Teosinte (Zea mays ssp parviglumis) growth and transcriptomic response to weed stress identifies similarities and differences between varieties and with modern maize varieties.

Transcriptomic responses of plants to weed presence gives insight on the physiological and molecular mechanisms involved in the stress response. This study evaluated transcriptomic and morphological responses of two teosinte (Zea mays ssp parviglumis) (an ancestor of domesticated maize) lines (Ames 21812 and Ames 21789) to weed presence and absence during two growing seasons. Responses were compared after 6 weeks of growth in Aurora, South Dakota, USA. Plant heights between treatments were similar in Ames 21812, whereas branch number decreased when weeds were present. Ames 21789 was 45% shorter in weedy vs weed-free plots, but branch numbers were similar between treatments. Season-long biomass was reduced in response to weed stress in both lines. Common down-regulated subnetworks in weed-stressed plants were related to light, photosynthesis, and carbon cycles. Several unique response networks (e.g. aging, response to chitin) and gene sets were present in each line. Comparing transcriptomic responses of maize (determined in an adjacent study) and teosinte lines indicated three common gene ontologies up-regulated when weed-stressed: jasmonic acid response/signaling, UDP-glucosyl and glucuronyltransferases, and quercetin glucosyltransferase (3-O and 7-O). Overall, morphologic and transcriptomic differences suggest a greater varietal (rather than a conserved) response to weed stress, and implies multiple responses are possible. These findings offer insights into opportunities to define and manipulate gene expression of several different pathways of modern maize varieties to improve performance under weedy conditions.

Chlortetracycline and tylosin runoff from soils treated with antimicrobial containing manure.

This study assessed the runoff potential of tylosin and chlortetracycline (CTC) from soils treated with manure from swine fed rations containing the highest labeled rate of each chemical. Slurry manures from the swine contained either CTC at 108 microg/g or tylosin at 0.3 microg/g. These manures were surface applied to clay loam, silty clay loam, and silt loam soils at a rate of 0.22 Mg/ha. In one trial, tylosin was applied directly to the soil surface to examine runoff potential of water and chemical when manure was not present. Water was applied using a sprinkler infiltrometer 24-hr after manure application with runoff collected incrementally every 5 min for about 45 min. A biofilm crust formed on all manure-treated surfaces and infiltration was impeded with > 70% of the applied water collected as runoff. The total amount of CTC collected ranged from 0.9 to 3.5% of the amount applied whereas tylosin ranged from 8.4 to 12%. These data indicate that if surface-applied manure contains antimicrobials, runoff could lead to offsite contamination.

Manure placement depth impacts on crop yields and N retained in soil.

The objective of this study was to determine the impact of manure placement depth on crop yield and N retention in soil. Experimental treatments were deep manure injection (45 cm), shallow manure injection (15 cm), and conventional fertilizer-based management with at least three replications per site. Water infiltration, and changes in soil N and P amounts were measured for up to 30 months and crop yield monitored for three seasons following initial treatment. Deep and shallow manure injections differed in soil inorganic N distributions. For example, in the manure slot the spring following application, NO(3)-N in the surface 60 cm was higher (p < .01) when injected 15 cm (21.4 micro g/g) into the soil than 45 cm (11.7 micro g/g), whereas NH(4)-N had opposite results with shallow injection having less (p = 0.045) NH(4)-N (102 micro g/g) than deep (133 micro g/g) injection. In the fall one year after the manure was applied, NO(3)-N and NH(4)-N were lower (p = 0.001) in the shallow injection than the deep injection. The net impact of manure placement on total N was that deep injection had 31, 59, and 44 more kg N ha(- 1) than the shallow injection treatment 12, 18, and 30 months after application, respectively. Deep manure injection did not impact soybean (Glycine max L.) yield, however corn (Zea mays L.) yield increased if N was limiting. The higher corn yield in the deep injected treatment was attributed to increased N use efficiency. Higher inorganic N amounts in the deep injection treatment were attributed to reduced N losses through ammonia volatilization, leaching, or denitrification. Results suggest that deep manure placement in glacial till soil may be considered a technique to increase energy, N use efficiency, and maintain surface and ground water quality. However, this technique may not work in glacial outwash soils due to the inability to inject into a rocky subsurface.

Tylosin sorption to silty clay loam soils, swine manure, and sand.

The objectives of this study were to assess sorption and desorption of tylosin, a macrolide antimicrobial chemical used in swine, cattle, and poultry production, in three silty clay loam soils of South Dakota and compare soil sorption to sand and manure sorption. The silty clay loam soils, from a toposequence in eastern South Dakota, standardized sand samples, and swine manure were used in 24-h batch sorption studies with tylosin concentrations ranging from 25 to 232 micro mole/L. Desorption from soil was conducted over a four-day period. Partition coefficients, based on the Freundlich isotherm (K(f)) or K(d) values, were calculated. K(f) values for the silty clay loams were similar, not influenced by landscape position, and averaged 1,350 with isotherm slopes ranging from 0.85 to 0.93. K(f) values for sand were dependent on solution/sand ratios and pH, ranging from 1.4 to 25.1. K(d) values of manure were dependent on the solution type and ranged from 840 L/kg with urine to about 175 L/kg when sorbed from water. Desorption of tylosin from each soil over the four-day period was < 0.2% of the amount added. The soils' high K(f) values and low desorption amounts suggest that once tylosin is in these soils, leaching to lower depths may not occur. However, this does not preclude runoff with soil eroded particles. If tylosin reaches a sand aquifer, through bypass flow or other mechanism(s), movement in the aquifer most likely would occur.

Bromide and nitrate movement through undisturbed soil columns.

Field experiments often assume that Br-, 14NO3(-)-N, and 15NO3(-)-N have similar leaching kinetics. This study tested this assumption. Twenty-four undisturbed soil columns (15-cm diameter) were collected from summit-shoulder, backslope, and footslope positions of a no-tillage field with a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Each of the landscape positions had a different soil series. After conditioning the columns with 4 L of 0.01 M CaCl2 (2 pore volumes), 15N-labeled Ca(NO3)2 and KBr were applied to the soil surface and leached with 4 L of 0.01 M CaCl2. Leachate was collected, weighed, and analyzed for NO3(-)-N, NH4(+)-N, 15N, 14N, and Br-. The total amount of 15NO3(-)-N and 14NO3(-)-N collected in 1000, 2000, and 3000 mL of leachate was similar. These data suggest that 15N discrimination during leaching did not occur. Bromide leached faster through the columns than NO3(-)-N. The more rapid transport of Br- than NO3(-)-N was attributed to lower Br- (0.002 +/- 0.036 mg kg(-1)) than NO3(-)-N (0.17 +/- 0.03 mg kg(-1)) sorption. Results from this study suggest that (i) if Br- is used to estimate NO3(-)-N leaching loss, then NO3(-)-N leaching losses may be overestimated by 25%; (ii) the potential exists for landscape position to influence anion retention and movement in soil; and (iii) 15N discrimination was not detected during the leaching process.

Herbicide movement and dissipation at four Midwestern sites.

This study was conducted to evaluate atrazine (2-chloro-4-ethylamino-6-isopropyl-1,3,5-triazine) and alachlor (2-chloro-N-(methoxymethyl)acetamide) dissipation and movement to shallow aquifers across the Northern Sand Plains region of the United States. Sites were located at Minnesota on a Zimmerman fine sand, North Dakota on Hecla sandy loam, South Dakota on a Brandt silty clay loam, and Wisconsin on a Sparta sand. Herbicide concentrations were determined in soil samples taken to 90 cm four times during the growing season and water samples taken from the top one m of aquifer at least once every three months. Herbicides were detected to a depth of 30 cm in Sparta sand and 90 cm in all other soils. Some aquifer samples from each site contained atrazine with the highest concentration in the aquifer beneath the Sparta sand (1.28 microg L(-1)). Alachlor was detected only once in the aquifer at the SD site. The time to 50% atrazine dissipation (DT50) in the top 15 cm of soil averaged about 21 d in Sparta and Zimmerman sands and more than 45 d for Brandt and Hecla soils. Atrazine DT50 was correlated positively with % clay and organic carbon (OC), and negatively with % fine sand. Alachlor DT50 ranged from 12 to 32 d for Zimmerman and Brandt soils, respectively, and was correlated negatively with % clay and OC and positively with % sand.

Atrazine, alachlor, and total inorganic nitrogen concentrations of winter wind-eroded sediment samples.

The objective of this study was to determine if atrazine (2-chloro-4-ethylamino-6-isopropyl-1,3,5-triazine), alachlor [2-chloro-N-(2,6-diethylphenyl-N-(methoxymethyl)acetamide], or inorganic nitrogen was present on wind-eroded sediments collected from road ditch areas in mid to late winter. Sediment samples that had been deposited in ditches on top of snow were collected during the winters of 1994, 1995, and 1996 at randomly selected sites in eastern South Dakota and western Minnesota. Atrazine, atrazine metabolites [deethylatrazine (DEA)(6-chloro-N-1-methylethyl-1,3,5-triazine-2,4-diamine], and deisopropylatrazine (DIA) (6-chloro-N-ethyl-1,3,5-triazine-2,4-diamine), and alachlor were determined by gas chromatography. Total inorganic N (NO(3-) + NH4+) concentration was determined with a nitrogen analyzer. In all years, atrazine was detected in at least 72% of the samples, with a mean concentration of 8.9 ug kg-1 and, while DEA was detected in at least 18% of the samples. Alachlor was detected in at least 27% of the soil samples for all three years with mean sediment concentration of > 5 ug kg-1. Inorganic N concentration of all samples averaged 33 mg kg-1. These data suggest that deposition of wind-eroded sediment contributes to nonpoint source contamination of nontarget areas by agrichemicals.

Factors affecting atrazine fate in north central U.S. soils.

Atrazine persistence and fate are influenced by many factors, the interactions of which are difficult to predict. Several models, such as LEACHP (Wagenet and Hutson 1989), have been used as tools to estimate losses and identify variables that will impact the magnitude of loss. The LEACHP model was evaluated for predicting atrazine movement in sandy loam, silt loam, and clay loam soils during three consecutive years (two dry and one wet) in Minnesota (Khakural et al. 1995). Considering the broad range in soil properties and climatic conditions used in testing, the model performed well. However, these are only estimates, and additional field studies need to be conducted to verify model results. In a report by Fausey et al. (1995), the amount of atrazine found in groundwater throughout the Midwestern region was reported to be much below the MCL. However, specific sites in the Midwest may struggle with atrazine problems from both point and nonpoint sources of contamination. Some states, such as South Dakota, have created groundwater protection areas that alert growers and the public to sensitive areas where contamination may occur because of soil type, depth to groundwater, and distance to public wellheads. Wisconsin has developed a tiered managerial strategy, or zoning approach, in which restrictions are matched to pollution detections (Wolf and Nowak 1996). The USEPA has mandates for states to implement generic management plans to prevent pesticide contamination of groundwater. Chemical-specific plans by states will be required for at least five pesticides, one of which will be atrazine. Best management practices have been and are continuing to be developed to aid the grower in lessening the adverse impacts of atrazine. With continuing research into understanding the problem and developing solutions, and with adaptation of these recommendations by growers, the use of effective, inexpensive herbicides may continue with minimal off-site environmental effects.

Educating girls: a model program from Guatemala.

PIP: A consistent, positive association has been found between female education and socioeconomic development indicators such as infant and child mortality, family nutrition, and family planning acceptance. The World Bank has estimated that investments in female primary education yield a return of 20%. In Guatemala, where fewer than one in every eight girls who enrolls in first grade graduates from the sixth grade, government and business leaders have developed a national plan of action aimed at encouraging female school attendance. A National Commission on Girls' Education, formed in 1991, has formulated 40 projects that can be implemented by public and private institutions. These projects emerged from an analysis of specific obstacles to primary school completion and the identification of the most effective incentives for encouraging family and community support of female education. The Educate Girls Project, scheduled to be implemented in the 20 Guatemalan communities with the highest differentials between the school attendance and graduation rates of girls and boys, will include tutoring for girls, scholarships to help offset the costs to families of the loss of daughters' labor, teacher training on strategies for motivating girls, training for parent committees, and educational materials that feature female role models. Examples of other projects are mobile schools for families who migrate to the coast during the harvest and weekend schools for girls whose families are unable to release them from economic responsibilities during the school week.^ieng

Osteomyelitis as a cause of brachial plexus neuropathy.

Two infants, younger than 2 months of age, had brachial plexus involvement and true paralysis secondary to osteomyelitis of the proximal humerus. To date, no previous cases of this association have been reported. Electromyography (EMG) demonstrated significant denervation in muscles innervated by the upper trunk, with scattered involvement of other muscles. Nerve conduction velocities were normal in both patients. Both patients had significant residual weakness after appropriate antibiotic therapy. One patient, 12 months after therapy for osteomyelitis, continued to demonstrate both clinical and EMG evidence of a lower motor neuron neuropathy. The pathophysiologic cause was thought to be ischemic nerve damage secondary to occlusion of vasa nervorum.

Triosephosphate isomerase deficiency. A case report with neuropathological findings.

A 12-year-old girl had chronic nonspherocytic hemolytic anemia due to triosephosphate isomerase deficiency. Developmental and motor delay and muscular weakness were followed by cerebellar dysfunction and finally spasticity with hyperreflexia. Abnormal histopathological findings were hyaline cell bodies and axonal "spheroids" in the hypothalamus and cerebellar cortex, severe neuronal loss in the dentate and olivary nuclei, and partial loss of cerebellar Purkinje's and granular layer cells (olivocerebellar atrophy).

The orbicularis oculi reflex: pathologic studies in childhood.

The orbicularis oculi reflex was studied in 12 children with intrinsic brain stem gliomas and in six children with other posterior fossa pathology. The results were compared with previously established childhood normal values. Seventy-eight percent of the children demonstrated a pathologic alteration of the reflex comparable to reported results in adult patients. The orgicularis oculi reflex test in childhood in a relatively simple and risk-free procedure in the evaluation of brain stem disease in childhood.

Infant botulism. Epidemiological, clinical, and laboratory aspects.

Clostridium botulinum organisms and toxin were identified in the feces of six infants, aged 5 to 20 weeks, who had illnesses clinically consistent with botulism. Five of the infants lived in California and became ill within a six-month period in 1976; one infant became ill in New Jersey in 1975. Three cases were type A botulism, and three were type B. No source of ingested botulinal toxin could be found in any case. However, one infant with type B botulism had ingested a food containing C botulinum type B organisms, and no toxin was found in it. The clinical findings in these cases include constipation, weak sucking and crying ability, pooled oral secretions, cranial nerve deficits, generalized weakness, and, on occasion, sudden apnea. A characteristic electromyographic pattern termed "brief, small, abundant, motor-unit action potentials" (BSAP) was observed. The sources of C botulinum toxin for these six infants is thought to have been in vivo (gastrointestinal) production following ingestion of C botulinum organisms. Studies are underway to determine the full clinical spectrum, incidence, and potential public health importance of this infectious disease newly recognized in infants.

Acute infantile motor unit disorder. Infantile botulism?

Eight infants with an acute reversible motor unit disorder are described, including two infants from whom Clostridum botulinum type A was isolated from stool specimens. The clinical spectrum includes constipation, cranial nerve deficits, pupillary involvement, and generalized hypotonic weakness. There were no deaths, and all infants have had complete clinical recovery. A characteristic electromyographic (EMG) pattern was present in part until clinical recovery. This distinctive pattern consisted of brief, small, abundant for power exerted motor unit potentials. This EMG pattern in the context of the clinical syndrome may well be diagnostic for acute infantile motor unit disorder.

The orbicularis oculi reflex in infancy and childhood. Establishment of normal values.

The orbicularis oculi reflex and direct facial nerve conduction were studied in 38 normal children ranging in age from 1 month to 9 years. Direct facial nerve conduction in all groups was within adult normal values. The early response of the orbicularis oculi reflex obtains normal adult values by age 24 months. Both ipsilateral and contralateral delayed responses are absent under 20 months, are widely variable between 21 and 56 months, and obtain adult normal values beginning at age 6 years. The expression of the orbicularis oculi reflex is an age-related phenomenon presumably reflecting brain stem anatomic and functional maturation.