Factors affecting abundance of bowhead whales Balaena mysticetus in the eastern arctic of North America, 1915–1980

The severely depleted bowhead whale Balaena mysticetus has failed to recover from overexploitation during the 18th and 19th centuries in the Eastern Arctic. Although commercial whaling for bowheads ended in this region about 1915, bowhead whaling by native people has continued until recently in parts of the Eastern Arctic. Low-level but persistent hunting by Inuit (Eskimos) may have inhibited bowhead population increase. Two natural mortality factors can be documented—ice entrapment and predation by killer whales Orcinus orca. There is little direct evidence of ice-related mortality but a strong circumstantial argument that ice conditions affect survival. Killer whales are known to prey on most species of large whales, and we believe bowhead whales and right whales Eubalaena glacialis are especially vulnerable. The bowhead's apparent failure to recover in the Eastern Arctic may be due to a combination of continued low-level hunting, habitat instability, and predation. Complete protection from all forms of hunting is necessary to ensure the bowhead's survival. Environmental disturbances due to industrial development in the Arctic may have direct and indirect impact on bowhead habitat and behaviour, creating an urgent need for further study.     

A CYLINDER GUIDE FOR USE IN PLATE ASSAY OF PENICILLIN

A guide or template is described which facilitates placing the cylinders on the agar surface in the plate assay of penicillin. The general plan of conducting the assay is discussed and several advantages of the use of the guide are noted. We wish to thank Mr. Albert G. Sterling, instrument maker, for fabricating the guide and the aluminum cylinders.     

No specific recognition of leader peptide by SecB, a chaperone involved in protein export

Most proteins destined for export from Escherichia coli are made as precursors containing amino-terminal leader sequences that are essential for export and that are removed during the process. The initial step in export of a subset of proteins, which includes maltose-binding protein, is binding of the precursor by the molecular chaperone SecB. This work shows directly that SecB binds with high affinity to unfolded maltose-binding protein but does not specifically recognize and bind the leader. Rather, the leader modulates folding to expose elements in the remainder of the polypeptide that are recognized by SecB.     

THE GOLDEN HAMSTER (CRICETUS AURATUS) AS A TEST ANIMAL FOR THE DIAGNOSIS OF LEPTOSPIROSIS

There is evidence that the golden hamster (Cricetus auratus) is the animal of choice for the isolation of leptospirae, especially of the Leptospira canicola type since young guinea pigs and mice are resistant to infection and rats are entirely refractory. Both the classical strain, L. icterohaemorrhagiae and L. canicola on isolation have been found to produce a fatal infection in hamsters. The present report deals with the isolation of L. canicola in two instances by the injection intraperitoneally into hamsters of urine obtained from dogs ill with suspected leptospirosis. Each of the dogs was apparently the source of infection for a human case of Canicola leptospirosis. The classical strain L. icterohaemorrhagiae was isolated from the dog for the first time in the United States. In this instance the organism was isolated by injecting both whole blood and urine from the patient intraperitoneally into young hamsters. The injection into hamsters of suitable material from patients infected with L. canicola and L. icterohaemorrhagiae is followed by a fatal leptospirosis in the test animal.     

Sympathetic outflows from cervical spinal cord in the dog

In some dogs there are preganglionic fibers leaving the cervical spinal cord through the ventral roots of the lower cervical nerves. When these fibers are stimulated electrically in the anesthetized dog with skeletal muscle paralysis (induced by decamethonium), the effects are vasoconstriction in the front footpad, cardiac acceleration and augmentation, and a rise in arterial blood pressure.     

Entropically driven helix formation

The helix is a ubiquitous motif for biopolymers. We propose a heuristic, entropically based model that predicts helix formation in a system of hard spheres and semiflexible tubes. We find that the entropy of the spheres is maximized when short stretches of the tube form a helix with a geometry close to that found in natural helices. Our model could be directly tested with wormlike micelles as the tubes, and the effect could be used to self-assemble supramolecular helices.