunum in vitro

The uptake of free and liposome-entrapped ¹²⁵I-labelled poly(vinylpyrrolidone) was measured in an intestinal sac preparation from adult rats. An an equal concentration of ¹²⁵I-labelled poly(vinylpyrrolidone), the rate of uptake of the liposome-entrapped material was four times that of the free macromolecule.     

2-keto-3-deoxygluconate transport system in Erwinia chrysanthemi.

In Erwinia chrysanthemi, the gene kdgT encodes a transport system responsible for the uptake of ketodeoxyuronates. We studied the biochemical properties of this transport system. The bacteria could grow on 2,5-diketo-3-deoxygluconate but not on 2-keto-3-deoxygluconate. The 2-keto-3-deoxygluconate entry reaction displayed saturation kinetics, with an apparent Km of 0.52 mM (at 30 degrees C and pH 7). 5-Keto-4-deoxyuronate and 2,5-diketo-3-deoxygluconate appeared to be competitive inhibitors, with Kis of 0.11 and 0.06 mM, respectively. The 2-keto-3-deoxygluconate permease could mediate the uptake of glucuronate with a low affinity. kdgT was cloned on an R-prime plasmid formed by in vivo complementation of a kdgT mutation of Escherichia coli. After being subcloned, it was mutagenized with a mini-Mu-lac transposable element able to form fusions with the lacZ gene. We introduced a kdgT-lac fusion into the E. chrysanthemi chromosome by marker exchange recombination and studied its regulation. kdgT product synthesis was not induced by external 2-keto-3-deoxygluconate in the wild-type strain but was induced by galacturonate and polygalacturonate. Two types of regulatory mutants able to grow on 2-keto-3-deoxygluconate as the sole carbon source were studied. Mutants of one group had a mutation in the operator region of kdgT; mutants of the other group had a mutation in kdgR, a regulatory gene controlling kdgT expression.     

In vitro study of lipid metabolism in the mealworm larval fat body

Lipid metabolism in Tenebrio larval fat body has been studied in vitro. Lipid release required the presence of diluted hemolymph in the incubation medium. This time-dependent release of lipid was strongly stimulated in a dose-dependent manner by Tenebrio corpora cardiaca (CC) extracts or synthetic adipokinetic hormone (AKH I). Furthermore, some glycerol was released when larval fat body was incubated without hemolymph, and this phenomenon was also dose dependent for added CC extracts. Lipid synthesis was estimated in vitro by following the incorporation of radioactivity from [6-¹⁴C] glucose into fatty acids. Lipogenesis occurred in the absence of added carbohydrates in the medium, but it was stimulated by the addition of glucose, and especially trehalose (10 mg ml^?1). Intestinal insulin-like peptide (ILP) also stimulated in vitro lipogenesis in a dose-dependent fashion. We conclude that lipolytic and lipogenetic activities of larval mealworm fat body in vitro are effectively under hormonal control.     

Cloning of genes encoding pectolytic enzymes from a genomic library of the phytopathogenic bacterium, Erwinia chrysanthemi

Erwinia chrysanthemi are phytopathogenic enterobacteria causing soft-rot disease due to pectolytic enzymes degrading plant cell walls. We constructed a genomic library from Sau3A-digested E. chrysanthemi B374 DNA cloned in the BamHI site of the broad-host-range cosmid pMMB33 grown in Escherichia coli. Out of 1500 kanamycin-resistant (KmR) transductants of E. coli, nine pectolytic-enzyme-positive clones were identified. One of these contained the pEW325 cosmid with a 35-kb insert of Erwinia DNA. Cell extracts of E. coli harboring the cosmid pEW325 were fractionated on a polyacrylamide electrofocusing gel; bands with pectolytic activity were found to co-focus with pectolytic enzymes of E. chrysanthemi B374 strain. Cosmid pEW325 encodes three pectolytic enzymes PL10, PL20 and PL130 with isoelectric points of about 9.3, 9.2 and 4.6, respectively. These enzymes are lyases that cleave polygalacturonate by transelimination, and give rise to unsaturated products. A 15-kb HindIII fragment coding for polygalacturonate lyases was subcloned in pBR322, and a physical map of the resulting plasmid pPL01 was constructed. Starting from the pPL01, various endonuclease-generated fragments were subcloned into pBR322. Genes encoding pectate lyases were localized within an 8-kb fragment (pPL04) and then in a 2.7-kb fragment (pPL03). Polygalacturonate lyases are expressed at various levels; they accumulated in the periplasmic space of E. coli host, whereas E. chrysanthemi secreted these enzymes into the culture medium.     

Protein Synthesis in Sonically Damaged Escherichia coli

By gentle sonic treatment, Escherichia coli cells were modified to permit penetration of actinomycin D, adenosine triphosphate, trypsin, ribonuclease, and polyuridylic acid. The behavior of these "soniplasts" as protein-synthesizing particles was investigated.     

Etude de la Faune submicroscopique de quelques tourbières à sphagnum

Sans résumé     

Isolation of Erwinia chrysanthemi mutants altered in pectinolytic enzyme production

Various mutations in the pectin catabolic pathway of Erwinia chrysanthemi were isolated by selection of Mu-lac insertions, resulting in expression of the lac genes inducible by pectin degradation products. This approach allowed us to isolate lacZ fusions with the genes pelC, pelD, ogl and pem, encoding pectate lyases PLc and PLd, oligogalacturonate lyase and pectin methytesterase, respectively. Moreover, we obtained mutations affecting the regulation of pectinolytic enzymes; a locus called peel appeared to be involved in induction of pectate tyases and pectin methylesterase. A second locus, called pect, may encode an activator protein acting on pectate lyase production. Both peel and pecL expression are induced in the presence of pectic polymers. The expression of the pem gene was studied in more detail by analysis of the pem-lacZ fusions. The expression of pem appears to be controlled by the negative regulatory gene kdgR, which controls alt the genes involved in pectin degradation (pem, pel, ogl, kduD, kduf, kdgK, kdgA). This study confirmed that 2-keto-3-deoxy-gluconate is a key intermediate for the induction of the pectin catabolic pathway. The three genes pem, pelD and pecl were localized in the same region, near the ade-377 marker on the genetic map of the E. chrysanthemi strain 3937. The pem gene was located more precisely on an 18kb DNA fragment containing the pelADE cluster. However, this 18 kb DNA fragment did not complement the pecl mutation. The pecL mutations were located near the ile-2 marker on the genetic map of E. chrysanthemi strain 3937.