Andrew C. Mason

Rising Incidence of Hepatocellular Carcinoma in the United States

BACKGROUND AND METHODS Clinical observations have suggested that the number of cases of hepatocellular carcinoma has increased in the United States. We analyzed data from the Surveillance, Epidemiology, and End Results (SEER) data base to determine the age-adjusted incidence of hepatocellular carcinoma from 1976 to 1995, data from the U.S. vital-statistics data base to determine age-adjusted mortality rates from 1981 to 1995, and data from the Department of Veterans Affairs to determine age-adjusted rates of hospitalization for the disease from 1983 to 1997. RESULTS The incidence of histologically proved hepatocellular carcinoma increased from 1.4 per 100,000 population (95 percent confidence interval, 1.3 to 1.4) for the period from 1976 to 1980 to 2.4 per 100,000 (95 percent confidence interval, 2.3 to 2.4) for the period from 1991 to 1995. Among black men, the incidence was 6.1 per 100,000 for the period from 1991 to 1995, and among white men, it was 2.8 per 100,000. There was a 41 percent increase in the mortality rate from primary liver cancer and a 46 percent increase in the proportion of hospitalizations attributable to this disease during the periods studied. The incidence increased significantly among younger persons (40 to 60 years old) during the period from 1991 to 1995 as compared with earlier periods. CONCLUSIONS An increase in the number of cases of hepatocellular carcinoma has occurred in the United States over the past two decades. The age-specific incidence of this cancer has progressively shifted toward younger people.

Temporal trends (1973-1997) in survival of patients with esophageal adenocarcinoma in the United States: a glimmer of hope?

OBJECTIVE:The incidence and mortality related to esophageal adenocarcinoma (EAC) has been rising in the United States. Meanwhile, the number of diagnostic and therapeutic procedures has increased in number and improved technologically. However, the impact of these advances on the survival of EAC in clinical practice remains unknown.METHODS:Patients with histologically proven EAC between 1973 and 1997 were identified in registries of the Surveillance, Epidemiology, and End Results database, and analyzed in 5-yr time periods. The observed and relative survival rates were calculated. The joint influence of the time of diagnosis, stage and grade of cancer, demographic features, surgical therapy, and radiotherapy were assessed in Cox proportional hazard survival analyses.RESULTS:Between 1973 and 1997, we identified 4835 patients with EAC. The 1-yr and 5-yr observed survival rates increased from 34% and 5% during 1973–1977 to 44% and 13% during 1993–1997 (p < 0.05). In the Cox survival analysis, the more recent year of diagnosis, early stage of tumor, younger age at presentation, receiving radiotherapy or surgery were independent predictors of reduced risk of mortality. The proportion of patients with in situ EAC and those with local spread increased progressively from 0.3% and 17.7% in 1973–1977 to 2.3% and 25.3%, respectively, in 1993–1997 (p < 0.05). The proportion of patients receiving radiation therapy either before or after surgery has increased from 7% in 1973–1977 to 16% in 1993–1997 (p < 0.05).CONCLUSIONS:The short- and long-term survival of patients with EAC has improved slightly in the United States over the past 25 yr. Some of the improvement may be related to an increase in the number of younger patients, and in cases with in situ and localized cancers. However, the overall survival of patients with EAC remains dismal.

Hyperacute directional hearing in a microscale auditory system.

The physics of sound propagation imposes fundamental constraints on sound localization: for a given frequency, the smaller the receiver, the smaller the available cues. Thus, the creation of nanoscale acoustic microphones with directional sensitivity is very difficult. The fly Ormia ochracea possesses an unusual ‘ear’ that largely overcomes these physical constraints; attempts to exploit principles derived from O. ochracea for improved hearing aids are now in progress. Here we report that O. ochracea can behaviourally localize a salient sound source with a precision equal to that of humans. Despite its small size and minuscule interaural cues, the fly localizes sound sources to within 2° azimuth. As the flys eardrums are less than 0.5 mm apart, localization cues are around 50 ns. Directional information is represented in the auditory system by the relative timing of receptor responses in the two ears. Low-jitter, phasic receptor responses are pooled to achieve hyperacute timecoding. These results demonstrate that nanoscale/microscale directional microphones patterned after O. ochracea have the potential for highly accurate directional sensitivity, independent of their size. Notably, in the fly itself this performance is dependent on a newly discovered set of specific coding strategies employed by the nervous system.

FEMALE CHOICE FOR AN INDICATOR OF MALE SIZE IN THE SONG OF THE BLACK-HORNED TREE CRICKET, OECANTHUS NIGRICORNIS (ORTHOPTERA: GRYLLIDAE: OECANTHINAE)

The calling song of male crickets, including Oecanthus nigricornis (Walker), attracts females for mating and provides a model system of sexual communication. We give the first conclusive identification of a feature of cricket song that is both attractive to females and indicates a phenotypic feature (body size) that determines male mating success and female reproductive benefits. We do this by first testing for correlations between song characteristics and aspects of male phenotype that are hypothesized to indicate male quality. We show that song is a reliable indicator of male size and male age, and that large male size is associated with increased female fecundity. We then use playbacks of synthetic songs that mimic natural variation in song parameters to study song preferences and we compare preferences under different presentation regimes to determine whether choices are based on relative song quality or some fixed criterion. Females show a preference for the lower frequency songs produced by large males, but only during simultaneous playbacks. Thus female choice is based on the relative quality of calls that can be sampled simultaneously. These results provide strong support for the hypothesis that females use variation in calling song to assess male mate quality.

The effect of substrate on the efficacy of seismic courtship signal transmission in the jumping spider Habronattus dossenus (Araneae: Salticidae)

SUMMARY The jumping spider Habronattus dossenus Griswold 1987 (Salticidae) communicates using seismic signals during courtship and can be found on rocks, sand and leaf litter. We examined the filtering properties of, and tested the efficacy of male courtship signals on, these natural substrates. These substrates have drastically different filtering properties at the distances at which the males court. Rocks sharply attenuated all frequencies, with considerable variability among different rocks. Desert sand showed band-pass properties, attenuating frequencies contained in the animals signal. Leaf litter passed all frequencies and was the most favourable signalling environment. In behavioural trials, the proportion of males mating successfully was significantly higher on leaf litter than on rocks or desert sand. Males did not modify their courtship behaviour on different substrates. Therefore, the effectiveness of male courtship seismic signals appears to be strongly constrained by the available substratum resources.

Seismic signals are crucial for male mating success in a visual specialist jumping spider (Araneae: Salticidae)

The diversity of courtship displays throughout the animal kingdom is immense and displays can range from seemingly simple, to incredibly complex. Signallers often possess elaborate morphological adaptations for signals directed at a specific sensory modality in receivers. In some cases, these signals are so compelling to human observers, the possibility that important signals exist in other sensory modalities is ignored, potentially resulting in an incomplete characterization of the communication system. Jumping spiders (Salticidae) have remarkable visual capabilities. Yet one species, Habronattus dossenus, has recently been shown to have a complex repertoire of multicomponent seismic courtship signals in addition to and produced in concert with its multiple visual ornaments and movement displays. Here, we demonstrate the importance of these seismic signals in the courtship display of H. dossenus by comparing mating frequencies across experimentally manipulated treatments. Virgin females were paired with males from one of two experimental groups: nonmuted males or muted males. We found that females were significantly more likely to copulate with nonmuted males than with muted males. Furthermore, in all pairs that copulated, the latency to copulation was significantly shorter in nonmuted pairings than in muted pairings and precopulatory cannibalism rates were significantly lower. These results demonstrate that seismic signals are a critical component of male H. dossenus courtship displays. Additionally, we demonstrate that many other Habronattus species include a diversity of seismic signals in their courtship displays and we discuss potential selection pressures that may drive the evolution of multimodal displays even in species that already possess elaborate morphological adaptations for signals directed at one sensory modality.

Generation of extreme ultrasonics in rainforest katydids

SUMMARY The calling song of an undescribed Meconematinae katydid (Tettigoniidae) from South America consists of trains of short, separated pure-tone sound pulses at 129 kHz (the highest calling note produced by an Arthropod). Paradoxically, these extremely high-frequency sound waves are produced by a low-velocity movement of the stridulatory forewings. Sound production during a wing stroke is pulsed, but the wings do not pause in their closing, requiring that the scraper, in its travel along the file, must do so to create the pulses. We hypothesize that during scraper pauses, the cuticle behind the scraper is bent by the ongoing relative displacement of the wings, storing deformation energy. When the scraper slips free it unbends while being carried along the file and its deformation energy contributes to a more powerful, higher-rate, one-tooth one-wave sound pulse, lasting no more than a few waves at 129 000 Hz. Some other katydid species make pure-tone ultrasonic pulses. Wing velocities and carriers among these pure-tone species fall into two groups: (1) species with ultrasonic carriers below 40 kHz that have higher calling frequencies correlated with higher wing-closing velocities and higher tooth densities: for these katydids the relationship between average tooth strike rate and song frequency approaches 1:1, as in cricket escapement mechanisms; (2) a group of species with ultrasonic carriers above 40 kHz (that includes the Meconematinae): for these katydids closing wing velocities are dramatically lower and they make short trains of pulses, with intervening periods of silence greater than the duration of the pulses they separate. This signal form may be the signature of scraper-stored elastic energy.

Hearing in a primitive ensiferan: the auditory system of Cyphoderris monstrosa (Orthoptera: Haglidae)

Summary1.Insects of the family Haglidae are relicts of primitive Ensifera. Members of this group display acoustic behaviour in the typical ensiferan pattern, with males producing stereotyped acoustic signals by tegminal stridulation. They are closely related to the major groups of acoustic Ensifera, but their auditory system has not been previously studied. I present here a description of the morphology, and physiology of the peripheral auditory system of Cyphoderris monstrosa.2.The tympana of C. monstrosa are similar to those of Tettigoniidae, but less well-differentiated from normal leg cuticle. The acoustic trachea is well-developed, but does not form a single, continuous tube in the leg proximal to the tympana. The organization of the auditory organ is similar to the Tettigoniidae, with the tibial organ comprising the subgenual organ, intermediate organ, and crista acustica. Projections of the tibial organ sensory cells to the prothoracic ganglion are also typical of acoustic Orthoptera. The meso- and metathoracic legs possess tibial organs similar to that of the prothoracic leg, although lacking tympana and well-developed acoustic tracheae. Central projections of the mesothoracic tibial organ are similar to those of the prothoracic.3.Auditory whole nerve responses are not tuned to the frequency of the species calling song. Auditory best frequency (BF) is 2 kHz; calling song frequency is 12 kHz. Threshold intensity levels at BF are typical for insect hearing organs (35–45 dB SPL). The response of the auditory organ is not strongly directional at the calling song frequency. Occlusion of the acoustic trachea has no effect on the sensitivity, tuning, or directionality of the auditory system. Occlusion of either of the tympana alone also has no effect on auditory responses, but occlusion of both tympana leads to a marked decrease in sensitivity. Tuning is not affected. The tibial organ of the mesothoracic leg is sensitive to airborne sound at low frequencies (BF = 1 kHz) with thresholds comparable to the ear.4.The auditory system of C. monstrosa is a pressure receiver, adapted to low frequency sensitivity. This low frequency tuning, in contrast to the calling song frequency, suggests an auditory system adapted to another function in addition to intraspecific communication.

The mechanics of sound production in Panacanthus pallicornis (orthoptera: tettigoniidae: conocephalinae) : the stridulatory motor patterns

SUMMARY To examine whether sound production in katydids relies on an escapement mechanism similar to that of crickets we investigated the functional anatomy and mechanical properties of the stridulatory apparatus in the katydid Panacanthus pallicornis. Males of this species produce sustained pulses with a sharp low frequency peak of ∼5 kHz and a broad band spectrum between 15 and 25 kHz. Simultaneous recordings of movement and sound indicate that the entire stridulatory file is used for sound production and there is nearly a 1:1 correspondence between the number of cycles in a song and the number of teeth on the file. There is an overall tendency for both the spacing of teeth to increase along the file and the velocity of wing closure to increase as the scraper traverses the file. There is considerable variation, however, in the evenness of tooth spacing and in the instantaneous velocity of wing closure during sound production. The production of sustained pulses appears to depend on resonance in the right tegmen, with the left tegmen acting primarily as a damping element. This resonance is not strongly coupled to the scraper and, unlike crickets, the timing of file-scraper interactions, and therefore the phasing of energy input to wing oscillations, is variable. Similarly, the quality of the sound spectrum varies over the course of a single stridulatory wing-stroke. Based on measurements of tooth spacing on the stridulatory file and cycle-by-cycle frequency of sound output, we predicted the velocity of wing movement that would provide consistent phasing of file-scraper interactions with respect to sound-radiating wing oscillations and compared this with measurements of wing velocity. Acceleration of wing velocity during stridulation results in a closer match to the velocity required for optimal phasing during a portion of the call, and this corresponds with higher amplitudes of radiated sound and the excitation of higher order modes of vibration (evident as distinct harmonic peaks in spectrograms). Our results suggest that in katydid stridulation, the movement of the scraper along the file is not regulated by an escapement mechanism as it is in crickets. Instead, katydids that produce pure-tone songs sweep their wings over a range of velocities, within which some portion matches file tooth spacing to give optimal phasing of energy input to excite a resonance in the right tegmen.

Substrate-dependent signalling success in the wolf spider, Schizocosa retrorsa

Signals used in communication are often hypothesized to be optimally designed for their signalling environment. Here, we explore the importance of signalling substrate on seismic signal efficacy and reproductive behaviour in the wolf spider, Schizocosa retrorsa: a species found on multiple signalling substrates (pine litter and/or red clay or sand). In this multimodal signalling species, simultaneous with conspicuous visual displays, males produce percussive seismic signals via an impulse mechanism which tends to excite a substrate evenly across a wide band of frequencies. We first quantified the transmission characteristics of this broadband percussive signal by playing recorded signals back across three naturally occurring substrates, two of which represent substrates upon which S. retrorsa is commonly found: leaf litter, pine litter and red clay (the latter two exemplify their natural habitat). The substrates varied in their transmission characteristics with respect to both attenuation (higher on red clay) and filtering. Next, we compared copulation success, courtship behaviour and microhabitat choice among these same substrates. Copulation frequency was higher on the natural substrates of pine litter and red clay as compared with leaf litter. Males took longer to initiate courtship on leaf litter, but once initiated, courtship behaviour did not vary across substrates and we were not able to discern any choice with respect to the first, or the most common, substrate chosen. Our results show that while S. retrorsas percussive signals may not be matched to the specific properties of any one substrate, copulation success was substrate dependent and we discuss potential explanations for this substrate-dependent signalling success.