Immediate breast reconstruction with saline-filled implants: no interference with the oncologic outcome?

The possible adverse effects on cancer control due to immediate breast reconstruction have been addressed recently for both silicone-filled implants and flap reconstruction. To evaluate those possible effects after immediate breast reconstruction with saline-filled implants, 49 patients reconstructed with saline-filled breast implants at the Jules Bordet Cancer Institute were studied. Selection was only based on the possibility to find a matched patient. These patients were matched with a control group of 49 matched women with breast cancer treated in the same center by mastectomy without any type of breast reconstruction. The two groups were comparable according to age at diagnosis (within 3 years), year of diagnosis (same year), stage of the tumor, histology, and nodal status. The only difference between the two groups was that radiation therapy was applied to some of the patients who were not reconstructed (due to tumor location). The results show, in terms of local recurrences, distant metastasis, and deaths, no significant difference between the two groups, even for the irradiated patients, within a mean follow-up period of 72 months (range, 24 to 108) months.     

Gas treatment in trickle-bed biofilters: biomass, how much is enough?

The objective of this article is to define and validate a mathematical model that desribes the physical and biological processes occurring in a trickle-bed air biofilter for waste gas treatment. This model considers a two-phase system, quasi-steady-state processes, uniform bacterial population, and one limiting substrate. The variation of the specific surface area with bacterial growth is included in the model, and its effect on the biofilter performance is analyzed. This analysis leads to the conclusion that excessive accumulation of biomass in the reactor has a negative effect on contaminant removal efficiency. To solve this problem, excess biomass is removed via full media fluidization and backwashing of the biofilter. The backwashing technique is also incorporated in the model as a process variable. Experimental data from the biodegradation of toluene in a pilot system with four packed-bed reactors are used to validate the model. Once the model is calibrated with the estimation of the unknown parameters of the system, it is used to simulate the biofilter performance for different operating conditions. Model predictions are found to be in agreement with experimental data. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 583-594, 1997.     

Detection of direct versus indirect effects: were experiments long enough?

To evaluate the hypothesis that indirect effects generally take much longer to become evident in manipulative studies of community regulation than do direct effects and thus may often be missed, I studied the effect of experiment duration in a survey of marine intertidal interaction webs. Contrary to expectation, indirect effects appeared either simultaneously with direct effects or shortly after direct effects were evident. While experiment durations varied greatly, on average most direct and indirect effects became statistically significant within the first 20%-40% of the total experiment duration. Further, the duration of most experiments appeared sufficient so that most indirect effects that would be generated by the manipulation could be observed. On average, a period of "constancy" (i.e., of no further change) lasting roughly 20%-60% of the total experiment duration occurred after the last indirect effect was observed. Experiment duration did not vary with web species richness, which suggests no tendency to perform manipulations for more (or less) time in more complex webs. The number of indirect effects per species did not increase with increasing experiment duration, nor did the number of longer interaction chains (four species vs. three species), which suggests no trends for increased complexity of indirect effects with longer experiments. Ecological theory states that, in interaction webs whose dynamics are imperfectly known, indirect effects may compromise the predictability of species manipulations. However, empirical results suggest that, despite incomplete knowledge of indirect effects, community dynamics may be more predictable than expected.     

Pathogenesis of rheumatoid arthritis: how early is early?

Studies of cytokine expression in rheumatoid arthritis have provided key insights into the pathogenesis of disease and have offered clues for effective therapy. Patterns of T-cell products in chronic rheumatoid synovitis suggest that T helper type 1 cells contribute to the perpetuation of disease. However, there is no guarantee that the mechanisms of late disease are identical to very early rheumatoid arthritis. Evaluation of the cytokine profile at the earliest time points after onset of symptoms could identify novel targets that prevent progression to chronic arthritis.     

Long-term (5–11 years) follow-up of general immune competence in breast cancer

Summary General immune competence was measured before treatment in 185 breast cancer patients. They were then followed for 5 to 11 years to determine its relationship to recurrence and its clinical value in predicting prognosis. The tests of immune competence used were immunoglobulins IgG, IgA, IgM, leucocyte counts, percentage and total lymphocyte counts and Mantoux and DNCB skin hypersensitivity tests.None of these tests was strongly predictive of recurrence on an individual basis, a finding similar to our results at 2 years. The longer period of follow-up now reported has provided no findings of unequivocal statistical significance, but suggests a biphasic host response to early tumours. The patients who developed recurrence within 5–11 years due to micrometastasis had higher lymphocyte counts in their preoperative assessment than patients who remained recurrence free. This suggests that small tumour volumes do not stimulate immunity and that large volumes depress it; tumours in between these groups are associated with higher levels. Examination of studies by a number of authors reveal parallel findings which have not been previously noted. It is not possible to confirm the significance of these findings from this study because of the heterogeneity of human breast cancer. However, if they indicate a general principle of a dynamic host-tumour interplay they have important implications for assessing immune competence at any single point of time and for the theory that cancer may arise during an anergic state. We hope that these findings will stimulate other workers to examine host-tumour interaction from this point of view.     

Success of ectoparasites: how important is timing of host contact?

Hosts often differ in their degree of parasitism and their expression of resistance. Yet very little is known about how the availability (and allocation) of resources to parasites at pre-infective stages influences their success in initiating parasitism, or in inducing and succumbing to resistance from hosts. We studied a damselfly-mite association to address how experimental variation in the age of first contact with hosts (timing) influenced subsequent parasite fitness. We demonstrate that timing influenced the ability of larval mites to make the transition to parasitism, but was not associated with measures of physiological resistance by hosts. Timing presumably relates to the availability of resources remaining for individuals to exploit their hosts. More research is needed on the importance of such factors, from variation in host resistance and parasite success and, ultimately, to the numbers and distributions of parasites on hosts.     

What exactly was wrong with the Trilucent breast implants? A unifying hypothesis

Trilucent soybean oil-filled breast implants were initially announced as the ultimate prostheses for breast augmentation. However, after an increasing number of reports of local complications and hazardous metabolites attributable to lipid oxidation, first the United Kingdom Medical Devices Agency and later the Belgian National Ministry of Health urged all plastic surgeons to contact their patients and advise them to have the implants removed and, if desired, replaced with another type of prosthesis. In our plastic surgery department, 13 patients received bilateral implants with triglyceride-filled prostheses between February and July of 1996, for primary breast augmentation or replacement of previously implanted prostheses. For 12 of those 13 patients, the prostheses have been explanted, because of unilateral breast enlargement attributable to a ruptured prosthesis for five patients and following the recommendation of the Belgian National Ministry of Health for the other seven patients. Before explantation, all patients underwent standard clinical examinations, with assessments of breast shape, volume, and firmness. Blood analyses were performed, with a special focus on liver enzymes, as were urinalyses. Magnetic resonance imaging scans were obtained before explantation; for two patients, the scans revealed a fluid level separating two liquid layers in an intact prosthesis. This is the first report of such a finding. The removed implants were examined for any damage or shell deterioration and for changes in color and viscosity, the weights and volumes were measured and compared with the initial values for the implanted prostheses, and complete biochemical analyses of the accumulated fluid in cases of ruptured prostheses and of the filler material in cases of intact prostheses were performed. This small but well-documented series illustrates the multitude of problems associated with triglyceride-filled implants, including bleeding of the triglyceride filler; shell deterioration, as indicated by a loss of texture and extreme fragility of the implant (with rupture or delamination with a simple finger touch); an increase in osmotic pressure exerted by the degraded filler material; progressive weakening of the outer silicone shell, with influx of plasma proteins of up to 750 kDa, eventually resulting in rupture of the prosthesis; a lack of oxidative stability and the formation of toxic oxidation products; a lack of biocompatibility, with the formation of insoluble organic soap-like material; and a pronounced inflammatory reaction. It is concluded that the sequential and/or simultaneous occurrence of (1) implant bleeding, (2) lipid infiltration of the silicone elastomer, and (3) inflammation attributable to oxidation products provides an overall explanation or unifying hypothesis for the wide variety of adverse events related to soybean oil-filled implants.     

When is enough … enough? Effective sampling protocols for estimating the survival rates of seabirds with mark-recapture techniques

Capsule: Lower intensity mark-recapture studies, such as those undertaken by citizen scientists, provide an opportunity to improve the spatial representation of survival estimates for birds. Colonial nesting birds are particularly suited to this because, for many species, large numbers of breeding birds and chicks can be located relatively easily. The minimum level of recapture effort required to accurately estimate true survival rates and detect temporal variation largely depended on the respective ringing effort. Therefore, mark-recapture studies should consider both aspects of the field study when setting or adjusting minimum effort guidelines. Furthermore, achieving reliable estimation with short time-series required more intensive survey designs, highlighting the importance of longevity when planning these studies.

Aims: To provide minimum guidelines of field effort that can be used to manage smaller projects that monitor survival rates, such as those reliant on citizen scientists.

Methods: We conducted a sensitivity analysis that evaluated the statistical power associated with using different mark-recapture survey designs to estimate a fixed ‘true’ survival rate and detect sources of temporal variation and individual heterogeneity within the population.

Results: Isolating temporal variation with a good degree (90%) of certainty required the highest levels of survey effort. Based on the assessed survey designs, we recommend studies that have a ten-year trajectory and a recapture rate of 0.6, aim to mark at least 200 new adults per year. The recommended number of marked individuals will decrease if it is possible to achieve higher rates of recapture. Lower rates of juvenile survival and delayed reproduction mean that seabird mark-recapture survey designs that target both chicks and adults offer only marginal improvements in resolving the survival rates of adults, when compared to designs targeting adults only. However, collecting juvenile mark-recapture data provide access to age-specific vital rates that are also valuable for assessing the population dynamics of seabirds.

Conclusion: The addition of chicks is unlikely to improve the resolution of adult survival rates markedly, although for species with low natal dispersal and earlier ages of maturity, these data may allow the estimation of other vital rates, such as juvenile survival rates and age of maturity. Implementing minimum effort guidelines potentially enables the effective management of smaller mark-recapture studies, thus minimising the risk that studies fail to achieve the data conditions necessary for robust estimation of survival rates.