Meta-analysis reveals that pollinator functional diversity and abundance enhance crop pollination and yield.

How insects promote crop pollination remains poorly understood in terms of the contribution of functional trait differences between species. We used meta-analyses to test for correlations between community abundance, species richness and functional trait metrics with oilseed rape yield, a globally important crop. While overall abundance is consistently important in predicting yield, functional divergence between species traits also showed a positive correlation. This result supports the complementarity hypothesis that pollination function is maintained by non-overlapping trait distributions. In artificially constructed communities (mesocosms), species richness is positively correlated with yield, although this effect is not seen under field conditions. As traits of the dominant species do not predict yield above that attributed to the effect of abundance alone, we find no evidence in support of the mass ratio hypothesis. Management practices increasing not just pollinator abundance, but also functional divergence, could benefit oilseed rape agriculture.

Fluctuating silicate:nitrate ratios and coastal plankton food webs.

Marine diatoms require dissolved silicate to form an external shell, and their growth becomes Si-limited when the atomic ratio of silicate to dissolved inorganic nitrogen (Si:DIN) approaches 1:1, also known as the "Redfield ratio." Fundamental changes in the diatom-to-zooplankton-to-higher trophic level food web should occur when this ratio falls below 1:1 and the proportion of diatoms in the phytoplankton community is reduced. We quantitatively substantiate these predictions by using a variety of data from the Mississippi River continental shelf, a system in which the Si:DIN loading ratio has declined from around 3:1 to 1:1 during this century because of land-use practices in the watershed. We suggest that, on this shelf, when the Si:DIN ratio in the river decreases to less than 1:1, then (i) copepod abundance changes from >75% to <30% of the total mesozooplankton, (ii) zooplankton fecal pellets become a minor component of the in situ primary production consumed, and (iii) bottom-water oxygen consumption rates become less dependent on relatively fast-sinking (diatom-rich) organic matter packaged mostly as zooplankton fecal pellets. This coastal ecosystem appears to be a pelagic food web dynamically poised to be either a food web composed of diatoms and copepods or one with potentially disruptive harmful algal blooms. The system is directed between these two ecosystem states by Mississippi River water quality, which is determined by land-use practices far inland.

The use of logistic models for the analysis of codon frequencies of DNA sequences in terms of explanatory variables.

The development of the regressive logistic model applicable to the analysis of codon frequencies of DNA sequences in terms of explanatory variables is presented. A codon is a triplet of nucleotides that code for an amino acid, and may be considered as a trivariate response (B1, B2, B3), where Bi (i = 1, 2, 3) is a categorical random variable with values A, C, G, T. The linear order of bases in the DNA and possible statistical dependence of the bases in a given codon make the regressive logistic model a suitable tool for the analysis of codon frequencies. A problem of structural zeros arises from the fact that the stopping codons (terminators) do not code for amino acids; this is solved by normalizing the likelihood function. Codon frequencies may also depend on the function of the gene and they are known to differ between genes of the same genome. Differences also occur between synonymous codons for the same amino acid. Thus, the use of covariates that differ between synonymous codons as well as covariates that are constant within codons of the same amino acid may be useful in explaining the frequencies. As an illustration, the method is applied to the human mitochondrial genome using the following as explanatory variables: (1) TSCORE, a measure of the number of single base mutations required for a given codon to become a terminator; (2) AARISK, an indicator of a codon's ability of changing by a single base substitution to triplets coding for amino acids with very different characteristics; (3) AVDIST, a measure of the typicality of the amino acid coded for by the triplets. The results indicate that models that incorporate dependency structure and covariates are to be preferred to either the models comprising covariates alone or dependency structure alone.

The question of natural selection against mutable-to-terminator codons.

Codons that differ from a terminator triplet by only a single base are sometimes thought, because of their greater risk of undergoing a harmful mutation, to be kept at a reduced frequency by natural selection. The present study on human genes shows that these codons are infrequent, but their low frequency is not directly related to their risk of mutation to terminator. Rather, it is a consequence of their ending in A or G; comparable A-ending and G-ending codons that are not mutable to terminator are also infrequent. Natural selection does not appear to have depressed the frequency of mutable-to-terminator codons by directly eliminating some of them individually. It may have depressed their frequency indirectly by adjusting mutation rates in the population so that most of the purine-ending codons--and consequently most of the mutable-to-terminator ones as well--are infrequent.

Ethchlorvynol ingestion in San Diego County: a 14-year review of cases with blood concentrations and findings.

Cases of nonfatal (51) and fatal (38) ingestions involving ethchlorvynol over a 14-year period (1975 through 1988) were reviewed in order to evaluate the current status of ingestion of this drug. In both series of cases men and women were involved approximately equally. Sixty-three percent of cases in both series occurred during the period 1975 through 1980. Most (78% of nonfatal and 89% of fatal) ingestions involved other drugs in addition to ethchlorvynol. Physical findings for nonfatal ingestions and causes of death for fatal ingestions are presented. Blood ethchlorvynol concentrations are discussed, and a composite of the average patient for each series is presented. Although ethchlorvynol abuse appears to be decreasing with time, it still occurs, and a search for this sedative-hypnotic agent should be included in the so-called "toxicology screen."

Cocaine- and methamphetamine-related deaths in San Diego County (1987): homicides and accidental overdoses.

Cocaine- and methamphetamine-related homicides and fatal accidental overdoses in San Diego County were studied retrospectively for the 1987 calendar year. Cocaine was involved in 66 cases (39 homicides, 27 accidental overdoses), methamphetamine in 32 cases (23 homicides, 9 accidental overdoses), and a combination of cocaine and methamphetamine in 10 cases (4 homicides, 6 accidental overdoses). The composite for cocaine-related deaths was a 30-year-old black man in whom was also found at least 1 other drug, usually ethanol or morphine. The composite for methamphetamine-related deaths was a 32-year-old Caucasian man who used methamphetamine with at least 1 other drug (usually ethanol). For cases involving both cocaine and methamphetamine, the composite was a 36-year-old Caucasian man in whom was also found at least 1 other drug, usually ethanol, codeine, or morphine. Mean tissue concentrations of cocaine and benzoylecgonine were significantly higher in accidental overdoses than in homicides except for cocaine concentrations in liver, which did not differ significantly between the two groups. For methamphetamine-related deaths there was no significant difference between mean tissue concentrations in accidental overdoses and in homicides. Cocaine or methamphetamine or both were involved in approximately one third of homicides in San Diego County in 1987, and when fatal accidental overdoses were included, cocaine was involved in twice as many cases as methamphetamine.

A fatal poisoning from Nicotiana glauca.

A young adult male was found dead in a field. No cause of death was apparent at autopsy, and the only positive toxicological finding was the presence of a nicotine-like alkaloid isolated from the liver. Anabasine, the major, highly toxic alkaloid of the shrub, Nicotiana glauca (tree tobacco) was subsequently identified in all body specimens examined using gas chromatography/mass spectrometry. Concentrations of anabasine in blood, urine and other body organs are reported.

Effect of sodium fluoride on cholinesterase activity in postmortem blood.

Thirty-two postmortem blood specimens, with and without sodium fluoride as preservative, were analyzed for cholinesterase activity by the Michel method. The fluoridated specimens, which contained from 0.7 to 31 mg/mL (average 6.3) of sodium fluoride, were found to exhibit cholinesterase activities that were 5 to 59% (average 25%) lower than the duplicate unfluoridated specimens. We concluded that, while this decrease is quite significant, a fluoridated postmortem blood specimen may be used for the measurement of cholinesterase activity when a non-fluoridated specimen is unavailable.

Blood concentrations and clinical findings in nonfatal and fatal intoxications involving glutethimide and codeine.

Blood concentrations and clinical findings were evaluated in twenty-six nonfatal and twelve fatal intoxications involving the combination of glutethimide and codeine ("loads"). The mean glutethimide concentration was 10 +/- 5 mg/L for nonfatal cases (range 2-18 mg/L) and 13.9 +/- 6.6 mg/L for fatal cases (range 4.6-26.4 mg/L). The mean codeine concentration for fatal intoxications was 1.21 +/- 1.17 mg/L (range 0.13-4.32 mg/L). Codeine concentrations were not measured in cases of nonfatal intoxication. Nine nonfatal cases required hospitalization on a medical ward (mean length of stay 3 +/- 3 days). Depressed level of consciousness was the most common abnormal physical finding (24 cases); 18 patients were lethargic but arousable with nonpainful stimulation and 6 patients with serum glutethimide concentrations of 10 mg/L or greater were comatose. The level of consciousness showed statistically significant correlation with the glutethimide concentration (P less than 0.01). Twenty-four nonfatal intoxications involved at least one other drug in addition to glutethimide and codeine (salicylates in 12 and acetaminophen in 4), while only 7 fatal cases involved at least one additional drug (acetaminophen and diazepam in 3 each). The finding of glutethimide should prompt a search for codeine and vice versa, especially when the presence of either does not in and of itself explain the clinical condition of the patient.

Interpretation of blood glutethimide, meprobamate, and methyprylon concentrations in nonfatal and fatal intoxications involving a single drug.

We evaluated blood concentrations of three nonbarbiturate sedative-hypnotics in 19 nonfatal (NF) and five fatal (F) intoxications which were "pure" (i.e. which involved only one drug each): glutethimide, 4 (NF), 3 (F); meprobamate, 9 (NF), 1 (F); and methyprylon, 6 (NF), 1 (F). For each of the 24 cases, both a comprehensive toxicology panel (including blood and urine) and the clinical history established that only a single drug had been ingested. Blood drug concentrations showed statistically significant correlation with the level of consciousness for nonfatal meprobamate intoxication (p less than 0.01) and nonfatal methyprylon intoxication (p less than 0.05). Blood glutethimide concentrations did not show such correlation. Death was associated with a mean blood glutethimide concentration in excess of 4.0 mg/dL, a blood meprobamate concentration of 20.5 mg/dL, and a blood methyprylon concentration of 11.7 mg/dL. Interpretation of blood concentrations of these compounds is discussed, and physical findings and demographic data are presented.

A study of salicylate and caffeine excretion in the breast milk of two nursing mothers.

Salicylate excretion was studied in the breast milk of a nursing mother (Patient A) taking chronic therapeutic doses of aspirin, and caffeine excretion was monitored in the breast milk of a nursing mother (Patient B) who was a heavy coffee drinker. Salicylate concentrations were maximal in serum at 2.25 hours (10.8 mg/dL) and in milk at 3.00 hours (1.0 mg/dL) following 975 mg of aspirin in Patient A. Caffeine concentrations peaked at 5.50 hours in serum (2.14 micrograms/mL) and at 2.00 hours in milk (1.15 micrograms/mL) during a period of steady coffee drinking by Patient B. Milk:serum concentration ratios ranged up to 0.08 for patient A and up to 0.63 for Patient B, demonstrating that relatively more caffeine than salicylate was excreted into milk. Sodium, potassium, pH, and percent solute remained essentially unchanged in milk samples from both patients throughout the study periods so that changes in the state of hydration of pH of the milk could not be implicated for the observed excretion patterns. More than 25 liters of milk at its peak drug concentration would have to be consumed by the infants of Patients A and B respectively to provide the salicylate content of one aspirin tablet or the caffeine content of an average cup of coffee.

Propoxyphene in postmortem toxicology 1976-1978.

A total of 1859 cases provides the basis for this study in which propoxyphene, and often its major metabolite, was demonstrated by toxicological analysis in the blood or tissues of the deceased at 27 medical examiner or coroner's offices across the United States and Canada. The study period includes the last five months of 1975 through December 1978. The cases describe a clearly defined adult population with a marked tendency toward hypochondria, chronic minor illness, and severe psychiatric problems. The high proportion of suicides (44.1% of the total cases and 54.0% of the drug-caused deaths) and multiple-drug toxicities (88.6%) suggests that the involvement of propoxyphene in many of these fatalities may be of less significance than the phenomenon of "polypharmacy" and self-medication without appropriate medical supervision. This evaluation of propoxyphene provides no evidence that propoxyphene is responsible for "street-drug" fatalities. Its appearance in postmortem toxicological examinations has been declining sharply since 1977, but it continues to be dangerous when used excessively, particularly in combination with alcohol and other central nervous system depressant drugs.

Interpretation of blood and tissue concentrations in fatal self-ingested overdose involving amitriptyline: an update (1978-1979).

Thirty-two cases of fatal self-ingested overdose involving amitriptyline were studied over the two-year period 1978 to 1979. The average decedent was a 44-year-old woman who ingested amitriptyline and at least one other drug (usually ethanol, diazepam, propoxyphene, or codeine). The mean concentrations of amitriptyline and nortriptyline were significantly higher in liver than in myocardium, and they were significantly higher in myocardium than in blood. In addition, concentrations in these tissues showed significant correlation with each other. The mean tissue concentrations of amitriptyline and nortriptyline in this series of overdoses were significantly greater than those in fourteen other decedents whose deaths were not due to drug overdose but involved amitriptyline as an incidental finding. The mean ratio of amitriptyline to nortriptyline in each tissue was also significantly higher in overdose than those in the corresponding tissues of the non-overdose group, suggesting that the former ingestions were more acute. The estimated survival times showed no significant correlation with tissue concentrations of either amitriptyline or nortriptyline.