Metaheuristic optimization of data preparation and machine learning hyperparameters for prediction of dynamic methane production

Machine learning algorithms provide detailed description of the anaerobic digestion process, but the impact of data preparation procedures and hyperparameter optimization has rarely been investigated. A genetic algorithm was developed for optimizing data preparation and model hyperparameters to simulate dynamic methane production from steady-state anaerobic digestion of agricultural residues at full-scale. A long short-term memory neural network was used as prediction model. Results indicate that batch size, learning rate and number of neurons are the most important model parameters for accurate description of methane production rates, whereas combination of hyperparameter and data preparation optimization shows best model efficiencies, with a root mean square scaled error of 76.5 %. Mass of solid feed, time and mass of volatile solids are the most relevant input features. This study provides fundamental steps for optimal prediction of dynamic biomethane production, as a reliable basis for improving bioconversion efficiency during anaerobic digestion of agricultural residues.

Demand-oriented biogas production to cover residual load of an electricity self-sufficient community using a simple kinetic model

Flexible biogas production can enable demand-oriented energy supply without the need for expensive gas storage expansions, but poses challenges to the stability of the anaerobic digestion (AD) process. In this work, biogas production of laboratory-scale AD of maize silage and sugar beets was optimized to cover the residual load of an electricity self-sufficient community using a simple process model based on first-order kinetics. Experiments show a good agreement between biogas demand, predicted, and measured biogas production. By optimizing biogas conversion schedules based on the measured gas production, a gas storage capacity of 7-8 h was identified for maximum flexibility, which corresponds to typical gas storage sizes at industrial biogas plants in Germany. Various stability indicators were continuously monitored and proved resilient process conditions. These results demonstrate that demand-oriented biogas production using model predictive control is a promising approach to enable existing biogas plants to provide balancing energy.

Systematic simplification of the Anaerobic Digestion Model No. 1 (ADM1) - Laboratory experiments and model application

Due to a limited number of available measurements on agricultural biogas plants, established process models, such as the Anaerobic Digestion Model No. 1 (ADM1), are rarely applied in practise. To provide a reliable basis for model-based monitoring and control, different model simplifications of the ADM1 were implemented for process simulation of semi-continuous anaerobic digestion experiments using agricultural substrates (maize silage, sugar beet silage, rye grain and cattle manure) and industrial residues (grain stillage). Individual model structures enable a close depiction of biogas production rates and characteristic intermediates (ammonium nitrogen, propionic and acetic acid) with equal accuracy as the original ADM1. The impact of different objective functions and standard parameter values on parameter estimates of first-order hydrolysis constants and microbial growth rates were evaluated. Due to the small number of required model parameters and suitable system characteristics, simplified model structures show clear advantages for practical application on agricultural biogas plants.

Systematic simplification of the Anaerobic Digestion Model No. 1 (ADM1) - Model development and stoichiometric analysis

Rigorous process models provide a reliable basis for model-based monitoring and control of anaerobic digestion plants. Due to the complex model structure and non-linear system characteristics, the established Anaerobic Digestion Model No. 1 (ADM1) is rarely applied in industrial plant operation. The present investigation proposes a systematic procedure for successive model simplification and presents the description of five model variants of a mass-based ADM1. Individual model structures greatly differ in their number of implemented process phases, characteristic components and required parameters. Simplified model variants combine nutrient degradation and biogas formation based on first-order sum reactions, whereas complex model structures describe individual degradation pathways and intermediates during acido- and acetogenesis. Characteristic features of the derived model structures as well as the stoichiometric methane potentials and microbial biomass yields of the underlying degradation pathways of individual model variations are evaluated and discussed in detail.

Methane emissions from the storage of liquid dairy manure: Influences of season, temperature and storage duration

Methane emissions from livestock manure are primary contributors to GHG emissions from agriculture and options for their mitigation must be found. This paper presents the results of a study on methane emissions from stored liquid dairy cow manure during summer and winter storage periods. Manure from the summer and winter season was stored under controlled conditions in barrels at ambient temperature to simulate manure storage conditions. Methane emissions from the manure samples from the winter season were measured in two time periods: 0 to 69 and 0 to 139 days. For the summer storage period, the experiments covered four time periods: from 0 to 70, 0 to 138, 0 to 209, and 0 to 279 continuous days, with probing every 10 weeks. Additionally, at the end of all storage experiments, samples were placed into eudiometer batch digesters, and their methane emissions were measured at 20 °C for another 60 days to investigate the potential effect of the aging of the liquid manure on its methane emissions. The experiment showed that the methane emissions from manure stored in summer were considerably higher than those from manure stored in winter. CH₄ production started after approximately one month, reaching values of 0.061 kg CH₄ kg^-1 Volatile Solid (VS) and achieving high total emissions of 0.148 kg CH₄ kg^-1 VS (40 weeks). In winter, the highest emissions level was 0.0011 kg CH₄ kg^-1 VS (20 weeks). The outcomes of these experimental measurements can be used to suggest strategies for mitigating methane emissions from manure storage.

Towards a standardization of biomethane potential tests: a commentary

Inter-laboratory reproducibility of biomethane potential (BMP) is dismal, with differences in BMP values for the same sample exceeding a factor of two in some cases. A large group of BMP researchers directly addressed this problem during a workshop held in Leysin, Switzerland, in June 2015. The workshop resulted in a new set of guidelines for BMP tests published in 2016, which is the subject of the present commentary. The work has continued with two international inter-laboratory studies and one additional workshop held in Freising, Germany, in 2018. The dataset generated by the two inter-laboratory studies were used to refine the validation criteria for BMP tests. Based on these new results an update to the original guidelines is proposed here.

The Influence of Pressure-Swing Conditioning Pre-Treatment of Cattle Manure on Methane Production

Cattle manure is an agricultural residue, which could be used as source to produce methane in order to substitute fossil fuels. Nevertheless, in practice the handling of this slowly degradable substrate during anaerobic digestion is challenging. In this study, the influence of the pre-treatment of cattle manure with pressure-swing conditioning (PSC) on the methane production was investigated. Six variants of PSC (combinations of duration 5 min, 30 min, 60 min and temperature 160 °C, 190 °C) were examined with regards to methane yield in batch tests. PSC of cattle manure showed a significant increase up to 109% in the methane yield compared to the untreated sample. Kinetic calculations proved also an enhancement of the degradation speed. One PSC-variant (190 °C/30 min) and untreated cattle manure were chosen for comparative fermentation tests in continuously stirred tank reactors (CSTR) in lab-scale with duplicates. In the continuous test a biogas production of 428 mL/g volatile solids (VS) (54.2% methane) for untreated manure was observed and of 456 mL/g VS (53.7% methane) for PSC-cattle-manure (190 °C/30 min). Significant tests were conducted for methane yields of all fermentation tests. Furthermore, other parameters such as furfural were investigated and discussed.

Augmenting Biogas Process Modeling by Resolving Intracellular Metabolic Activity

The process of anaerobic digestion in which waste biomass is transformed to methane by complex microbial communities has been modeled for more than 16 years by parametric gray box approaches that simplify process biology and do not resolve intracellular microbial activity. Information on such activity, however, has become available in unprecedented detail by recent experimental advances in metatranscriptomics and metaproteomics. The inclusion of such data could lead to more powerful process models of anaerobic digestion that more faithfully represent the activity of microbial communities. We augmented the Anaerobic Digestion Model No. 1 (ADM1) as the standard kinetic model of anaerobic digestion by coupling it to Flux-Balance-Analysis (FBA) models of methanogenic species. Steady-state results of coupled models are comparable to standard ADM1 simulations if the energy demand for non-growth associated maintenance (NGAM) is chosen adequately. When changing a constant feed of maize silage from continuous to pulsed feeding, the final average methane production remains very similar for both standard and coupled models, while both the initial response of the methanogenic population at the onset of pulsed feeding as well as its dynamics between pulses deviates considerably. In contrast to ADM1, the coupled models deliver predictions of up to 1,000s of intracellular metabolic fluxes per species, describing intracellular metabolic pathway activity in much higher detail. Furthermore, yield coefficients which need to be specified in ADM1 are no longer required as they are implicitly encoded in the topology of the species’ metabolic network. We show the feasibility of augmenting ADM1, an ordinary differential equation-based model for simulating biogas production, by FBA models implementing individual steps of anaerobic digestion. While cellular maintenance is introduced as a new parameter, the total number of parameters is reduced as yield coefficients no longer need to be specified. The coupled models provide detailed predictions on intracellular activity of microbial species which are compatible with experimental data on enzyme synthesis activity or abundance as obtained by metatranscriptomics or metaproteomics. By providing predictions of intracellular fluxes of individual community members, the presented approach advances the simulation of microbial community driven processes and provides a direct link to validation by state-of-the-art experimental techniques.

Ensiling fermentation reveals pre-treatment effects for anaerobic digestion of sugarcane biomass: An assessment of ensiling additives on methane potential

Ensiling of sugarcane trash (SCT) and sugarcane stalks (SCS) was studied to assess the effects of molasses (MOL) and lactic acid bacteria (LAB) inoculant on methane potential. The experiment was run for 70 days and monitoring parameters were analyzed at days 0, 5, 15 and 70. Biochemical methane potential (BMP) tests performed with fresh and ensiled material at day 70 showed an increase in methane potential by 24.0%, 23.4%, 1.7% and 71.1% for SCS_ctr, SCT_ctr, SCT_mol and SCT_{mol + lab}, respectively. Such improved performance is explained by the formation of organic acids (mostly acetate and lactate) which were able to decrease the pH of the silages from 5.7-5.9 to 3.8-4.2 for all SCT treatments and from 5.9 up to 3.4 for SCS treatment. Thus, the ensiling process provided similar effects to a pre-treatment at low acid concentrations, which in turn improved the digestibility of the cellulosic biomass for methane production.

Abstract P6-20-06: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Dann S, Chionis J, Eisele K, Zhang Q, Liu C, Yuan J, Miller N, Murray B, Xu M, Solowiej J, Wei P, Weinrich S, Sutton S, Behenna D, Ninkovic S, Hoffman R, Freeman-Cook K, Jessen B, Huser N, Zhang C, Visswanathan R, Boras B, VanArsdale T, White MA. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-20-06.

Determination of Microbial Maintenance in Acetogenesis and Methanogenesis by Experimental and Modeling Techniques

For biogas-producing continuous stirred tank reactors, an increase in dilution rate increases the methane production rate as long as substrate input can be converted fully. However, higher dilution rates necessitate higher specific microbial growth rates, which are assumed to have a strong impact on the apparent microbial biomass yield due to cellular maintenance. To test this, we operated two reactors at 37°C in parallel at dilution rates of 0.18 and 0.07 days-1 (hydraulic retention times of 5.5 and 14 days, doubling times of 3.9 and 9.9 days in steady state) with identical inoculum and a mixture of volatile fatty acids as sole carbon sources. We evaluated the performance of the Anaerobic Digestion Model No. 1 (ADM1), a thermodynamic black box approach (TBA), and dynamic flux balance analysis (dFBA), to describe the experimental observations. All models overestimated the impact of dilution rate on the apparent microbial biomass yield when using default parameter values. Based on our analysis, a maintenance coefficient value below 0.2 kJ per carbon mole of microbial biomass per hour should be used for the TBA, corresponding to 0.12 mmol ATP per gram dry weight per hour for dFBA, which strongly deviates from the value of 9.8 kJ Cmol h-1 that has been suggested to apply to all anaerobic microorganisms at 37°C. We hypothesized that a decrease in dilution rate might select taxa with minimized maintenance expenditure. However, no major differences in the dominating taxa between the reactors were observed based on amplicon sequencing of 16S rRNA genes and terminal restriction fragment length polymorphism analysis of mcrA genes. Surprisingly, Methanosaeta dominated over Methanosarcina even at a dilution rate of 0.18 days-1, which contradicts previous model expectations. Furthermore, only 23-49% of the bacterial reads could be assigned to known syntrophic fatty acid oxidizers, indicating that unknown members of this functional group remain to be discovered. In conclusion, microbial maintenance was found to be much lower for acetogenesis and methanogenesis than previously assumed, likely due to the exceptionally low growth rates in anaerobic digestion. This finding might also be relevant for other microbial systems operating at similarly low growth rates.

Ammonia Inhibition of Anaerobic Volatile Fatty Acid Degrading Microbial Communities

Ammonia inhibition is an important reason for reactor failures and economic losses in anaerobic digestion. Its impact on acetic acid degradation is well-studied, while its effect on propionic and butyric acid degradation has received little attention and is consequently not considered in the Anaerobic Digestion Model No. 1 (ADM1). To compare ammonia inhibition of the degradation of these three volatile fatty acids (VFAs), we fed a mixture of them as sole carbon source to three continuous stirred tank reactors (CSTRs) and increased ammonium bicarbonate concentrations in the influent from 52 to 277 mM. The use of this synthetic substrate allowed for the determination of degradation efficiencies for the individual acids. While butyric acid degradation was hardly affected by the increase of ammonia concentration, propionic acid degradation turned out to be even more inhibited than acetic acid degradation with degradation efficiencies dropping to 31 and 65% for propionic and acetic acid, respectively. The inhibited reactors acclimatized and approximated pre-disturbance degradation efficiencies toward the end of the experiment, which was accompanied by strong microbial community shifts, as observed by amplicon sequencing of 16S rRNA genes and terminal restriction fragment length polymorphism (T-RFLP) of mcrA genes. The acetoclastic methanogen Methanosaeta was completely replaced by Methanosarcina. The propionic acid degrading genus Syntrophobacter was replaced by yet unknown propionic acid degraders. The butyric acid degrading genus Syntrophomonas and hydrogenotrophic Methanomicrobiaceae were hardly affected. We hypothesized that the ammonia sensitivity of the initially dominating taxa Methanosaeta and Syntrophobacter led to a stronger inhibition of the acetic and propionic acid degradation compared to butyric acid degradation and hydrogenotrophic methanogenesis, which were facilitated by the ammonia tolerant taxa Syntrophomonas and Methanomicrobiaceae. We implemented this hypothesis into a multi-taxa extension of ADM1, which was able to simulate the dynamics of both microbial community composition and VFA concentration in the experiment. It is thus plausible that the effect of ammonia on VFA degradation strongly depends on the ammonia sensitivity of the dominating taxa, for syntrophic propionate degraders as much as for acetoclastic methanogens.

Intermittent fasting for microbes: how discontinuous feeding increases functional stability in anaerobic digestion

BACKGROUND

Demand-driven biogas production could play an important role for future sustainable energy supply. However, feeding a biogas reactor according to energy demand may lead to organic overloading and, thus, to process failures. To minimize this risk, digesters need to be actively steered towards containing more robust microbial communities. This study focuses on acetogenesis and methanogenesis as crucial process steps for avoiding acidification. We fed lab-scale anaerobic digesters with volatile fatty acids under various feeding regimes and disturbances. The resulting microbial communities were analyzed on DNA and RNA level by terminal restriction fragment length polymorphism of the mcrA gene, 16S rRNA gene amplicon sequencing, and a [2-13C]-acetate assay. A modified Anaerobic Digestion Model 1 (ADM1) that distinguishes between the acetoclastic methanogens Methanosaeta and Methanosarcina was developed and fitted using experimental abiotic and biotic process parameters.

RESULTS

Discontinuous feeding led to more functional resilience than continuous feeding, without loss in process efficiency. This was attributed to a different microbial community composition. Methanosaeta dominated the continuously fed reactors, while its competitor Methanosarcina was washed out. With discontinuous feeding, however, the fluctuating acetic acid concentrations provided niches to grow and co-exist for both organisms as shown by transcription analysis of the mcrA gene. Our model confirmed the higher functional resilience due to the higher abundance of Methanosarcina based on its higher substrate uptake rate and higher resistance to low pH values. Finally, we applied our model to maize silage as a more complex and practically relevant substrate and showed that our model is likely transferable to the complete AD process.

CONCLUSIONS

The composition of the microbial community determined the AD functional resilience against organic overloading in our experiments. In particular, communities with higher share of Methanosarcina showed higher process stability. The share of these microorganisms can be purposefully increased by discontinuous feeding. A model was developed that enables derivation of the necessary feeding regime for a more robust community with higher share of Methanosarcina.

Optimization of semi-continuous anaerobic digestion of sugarcane straw co-digested with filter cake: Effects of macronutrients supplementation on conversion kinetics

Anaerobic digestion of sugarcane straw co-digested with sugarcane filter cake was investigated with a special focus on macronutrients supplementation for an optimized conversion process. Experimental data from batch tests and a semi-continuous experiment operated in different supplementation phases were used for modeling the conversion kinetics based on continuous stirred-tank reactors. The semi-continuous experiment showed an overall decrease in the performance along the inoculum washout from the reactors. By supplementing nitrogen alone or in combination to phosphorus and sulfur the specific methane production significantly increased (P<0.05) by 17% and 44%, respectively. Although the two-pool one-step model has fitted well to the batch experimental data (R²>0.99), the use of the depicted kinetics did not provide a good estimation for process simulation of the semi-continuous process (in any supplementation phase), possibly due to the different feeding modes and inoculum source, activity and adaptation.

Optimization of hydrolysis and volatile fatty acids production from sugarcane filter cake: Effects of urea supplementation and sodium hydroxide pretreatment

Different methods for optimization the anaerobic digestion (AD) of sugarcane filter cake (FC) with a special focus on volatile fatty acids (VFA) production were studied. Sodium hydroxide (NaOH) pretreatment at different concentrations was investigated in batch experiments and the cumulative methane yields fitted to a dual-pool two-step model to provide an initial assessment on AD. The effects of nitrogen supplementation in form of urea and NaOH pretreatment for improved VFA production were evaluated in a semi-continuously operated reactor as well. The results indicated that higher NaOH concentrations during pretreatment accelerated the AD process and increased methane production in batch experiments. Nitrogen supplementation resulted in a VFA loss due to methane formation by buffering the pH value at nearly neutral conditions (∼ 6.7). However, the alkaline pretreatment with 6g NaOH/100g FCFM improved both the COD solubilization and the VFA yield by 37%, mainly consisted by n-butyric and acetic acids.

Critical comparison of different model structures for the applied simulation of the anaerobic digestion of agricultural energy crops

Different model structures were compared to simulate the characteristic process variables of the anaerobic digestion of maize, sugar beet and grain silage. Depending on the type and number of the required components, it can be shown that in comparison to the complex Anaerobic Digestion Model No. 1 (ADM1) different simplified model structures can describe the gas production rate, ammonia nitrogen and acetate concentration or pH value equally well. Since the reduction of the predominantly fast kinetics of the methanogenesis, acetogenesis or acidogenesis will only have little effect on the simulation of the specific gas production, it can be proven that the hydrolysis is the rate-limiting step during the uninhibited anaerobic digestion of complex particulate substrates. However, the stoichiometric comparison reveals that the model protein gelatine is not suitable for a representative characterization of agricultural energy crops.

A common nonsense mutation in EphB2 is associated with prostate cancer risk in African American men with a positive family history

BACKGROUND

The EphB2 gene was recently implicated as a prostate cancer (PC) tumour suppressor gene, with somatic inactivating mutations occurring in approximately 10% of sporadic tumours. We evaluated the contribution of EphB2 to inherited PC susceptibility in African Americans (AA) by screening the gene for germline polymorphisms.

METHODS

Direct sequencing of the coding region of EphB2 was performed on 72 probands from the African American Hereditary Prostate Cancer Study (AAHPC). A case-control association analysis was then carried out using the AAHPC probands and an additional 183 cases of sporadic PC compared with 329 healthy AA male controls. In addition, we performed an ancestry adjusted association study where we adjusted for individual ancestry among all subjects, in order to rule out a spurious association due to population stratification.

RESULTS

Ten coding sequence variants were identified, including the K1019X (3055A-->T) nonsense mutation which was present in 15.3% of the AAHPC probands but only 1.7% of 231 European American (EA) control samples. We observed that the 3055A-->T mutation significantly increased risk for prostate cancer over twofold (Fisher's two sided test, p = 0.003). The T allele was significantly more common among AAHPC probands (15.3%) than among healthy AA male controls (5.2%) (odds ratio 3.31; 95% confidence interval 1.5 to 7.4; p = 0.008). The ancestry adjusted analyses confirmed the association.

CONCLUSIONS

Our data show that the K1019X mutation in the EphB2 gene differs in frequency between AA and EA, is associated with increased risk for PC in AA men with a positive family history, and may be an important genetic risk factor for prostate cancer in AA.

Clinical characteristics of African-American men with hereditary prostate cancer: the AAHPC study

INTRODUCTION

The African-American Hereditary Prostate Cancer (AAHPC) Study was designed to recruit African-American families fulfilling very stringent criteria of four or more members diagnosed with prostate cancer at a combined age at diagnosis of 65 years or less. This report describes the clinical characteristics of a sample of affected AAHPC family members.

METHODS

In all, 92 African-American families were recruited into the study between 1998 and 2002. Complete clinical data including age and PSA at diagnosis, number of affected per family, stage, grade, and primary treatment were available on 154 affected males. Nonparametric Wilcoxon two-sample tests and Fisher's exact test (two-tailed), were performed to compare families with 4-6 and >6 affected males with respect to clinical characteristics.

RESULTS

The mean number of affected men per family was 5.5, with a mean age at diagnosis of 61.0 (+/-8.4) years. Age at diagnosis, PSA and Gleason score did not show significant differences between the two groups of families. Based on the Gleason score, 77.2% of affected males had favorable histology. Significantly, there were marked differences between the two groups in the frequency of node-positive disease (P=0.01) and distant metastases (P=0.0001). Radical prostatectomy was the preferred primary therapy for 66.2% of all affected men followed by 20.8% who chose radiation therapy.

CONCLUSIONS

Our findings suggest that affected males who carry the highest load of genetic factors are at the highest risk for early dissemination of disease, thus efforts at early diagnosis and aggressive therapeutic approaches may be warranted in these families. Since the primary therapy choices in our study favored definitive treatment (87.0%) when compared to the 1983 and 1995 SEER data in which 28 and 64% received definitive treatment, respectively, it appears that affected African-American men in multiplex families may be demonstrating the reported psycho-social impact of family history on screening practices and treatment decisions for prostate cancer.

Influence of exogenous GnRH on sexual behavior and frozen/thawed semen viability in stallions during the non-breeding season

Twelve fertile stallions were divided into two groups, either receiving gonadotropin-releasing hormone (GnRH) (n = 6) or Placebo (n = 6). Based on the history of frozen/thawed semen characteristics three stallions within each group were assigned as being "good freezers" [GnRH (+); Placebo (+)] and three stallions were assigned as being "poor freezers" [GnRH (-); Placebo (-)]. The study was performed as a "blinded" investigation and stallions were treated twice daily by an intramuscular injection of 1 ml GnRH (Buserelin), 50 microg) or Placebo. The experiment was divided into three time periods. Period A (pre-treatment) was performed between 16 November and 20 December; Period B (treatment) was performed during 6 weeks between 21 December and 31 January; and Period C (post-treatment) was performed between 1 February and 12 February. Semen was collected every Monday, Wednesday, Friday, and analysed for motion characteristics by the use of a computerized semen analyser, and sperm morphology immediately after collection. The spermatozoa were cryopreserved, stored in liquid nitrogen, and evaluated for motility (computer assisted semen analysis), membrane integrity (carboxyfluoresceine diacetate (CFDA) combined with propidium-iodide (PI), CFDA/PI), viability and sperm morphology (Eosine-Nigrosine, EN), and osmotic reactivity (hypo-osmotic swelling test, HOS) following thawing in a water bath. The viability of spermatozoa was expressed as the difference between pre-freeze and post-thaw values. A libido score of 1-4, the number of mounts on the phantom before ejaculation, and ejaculation latency were used to evaluate the stallions sexual behavior. Effect of treatment was analysed by comparing time intervals within groups as well as comparing groups within time intervals using SAS statistics software. GnRH treatment decreased the number of mounts before ejaculation (GnRH (total): 2.5 +/- 1.14 versus 1.8 +/- 1.06, P < 0.05), and shortened ejaculation latency. Cessation of treatment increased ejaculation latency in the GnRH group (4.7 +/- 4.98 min versus 7.2+/-7.88min, P<0.05). With the exception of libido score all parameters of sexual behavior were superior in the GnRH (+) group compared to the Placebo (-) group during the treatment period (P < 0.05). GnRH administration increased progressive motility (GnRH (+): 30.7 +/- 10.74% versus 38.4 +/- 15.1%, P < 0.05; GnRH (total): 24.9 +/- 11.80% versus 31.9 +/- 14.68%, P < 0.05), membrane intact spermatozoa CFDA/PI (GnRH (-): 16.8 +/- 7.17% versus 26.2 +/- 7.02%, P < 0.05; GnRH (total): 23.1 +/- 12.33% versus 29.5 +/- 10.77%, P < 0.05) and HOS positive spermatozoa (GnRH (+): 33.2 +/- 11.29% versus 42.2 +/- 10.36%, P < 0.05; GnRH (total): 32.9 +/- 10.23% versus 40.1 +/- 10.30%, P < 0.05) of frozen/thawed spermatozoa. Following cessation of treatment, the viability of frozen/thawed spermatozoa decreased. GnRH treated stallions had lower losses of live stained spermatozoa (EN) compared to the Placebo group (GnRH (total): 17.6 +/- 4.77 versus Placebo (total): 27.2 +/- 5.44, P < 0.05). This was particularly observed in the "poor freezer" group (GnRH (-): 16.6 +/- 4.35 versus Placebo (-): 31.3 +/- 5.87; P < 0.05). In conclusion, exogenous GnRH was shown to improve sexual behavior and increase the quality of frozen/thawed spermatozoa in fertile stallions during the non-breeding season. Nevertheless, it seems that, although significance was achieved relative to improvement to post-thaw sperm quality, that the "real" change in sperm quality seems negligible in fertile stallions. The mechanism of GnRH effect was not determined but this study may support the possibility of a direct gonadal or epididymal effect of exogenous GnRH in the stallion.

African-American heredity prostate cancer study: a model for genetic research

A genome-wide scan of high-risk prostate cancer families in North America has demonstrated linkage of a particular marker to Chromosome Iq (HPC11. An even greater proportion of African-American families have shown linkage to HPC 1. Therefore, investigators at the National Human Genome Research Institute [NHGRI] in collaboration with Howard University and a predominantly African-American group of urologists established the African-American Hereditary Prostate Cancer (AAHPC) Study Network to confirm the suggested linkage of HPC in African Americans with a gene on Chromosome 1. Blood samples from recruited families were sent to Howard University for extraction of DNA. The DNA was sent to NHGRI at NIH where the genotyping and genetic sequence analysis was conducted. Genotype data are merged with pedigree information so that statistical analysis can be performed to establish potential linkage. From March 1, 1998, to June 1, 1999, a total of 40 African-American families have been recruited who met the study criteria. Preliminary results suggest that racial/ethnicity grouping may affect the incidence and extent of linkage of prostate cancer to specific loci. The importance of these findings lays in the future treatment of genetic-based diseases.

Problem behaviour, caregiver reactions, and impact among caregivers of persons with Alzheimer's disease

BACKGROUND

Problem behaviours that occur during Alzheimer's disease (AD) can have major impact on caregivers. How caregivers react to these behaviours may determine the total impact experienced from caregiving.

PURPOSE

This study examined the relationships between problematic behaviours and caregiving impact in 30 primary caregivers of persons with AD. The first question explored the relationship between frequency of problem behaviour and impact; the second explored the relationship between caregiver reactions to problem behaviours and impact from caregiving.

METHODS

The frequency of problem behaviour and the caregiver reaction was measured using The Revised Memory and Behaviour Problem Checklist (Teri et al. 1992). The impact from caregiving was operationalized using the Cost of Care Index developed by Kosberg and Cairl (1986).

RESULTS

Significant associations were found for 11 of the 20 subscales that measured the association between the frequency of problem behaviour in the client and the impact from caregiving experienced by the caregiver. In comparison, the association between caregiver's reaction to problem behaviours and impact from caregiving was even more significant in value with 15 subscales of 20 being significant. Female caregivers experienced a greater reaction to disruptive and depressive behaviour when compared with male caregivers even though both genders reported similar frequencies of problem behaviours. In regard to findings about the impact from caregiving, four of the six indicators were higher for women than for men.

CONCLUSIONS

Caregiver reaction to problem behaviours was more highly associated with impact from caregiving than the actual frequency of the behaviours. These findings have great implications for intervention programs. Caregivers, especially females, need to receive individualized, specific education/training on how to understand and manage disruptive and depressive behaviour in persons with AD.

Extent of linkage disequilibrium between the androgen receptor gene CAG and GGC repeats in human populations: implications for prostate cancer risk

While studies have implicated alleles at the CAG and GGC trinucleotide repeats of the androgen receptor gene with high-grade, aggressive prostate cancer disease, little is known about the normal range of variation for these two loci, which are separated by about 1.1 kb. More importantly, few data exist on the extent of linkage disequilibrium (LD) between the two loci in different human populations. Here we present data on CAG and GGC allelic variation and LD in six diverse populations. Alleles at the CAG and GGC repeat loci of the androgen receptor were typed in over 1000 chromosomes from Africa, Asia, and North America. Levels of linkage disequilibrium between the two loci were compared between populations. Haplotype variation and diversity were estimated for each population. Our results reveal that populations of African descent possess significantly shorter alleles for the two loci than non-African populations (P<0.0001). Allelic diversity for both markers was higher among African Americans than any other population, including indigenous Africans from Sierra Leone and Nigeria. Analysis of molecular variance revealed that approx. 20% of CAG and GGC repeat variance could be attributed to differences between the populations. All non-African populations possessed the same common haplotype while the three populations of African descent possessed three divergent common haplotypes. Significant LD was observed in our sample of healthy African Americans. The LD observed in the African American population may be due to several reasons; recent migration of African Americans from diverse rural communities following urbanization, recurrent gene flow from diverse West African populations, and admixture with European Americans. This study represents the largest genotyping effort to be performed on the two androgen receptor trinucleotide repeat loci in diverse human populations.

The debate about prostate cancer screening: what nurses need to know

OBJECTIVES

Special challenges and unique opportunities for nurses in the 21st century related to prostate cancer screening are reviewed.

DATA SOURCES

Current health care literature pertaining to prostate cancer screening issues.

CONCLUSIONS

Decisions that weigh the immediate risks of incontinence and erectile dysfunction against the long-term potential risk of death from advanced cancer must be made with conflicting values and incomplete data.

IMPLICATIONS FOR NURSING PRACTICE

With their expertise in patient education nurses are in a unique position to communicate the risks and benefits of prostate cancer screening in a manner in which patients can understand. A sample nursing care plan is presented for shared decision making.

African-American heredity prostate cancer study: a model for genetic research

A genome-wide scan of high-risk prostate cancer families in North America has demonstrated linkage of a particular marker to Chromosome 1q (HPC1). An even greater proportion of African-American families have shown linkage to HPC1. Therefore, investigators at the National Human Genome Research Institute (NHGRI) in collaboration with Howard University and a predominantly African-American group of urologists established the African-American Hereditary Prostate Cancer (AAHPC) Study Network to confirm the suggested linkage of HPC in African Americans with a gene on Chromosome 1. Blood samples from recruited families were sent to Howard University for extraction of DNA. The DNA was sent to NHGRI at NIH where the genotyping and genetic sequence analysis was conducted. Genotype data are merged with pedigree information so that statistical analysis can be performed to establish potential linkage. From March 1, 1998, to June 1, 1999, a total of 40 African-American families have been recruited who met the study criteria. Preliminary results suggest that racial/ethnicity grouping may affect the incidence and extent of linkage of prostate cancer to specific loci. The importance of these findings lays in the future treatment of genetic-based diseases.

Barriers to prostate cancer screening in African American men

Prostate cancer is one of the most significant health problems facing men today, especially African American men. Decreased participation in prostate cancer screening by African American men is a serious problem, as decreased survival rates occur when the diagnosis of prostate cancer is delayed. This descriptive correlational study focuses on identifying the relationship between perceived barriers and participation in a free prostate cancer screening program. A purposive sample of African American men (n = 1,395) was drawn from multiple community sites in the southeast United States. All significant variables (age, income group, marital status, and educational intervention were used as covariants for the multiple logistic regression. With the addition of the covariants, the barrier suggesting "would be embarrassed" remained significant (p = 0.03). Two other barriers, "no way to get there" and "refuse to go" approached significance (p = 0.08 and p = 0.09, respectively). Nurses can use knowledge about barriers identified in this study to develop interventions aimed at increasing participation in prostate cancer screening among African American men.

Localization of telomerase hTERT protein and hTR in benign mucosa, dysplasia, and squamous cell carcinoma of the cervix

Telomerase has been detected by telomerase repeat amplification protocol (TRAP) assay in cervical dysplasia and squamous cell carcinoma but not in most normal cervical tissues. In the present study, the cellular localization of the protein catalytic subunit of telomerase (hTERT) and the RNA component (hTR) were investigated by a sensitive immunohistochemical technique and by in situ hybridization, respectively. hTERT protein was detected in all diagnostic categories of cervical specimens. hTERT was localized predominantly to the lower suprabasal levels of normal squamous mucosa but was detected throughout virtually all levels of the lesional epithelium in low-grade squamous intraepithelial lesions (LSILs), high-grade squamous intraepithelial lesions (HSILs), and squamous cell carcinoma (SCC). Telomerase expression correlated with hTERT detection in SCC and HSIL but was not detected by TRAP assay in most samples of normal mucosa or LSIL. The distribution of hTR correlated with the localization of hTERT in HSIL and SCC but was restricted to the basal and suprabasal cell layers in normal mucosa and LSIL.

Recruitment experience in the first phase of the African American Hereditary Prostate Cancer (AAHPC) study

The African American Hereditary Prostate Cancer (AAHPC) Study is an ongoing multicenter genetic linkage study organized by Howard University and the National Human Genome Research Institute (NHGRI), with support from the Office for Research on Minority Health and the National Cancer Institute. The goals of the study are to: (i) look for evidence of involvement of chromosome 1q24-25 (HPC1) in African American men with hereditary prostate cancer (HPC) and (ii) conduct a genome-wide search for other loci associated with HPC in African American men. To accomplish these goals, a network has been established including Howard University, the NHGRI, and six Collaborative Recruitment Centers (CRCs). The CRCs are responsible for the identification and enrollment of 100 African American families. To date, 43 families have been enrolled. Recruitment strategies have included mass media campaigns, physician referrals, community health-fairs/prostate cancer screenings, support groups, tumor registries, as well as visits to churches, barber shops, and universities. By far, the most productive recruitment mechanisms have been physician referrals and tumor registries, yielding a total of 35 (81%) families. Approximately 41% (n = 3400) of probands initially contacted by phone or mail expressed interest in participating; the families of 2% of these met the eligibility criteria, and 75% of those families have been enrolled in the study, indicating a 0.5% recruitment yield (ratio of participants to contacts). As the first large-scale genetic linkage study of African Americans, on a common disease, the challenges and successes of the recruitment process for the AAHPC Study should serve to inform future efforts to involve this population in similar studies.

Effects of psychological distress on blood pressure in adolescents

This cross-sectional survey measured relationships among blood pressure and measures of psychologic distress, family structure, and economic status in a sample of adolescents exposed to Hurricane Hugo. Spielberger's Anger Scale and Derogatis' Brief Symptom Inventory were used. Data analysis revealed 5% of the 1079 adolescents were hypertensive. Multiple regression analyses revealed the following predictors of higher diastolic blood pressure: African-American race, recipient of subsidized lunch, exposure to Hurricane Hugo, and higher anger-in scores in males. The effects of a catastrophic event such as a hurricane on blood pressure and the effects of introjected anger have implications for both health care consumers and providers.

Immunohistochemical localization of telomerase hTERT protein and analysis of clonality in multifocal vulvar intraepithelial neoplasia

Vulvar intraepithelial neoplasias (VINs) are potentially premalignant lesions of the squamous mucosa. The immunohistochemical distribution of the catalytic protein subunit of telomerase (hTERT) and the patterns of X chromosome inactivation were investigated as markers of neoplasia in samples from a patient with multifocal and diffuse VIN. hTERT nuclear staining in VIN correlated with squamous maturation and the degree of nuclear atypia. Normal mucosa revealed faint nuclear staining of parabasal cells and lower intermediate layer squamous cells. Monoclonal composition was demonstrated in 0 of 3 samples of VIN1, 2 of 3 samples of VIN2, and 13 of 13 samples of VIN3. The patterns of X chromosome inactivation indicated intramucosal extension and multifocal origin of individual lesions. Five samples of histologically normal vulvar squamous epithelium revealed a random pattern of X chromosome inactivation, consistent with polyclonal composition. All 19 samples from 9 lesions contained human papillomavirus (HPV)-16 sequences. Neither mutations in the p53 tumor suppressor gene or K-ras oncogenes nor loss of heterozygosity at 7 chromosomal loci were detected in any of the 19 samples of VIN. These results demonstrate that HPV-associated VIN may result from multifocal and diffuse 2-dimensional intraepithelial expansion of an immortalized monoclonal cell population.

An intervention to decrease cancer fatalism among rural elders

PURPOSE/OBJECTIVES

To evaluate the effectiveness of a video intervention in decreasing cancer fatalism, increasing knowledge of colorectal cancer, and increasing participation in fecal-occult blood testing (FOBT).

DESIGN

Repeated measures, pretest/post-test.

SETTING

Senior citizen centers in a rural southern state.

SAMPLE

Individuals were selected and assigned to the study group based on the center they attended. Centers were selected and assigned randomly to an intervention (n = 42) or control (n = 28) group. The age of the participants ranged from 52-92 years (X = 75).

METHODS

Pretest measures included the Powe Fatalism inventory, the Colorectal Cancer Knowledge Questionnaire, and the Demographic Data Questionnaire. The intervention group viewed the Medical University of South Carolina's video Telling the Story ... To Live is God's Will, and the control group viewed the American Cancer Society (ACS) video Colorectal Cancer: The Cancer No One Talks About. Hemoccult II kits were distributed to both groups at no cost. Post-test data were collected using the Powe Fatalism Inventory and the Colorectal Cancer Knowledge Questionnaire.

MAIN RESEARCH VARIABLES

Cancer fatalism, knowledge of colorectal cancer, and participation in FOBT.

FINDINGS

People who viewed the intervention video had a greater decrease in cancer fatalism scores and a greater increase in knowledge of colorectal cancer scores than the control group. Both groups had greater than 60% participation in FOBT.

CONCLUSIONS

Telling the Story ... To Live is God's Will is an effective, self-contained, cost-effective intervention to decrease cancer fatalism and increase knowledge of colorectal cancer. The video was as effective as the ACS video on colorectal cancer in increasing participation in FOBT among rural elders. But, because Telling the Story ... To Live is God's Will also decreases cancer fatalism and increases knowledge, the potential exists for the increased screening behaviors to be maintained over time.

IMPLICATIONS FOR NURSING PRACTICE

Showing the video in waiting areas of community health centers to facilitate the discussion of colorectal cancer and cancer screening with the healthcare professional is a possibility. Nursing students may benefit from using the video as a model for the integration of beliefs and attitudes in developing culturally appropriate, community-based interventions. More research is needed to determine if the positive outcomes of the intervention (i.e., decreased cancer fatalism, increased knowledge, increased participation in colorectal cancer screening) can be maintained over time.

Prostate cancer education in African American churches

The use of churches as recruitment sites of African Americans into health promotion activities is a popular theme in the 1990s literature. This research measured the impact of previous exposure to cancer on participation in an educational program and a free prostate cancer screening. Cues to action from the Health Belief Model provided the conceptual framework. Over 500 men attended a prostate cancer educational program at their church. Men who participated in the educational program and completed the questionnaire were given a voucher that they could take to their doctor of choice for a free prostate cancer examination. Having a member of the congregation who was previously diagnosed with cancer was a significant cue to attendance at the educational program (P = 0.03). Recommendations for future cancer screening in churches are given.

Agitation: measurement, management, and intervention research

Strategies for controlling and managing agitation of patients in long-term care populations has been identified as a research priority. Unfortunately, there is a paucity of literature on empirically tested therapeutic interventions for agitation. This manuscript summarizes the literature related to the measurement, management, and interventions for agitation and identifies a nursing research agenda for conducting research in this area. Nonpharmacological and nonrestraint interventions are highlighted and categorized by (1) alterations in care given, (2) environmental adaptations, and (3) behavioral approaches. Future research areas identified by the authors focus on additional types of environmental, interpersonal, and behavioral interventions as well as theoretical predictors of agitation; the influence and role of nursing personnel and caregiver; and the legal and ethical issues involved in caring for patients who manifest agitation.

Predictors of Pap smear screening in socioeconomically disadvantaged elderly women

OBJECTIVE

The objective for this study was to identify predictors for participation in Pap smear screening in a socioeconomically disadvantaged older population.

DESIGN AND SAMPLE

A cross-sectional survey design was used to examine data from 238 southern women 50 years of age and older who were recruited from 24 randomly selected congregate meal sites of the Council on Aging.

MEASUREMENTS

The 45-item questionnaire covered demographics, Pap smear screening history, and colorectal cancer screening history.

RESULTS

Among this older, very low income population, women who had never had Pap smears (17.2%) were significantly more likely to have no phone or to be unable to use a phone (adjusted odds ratio (aOR) = 4.1; 95% confidence interval (CI) 1.6-10.6), to have annual incomes of less than $5,800 (aOR = 3.1; 95% CI 1.1-9.0), to be widowed (aOR = 2.8; 95% CI 1.1-7.3), to have no family history of cancer (aOR = 3.3, 95% CI 1.3-10.0), to report having never had a rectal examination (aOR = 5.4, 95% CI 1.8-16.0), and not to have participated in a free fecal occult blood testing program (aOR = 5.0, 95% CI 2.0-10.0).

CONCLUSIONS

These data, unique in including very low income (< $10,000) and older women (65 and over), found that income and access to a phone were strongly correlated with cervical cancer screening participation. Women who lacked external incentives for screening (being widowed and not having a family history of cancer) were less likely to obtain screening. This study's finding that "not having a phone" was a strong predictor for nonparticipation in cervical cancer screening has implications for national telephone-derived estimates of cervical cancer screening.

Delirium in the older person with cancer

Delirium occurs in 25-40% of patients with cancer and in as many as 85% of patients with advanced cancer. Delirium, or acute confusion, can be short term and reversible and differs from dementia, which is chronic and irreversible. Accurate assessment is critical for effective treatment and to reduce the increased mortality associated with delirium. Assessment for differentiating depression as well as dementia is needed, because mistaken diagnoses often prolong and exacerbate the symptoms of delirium. Different treatment strategies are appropriate depending on the cause(s) of confusion. In this article, risk factors and assessment tools are reviewed, and interventions for delirium in older persons with cancer are presented. Future areas for research are identified, because there is a paucity of research on delirium in older patients with cancer.

Psychological distress of adolescents exposed to Hurricane Hugo

To ascertain the effects of a natural disaster on adolescents, 1482 South Carolina high school students who were exposed to Hurricane Hugo were surveyed 1 year after the disaster. Subjects completed a self-administered questionnaire measuring Hugo exposure, nonviolent and violent life events, social support, self-efficacy, and psychological distress. Results showed that the students reported minimal exposure to the hurricane and psychological distress variables approximated national norms. As exposure increased, adolescents reported increased symptoms of psychological distress; i.e., anger, depression, anxiety, and global mental distress. Females and white students experienced higher levels of distress. In most cases, other stressful life events were at least as strong a predictor of psychological distress as was exposure to the hurricane. Self-efficacy and social support were protective.

Post-traumatic stress disorder in adolescents after a hurricane

A school-based study conducted in 1990, 1 year after Hurricane Hugo, investigated the frequency and correlates of post-traumatic stress disorder (PTSD) in 1,264 adolescents aged 11-17 years residing in selected South Carolina communities. Data were collected via a 174-item self-administered questionnaire that included a PTSD symptom scale. A computer algorithm that applied decision rules of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised to the symptoms reported was used to assign a diagnosis of PTSD and to designate the number of individuals who met the reexperiencing (20%), avoidance (9%), and arousal (18%) criteria. Rates of PTSD were lowest in black males (1.5%) and higher, but similar, in the remaining groups (3.8-6.2%). Results from a multivariable logistic model indicated that exposure to the hurricane (odds ratio (OR) = 1.26, 95% confidence interval 1.13-1.41), experiencing other violent traumatic events (OR = 2.46, 95% confidence interval 1.75-3.44), being white (OR = 2.03, 95% confidence interval 1.12-3.69) and being female (OR = 2.17, 95% confidence interval 1.15-4.10) were significant correlates of PTSD.

Group protocol to mitigate disaster stress and enhance social support in adolescents exposed to Hurricane Hugo

Literature reports that cognitive understanding and social support can mitigate stress in both adults and adolescents. As a subcomponent of the Carolina Adolescent Health Project (CAHP), this research evaluated the efficacy of a Cognitive Social Support (CSS) group protocol designed to mitigate the disaster stress of adolescents who had been exposed seriously to Hurricane Hugo. A purposive sample of 259 students participated in and evaluated the CSS. This article reports the specific structure, content, process, rationale, and cost of the CSS. Evaluations indicated that 82% of the students evaluated the small-group component of the CSS as "very good" or "excellent," while 70% rated the large-group component as "very good" or "excellent."

Self-efficacy in normal adolescents

This descriptive study, one component of the Carolina Adolescent Health Project (CAHP), measured self-efficacy in a voluntary sample of 432 normal freshmen and sophomore urban high school students. Using Coppel's Self-Efficacy Scale (SES), which is based on Bandura's conceptualization of self-efficacy, the research also examined the effect of gender, race, socioeconomic status, and self-reported religiosity on self-efficacy. The teenagers in this sample had a moderately high degree of self-efficacy with a mean SES score of 45.37 (SES range = 13-65). A series of t tests and one-way and two-way analyses of variance indicated no significant difference in SES scores by race, gender, socioeconomic status, or religiosity. Findings did not support the investigators' original expectation that these demographic and psychosocial variables would affect self-efficacy. The study provides normative data for future comparative studies using the SES.

Nurses respond to Hurricane Hugo victims' disaster stress

Hugo, a class IV hurricane, hit South Carolina September 22, 1989, and left behind a wake of terror and destruction. Sixty-one nursing students and five faculty were involved in disaster relief with families devastated by the hurricane. A review of the literature led these authors to propose a formulation of the concept of disaster stress, a synthesis of theories that explains response to disaster as a crisis response, a stress response, or as posttraumatic stress. With the concept of disaster stress serving as a theoretical foundation, the nurses observed, assessed, and intervened with one population of hurricane Hugo victims, noting their immediate psychosocial reactions and coping mechanisms. Victims' reactions to disaster stress included confusion, irritability, lethargy, withdrawal, and crying. The most frequently observed coping strategy of these hurricane Hugo victims was talking about their experiences; other coping tactics involved humor, religion, and altruism.