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A single catalytic site model is proposed to account for the multiphasic kinetics of oxidation of ferrocytochrome c by cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1). This model involves nonproductive binding of substrate .to sites near the catalytic site on cytochrome c oxidase for cytochrome c, decreasing the binding constant for cytochrome c at the catalytic site. This substrate inhibition results in an increase.in the first-order rate constant for the dissociation of the ferricytochrome c-cytochrome c oxidase complex, the rate-limiting step in the steady-state turnover of electrons between cytochrome c and cytochrome c oxidase in the spectrophotometric assay, yielding increases in the initial rate as well as the Michaelis constant-namely, multiple kinetic phases. (2) and Borei (3) proposed that the reaction involved the formation of an enzyme-substrate complex. In 1949, Slater (4) confirmed and extended the observations of these authors, demonstrating that at any single concentration of enzyme [provided in the form of a KeilinHartree heart muscle particle preparation (5)], the kinetics indeed fit the Michaelis-Menten relation. However, the oxidation of ferrocytochrome c monitored spectrophotometrically (namely, in the absence of any added reducing agent) was generally observed to follow a first-order time course (6-13). Because the observed first-order rate constants decrease with increasing cytochrome c concentration rather than remaining unchanged, as one would expect for a simple bimolecular collisional mechanism with no precursor-pair formation, Smith and Conrad (13) suggested that the hyperbolic dependence of the initial velocity on cytochrome c concentration was due to inhibition of the reaction by cytochrome c itself.That this was not the only possible explanation of these kinetics followed from Minnaert's (14) elegant analysis, in which it was shown that a first-order time course could arise from equal binding of ferro-and ferricytochromes c to cytochrome oxidase, with ferrocytochrome c forming a productive complex while ferricytochrome c acted as a competitive inhibitor. This hypothesis was supported by Yonetani and Ray (15), who demonstrated that (i) under conditions in which first-order kinetics are observed, the K1 for ferricytochrome c is the same as the apparent Michaelis constant for ferrocytochrome c and (ii) at more alkaline pH values, where the kinetics deviate from a first-order time course, the K1 for ferricytochrome c is no longer equal to the apparent Km for the reaction.Indeed, inspection of the Michaelis-Menten equation, which takes into account binding of product to the enzyme, leads to the expression: dp _ Vmax 15= kobS, dt LKm + (s + P)when Km is a good approximation of Ks, the equilibrium substrate binding constant, and the binding of substrate and product are equivalent, namely K, = Kp (16). Thus, kobs is a first-order rate constant that is distinguishable from an ordinary first-order rate constant because it is a function of s + p, the tot...

Physiologically based pharmacokinetic (PBPK) models need the correct organ/tissue weights to match various total body weights in order to be applied to children and the obese individual. Baseline data from Reference Man for the growth of human organs (adrenals, brain, heart, kidneys, liver, lungs, pancreas, spleen, thymus, and thyroid) were augmented with autopsy data to extend the describing polynomials to include the morbidly obese individual (up to 250 kg). Additional literature data similarly extends the growth curves for blood volume, muscle, skin, and adipose tissue. Collectively these polynomials were used to calculate blood/organ/tissue weights for males and females from birth to 250 kg, which can be directly used to help parameterize PBPK models. In contrast to other black/white anthropomorphic measurements, the data demonstrated no observable or statistical difference in weights for any organ/tissue between individuals identified as black or white in the autopsy reports.

BACKGROUND Recent civilian and military data from the United States and the United Kingdom suggest that further reductions in mortality will require prehospital or preoperating room hemorrhage control and blood product resuscitation. The aims of this study were to examine the potential preventability of prehospital and early in-hospital fatalities, and to consider the geographical location of such incidents, to contextualize how the use of advanced resuscitative techniques could be operationalized. METHODS Retrospective analysis of prehospital and early in-hospital trauma deaths from January to December 2017. Data were obtained from the Coroner/ME's Office. Each death was reviewed by a panel of two trauma surgeons and a forensic pathologist. Anatomical and physiological survivabilities were evaluated separately, and then combined, leading to a holistic assessment of preventability. Incident locations were mapped and analyzed using ArcGIS. RESULTS Three hundred sixteen trauma deaths were identified. Two hundred thirty-one (73%) were deemed anatomically not survivable; 29 (9%) anatomically survivable, but only with hospital care; 43 (14%) anatomically survivable with advanced prehospital care; and 13 (4%) anatomically survivable with basic prehospital care. Physiologically, 114 (36%) of the patients had been dead for some time when found; 137 (43%) had no cardiorespiratory effort on arrival of Emergency Medical Services (EMS) at the scene; 24 (8%) had cardiorespiratory effort at the scene, but not on arrival at the emergency department; and 41 (13%) had cardiorespiratory effort on arrival at the emergency department, but died shortly after. Combining the assessments, 10 (3%) deaths were deemed probably not preventable, 38 (12%) possibly preventable, and the remaining 278 (85%) not preventable. CONCLUSION Twelve percent of trauma deaths were potentially preventable and might be amenable to advanced resuscitative interventions. Operationalizing this type of care will be challenging and will require either prehospital doctors, or very highly trained paramedics, nurses, or physician assistants. LEVEL OF EVIDENCE Epidemiological, level III.

PurposeHeroin has a half-life of 2–6 min and is metabolized too quickly to be detected in autopsy samples. The presence of 6-acetylmophine (6-AM) in urine, blood, or other samples is convincing evidence of heroin use by a decedent, but 6-AM itself has a half-life of 6–25 min before it is hydrolyzed to morphine, so 6-AM may not be present in sufficient concentration to detect in postmortem samples. Codeine is often present in heroin preparations as an impurity and is not a metabolite of heroin. Studies report that a ratio of morphine to codeine greater than one indicates heroin use. We hypothesize that the ratio of morphine to codeine in our decedents abusing drugs intravenously will be no different in individuals with 6-AM present than in individuals where no 6-AM is detected, and we report our study of this hypothesis.MethodsAll accidental deaths investigated by the Jefferson County Coroner/Medical Examiner Office from 2010 to 2013 with morphine detected in blood samples collected at autopsy were reviewed. Five deaths where trauma caused or contributed to death were excluded from the review. The presence or absence of 6-AM and the concentrations of morphine and codeine were recorded for each case. The ratio of morphine to codeine was calculated for all decedents. Any individual in whom no morphine or codeine was detected in a postmortem sample was excluded from further study. Absence or presence of drug paraphernalia or evidence of intravascular (IV) drug use was documented in each case to identify IV drug users. The proportion of the IV drug users with and without 6-AM present in a postmortem sample was compared to the M/C ratio for the individuals.ResultsOf the 230 deaths included in the analysis, 103 IV drug users with quantifiable morphine and codeine in a postmortem sample were identified allowing for calculation of an M/C ratio. In these IV drug users, the M/C ratio was greater than 1 in 98 % of decedents. When controlling for the absence or presence of 6-AM there was no statistically significant difference in the proportion of IV drug users when compared to non IV drug users with an M/C ratio of greater than 1 (p = 1.000).ConclusionThe M/C ratio in IV drug users, if greater than 1, is seen in deaths due to heroin toxicity where 6-AM is detected in a postmortem sample. This study provides evidence that a M/C ratio greater than one in an IV drug user is evidence of a death due to heroin toxicity even if 6-AM is not detected in the blood. Using the M/C ratio, in addition to scene and autopsy findings, provides sufficient evidence to show heroin is the source of the morphine and codeine. Listing heroin as a cause or contributing factor in deaths with evidence of IV drug abuse and where the M/C ratio exceeds 1 will improve identification of heroin fatalities, which will allow better allocation of resources for public health initiatives.