Cathepsin B, L, and S cleave and inactivate secretory leucoprotease inhibitor.

A number of serine proteases, matrix metalloproteases, and cysteine proteases were evaluated for their ability to cleave and inactivate the antiprotease, secretory leucoprotease inhibitor (SLPI). None of the serine proteases or the matrix metalloproteases examined cleaved the SLPI protein. However, incubation with cathepsins B, L, and S resulted in the cleavage and inactivation of SLPI. All three cathepsins initially cleaved SLPI between residues Thr(67) and Tyr(68). The proteolytic cleavage of SLPI by all three cathepsins resulted in the loss of the active site of SLPI and the inactivation of SLPI anti-neutrophil elastase capacity. Cleavage and inactivation were catalytic with respect to the cathepsins, so that the majority of a 400-fold excess of SLPI was inactivated within 15 min by cathepsins L and S. Analysis of epithelial lining fluid samples from individuals with emphysema indicated the presence of cleaved SLPI in these samples whereas only intact SLPI was observed in control epithelial lining fluid samples. Active cathepsin L was shown to be present in emphysema epithelial lining fluid and inhibition of this protease prevented the cleavage of recombinant SLPI added to emphysema epithelial lining fluid. Taken together with previous data that demonstrates that cathepsin L inactivates alpha(1)-antitrypsin, these findings indicate the involvement of cathepsins in the diminution of the lung antiprotease screen possibly leading to lung destruction in emphysema.     

Laboratory Evaluations of Factors Affecting Biodegradation of Sulfolane and Diisopropanolamine

Sulfolane and diisopropanolamine (DIPA) are used in the Sulfinol® process to remove hydrogen sulfide from sour natural gas. This process has been used in western Canada since the early 1960s, and contamination of groundwater has occurred from surface spills and from seepage from landfills and unlined process water storage ponds. Aquifer sediments from contaminated and uncontaminated areas, and muds in a wetland downgradient from the contaminated plume, were collected from a gas plant. Vigorously agitated shake-flask cultures and gently agitated 2.5-L microcosms consisting of contaminated sediment, mud and groundwater, or wetland water were used to study the biodegradation of sulfolane and DIPA. The aerobic shake-flask method showed that all five of these materials contained microbial communities that biodegraded both compounds. Microorganisms in all samples, except the uncontaminated aquifer sediment, degraded both compounds in the aerobic 2.5-L microcosms. In general, the biodegradation occurred more rapidly in the shake-flask cultures. The addition of P greatly enhanced the degradation of sulfolane and DIPA, whereas the addition of N yielded little stimulation.     

Sizing up size ratios

The investigation of the causes of observed size differences between coexisting related animal species requires a knowledge of the statistical distributions of size ratios in randomly constructed guilds. Null models can be useful, but are often subject to constraints that severely limit their applicability. New work on the statistics of size distributions may lead to a better understanding of why animals are the sizes they are.     

Using Amphibians and Reptiles to learn the Process of Science

The National Research Council's document, Inquiry and the National Science Education Standards (2000) describes an elementary science classroom as one that is composed of learners who are engaged in scientific processes. In such a setting, children ask real-world questions and seek real-world solutions. As students pursue their inquiries, they often move away from science textbooks, and they implement mathematical skills, read literature, conduct research in electronic databases, write stories, and so forth in a larger context. What was originally a regular science lesson becomes an opportunity for integration across the curriculum. This article describes an integrated unit on bats and specifically addresses the National Science Education Standards.     

Retinal encoding of ultrabrief shape recognition cues

Shape encoding mechanisms can be probed by the sequential brief display of dots that mark the boundary of the shape, and delays of less that a millisecond between successive dots can impair recognition. It is not entirely clear whether this is accomplished by preserving stimulus timing in the signal being sent to the brain, or calls for a retinal binding mechanism. Two experiments manipulated the degree of simultaneity among and within dot pairs, requiring also that the pair members be in the same half of the visual field or on opposite halves, i.e., across the midline from one another. Recognition performance was impaired the same for these two conditions. The results make it likely that simultaneity of cues is being registered within the retina. A potential mechanism is suggested, calling for linkage of stimulated sites through activation of PA1 cells. A third experiment confirmed a prior finding that the overall level of recognition deficit is partly a function of display-set size, and affirmed submillisecond resolution in binding dot pairs into effective shape-recognition cues.