Association between SARS-CoV-2 Infection and Adverse Perinatal Outcomes by Race/Ethnicity in a Large Integrated Health Care System.

OBJECTIVE: Recent studies have reported associations between severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection during pregnancy and adverse perinatal outcomes but the extent to which these associations vary by race/ethnicity remains uncertain. Therefore, we examined how the association between prenatal SARS-CoV-2 infection and adverse perinatal outcomes may be modified by race/ethnicity. STUDY DESIGN: A retrospective cohort study was performed using data on 67,986 pregnant women extracted from the Kaiser Permanente Southern California electronic health records between April 6, 2020, and December 31, 2021. Upon admission to labor and delivery, all women were routinely tested for coronavirus disease 2019 (COVID-19) using real-time reverse-transcriptase polymerase chain reaction test. Adjusted odds ratios (aORs) were used to estimate associations. RESULTS: During the study period, COVID-19 was diagnosed in 4,960 (7%) of singleton pregnancies, with the highest rates observed among Hispanics (9.4%) and non-Hispanic Blacks (6.2%). Compared with non-Hispanic Whites, Hispanics (aOR: 1.12, 95% CI: 1.03, 1.21) with SARS-CoV-2 infection had the highest odds of a pregnancy associated with nonreassuring fetal heart rate tracing. Neonates of all races/ethnicities, except for non-Hispanic Blacks, showed significantly increased odds of SARS-CoV-2 infection, with the highest risk observed among Asians/Pacific Islanders (aOR: 10.88, 95% CI: 1.33, 89.04). Non-Hispanic White mothers who tested positive were admitted to intensive care unit (ICU) at a higher rate at delivery and within 7 days of delivery (aOR: 34.77, 95% CI: 11.3, 107.04; aOR: 26.48, 95% CI: 9.55, 73.46, respectively). Hispanics were also at a significantly higher odds of admission to ICU (aOR: 4.62, 95% CI: 2.69, 7.94; aOR: 4.42, 95% CI: 2.58, 7.56, respectively). Non-Hispanic Black, Hispanic, and Asian/Pacific Islander mothers who tested positive for SARS-CoV-2 prenatally, were at increased risk for preeclampsia/eclampsia, and preterm birth as compared to non-Hispanic White mothers. CONCLUSION: The findings highlight racial/ethnic disparities in the association between SARS-CoV-2 infection and adverse perinatal outcomes. The risk of neonatal SARS-CoV-2 infection was highest for Asian/Pacific Islanders. We also observed a remarkably high risk of ICU admission for non-Hispanic White mothers infected with SARS-CoV-2. KEY POINTS: · Race/ethnicity influences perinatal outcomes in pregnancies impacted by SARS-CoV-2.. · The risk of neonatal SARS-CoV-2 infection was highest for Asian/Pacific Islanders.. · White mothers had a notably high risk of ICU admission at delivery following SARS-CoV-2 infection..

The economy of pollen dispersal in flowering plants.

Mating success of flowering plants depends strongly on the efficiencies of pollen removal from flowers and its subsequent dispersal to conspecific stigmas. We characterized the economy of pollen dispersal in flowering plants by analysing pollen fates and their correlates for 228 species. The mean percentage of pollen removed from flowers (removal efficiency) varied almost twofold according to the type of pollen-dispersal unit, from less than 45% for orchids and milkweeds with solid pollinia, to greater than 80% for species with granular monads or sectile (segmented) pollinia. The mean percentage of removed pollen reaching stigmas (pollen transfer efficiency, PTE) varied from 2.4% for species with separate monads to 27.0% for orchids with solid pollinia. These values tended to be higher in plants with single pollinator species and in those with non-grooming pollinators. Nectar production increased removal efficiency, but did not influence PTE. Among types of pollen-dispersal units, the net percentage of produced pollen that was dispersed to stigmas varied negatively with removal efficiency and positively with PTE, indicating the relative importance of the latter for overall pollen economy. These findings confirm the key importance of floral traits, particularly pollen packaging, for pollen dispersal outcomes and highlight the under-appreciated pollination efficiency of non-grooming pollinators.

Flavonoid glycoside fraction of Ginkgo biloba extract modulates antioxidants imbalance in vanadium-induced brain damage.

Human and animal diseases have always been reported to be treated by medicinal herbs owing to their constituents. Excess sodium metavanadate is a potential environmental toxin when consumed and could induce oxidative damage leading to various neurological disorders and Parkinsons-like diseases. This study is designed to investigate the impact of the flavonoid Glycoside Fraction of Ginkgo Biloba Extract (GBE) (at 30 mg/kg body weight) on vanadium-treated rats. Animals were divided randomly into four groups: Control (Ctrl, normal saline), Ginkgo Biloba (GIBI, 30mg/kg BWT), Vanadium (VANA, 10 mg/kg BWT) and Vanadium + Ginkgo biloba (VANA + GIBI). Markers of oxidative stress (Glutathione Peroxidase and Catalase) were assessed and found to be statistically increased with GIBI when compared with CTRL and treatment groups. Results from routine staining revealed that the control and GIBI group had a normal distribution of cells and a pronounced increase in cell count respectively compared to the VANA group. When compared to the VANA group, the NeuN photomicrographs revealed that the levels of GIBI were within the normal range (***p < 0.001; ** p < 001). The treatment with GIBI showed a better response by increasing the neuronal cells in the VANA+GIBI when compared with the VANA group. The NLRP3 Inflammasome photomicrographs denoted that there was a decrease in NLRP3-positive cells in the control and GIBI groups. The treatment group shows fewer cells compared to that of the VANA group. The treatment group shows fewer cells compared to that of the VANA group. The findings of the study confirmed that ginkgo biloba extract via its flavonoid glycoside fraction has favorable impacts in modulating vanadium-induced brain damage with the potential ability to lower antioxidant levels and reduce neuroinflammation.

Beyond pollen:ovule ratios: Evolutionary consequences of pollinator dependence and pollination efficiency for pollen and ovule production in angiosperms.

PREMISE: The relative per-flower production of ovules and pollen varies broadly with angiosperm mating systems, with outcrossing types commonly producing more pollen grains per ovule than selfing types. The evolutionary causes of this variation are contentious, especially the relevance of pollination risk. Resolution of this debate may have been hampered by its focus on pollen:ovule (P:O) ratios rather than on the evolution of pollen and ovule numbers per se. METHODS: Using published mean ovule and pollen counts, we analyzed associations with the proportion of removed pollen that reaches stigmas (pollen-transfer efficiency) and differences between pollinator-dependent and autogamous forms within and among species. Analyses involved Bayesian methods that simultaneously considered variation in pollen and ovule numbers and accounted for phylogenetic relatedness. We also assessed the utility of P:O ratios as mating-system proxies and their association with female outcrossing rates. RESULTS: Median pollen number declined consistently with pollen-transfer efficiency among species, whereas median ovule number did not. Similarly, in both intraspecific and interspecific analyses, pollinator-dependent plants produced more pollen than autogamous plants, whereas ovule production did not differ statistically. Distributions of P:O ratios overlapped extensively for self-incompatible and self-compatible species and for different mating-system classes, and P:O ratios correlated weakly with outcrossing rate. CONCLUSIONS: Our findings demonstrate that pollinator dependence and pollination efficiency commonly influence the evolution of pollen number per flower but have more limited effects on ovule number. P:O ratios provide ambiguous, possibly misleading, information about mating systems, especially when compared among clades.

NSABP FC-6: Surgical conversion rate in colorectal cancer patients with unresectable, KRAS wild-type liver metastases receiving mFOLFOX7 plus cetuximab.

PURPOSE: This study sought to determine the R0 resection rate in KRAS wild-type (WT), liver-only metastatic colorectal cancer (CRC) patients initially identified as having unresectable disease who were treated with FOLFOX7 plus cetuximab. Exploratory molecular analyses were undertaken before and after treatment. METHODS: Twenty patients were enrolled. None had prior adjuvant chemotherapy. Cetuximab was added to a FOLFOX7 backbone and administered at 500 mg/m2 every 14 days with dose reductions to 400 and 300 mg/m2 in the event of toxicity. In the absence of toxicity, dose-escalations to 600, 700, and 800 mg/m2 were allowed. The mean dose of cetuximab (mg/m2 /week) throughout the study was 289 mg/m2 . Paired samples were collected for correlative studies, where feasible. RESULTS: We assessed the conversion rates from unresectable to resectable in hepatic-only, KRAS exon 2 WT mCRC. Seventeen of 20 patients undergoing chemotherapy were considered resectable by imaging criteria; R0 resection was achieved in 15/20 patients. Molecular profiling revealed heterogeneity between patients at the gene-expression, pathway signaling, and immune-profile levels. CONCLUSIONS: Although 15/20 (75%) converted to R0 resection, by 2 years, 10/15 R0 resections had recurred. Therefore, chemotherapy plus cetuximab is of limited long-term benefit in this setting. ctDNA analysis may guide additional therapy including immunotherapy.

Aminofutalosine Deaminase in the Menaquinone Pathway of Helicobacter pylori.

Helicobacter pylori is a Gram-negative bacterium that is responsible for gastric and duodenal ulcers. H. pylori uses the unusual mqn pathway with aminofutalosine (AFL) as an intermediate for menaquinone biosynthesis. Previous reports indicate that hydrolysis of AFL by 5'-methylthioadenosine nucleosidase (HpMTAN) is the direct path for producing downstream metabolites in the mqn pathway. However, genomic analysis indicates jhp0252 is a candidate for encoding AFL deaminase (AFLDA), an activity for deaminating aminofutolasine. The product, futalosine, is not a known substrate for bacterial MTANs. Recombinant jhp0252 was expressed and characterized as an AFL deaminase (HpAFLDA). Its catalytic specificity includes AFL, 5'-methylthioadenosine, 5'-deoxyadenosine, adenosine, and S-adenosylhomocysteine. The kcat/Km value for AFL is 6.8 × 104 M-1 s-1, 26-fold greater than that for adenosine. 5'-Methylthiocoformycin (MTCF) is a slow-onset inhibitor for HpAFLDA and demonstrated inhibitory effects on H. pylori growth. Supplementation with futalosine partially restored H. pylori growth under MTCF treatment, suggesting AFL deamination is significant for cell growth. The crystal structures of apo-HpAFLDA and with MTCF at the catalytic sites show a catalytic site Zn2+ or Fe2+ as the water-activating group. With bound MTCF, the metal ion is 2.0 Å from the sp3 hydroxyl group of the transition state analogue. Metabolomics analysis revealed that HpAFLDA has intracellular activity and is inhibited by MTCF. The mqn pathway in H. pylori bifurcates at aminofutalosine with HpMTAN producing adenine and depurinated futalosine and HpAFLDA producing futalosine. Inhibition of cellular HpMTAN or HpAFLDA decreased the cellular content of menaquinone-6, supporting roles for both enzymes in the pathway.

Mechanisms of Male-Male Interference during Dispersal of Orchid Pollen.

AbstractSiring success of flowering plants depends on the fates of male gametophytes, which compete for access to stigmas, stylar resources, and ovules. Although rarely considered, pollen may often compete during dispersal, affecting the processes required for export to stigmas: pollen pickup, transport, and deposition. We quantified dispersal interference by tracking bee-mediated dispersal of stained Anacamptis morio (Orchidaceae) pollen from individual donor flowers and inferred the affected dispersal mechanisms on the basis of the fit of a process-based model. During individual trials, all recipient flowers were either emasculated, precluding interference with donor pollen, or intact, adding potentially interfering pollen to the pollinator. The presence of competing pollinaria on bees reduced pickup of additional pollinaria, doubled the overall proportion of lost donor pollen, and reduced total pollen export by 27%. Interference specifically increased loss of donor pollen between successive flower visits and variation in deposition among trials, and it likely also reduced pollen contact with stigmas and pollen deposition when contact occurred. Thus, by altering pollen removal, transport, and deposition, male-male interference during pollen dispersal can significantly-and perhaps commonly-limit plant-siring success.

Universal SARS-Cov-2 Screening in Women Admitted for Delivery in a Large Managed Care Organization.

OBJECTIVE: The coronavirus disease 2019 (COVID-19) pandemic has created a need for data regarding the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in pregnant women. After implementing universal screening for COVID-19 in women admitted for delivery, we sought to describe the characteristics of COVID-19 in this large cohort of women. STUDY DESIGN: An observational study of women admitted to labor and delivery units in Kaiser Permanente Southern California (KPSC) hospitals between April 6 and May 11, 2020 who were universally offered testing for SARS-CoV-2 infection (n = 3,963). Hospital inpatient and outpatient physician encounter, and laboratory records were used to ascertain universal testing levels, test results, and medical and obstetrical histories. The prevalence of SARS-CoV-2 infection was estimated from the number of women who tested positive during labor per 100 women delivered. RESULTS: Of women delivered during the study period, 3,923 (99.0%) underwent SARS-CoV-2 testing. A total of 17 (0.43%; 95% confidence interval: 0.23-0.63%) women tested positive, and none of them were symptomatic on admission. There was no difference in terms of characteristics between SARS-CoV-2 positive and negative tested women. One woman developed a headache attributed to COVID-19 3 days postpartum. No neonates had a positive test at 24 hours of life. CONCLUSION: The findings suggest that in pregnant women admitted for delivery between April 6 and May 11, 2020 in this large integrated health care system in Southern California, prevalence of SARS-CoV-2 test positive was very low and all patients were asymptomatic on admission. KEY POINTS: · The prevalence of SARS-CoV-2 infection in a large diverse cohort of term pregnant women was 0.43%.. · 99% of women accepted SARS-CoV-2 screening on admission to labor and delivery.. · All women with positive test results were asymptomatic at the time of testing..

Mating consequences of contrasting hermaphroditic plant sexual systems.

For hermaphroditic angiosperms with multiple flowers, the sex roles can be exclusively combined in bisexual flowers (monocliny), strictly separated among different flowers (monoecy), or arrayed in mixtures of bisexual flowers with female flowers (gynomonoecy) or male flowers (andromonoecy). The hypothesized benefits favoring the evolution of these contrasting hermaphroditic sexual systems are typically examined individually, usually by assessing success through only one sex role. We tested predictions of most hypotheses experimentally with an andromonoecious species, Anticlea occidentalis (Melanthiaceae), based on the performance of intact plants (andromonoecy) and those with emasculated bisexual flowers (functionally monoecious) or emasculated male flowers (functionally monoclinous with sterile peripheral flowers). Andromonoecy in this species enables efficient, size-dependent resource allocation, emphasizing female function in large plants. Emasculation revealed that anthers in male flowers promote female mating quality (outcrossing rate and mate diversity), whereas anthers in bisexual flowers promote male mating quantity (pollen dispersal distance and probability of any siring success). Thus, different hermaphroditic sexual systems likely evolve to capitalize on suites of benefits, rather than just one, and provide compromises between quantitative and qualitative reproductive components. These compromises apparently maximize an individual's combined genetic contributions through female and male functions, rather than separate contributions through each sex role.

Histidine catabolism is a major determinant of methotrexate sensitivity.

The chemotherapeutic drug methotrexate inhibits the enzyme dihydrofolate reductase1, which generates tetrahydrofolate, an essential cofactor in nucleotide synthesis2. Depletion of tetrahydrofolate causes cell death by suppressing DNA and RNA production3. Although methotrexate is widely used as an anticancer agent and is the subject of over a thousand ongoing clinical trials4, its high toxicity often leads to the premature termination of its use, which reduces its potential efficacy5. To identify genes that modulate the response of cancer cells to methotrexate, we performed a CRISPR-Cas9-based screen6,7. This screen yielded FTCD, which encodes an enzyme-formimidoyltransferase cyclodeaminase-that is required for the catabolism of the amino acid histidine8, a process that has not previously been linked to methotrexate sensitivity. In cultured cancer cells, depletion of several genes in the histidine degradation pathway markedly decreased sensitivity to methotrexate. Mechanistically, histidine catabolism drains the cellular pool of tetrahydrofolate, which is particularly detrimental to methotrexate-treated cells. Moreover, expression of the rate-limiting enzyme in histidine catabolism is associated with methotrexate sensitivity in cancer cell lines and with survival rate in patients. In vivo dietary supplementation of histidine increased flux through the histidine degradation pathway and enhanced the sensitivity of leukaemia xenografts to methotrexate. The histidine degradation pathway markedly influences the sensitivity of cancer cells to methotrexate and may be exploited to improve methotrexate efficacy through a simple dietary intervention.

Neural Mechanisms Underlying Cross-Modal Phonetic Encoding.

Audiovisual (AV) integration is essential for speech comprehension, especially in adverse listening situations. Divergent, but not mutually exclusive, theories have been proposed to explain the neural mechanisms underlying AV integration. One theory advocates that this process occurs via interactions between the auditory and visual cortices, as opposed to fusion of AV percepts in a multisensory integrator. Building upon this idea, we proposed that AV integration in spoken language reflects visually induced weighting of phonetic representations at the auditory cortex. EEG was recorded while male and female human subjects watched and listened to videos of a speaker uttering consonant vowel (CV) syllables /ba/ and /fa/, presented in Auditory-only, AV congruent or incongruent contexts. Subjects reported whether they heard /ba/ or /fa/. We hypothesized that vision alters phonetic encoding by dynamically weighting which phonetic representation in the auditory cortex is strengthened or weakened. That is, when subjects are presented with visual /fa/ and acoustic /ba/ and hear /fa/ (illusion-fa), the visual input strengthens the weighting of the phone /f/ representation. When subjects are presented with visual /ba/ and acoustic /fa/ and hear /ba/ (illusion-ba), the visual input weakens the weighting of the phone /f/ representation. Indeed, we found an enlarged N1 auditory evoked potential when subjects perceived illusion-ba, and a reduced N1 when they perceived illusion-fa, mirroring the N1 behavior for /ba/ and /fa/ in Auditory-only settings. These effects were especially pronounced in individuals with more robust illusory perception. These findings provide evidence that visual speech modifies phonetic encoding at the auditory cortex.SIGNIFICANCE STATEMENT The current study presents evidence that audiovisual integration in spoken language occurs when one modality (vision) acts on representations of a second modality (audition). Using the McGurk illusion, we show that visual context primes phonetic representations at the auditory cortex, altering the auditory percept, evidenced by changes in the N1 auditory evoked potential. This finding reinforces the theory that audiovisual integration occurs via visual networks influencing phonetic representations in the auditory cortex. We believe that this will lead to the generation of new hypotheses regarding cross-modal mapping, particularly whether it occurs via direct or indirect routes (e.g., via a multisensory mediator).

Multiple health benefits of urban tree canopy: The mounting evidence for a green prescription.

The purpose of this study was to enhance the understanding of the health-promoting potential of trees in an urbanized region of the United States. This was done using high-resolution LiDAR and imagery data to quantify tree cover within 250m of the residence of 7910 adult participants in the California Health Interview Survey, then testing for main and mediating associations between tree cover and multiple health measures. The results indicated that more neighborhood tree cover, independent from green space access, was related to better overall health, primarily mediated by lower overweight/obesity and better social cohesion, and to a lesser extent by less type 2 diabetes, high blood pressure, and asthma. These findings suggest an important role for trees and nature in improving holistic population health in urban areas.

Diverse ecological relations of male gametophyte populations in stylar environments.

PREMISE OF STUDY: Pollen on a stigma represents a local population of male gametophytes vying for access to female gametophytes in the associated ovary. As in most populations, density-independent and density-dependent survival depend on intrinsic characteristics of male gametophytes and environmental (pistil) conditions. These characteristics and conditions could differ among flowers, plants, populations, and species, creating diverse male-gametophyte population dynamics, which can influence seed siring and production. METHODS: For nine species, we characterized the relations of both the mean and standard deviation of pollen-tube number at the style base to pollen receipt with nonlinear regression. Models represented asymptotic or peaked relations, providing information about the incidence and magnitude of facilitation and competition, the spatial and temporal characteristics of competition, and the intensity and relative timing of density-independent mortality. KEY RESULTS: We infer that pollen tubes of most species competed sequentially, their tips ceasing growth if earlier tubes had depleted stylar space/resources; although two species experienced simultaneous competition. Tube success of three species revealed positive density dependence (facilitation) at low density. For at least four species, density-independent mortality preceded competition. Tube success varied mostly within plants, rather than among plants or conspecific populations. Pollen quality influenced tube success for two of three species; affecting density-independent survival in one and density-dependent performance in the other. CONCLUSIONS: The diverse relations of pollen-tube success to pollen receipt evident among just nine species indicate significant contributions of the processes governing pollen germination and tube growth to the reproductive diversity of angiosperms.

The population ecology of male gametophytes: the link between pollination and seed production.

The fate of male gametophytes after pollen reaches stigmas links pollination to ovule fertilisation, governing subsequent siring success and seed production. Although male gametophyte performance primarily involves cellular processes, an ecological analogy may expose insights into the nature and implications of male gametophyte success. We elaborate this analogy theoretically and present empirical examples that illustrate associated insights. Specifically, we consider pollen loads on stigmas as localised populations subject to density-independent mortality and density-dependent processes as they traverse complex stylar environments. Different combinations of the timing of pollen-tube access to limiting stylar resources (simultaneous or sequential), the tube distribution among resources (repulsed or random) and the timing of density-independent mortality relative to competition (before or after) create signature relations of mean pollen-tube success and its variation among pistils to pollen receipt. Using novel nonlinear regression analyses (two-moment regression), we illustrate contrasting relations for two species, demonstrating that variety in these relations is a feature of reproductive diversity among angiosperms, rather than merely a theoretical curiosity. Thus, the details of male gametophyte ecology should shape sporophyte reproductive success and hence the dynamics and structure of angiosperm populations.

Long-term outcomes of patients with intermediate-risk acute myeloid leukemia treated with autologous hematopoietic cell transplant in first complete remission.

In 2014, autologous hematopoietic cell transplant (autoHCT) was removed from the National Comprehensive Cancer Network guidelines as a recommended treatment for patients with intermediate-risk AML in first complete remission (CR1). We reviewed the outcomes of all patients with intermediate-risk AML treated with autoHCT in CR1 at our institution. Of 334 patients who underwent autoHCT for AML between 1988 and 2013, 133 patients with intermediate-risk AML in CR1 were identified. Cytogenetics were diploid in 97 (73%). With a median follow-up of 4.1 years (range 0.1-17), median overall survival (OS) is 6.7 years; at 5 years post-transplant, 59% of patients remain alive and 43% remain relapse-free. Forty-eight percent of relapsing patients proceeded to salvage alloHCT. Our findings demonstrate that nearly half of patients with intermediate-risk AML in CR1 achieve sustained remissions, and that salvage alloHCT is feasible in those who relapse. AutoHCT therefore remains a reasonable option for intermediate-risk patients with AML in CR1.

Local and systemic vasodilatory effects of low molecular weight S-nitrosothiols.

S-nitrosothiols (SNOs) such as S-nitroso-L-cysteine (L-cysNO) are endogenous compounds with potent vasodilatory activity. During circulation in the blood, the NO moiety can be exchanged among various thiol-containing compounds by S-transnitrosylation, resulting in SNOs with differing capacities to enter the cell (membrane permeability). To determine whether the vasodilating potency of SNOs is dependent upon membrane permeability, membrane-permeable L-cysNO and impermeable S-nitroso-D-cysteine (D-cysNO) and S-nitroso-glutathione (GSNO) were infused into one femoral artery of anesthetized adult sheep while measuring bilateral femoral and systemic vascular conductances. L-cysNO induced vasodilation in the infused hind limb, whereas D-cysNO and GSNO did not. L-cysNO also increased intracellular NO in isolated arterial smooth muscle cells, whereas GSNO did not. The infused SNOs remained predominantly in a low molecular weight form during first-passage through the hind limb vasculature, but were converted into high molecular weight SNOs upon systemic recirculation. At systemic concentrations of ~0.6 µmol/L, all three SNOs reduced mean arterial blood pressure by ~50%, with pronounced vasodilation in the mesenteric bed. Pharmacokinetics of L-cysNO and GSNO were measured in vitro and in vivo and correlated with their hemodynamic effects, membrane permeability, and S-transnitrosylation. These results suggest local vasodilation by SNOs in the hind limb requires membrane permeation, whereas systemic vasodilation does not. The systemic hemodynamic effects of SNOs occur after equilibration of the NO moiety amongst the plasma thiols via S-transnitrosylation.

Evolutionary and ecological consequences of multiscale variation in pollen receipt for seed production.

Variation in resource availability can select for traits that reduce the negative impacts of this variability on mean fitness. Such selection may be particularly potent for seed production in flowering plants, as they often experience variation in pollen receipt among individuals and among flowers within individuals. Using analytically tractable models, we examine the optimal allocations for producing ovules, attracting pollen, and maturing seeds in deterministic and stochastic pollen environments. In deterministic environments, the optimal strategy attracts sufficient pollen to fertilize every ovule and mature every zygote into a seed. Stochastic environments select for allocations proportional to the risk of seed production being limited by zygotes or seed maturation. When producing an ovule is cheap and maturing a seed is expensive, among-plant variation selects for attracting more pollen at the expense of producing fewer ovules and having fewer resources for seed maturation. Despite this increased allocation, such populations are likely to be pollen limited. In contrast, within-plant variation generally selects for an overproduction of ovules and, to a lesser extent, pollen attraction. Such populations are likely to be resource limited and exhibit low seed-to-ovule ratios. These results highlight the importance of multiscale variation in the evolution and ecology of resource allocations.

The exochelins of pathogenic mycobacteria: unique, highly potent, lipid- and water-soluble hexadentate iron chelators with multiple potential therapeutic uses.

SIGNIFICANCE: Exochelins are lipid- and water-soluble siderophores of Mycobacterium tuberculosis with unique properties that endow them with exceptional pharmacologic utility. Exochelins can be utilized as probes to decipher the role of iron in normal and pathological states, and, since they rapidly cross cell membranes and chelate intracellular iron with little or no toxicity, exochelins are potentially useful for the treatment of a number of iron-dependent pathological phenomena. RECENT ADVANCES: In animal models, exochelins have been demonstrated to have promise for the treatment of transfusion-related iron overload, restenosis after coronary artery angioplasty, cancer, and oxidative injury associated with acute myocardial infarction and transplantation. CRITICAL ISSUES: To be clinically effective, iron chelators should be able to rapidly enter cells and chelate iron at key intracellular sites. Desferri-exochelins, and other lipid-soluble chelators, can readily cross cell membranes and remove intracellular free iron; whereas deferoxamine, which is lipid insoluble, cannot do so. Clinical utility also requires that the chelators be nontoxic, which, we hypothesize, includes the capability to prevent iron from catalyzing free radical reactions which produce •OH or other reactive oxygen species. Lipid-soluble iron chelators currently available for clinical application are bidentate (deferiprone) or tridentate (desferasirox) molecules that do not block all six sites on the iron molecule capable of catalyzing free radical reactions. In contrast, desferri-exochelins are hexadentate molecules, and by forming a one-to-one binding relationship with iron, they prevent free radical reactions. FUTURE DIRECTIONS: Clinical studies are needed to assess the utility of desferri-exochelins in the treatment of iron-dependent pathological disorders.