Robert D. Black

DENSITY-DEPENDENT MORTALITY CAUSED BY PHYSICAL STRESS INTERACTING WITH BIOTIC HISTORY

The long-standing debate among ecologists as to whether physical factors act in a density-dependent or density-independent fashion may be partially resolved by recognizing that a history of crowding alters an organisms susceptibility to stress. Mortality following sedimentation for sand-flat bivalves is shown to be density-dependent solely because of the historical influence of crowding. Consequently, the density dependence is actually caused by the interaction between the stress of sedimentation and the density history of the organisms. The demonstrated importance of interactions with biotic history raises questions about the interpretation of bioassays, pollutant impacts, responses to weather, paleoecological changes, and results in experimental ecology and physiology whenever the equivalence of organisms is assumed without a knowledge of historical conditioning.

Experimental tests of the advantages and disadvantages of high density for two coexisting cockles in a southern ocean lagoon

As a strong test of the prevailing generalization that competition plays a relatively trivial role among suspension-feeding invertebrates in the soft sediments on the estuarine seafloor, we manipulated local densities of bivalves, two species of Katelysia, in a Western Australia lagoon, characterized by exceptionally high bivalve abundances (averaging 157 m −2 ). Competition appeared weakly and sporadically, evident in only one of five intervals, when survivorship was 20-30% lower, production of undamaged empty shells 3-5 times higher, and average growth of survivors 50% lower for both Katelysia scalarina Lamarck and Katelysia rhytiphora Lamarck in the highest density treatment (320 m −2 ) than in the others (20-160 m −2 )

Absence of preemption and interference competition for space between large suspension-feeding bivalves and smaller infaunal macroinvertebrates

Densities of large suspension-feeding bivalves were manipulated inside 1-m2 field enclosures at three Western Australian study sites to test their influence on density and diversity of smaller macroinfaunal invertebrates. At Princess Royal Harbour and at subtidal and intertidal sites at Shark Bay, the large bivalves had no significant effect on density or diversity of small bivalves, gastropods, polychaetes, amphipods, other taxa, and all taxa combined, despite maximum treatment densities that exceeded twice the ambient control levels at each site. Calculations of power against reasonable alternative hypotheses suggest that the failure to detect treatment effects was not a consequence of low statistical power, especially at Princess Royal Harbour where effects as small as 20% (diversity) and 40% (density) could have been detected with a power of 0.80 and where the treatment intensity varied over a 16-fold range. Consequently, over the range of densities used, the suspension-feeding bivalve component of the infauna neither exhibited any competitive interaction with the smaller macroinvertebrates nor provided any positive enhancement on a spatial scale of 1 m2.

The crash in suspension-feeding bivalve populations (Katelysia spp.) in Princess Royal Harbour: an unexpected consequence of eutrophication

Abstract Abundances of two species of suspension-feeding bivalves (Katelysia scalarina L. and K. rhytiphora L.) on the unvegetated sandflat of the southeastern shore of Princess Royal Harbour declined from around 160·m−2 in 1983–1985 to nearly zero in 1992. Based on replicated estimates of annual mortality from 1983–1985, 414 out of 2013 individually marked Katelysia were expected to remain alive after 7 years inside field enclosures. Not one marked Katelysia did survive and of the 166 marked empty shells recovered, 65–90% showed growth equivalent to just over a year of life beyond their last measurement in April 1985. Not only had adult abundances crashed, but recruitment of young Katelysia was negligible at levels two orders of magnitude less than observed in 1983–1985. These dramatic declines in abundances of a previously dominant component of the fauna of Princess Royal Harbour co-occurred with eutrophication, seagrass die-off and macroalgal blooms, suggesting that the environmental problems of this harbour have cascaded through the ecosystem to alter its ability to sustain natural secondary production and ecosystem function.

The Observed Variance Between Predicted and Measured Radiation Dose in Breast and Prostate Patients Utilizing an In Vivo Dosimeter

PURPOSEnReport the results of using a permanently implantable dosimeter in radiation therapy: determine specific adverse events, degree of migration, and acquire dose measurements during treatment to determine difference between expected and measured dose.nnnMETHODS AND MATERIALSnThe Dose Verification System is a wireless, permanently implantable metal-oxide semiconductor field-effect transistor dosimeter using a bidirectional antenna for power and data transfer. The study cohort includes 36 breast (33 patients received two devices) and 29 prostate (21 patients received two devices) cancer patients. A total of 1,783 and 1,749 daily dose measurements were obtained on breast and prostate patients, respectively. The measurements were compared with the planned expected dose. Biweekly computed tomography scans were obtained to evaluate migration and the National Cancer Institutes Common Toxicity Criteria, version 3, was used to evaluate adverse events.nnnRESULTSnOnly Grade I/II adverse events of pain and bleeding were noted. There were only four instances of dosimeter migration of >5 mm from known factors. A deviation of > or =7% in cumulative dose was noted in 7 of 36 (19%) for breast cancer patients. In prostate cancer patients, a > or =7% deviation was noted in 6 of 29 (21%) and 8 of 19 (42%) during initial and boost irradiation, respectively. The two patterns of dose deviation were random and systematic. Some causes for these differences could involve organ movement, patient movement, or treatment plan considerations.nnnCONCLUSIONSnThe Dose Verification System was not associated with significant adverse events or migration. The dosimeter can measure dose in situ on a daily basis. The accuracy and utility of the dose verification system complements current image-guided radiation therapy and intensity-modulated radiation therapy techniques.

Recent Advances in Translational Work on Implantable Sensors

This review evaluates example technologies from the point-of-view of likely translation into human use, including regulatory clearance, insertion into common medical practice and reimbursability. The intent is to highlight recent innovations in implantable sensors with a focus on the translational process itself in a holistic fashion. As well as looking at success stories, this review will also examine several seemingly promising technologies that have failed for reasons having nothing to do with the operational aspects of the sensors and systems involved. Innovation must be viewed as a multifaceted process, all segments of which must be fully addressed to achieve success. No party to the process can work in isolation and expect to achieve the end goal of providing new advances to patients. This review will have succeeded if it provides the reader with a better appreciation of the complex environment in which implantable sensor discoveries that seek to be translated into human medicine must navigate.

Editorial Introduction for the Special Issue of the Sensors Journal: In Vivo Sensors for Medicine

The 16 papers in this special issue describe some specific techniques for powering and enabling implanted sensors, overview some device types meant to guide therapeutic interventions (feedback on therapy), outline devices to look at pH and oxygen values, and introduce sensors for measuring analytes (especially glucose).

In Vivo Monitoring of a Fluorescently Labeled Antibody in Mice With Breast Cancer Xenografts

Following the uptake kinetics of a monoclonal antibody cancer therapy in vivo is addressed in this study via the use of a surface probe to assay a fluorescent label attached to the antibody. Female NCr-nu athymic mice were implanted with cells from a human breast cancer MCF7HER2 line that over expresses clinically relevant levels of the HER2/neu protein. Herceptin (trastuzumab) and a negative control antibody for mouse IgG Ab-1 were labeled with Alexa Fluor 647 fluorescent dye and the mice received a single bolus injection (tail vein) of one of the two antibodies. The relative signal in the tumor region was compared with that from normal tissue and a ratio of the signal levels was recorded as a function of time. As expected, Herceptin was found to concentrate in the HER2+ tumors (high tumor-to-normal ratio), whereas the tumor-to-normal ratio for the negative control antibody was flat in time and close to unity. It is suggested that fluorescence assays of this type might be possible in vivo in humans using a telemetric, implantable version of the probe used in this study.