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.     

In vitro replication of mouse hepatitis virus strain A59.

An in vitro replication system for mouse hepatitis virus (MHV) strain A59 was developed using lysolecithin to produce cell extracts. In extracts of MHV-infected cells, radiolabeled UMP was incorporated at a linear rate for up to 1 h into RNA, which hybridized to MHV-specific cDNA probes and migrated in denaturing formaldehyde-agarose gels to the same position as MHV genomic RNA. The incorporation of [32P]UMP into genome-sized RNA in vitro correlated with the observed increase of [3H]uridine incorporation in MHV-infected cells labeled in vivo. Incorporation of [32P]UMP into genome-sized RNA was inhibited when extracts were incubated with puromycin. The addition to the assay of antiserum to the MHV-A59 nucleocapsid protein N inhibited synthesis of genome-sized RNA by 90% compared with the addition of preimmune serum. In contrast, antiserum to the E1 or E2 glycoproteins did not significantly inhibit RNA replication. In vitro-synthesized RNA banded in cesium chloride gradients as a ribonucleoprotein complex with the characteristic density of MHV nucleocapsids isolated from virions. These experiments suggest that ongoing protein synthesis is necessary for replication of MHV genomic RNA and indicate that the N protein plays an important role in MHV replication.     

Primary structure analysis proves that protein phosphatases 2C1 and 2C2 are isozymes

The two recently discovered forms of protein phosphatase 2C, termed 2C1 and 2C2, were digested with CNBr or trypsin, and several peptides corresponding to two regions of the protein were sequenced. These studies revealed close homology between the two enzymes with 49 identities over the 62 residues that could be compared directly. The results establish that protein phosphatases 2C1 and 2C2 are the products of different genes. The C-terminus of protein phosphatase 2C2 has also been identified.     

The effect of dietary alteration of prostaglandin synthesis on blood pressure and the reversal of hypertension in the one-kidney, one-clip rat

This study examined the effect of diet-induced changes in prostaglandin synthesis on systolic blood pressure in one-kidney, one clip (1k, 1C) hypertensive rats and on the fall in blood pressure after unclipping. It tested the hypothesis that inhibition of prostaglandin synthesis exacerbates hypertension in this model and prevents complete reversal after unclipping. Rats with sustained hypertension within 8 weeks of renal artery clipping were fed synthetic diets supplemented to 20% of total energy with either safflower oil (linoleic acid) or a mixture of cod liver oil (90%) (containing eicosapentaenoic acid) and linseed oil (10%) (containing linolenic acid) for 4 weeks. The latter oil mixture resulted in a predictable reduction in kidney PGE2 and 6-keto PGF1 alpha (hydrolysis product of PGI2), aortic 6-keto PGF1 alpha and serum TXB2. However, at the end of 4 weeks dietary treatment there were no differences in systolic blood pressure between the two diet groups, and the blood pressure fall 24 hours after unclipping was similar. These findings therefore do not support a role for prostanoids in the maintenance or reversal of 1K, 1C hypertension.     

Relationships among negative life events, physiological reactivity, and health symptomatology

College undergraduates classified as high (n = 25) and low (n = 25) on recent life stress participated in an experiment involving a novel laboratory stressor. Heart rate and pulse arrival time (PAT) were measured during baseline, anticipation, testing, and recovery periods of the experiment. The results did not replicate those obtained by Pardine and Napoli in that high and low life stress subjects did not show differential physiological reactions. In addition, regression analyses failed to demonstrate that physiological reactivity moderated the relationship between life stress and subsequent self-reported psychiatric or physical health symptomatology. The present findings demonstrated neither the stress-buffering effects of physiological reactivity nor a relationship between life stress and reactivity when the latter was conceptualized as an outcome.     

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.