Lytic to temperate switching of viral communities.

Microbial viruses can control host abundances via density-dependent lytic predator-prey dynamics. Less clear is how temperate viruses, which coexist and replicate with their host, influence microbial communities. Here we show that virus-like particles are relatively less abundant at high host densities. This suggests suppressed lysis where established models predict lytic dynamics are favoured. Meta-analysis of published viral and microbial densities showed that this trend was widespread in diverse ecosystems ranging from soil to freshwater to human lungs. Experimental manipulations showed viral densities more consistent with temperate than lytic life cycles at increasing microbial abundance. An analysis of 24 coral reef viromes showed a relative increase in the abundance of hallmark genes encoded by temperate viruses with increased microbial abundance. Based on these four lines of evidence, we propose the Piggyback-the-Winner model wherein temperate dynamics become increasingly important in ecosystems with high microbial densities; thus 'more microbes, fewer viruses'.

The impact of in utero cannabis exposure on fetal growth.

BACKGROUND: The goal of this study was to examine if in utero cannabis exposure predicted reduced birth size and if these effects were evident in specific growth parameters as early as the second trimester. METHODS: Eligible women had an initial prenatal visit between January 1, 2010, and March 31, 2020, completed an anatomy ultrasound between 18-24 weeks' gestation, and had no self-reported alcohol, tobacco, or other biochemically verified drug use. The two primary study groups were cannabis users (n = 109) identified through self-report and urine toxicology screens, and a randomly selected control group of non-substance users (n = 171). Medical records were manually reviewed for background and medical information, anatomy ultrasound results, and birth size parameters. RESULTS: After controlling for significant confounders, regression results indicated significant (p < .05) deficits in birth weight associated with cannabis exposure, with a trend for increasing weight effects beginning in the second trimester. A significant decrease in head circumference was evident as early as the second trimester, with differences remaining significant until birth. Significant overall length and specific bone length deficits were not predicted by cannabis exposure, at birth or earlier in gestation, after control for confounding. CONCLUSIONS: Cannabis exposure predicted growth deficits at birth, with some effects evident as early as the second trimester. The biggest and earliest effects were seen for cranial size, with an adjusted deficit of more than 14 percentile points by birth. Overall weight was not impacted until at or near delivery.

Detection and expression of enterotoxin genes in endophytic strains of Bacillus cereus.

AIMS: The aim of this study was to determine whether endophytic Bacillus cereus isolates from agronomic crops possessed genes for the nonhaemolytic enterotoxin (Nhe) and haemolysin BL (HBL) and, therefore, have the potential to cause diarrhoeal illness in humans. METHODS AND RESULTS: PCR followed by sequencing confirmed the presence of enterotoxin genes nheA, nheB, nheC, hblA, hblC, hblD in endophytic B. cereus. All nhe genes were detected in 59% of endophytic B. cereus, while all hbl genes were detected in 44%. All six genes were detected in 41% of isolates. Enterotoxin genes were not detected in 15% of B. cereus isolates. Reverse transcriptase real-time PCR confirmed that endophytic B. cereus could express enterotoxin genes in pure culture. CONCLUSIONS: This study showed that endophytic B. cereus isolates that possess genes for enterotoxin production are present in agronomic crops. Other endophytic B. cereus isolates lacked specific genes or lacked all nhe and hbl genes. Additionally, host, country of origin and tissue of origin had no impact on the enterotoxin genes detected. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacillus cereus with the potential of causing diarrhoeal illness in humans is a cosmopolitan endophytic inhabitant of plants, not incidental surface inhabitants or contaminants, as often suggested by previous research.

The effect of an H2-receptor antagonist on food-stimulated acid secretion, serum gastrin, and gastric emptying in patients with duodenal ulcers. Comparison with an anticholinergic drug.

The purpose of the present series of experiments was to measure and compare the effects of an anticholinergic drug (isopropamide) and an antagonist of the histamine H2 receptor (metiamide) on food-stimulated acid secretion. Patients with duodenal ulcers were stimulated by a steak meal, and acid secretion was measured by in vivo intragastric titration. The largest dose of isopropamide that can be taken clinically without producing intolerable side effects (maximum tolerated dose) suppressed food-stimulated acid secretion by 35%. By contrast, metiamide in a 400-mg dose produced no side effects and almost completely abolished food-stimulated acid secretion. A dose-response curve revealed that a 50-mg dose of metiamide was required to suppress food-stimulated acid secretion by 50%. Further studies showed that metiamide and isopropamide are additive in suppressing food-stimulated acid secretion, and that metiamide has no effect on serum gastrin concentration or on gastric emptying.

Sensitivity to an Ethylene Biosynthesis-Inducing Endoxylanase in Nicotiana tabacum L. cv Xanthi Is Controlled by a Single Dominant Gene.

The ethylene biosynthesis-inducing xylanase (EIX) is known to be a potent elicitor of ethylene biosynthesis and other responses when applied to leaf tissue of Nicotiana tabacum L. cv Xanthi. In contrast, leaf tissue of the tobacco cultivar Hicks was insensitive to EIX at concentrations 100-fold higher than was needed to elicit responses from Xanthi. Cell-suspension cultures of Xanthi and Hicks showed similar differences in sensitivity to EIX. Equivalent levels of ethylene production were elicited in leaf discs of both cultivars after treatment with CuSO4. The F1 and Xanthi backcross progeny of Hicks and Xanthi crosses were all sensitive to EIX, whereas the F2 and Hicks backcross progeny segregated for sensitivity to EIX. Individual plants from the F2 and Hicks backcross that were insensitive to EIX produced only insensitive progeny when they were self-pollinated. Progeny from sensitive plants either segregated for sensitivity to EIX or produced all sensitive progeny (an F2 plant). Sensitivity to EIX is controlled by a single dominant gene, based on chi-square analysis of segregation ratios.

Stereospecific deuterium substitution at the alpha-carbon position of dopamine and its effect on oxidative deamination catalyzed by MAO-A and MAO-B from different tissues.

Stereospecific replacement of deuterium in the alpha-carbon side chain position of dopamine (DA) was achieved by decarboxylation of L-3,4-dihydroxyphenylalanine (L-dopa) using hog kidney aromatic aminoacid decarboxylase. The S[alpha-2H1]DA enantiomer was obtained by decarboxylation of L-[alpha-2H1]dopa in H2O, while the R[alpha-2H1]DA enantiomer was obtained by decarboxylation of unsubstituted L-dopa in 2H2O. An inverse solvent isotope effect of L-dopa decarboxylation was observed in 2H2O. The deaminated aldehyde products of the four DA analogues, i.e. undeuterated DA, [alpha, alpha-2H2] DA, R[alpha-2H1]DA and S[alpha-2H1]DA, have been analyzed by the gas chromatography-mass spectrometry (GC-MS) method. It is evident that monoamine oxidase (MAO) catalyzes the stereochemical removal of only R-deuterium and that S-deuterium was maintained at the alpha-carbon atom of 3,4-dihydroxyphenylacetaldehyde. The steady-state kinetics of the oxidative deamination of undeuterated, [alpha, alpha-2H2], R[alpha-2H1], and S[alpha-2H1] dopamine were assessed by determination of the aldehyde products directly by high performance liquid chromatography (HPLC) using electrochemical detection (ECD). MAO-A from rat liver mitochondria (deprenyl-treated) and from human placenta, as well as MAO-B from rat liver (clorgyline-treated) and from human platelet were used in this study. The apparent isotope effects, i.e. (V/K)H/(V/K)D ratios of [alpha, alpha-2H2]DA and R[alpha-2H1]DA, were quite similar (2.34 and 3.13) with respect to both MAO-A and MAO-B. S[alpha-2H1]DA exhibited a slight secondary isotope effect. Formula: see text.

A behavioural and neurochemical analysis of chronic and selective monoamine oxidase inhibition.

The effects of clorgyline were compared with the effects of (-)-deprenyl using measures of rewarding hypothalamic self-stimulation, regional monoamine metabolism and monoamine oxidase activity. Male Wistar rats trained to self-stimulate at half-maximal rates with unilateral bipolar lateral hypothalamic electrodes on a continuous reinforcement schedule were implanted subcutaneously with osmotic minipumps which delivered 1 mg X kg-1 drug per day or vehicle for 13 days. A response rate/stimulation frequency (reward summation) function was determined the day before minipump implantation and on days 5 and 13 of drug administration. Only clorgyline induced a shift to the left in the reward summation function at 5 and 13 days, indicating enhancement of reinforcement. Clonidine (50 micrograms X kg-1 IP) probe tests were run on days 2 and 10 to determine the sensitivity of alpha 2-noradrenaline receptors. Clorgyline induced an attenuation of the clonidine response on day 10 relative to day 2. The other groups exhibited no change in response to clonidine. Clorgyline also induced a progressive increase in self-stimulation rates; this effect was not observed with the other groups. The clorgyline effects were accompanied by an increase in regional brain levels of dopamine, noradrenaline and 5-hydroxytryptamine and a reduction of their acid metabolites. Clorgyline selectively inhibited type A monoamine oxidase, whereas (-)-deprenyl selectively inhibited type B monoamine oxidase.

Line copy presentation slides with Kodalith.

Line copy presentation slides with white letters on a blue background can be produced with a two-step process. The slides are more permanent than diazo slides, and the process is faster and less expensive.

Correlating students' undergraduate science GPAs, their MCAT scores, and the academic caliber of their undergraduate colleges with their first-year academic performances across five classes at Dartmouth Medical School.

Reviewing the predictive validity of admission criteria to improve the selection process is important to a school in maintaining quality in the entering class. For this reason, the authors studied how the academic criteria used to select the 420 students who entered Dartmouth Medical School from 1982 to 1986 compared with the students' first-year academic performances. The criteria used were Medical College Admission Test scores, undergraduate science grade-point averages, and college selectivity (i.e., the academic caliber of the students' undergraduate colleges). Results showed that a combination of these criteria were useful in identifying the students who were successful in their first year. The authors suggest that their findings also demonstrate the ability to an admission committee to subjectively weigh these academic criteria with consistent results in student performance.

Influence of the interview on the evaluation of applicants to medical school.

PURPOSE: To determine whether medical school admission interviewers change their evaluations and impressions of applicants as a direct result of the interview. METHOD: In 1991-92, 419 applicants to the University of Virginia School of Medicine were interviewed by members of the admission committee in two separate half-hour sessions. After reviewing each applicant's folder, interviewers rated the applicant before the interview on six objective scales. After the interview, ratings were again made on the same six scales, on the same form, below the ratings made before the interview. Data were examined using paired t-tests, Pearson correlations, and stepwise multiple-regression analysis. RESULTS: Of the six scales, only the ratings of Commitment to Serve Others were not significantly changed by the interview; the ratings of Familiarity with Issues in Medicine changed the most (p < .01 by paired t-test). The ratings of Overall Impression increased for accepted applicants and decreased for rejected applicants. CONCLUSION: The interview did influence interviewers' ratings made before the interview, and in the direction consistent with admission decisions, which supports the continued use of the interview. Although the magnitude of the changes was not large, the changes validate the conviction that the interview aids in the selection of individuals for medical school.

Expression of NEP1 by Fusarium oxysporum f. sp. erythroxyli After Gene Replacement and Overexpression Using Polyethylene Glycol-Mediated Transformation.

ABSTRACT The necrosis inducing extracellular protein Nep1 is produced by Fusarium oxysporum f. sp. erythroxyli in liquid culture. NEP1, the Nep1 protein structural gene, was disrupted in F. oxysporum f. sp. erythroxyli isolate EN-4 by gene replacement using polyethylene glycol (PEG)-mediated transformation. NEP1 disruption was verified by polymerase chain reaction (PCR), Southern blot, and northern blot analysis. NEP1-disrupted transformants failed to produce Nep1 in liquid culture. NEP1 disruption did not affect the pathogenicity of isolate EN-4 toward Erythroxylum coca. Transformation of isolate EN-4 with construct pPB-FO11-45 carrying NEP1 between the trpC promoter and terminator resulted in increased production of Nep1 in potato dextrose broth plus 1% casamino acids or Czapek-Dox broth plus 1% casamino acids but not in potato dextrose broth alone. Transformation of EN-4 with construct pPB-FO11-45 was verified by PCR and Southern blot analysis. Overexpression of NEP1 was confirmed by northern blot and Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. NEP1-overexpressing transformant 15 produced 64 to 128 times as much Nep1 as EN-4 wild type when grown in shake cultures. Transformants overexpressing Nep1 in liquid culture were no more or less pathogenic toward E. coca than wild-type isolates. Nep1 was not detected in E. coca seedlings infected with NEP1-overexpressing transformants or with EN-4 wild type. In large-scale fermentations of NEP1-overexpressing transformant 15, the amount of secreted protein including Nep1 was 15.1 times that of the wild-type EN-4, providing a ready source of Nep1 for future study.

Dendryphion penicillatum and Pleospora papaveracea, Destructive Seedborne Pathogens and Potential Mycoherbicides for Papaver somniferum.

ABSTRACT Dendryphion penicillatum and Pleospora papaveracea were isolated from blighted Papaver somniferum and Papaver bracteatum plants grown in growth chambers and the field in Beltsville, MD. The etiology of the diseases was determined, and the fungi are being investigated as potential mycoherbicides to control the narcotic opium poppy plant. P. papaveracea is known to be a highly destructive seedborne pathogen of Papaver somniferum, causing seedling blight, leaf blight, crown rot, and capsule rot. Single conidia and ascospores were isolated and cultures established from naturally infested seed and diseased foliage and pods of opium poppy from Iran, Colombia, Venezuela, Sweden, India, and the United States (Maryland and Washington). Mycelia and conidia of P. papaveracea and D. penicillatum produced on necrotic leaf tissues appear morphologically similar, and the fungi were previously considered to be anamorph and teleomorph. However, no anamorph/teleomorph connection could be established, and the fungi appear to be distinct taxa. P. papaveracea produced conidia, mature pseudothecia, and chlamydospores in vitro and on infected stems. D. penicillatum produced conidia, microsclerotia, and macronematous conidiophores. Although both fungi were pathogenic to three poppy cultivars, conidial inoculum from P. papaveracea cultures was more virulent than conidial inoculum from D. penicillatum. Eight-week-old plants became necrotic and died 8 days after inoculation with a conidial suspension of P. papaveracea at 2 x 10(5) spores per ml. Disease severity was significantly enhanced by inoculum formulations that contained corn oil, by higher conidial inoculum concentrations, and by increased wetness periods. Symptoms on plants inoculated with either pathogen included leaf and stem necrosis, stem girdling, stunting, necrotic leaf spots, and foliar and pod blight. Inoculated seedlings exhibited wire stem, damping-off, and root rot. Conidia, and less frequently pseudothecia, of P. papaveracea and conidia of D. penicillatum were produced abundantly on inoculated, necrotic foliage, pods, and seedlings. Cultures from conidia or ascospores reisolated from these tissues consistently produced fungi whose morphologies were typical of the fungus from which the inoculum was derived.

Genetic Characterization by RAPD Analysis of Isolates of Fusarium oxysporum f. sp. erythroxyli Associated with an Emerging Epidemic in Peru.

ABSTRACT An epidemic of vascular wilt caused by Fusarium oxysporum f. sp. erythroxyli is currently occurring on Erythroxylum coca var. coca in the coca-growing regions of the Huallaga Valley in Peru. Random amplified polymorphic DNA (RAPD) analysis of isolates of the pathogen was undertaken to elucidate its genetic complexity, as well as to identify a specific DNA fingerprint for the pathogen. Two hundred isolates of Fusarium were collected from 10 coca-growing regions in Peru. Of these, 187 were confirmed to be F. oxysporum, and 143 of the F. oxysporum were shown to be pathogens of coca by a root-dip pathogenicity test. The pathogens could be grouped into two subpopulations based on RAPD analysis, and no polymorphism in RAPD pattern was observed among isolates of either subpopulation. Both subpopulations were present in the central Huallaga Valley, where earliest reports of the epidemic occurred. RAPD analysis could easily distinguish the isolates of F. oxysporum f. sp. erythroxyli from the nonpathogenic isolates of F. oxysporum from E. coca var. coca, indicating its utility in DNA fingerprinting.

Dispersal of Formulations of Fusarium oxysporum f. sp. erythroxyli and F. oxysporum f. sp. melonis by Ants.

ABSTRACT A natural epidemic of Fusarium wilt on coca (Erythroxylum coca) in Peru prompted the suggestion of possibly using the pathogen Fusarium oxysporum f. sp. erythroxyli as a mycoherbicide against this narcotic plant. During field trials conducted in Kauai, HI, to test the pathogenicity of the coca wilt pathogen, ants were observed removing formulations from test plots. While removal of formulations by ants was considered detrimental with respect to conducting field tests, ant removal was considered potentially beneficial in disseminating the mycoherbicide. Thus, research was initiated to assess the ability of formulation additives to alter the preference of ants for the formulated mycoherbicide. In Hawaii, preference of indigenous ants for removing formulations was tested using three different food bases (rice, rice plus canola oil, and wheat flour [gluten]). Similar tests were conducted at Beltsville, MD, using F. oxysporum f. sp. melonis, in which the formulation based on wheat flour was replaced by a formulation based on canola meal. Formulations based on wheat were preferred by ants in both locations; up to 90% of the wheat plus rice flour granules (C-6) and the wheat gluten plus kaolin granules (pesta) were removed within 24 h, while only 20% of those containing rice without oils were taken. However, when either canola, sunflower (Maryland only), or olive oil was added to the rice formulation, up to 90% of the granules were taken. The formulation based on canola meal was less attractive to ants, as only 65% of the granules were removed within a period of 24 h. Ants showed no preference with respect to presence or absence of fungal biomass. To alter the attractiveness of the C-6 formulation to ants, C-6 was amended with three natural products. Canna and tansy leaves were added to C-6 at a ratio of 1:5 (wt/wt), while chili powder was added at 1:25 or 1:2.5 (wt/wt). Canna, tansy, and the higher rate of chili powder significantly reduced the number of C-6 granules removed by ants. Canna and tansy leaves affected neither germination nor sporulation of the mycoherbicide, while the high concentration of chili powder reduced viability of propagules in the formulation. More F. oxysporum f. sp. erythroxyli-type colonies were recovered from inside ant nests (9 cm depth) than from nest surfaces, indicating that ants may distribute the mycoherbicide in the soil profile. Ants passively carried propagules of F. oxysporum f. sp. erythroxyli outside their bodies, as well as either very closely adhering to the outside or within their bodies.

Evaluation of Infection Processes and Resulting Disease Caused by Dendryphion penicillatum and Pleospora papaveracea on Papaver somniferum.

ABSTRACT Two pathogenic fungi of opium poppy, Pleospora papaveracea and Dendryphion penicillatum, were isolated from field material in Beltsville, MD. The processes of infection by these two fungi were studied to determine the optimal environmental conditions for infection. Both fungi formed appressoria capable of penetrating directly through the plant epidermal layer. Of the two fungi, P. papaveracea was more aggressive, causing more rapid necrosis. Appressorial formation by P. papaveracea occurred as early as 4 h after application of a conidial suspension to poppy leaves. P. papaveracea formed more appressoria than did D. penicillatum, especially at cool temperatures (7 to 13 degrees C). In greenhouse studies, P. papaveracea caused more damage to opium poppy than did D. penicillatum when applied in 10% unrefined corn oil. In the field, P. papaveracea was more consistent in its effects on opium poppy from a local seed source designated Indian Grocery. P. papaveracea caused higher disease ratings, more stem lesions, and equal or greater yield losses than did D. penicillatum on Indian Grocery. The late-maturing opium poppy variety White Cloud was severely damaged by disease, regardless of formulation or fungal treatment. P. papaveracea was the predominant fungus isolated from poppy seed capsules and the only fungus reisolated from the field the following year. These studies provide a better understanding of the infection process and the differences between these two pathogenic fungi and will be beneficial for the development of the fungi as biological control agents.

Nep1 Protein from Fusarium oxysporum Enhances Biological Control of Opium Poppy by Pleospora papaveracea.

ABSTRACT The fungus Pleospora papaveracea and Nep1, a phytotoxic protein from Fusarium oxysporum, were evaluated for their biocontrol potential on opium poppy (Papaver somniferum). Four treatments consisting of a control, P. papaveracea conidia, Nep1 (5 mug/ml), and P. papaveracea conidia plus Nep1 (5 mug/ml) were used in detached-leaf and whole-plant studies. Conidia of P. papaveracea remained viable for 38 days when stored at 20 or 4 degrees C. Nep1 was stable in the presence of conidia for 38 days when stored at 4 degrees C or for 28 days at 20 degrees C. The presence of Nep1 did not affect conidia germination or appressoria formation. Nep1 was recovered from drops applied to opium poppy leaves in greenhouse and field studies 24 h after treatment. Opium poppy treated with the combination of Nep1 and P. papaveracea had higher necrosis ratings than the other treatments. There were changes in the intercellular protein profiles, determined by sodium dodecyl sulfate gel electrophoresis and silver staining, due to application of treatments; the most intense occurred in response to the combination of Nep1 and P. papaveracea. The combination of Nep1 and P. papaveracea enhanced the damage caused to opium poppy more than either component alone.

Potential for Dispersal of Fusarium oxysporum f. sp. erythroxyli by Infested Seed.

Fusarium oxysporum f. sp. erythroxyli causes a vascular wilt of the narcotic plant coca (Erythroxylum coca var. coca). To determine whether this pathogen can be transmitted by infested seed, fruit from symptomatic and asymptomatic plants was collected from different coca-growing areas in Peru and from an experimental field site in Hawaii. A total of 202 fruit from Peru and 69 fruit from Hawaii were surface-disinfested and separated into five parts: pedicel, pericarp, seed coat, endosperm, and cotyledons. After the pedicel and pericarp were removed from the seed coat, the seed was surface disinfested again. Each fruit part was plated separately. Both F. oxysporum and F. moniliforme were recovered from fruit collected in Peru. Both species were isolated from all parts of some fruit. F. oxysporum was isolated from 33% of the fruit plated and most (35%) of these isolates were obtained from the seed coat. Slightly greater numbers of isolates (57%) were recovered from asymptomatic plants than from symptomatic plants (43%). Only F. oxysporum was isolated from fruit collected in Hawaii. Most of these isolates (59%) were from the pedicels of fruit collected from symptomatic plants. Out of 91 isolates of F. oxysporum, 21 were pathogenic to coca seedlings in a bioassay. Six of these pathogenic isolates were originally from the pedicel of the fruit, eight from the pericarp, four from the seed coat, and three from the endosperm. No isolates from the cotyledons were pathogenic. Most of the pathogenic isolates (76%) were from symptomatic plants. The pathogenic isolates were characterized using random amplified polymorphic DNA analysis and vegetative compatibility groups. Based on these analyses, two different subpopulations of the forma specialis erythroxyli were found in Peru, whereas only one was present in Hawaii. These data indicate that infested seed may contribute significantly to dissemination of this pathogen because seed is collected by growers and planted fresh or fermented briefly before planting.

Effect of hatch on the distribution for failure of an embryo to survive incubation.

The objectives of this paper were to validate an improved model to describe failure to hatch by using data obtained from two hatches of a line of chickens and to examine the effect of hatch on the distribution for time of failure of an embryo to survive incubation. Breakout analysis of 11,254 eggs that failed to hatch was used to characterize the distribution for time of failure to survive and the probability of failure to hatch. The distribution for time of failure to survive was modeled by a diphasic Weibull distribution, corresponding to the two phases of increased embryonic mortality during incubation. Distribution parameters for time of failure to survive were estimated by maximum likelihood and minimum Hellinger distance. Goodness-of-fit statistics validated the appropriateness of the diphasic Weibull distribution. Overall, the proportion of infertility was 0.213, and the proportion of embryonic mortality by the end of incubation was 0.086. Among embryos that suffered mortality during incubation, the proportion that died during Phase 1 was 0.77; therefore, 0.23 died during Phase 2. For Phase 1, mean time of mortality was 2.6 d, and standard deviation was 3.3 d. For Phase 2, mean time was 17.4 d, and standard deviation was 2.0 d. Time of mortality was distributed differently in the two hatches; this difference occurred mostly during Phase 1. Failure rates of the two hatches were different during the first 3 d of incubation. The model is useful to assess probability of failure to hatch and the distribution for time of failure to survive during incubation.

Influence of storage days on the distribution for time of embryonic mortality during incubation.

Breakout analysis of 11,254 chicken eggs that failed to hatch was used to assess the influence of storage days on the distribution for time of embryonic mortality during incubation and on reproductive efficiency. Eggs were collected over 30 d, stored from 2 through 18 d, and incubated in two hatches. For each storage day within hatch, proportions of embryonic mortality during each of the 21 d of incubation, among embryos that did not survive incubation, were fitted by a diphasic Weibull distribution. Multivariate analysis was used to assess the influence of hatch and storage days within hatch on parameters of the distribution and on two measures of reproductive efficiency, proportions of embryonic mortality during incubation among all eggs incubated P(mort) and among fertile eggs incubated P(mort/fert), and to obtain partial correlation coefficients. Storage days influenced the distribution for time of embryonic mortality in each hatch, but the effect was different for each hatch. As the number of storage days increased, P(mort) and P(mort/fert) increased. Partial correlations showed that P(mort) and P(mort/fert) decreased as the proportion of embryos that died during the first phase decreased and as duration of the second phase increased. The shape of the distribution for time of mortality during incubation influenced reproductive efficiency. Factors that influence the shape of this distribution, other than hatch and storage days within hatch, should be studied to increase reproductive efficiency in the poultry industry.