Showing papers by "Queen's University published in 1998"

Epidemiology of Sarcopenia among the Elderly in New Mexico

Abstract: Muscle mass decreases with age, leading to "sarcopenia," or low relative muscle mass, in elderly people. Sarcopenia is believed to be associated with metabolic, physiologic, and functional impairments and disability. Methods of estimating the prevalence of sarcopenia and its associated risks in elderly populations are lacking. Data from a population-based survey of 883 elderly Hispanic and non-Hispanic white men and women living in New Mexico (the New Mexico Elder Health Survey, 1993-1995) were analyzed to develop a method for estimating the prevalence of sarcopenia. An anthropometric equation for predicting appendicular skeletal muscle mass was developed from a random subsample (n = 199) of participants and was extended to the total sample. Sarcopenia was defined as appendicular skeletal muscle mass (kg)/height2 (m2) being less than two standard deviations below the mean of a young reference group. Prevalences increased from 13-24% in persons under 70 years of age to >50% in persons over 80 years of age, and were slightly greater in Hispanics than in non-Hispanic whites. Sarcopenia was significantly associated with self-reported physical disability in both men and women, independent of ethnicity, age, morbidity, obesity, income, and health behaviors. This study provides some of the first estimates of the extent of the public health problem posed by sarcopenia.

Violent offenders: Appraising and managing risk.

Abstract: Federal Abortion Policy and Politics: 1973-1996 Why is Abortion Such a Controversial issue in the United States Barriers to Access to Abortion Services The Impact of Anti-abortion Activities on Women Seeking Abortions Black Women and the Question of Abortion Latinos and Abortion Abortion and Asian Pacific Islander Americans The Acceptability of Medical Abortion to Women Understanding the Relationship of Violence Against Women to Unwanted Pregnancy and it's Resolution Testing a Model of the Psychological Consequences of Abortion Men and Abortion: The Gender Politics of Pregnancy Resolution Abortion Among Adolescents A Cognitive Approach to Patient-Centered Abortion Care Abortion Issues in Psychotherapy Bringing Lessons Learned to the United States Improving Access to Abortion Services Abortion Practice, Policy, and Research: Recommendations for the 21st Century

Gauss–Newton and full Newton methods in frequency–space seismic waveform inversion

Abstract: SUMMARY By specifying a discrete matrix formulation for the frequency^space modelling problem for linear partial diierential equations (‘FDM’ methods), it is possible to derive a matrix formalism for standard iterative non-linear inverse methods, such as the gradient (steepest descent) method, the Gauss^Newton method and the full Newton method We obtain expressions for each of these methods directly from the discrete FDM method, and we refer to this approach as frequency-domain inversion (FDI)The FDI methods are based on simple notions of matrix algebra, but are nevertheless very general The FDI methods only require that the original partial diierential equations can be expressed as a discrete boundary-value problem (that is as a matrix problem) Simple algebraic manipulation of the FDI expressions allows us to compute the gradient of the mis¢t function using only three forward modelling steps (one to compute the residuals, one to backpropagate the residuals, and a ¢nal computation to compute a step length) This result is exactly analogous to earlier backpropagation methods derived using methods of functional analysis for continuous problems Following from the simplicity of this result, we give FDI expressions for the approximate Hessian matrix used in the Gauss^Newton method, and the full Hessian matrix used in the full Newton method In a new development, we show that the additional term in the exact Hessian, ignored in the Gauss^Newton method, can be e⁄ciently computed using a backpropagation approach similar to that used to compute the gradient vector The additional term in the Hessian predicts the degradation of linearized inversions due to the presence of ¢rst-order multiples (such as free-surface multiples in seismic data) Another interpretation is that this term predicts changes in the gradient vector due to second-order non-linear eiects In a numerical test, the Gauss^Newton and full Newton methods prove eiective in helping to solve the di⁄cult non-linear problem of extracting a smooth background velocity model from surface seismic-re£ection data

Cadaver validation of skeletal muscle measurement by magnetic resonance imaging and computerized tomography

Abstract: Magnetic resonance imaging (MRI) and computerized tomography (CT) are promising reference methods for quantifying whole body and regional skeletal muscle mass. Earlier MRI and CT validation studies...

Current Understanding of the Molecular Actions of Vitamin D

Abstract: The important reactions that occur to the vitamin D molecule and the important reactions involved in the expression of the final active form of vitamin D are reviewed in a critical manner. After an overview of the metabolism of vitamin D to its active form and to its metabolic degradation products, the molecular understanding of the 1alpha-hydroxylation reaction and the 24-hydroxylation reaction of the vitamin D hormone is presented. Furthermore, the role of vitamin D in maintenance of serum calcium is reviewed at the physiological level and at the molecular level whenever possible. Of particular importance is the regulation of the parathyroid gland by the vitamin D hormone. A third section describes the known molecular events involved in the action of 1alpha,25-dihydroxyvitamin D3 on its target cells. This includes reviewing what is now known concerning the overall mechanism of transcriptional regulation by vitamin D. It describes the vitamin D receptors that have been cloned and identified and describes the coactivators and retinoid X receptors required for the function of vitamin D in its genomic actions. The presence of receptor in previously uncharted target organs of vitamin D action has led to a study of the possible function of vitamin D in these organs. A good example of a new function described for 1alpha,25-dihydroxyvitamin D3 is that found in the parathyroid gland. This is also true for the role of vitamin D hormone in skin, the immune system, a possible role in the pancreas, i.e., in the islet cells, and a possible role in female reproduction. This review also raises the intriguing question of whether vitamin D plays an important role in embryonic development, since vitamin D deficiency does not prohibit development, nor does vitamin D receptor knockout. The final section reviews some interesting analogs of the vitamin D hormone and their possible uses. The review ends with possible ideas with regard to future directions of vitamin D drug design.

The effect of finasteride on the risk of acute urinary retention and the need for surgical treatment among men with benign prostatic hyperplasia

Abstract: Background Finasteride is known to improve urinary symptoms in men with benign prostatic hyperplasia, but the extent to which the benefit is sustained and whether finasteride reduces the incidence of related events, including the need for surgery and the development of acute urinary retention, are not known. Methods In this double-blind, randomized, placebo-controlled trial, we studied 3040 men with moderate-to-severe urinary symptoms and enlarged prostate glands who were treated daily with 5 mg of finasteride or placebo for four years. Symptom scores (on a scale of 1 to 34), urinary flow rates, and the occurrence of outcome events were assessed every four months in 3016 men. Prostate volume was measured in a subgroup of the men. Complete data on outcomes were available for 2760 men. Results During the four-year study period, 152 of the 1503 men in the placebo group (10 percent) and 69 of the 1513 men in the finasteride group (5 percent) underwent surgery for benign prostatic hyperplasia (reduction in risk with finasteride, 55 percent; 95 percent confidence interval, 41 to 65 percent). Acute urinary retention developed in 99 men (7 percent) in the placebo group and 42 men (3 percent) in the finasteride group (reduction in risk with finasteride, 57 percent; 95 percent confidence interval, 40 to 69 percent). Among the men who completed the study, the mean decreases in the symptom score were 3.3 in the finasteride group and 1.3 in the placebo group (P<0.001). Treatment with finasteride also significantly improved urinary flow rates and reduced prostate volume (P<0.001). Conclusions Among men with symptoms of urinary obstruction and prostatic enlargement, treatment with finasteride for four years reduces symptoms and prostate volume, increases the urinary flow rate, and reduces the probability of surgery and acute urinary retention.

Statistical Inference for Stochastic Dominance and for the Measurement of Poverty and Inequality

Abstract: We derive the asymptotic sampling distribution of various estimators frequently used to order distributions in terms of poverty, welfare and inequality. This includes estimators of most of the poverty indices currently in use, as well as estimators of the curves used to infer stochastic dominance of any order. These curves can be used to determine whether poverty, inequality or social welfare is greater in one distribution than in another for general classes of indices. We also derive the sampling distribution of the maximal poverty lines (or income censoring thresholds) up to which we may confidently assert that poverty or social welfare is greater in one distribution than in another. The sampling distribution of convenient estimators for dual approaches to the measurement of poverty is also established. The statistical results are established for deterministic or stochastic poverty lines as well as for paired or independent samples of incomes. Our results are briefly illustrated using data for 6 countries drawn from the Luxembourg Income Study data bases.

Age-related performance of human subjects on saccadic eye movement tasks.

Abstract: We measured saccadic eye movements in 168 normal human subjects, ranging in age from 5 to 79 years, to determine age-related changes in saccadic task performance. Subjects were instructed to look either toward (pro-saccade task) or away from (anti-saccade task) an eccentric target under different conditions of fixation. We quantified the percentage of direction errors, the time to onset of the eye movement (saccadic reaction time: SRT), and the metrics and dynamics of the movement itself (amplitude, peak velocity, duration) for subjects in different age groups. Young children (5–8 years of age) had slow SRTs, great intra-subject variance in SRT, and the most direction errors in the anti-saccade task. Young adults (20–30 years of age) typically had the fastest SRTs and lowest intra-subject variance in SRT. Elderly subjects (60–79 years of age) had slower SRTs and longer duration saccades than other subject groups. These results demonstrate very strong age-related effects in subject performance, which may reflect different stages of normal development and degeneration in the nervous system. We attribute the dramatic improvement in performance in the anti-saccade task that occurs between the ages of 5–15 years to delayed maturation of the frontal lobes.

A Multiple Time Step Symplectic Algorithm for Integrating Close Encounters

Abstract: We present a new symplectic algorithm that has the desirable properties of the sophisticated but highly efficient numerical algorithms known as mixed variable symplectic (MVS) methods and that, in addition, can handle close encounters between objects. This technique is based on a variant of the standard MVS methods, but it handles close encounters by employing a multiple time step technique. When the bodies are well separated, the algorithm has the speed of MVS methods, and whenever two bodies suffer a mutual encounter, the time step for the relevant bodies is recursively subdivided to whatever level is required. We demonstrate the power of this method using several tests of the technique. We believe that this algorithm will be a valuable tool for the study of planetesimal dynamics and planet formation.

Measurement of Symptoms, Lung Hyperinflation, and Endurance during Exercise in Chronic Obstructive Pulmonary Disease

Abstract: Changes in lung hyperinflation, dyspnea, and exercise endurance are important outcomes in assessing therapeutic responses in chronic obstructive pulmonary disease (COPD). Therefore, we studied the reproducibility of Borg dyspnea ratings, inspiratory capacity (IC; to monitor lung hyperinflation), and endurance time during constant-load symptom-limited cycle exercise in 29 patients with COPD (FEV1 = 40 ± 2% predicted; mean ± SEM). Responsiveness was also studied by determining the acute effects of nebulized 500 μ g ipratropium bromide (IB) or saline placebo (P) on these measurements. During each of four visits conducted over an 8-wk period, spirometry and exercise testing were performed before and 1 h after receiving IB or P (randomized, double-blinded). Highly reproducible measurements included: endurance time (intraclass correlation R = 0.77, p 0.6, p < 0.0001); and slopes of Borg ratings over time, ox...

Total Parenteral Nutrition in the Critically Ill Patient: A Meta-analysis

Abstract: Context.—Nutritional support has become a standard of care for hospitalized patients, but whether total parenteral nutrition (TPN) affects morbidity and mortality is unclear.Objective.—To examine the relationship between TPN and complication and mortality rates in critically ill patients.Data Sources.—Computerized search of published research on MEDLINE from 1980 to 1998, personal files, and review of relevant reference lists.Study Selection.—We reviewed 210 titles, abstracts, and papers. Primary studies were included if they were randomized clinical trials of critically ill or surgical patients that evaluated the effect of TPN (compared with standard care) on complication and mortality rates. We excluded studies comparing TPN with enteral nutrition.Data Extraction.—Relevant data were abstracted on the methodology and outcomes of primary studies. Data were abstracted in duplicate, independently.Data Synthesis.—There were 26 randomized trials of 2211 patients comparing the use of TPN with standard care (usual oral diet plus intravenous dextrose) in surgical and critically ill patients. When the results of these trials were aggregated, TPN had no effect on mortality (risk ratio [RR], 1.03; 95% confidence interval [CI], 0.81-1.31). Patients who received TPN tended to have a lower complication rate, but this result was not statistically significant (RR, 0.84; 95% CI, 0.64-1.09). We examined several a priori hypotheses and found that studies including only malnourished patients were associated with lower complication rates but no difference in mortality when compared with studies of nonmalnourished patients. Studies published since 1989 and studies with a higher methods score showed no treatment effect, while studies published in 1988 or before and studies with a lower methods score demonstrated a significant treatment effect. Complication rates were lower in studies that did not use lipids; however, there was no difference in mortality rates between studies that did not use lipids and those studies that did. Studies limited to critically ill patients demonstrated a significant increase in complication and mortality rates compared with studies of surgical patients.Conclusions.—Total parenteral nutrition does not influence the overall mortality rate of surgical or critically ill patients. It may reduce the complication rate, especially in malnourished patients, but study results are influenced by patient population, use of lipids, methodological quality, and year of publication.

Observations of Bullying and Victimization in the School Yard

Abstract: The purpose of this research was to describe bullying on the playground The subjects were children observed either bullying or being victimized on the playground. Bullying episodes were identified with 90% inter-rater agreement. Bullying occurred regularly on the playground, approximately once every seven minutes and was of short duration, 38 seconds. The majority of bullying episodes (68%) occurred within 120 feet of the school building. Adults were found to have intervened in 4% of the episodes, while peers intervened in 11% of the episodes. However, adults were more likely to intervene than peers if they were present. Peers were involved in some capacity in 85% of the episodes. Boys bullied more than girls and were more likely to bully victims of the same-sex and repeatedly target the same victim. There were no gender differences in the type of bullying and aggression. Children in the primary and junior grades were equally likely to be involved in bullying and tended to bully students from the same gra...

Ethnicity, patronage and the african state: the politics of uncivil nationalism

Abstract: Recent research has revealed that modern African ethnicity is a social construction of the colonial period through the reactions of pre-colonial societies to the social, economic, cultural and political forces of colonialism. Ethnicity is the product of a continuing historical process, always simultaneously old and new, grounded in the past and perpetually in creation. Colonial states were grounded in the alliances with local 'Big Men', incorporating ethnically-defined administrative units linked to the local population by incorporation of pre-colonial patron-client relations. This was reinforced by European assumptions of neatly bounded and culturally homogeneous 'tribes' and a bureaucratic preoccupation with demarcating, classifying and counting subject populations, as well as by the activities of missionaries and anthropologists. African ethnic invention emerged through internal struggles over moral economy and political legitimacy tied to the definition of ethnic communities—moral ethnicity; and external conflicts over differential access to the resources of modernity and economic accumulation—political tribalism. Ethnicities were, in particular, the creations of elites seeking the basis for a conservative modernization. The colonial legacy of bureaucratic authoritarianism, pervasive patron-client relations, and a complex ethnic dialectic of assimilation, fragmentation and competition has persisted in post-colonial societies. Patron-client networks remain the fundamental state-society linkage in circumstances of social crisis and uncertainty and have extended to the very centre of the state. This accounts for the personalistic, materialistic and opportunistic character of African politics. Such networks also penetrate institutions of civil society and liberal democracy, undermining programmes of socio-economic and political reform.

Lateral Inhibitory Interactions in the Intermediate Layers of the Monkey Superior Colliculus

Abstract: Munoz, Douglas P. and Peter J. Istvan. Lateral inhibitory interactions in the intermediate layers of the monkey superior colliculus. J. Neurophysiol. 79: 1193–1209, 1998. The intermediate layers of...

Clinical safety of oral sildenafil citrate (VIAGRA) in the treatment of erectile dysfunction.

Abstract: Sildenafil citrate has been shown to be effective in a wide range of patients with erectile dysfunction and has been approved in the United States for this indication. The overall clinical safety of oral sildenafil, a potent inhibitor of phosphodiesterase type 5, in the treatment of erectile dysfunction was evaluated in more than 3700 patients (with a total of 1631 years of exposure worldwide). Safety and tolerability data were analysed from a series of double-blind, placebo-controlled studies and from 10 open-label extension studies of sildenafil in the treatment of erectile dysfunction. A total of 4274 patients (2722 sildenafil, 1552 placebo; age range 19-87 y) received double-blind treatment over a period of up to six months' duration, and 2199 received long-term, open-label sildenafil for up to 1 y. The most commonly reported adverse events (all causes) were headache (16% sildenafil, 4% placebo), flushing (10% sildenafil, 1% placebo), and dyspepsia (7% sildenafil, 2% placebo) and they were predominantly transient and mild or moderate in nature. These adverse events reflect the pharmacology of sildenafil as a phosphodiesterase type 5 inhibitor. No cases of priapism were reported. The rate of discontinuation due to adverse events (all causes) was comparable for patients treated with sildenafil (2.5%) and placebo (2.3%). In open-label extension studies, 90% of patients completed long-term sildenafil treatment, with only 2% withdrawing due to adverse events. Sildenafil is a well-tolerated oral treatment for erectile dysfunction.

Saccadic probability influences motor preparation signals and time to saccadic initiation

Abstract: One must be prudent when selecting potential saccadic targets because the eyes can only move to one location at a time, yet movements must occur quickly enough to permit interaction with a rapidly changing world. This process of efficiently acquiring relevant targets may be aided by advanced planning of a movement toward an upcoming target whose location is gathered via environmental cues or situational experience. We studied how saccadic reaction times (SRTs) and early pretarget neuronal activity covaried as a function of saccadic probability. Monkeys performed a saccadic task in which the probability of the required saccade being directed into the response field of a neuron varied systematically between blocks of trials. We recorded simultaneously the early pretarget activity of saccade-related neurons in the intermediate layers of the superior colliculus. We found that, as the likelihood of the saccade being generated into the response field of the neuron increased, the level of neuronal activity preceding target presentation also increased. Our data suggest that this early activity codes motor preparation because its activity was related to not only the metrics but also the timing of the saccade, with 94% (29/31) of the neurons tested having significant negative correlations between discharge rate and SRT. This view is supported by cases in which exceptionally high levels of pretarget activity were associated with anticipatory saccades into the response field of a neuron that occurred in advance of the target being presented. This study demonstrates how situational experience can expedite motor behavior via the advanced preparation of motor programs.

Models and languages for parallel computation

Abstract: We survey parallel programming models and languages using six criteria to assess their suitability for realistic portable parallel programming. We argue that an ideal model should by easy to program, should have a software development methodology, should be architecture-independent, should be easy to understand, should guarantee performance, and should provide accurate information about the cost of programs. These criteria reflect our belief that developments in parallelism must be driven by a parallel software industry based on portability and efficiency. We consider programming models in six categories, depending on the level of abstraction they provide. Those that are very abstract conceal even the presence of parallelism at the software level. Such models make software easy to build and port, but efficient and predictable performance is usually hard to achieve. At the other end of the spectrum, low-level models make all of the messy issues of parallel programming explicit (how many threads, how to place them, how to express communication, and how to schedule communication), so that software is hard to build and not very portable, but is usually efficient. Most recent models are near the center of this spectrum, exploring the best tradeoffs between expressiveness and performance. A few models have achieved both abstractness and efficiency. Both kinds of models raise the possibility of parallelism as part of the mainstream of computing.

Characterization of vincristine transport by the M(r) 190,000 multidrug resistance protein (MRP): evidence for cotransport with reduced glutathione.

Abstract: The M(r) 190,000 multidrug resistance protein (MRP) confers resistance to a broad spectrum of natural product drugs. However, it has not been possible to demonstrate that MRP can actively transport unmodified forms of these compounds, although the protein has been shown to transport structurally diverse glutathione (GSH)- and glucuronide-conjugated molecules. Previously, we showed that ATP-dependent uptake of vincristine by MRP-enriched, inside-out membrane vesicles could be stimulated by physiological concentrations of GSH (Loe et al., J. Biol. Chem., 271: 9675-9682, 1996). We have now established that the ATP/GSH dependent vincristine uptake is both proportional to the level of MRP in the membrane vesicles and can be inhibited by monoclonal antibodies shown previously to inhibit transport of established MRP substrates, such as leukotriene C4. We also show that short-chain alkyl derivatives of GSH can stimulate drug uptake, which suggests that vincristine transport does not necessarily involve a change in redox state or glutathionylation of the protein. Furthermore, vincristine uptake is accompanied by ATP- and drug-dependent accumulation of GSH, which can also be stimulated to a lesser extent by vinblastine but not daunorubicin or doxorubicin. Although GSH or vincristine alone are very poor inhibitors of MRP-mediated transport of leukotriene C4, together they act as relatively potent competitive inhibitors. Overall, our data demonstrate that MRP can actively cotransport GSH and unmodified vincristine and that these compounds probably interact, either with the leukotriene C4 binding site(s) on the protein or with a mutually exclusive site.

Computation of different optical variables of looming objects in pigeon nucleus rotundus neurons.

Abstract: Three types of looming-selective neurons have been found in the nucleus rotundus of pigeons, each computing a different optical variable related to image expansion of objects approaching on a direct collision course with the bird. None of these neurons respond to simulated approach toward stationary objects. A detailed analysis of these neurons’ firing pattern to approaching objects of different sizes and velocities shows that one group of neurons signals relative rate of expansion τ (tau), a second group signals absolute rate of expansion ρ (rho), and a third group signals yet another optical variable η (eta). The ρ parameter is required for the computation of both τ and η, whose respective ecological functions probably provide precise ‘time-to-collision’ information and ‘early warning’ detection for large approaching objects.

ATM Mutations and Phenotypes in Ataxia-Telangiectasia Families in the British Isles: Expression of Mutant ATM and the Risk of Leukemia, Lymphoma, and Breast Cancer

Abstract: Summary We report the spectrum of 59 ATM mutations observed in ataxia-telangiectasia (A-T) patients in the British Isles Of 51 ATM mutations identified in families native to the British Isles, 11 were founder mutations, and 2 of these 11 conferred a milder clinical phenotype with respect to both cerebellar degeneration and cellular features We report, in two A-T families, an ATM mutation (7271T→G) that may be associated with an increased risk of breast cancer in both homozygotes and heterozygotes (relative risk 127; P =0025), although there is a less severe A-T phenotype in terms of the degree of cerebellar degeneration This mutation (7271T→G) also allows expression of full-length ATM protein at a level comparable with that in unaffected individuals In addition, we have studied 18 A-T patients, in 15 families, who developed leukemia, lymphoma, preleukemic T-cell proliferation, or Hodgkin lymphoma, mostly in childhood A wide variety of ATM mutation types, including missense mutations and in-frame deletions, were seen in these patients We also show that 25% of all A-T patients carried in-frame deletions or missense mutations, many of which were also associated with expression of mutant ATM protein

Multidrug resistance mediated by the atp-binding cassette transporter protein mrp

Abstract: Resistance to multiple natural product drugs associated with reduced drug accumulation in human tumor cells may be conferred by either the 170 kDa P-glycoprotein or the 190 kDa multidrug resistance protein, MRP. Both MRP and P-glycoprotein belong to the large and ancient ATP-binding cassette (ABC) superfamily of transport proteins but share only 15% amino acid identify. Unlike P-glycoprotein, MRP actively transports conjugated organic anions such as the cysteinyl leukotriene C4 and glutathione-conjugated aflatoxin B1. Transport of unconjugated chemotherapeutic agents appears to require cotransport of glutathione. MRP and several more recently discovered ABC proteins contain an additional NH2-proximal membrane-spanning domain not found in previously characterized ABC transporters. This domain, whose NH2-terminus is extracytosolic, is essential for MRP-mediated transport activity. This review summarizes current knowledge of the structural and transport characteristics of MRP which suggest that the physiologic functions of this protein could range from a protective role in chemical toxicity and oxidative stress to mediation of inflammatory responses involving cysteinyl leukotrienes.

Nitrogen isotope fractionation during the uptake and assimilation of nitrate, nitrite, ammonium, and urea by a marine diatom

Abstract: Knowledge of the fractionation of nitrogen isotopes by phytoplankton is a key requirement for the calibration of the new δ 15 N paleotracer. An essential part of information required in this calibration concerns the magnitude of isotopic fractionation during the incorporation of N substrates by phytoplankton. To this end, the δ 15 N of batch cultures of Thalassiosira pseudonana grown on nitrate, nitrite, ammonium, and urea was determined. This paper reports the first δ 15 N study of phytoplankton growth on urea (e.g. organic N substrate). The δ 15 N of the particulate nitrogen (PN) collected during the logarithmic growth phase, thus for N-sufficient cells, was lower than the δ 15 N of the source due to kinetic isotope fractionation. With increasing drawdown of the N substrate, the δ 15 N of the accumulating PN increased in accordance with the Rayleigh distillation model. Enrichment factors (e) derived from a least-squares analysis of the accumulated δ 15 N pN data were 5.2 ± 0.2‰, 0.9 ± 0.6‰, 20 ± 1‰, and 0.8 ± 0.6‰ for NO 3 - , NO 2 , NH 4 + , and urea incorporation, respectively. Overall, e values for nitrate incorporation were consistent with field estimates of ∼6‰, and could be used to estimate past relative nitrate utilization as estimated from the δ 15 N of bulk sedimentary organic matter.