Double-tap gene drive uses iterative genome targeting to help overcome resistance alleles

Homing CRISPR gene drives could aid in curbing the spread of vector-borne diseases and controlling crop pest and invasive species populations due to an inheritance rate that surpasses Mendelian laws. However, this technology suffers from resistance alleles formed when the drive-induced DNA break is repaired by error-prone pathways, which creates mutations that disrupt the gRNA recognition sequence and prevent further gene-drive propagation. Here, we attempt to counteract this by encoding additional gRNAs that target the most commonly generated resistance alleles into the gene drive, allowing a second opportunity at gene-drive conversion. Our presented "double-tap" strategy improved drive efficiency by recycling resistance alleles. The double-tap drive also efficiently spreads in caged populations, outperforming the control drive. Overall, this double-tap strategy can be readily implemented in any CRISPR-based gene drive to improve performance, and similar approaches could benefit other systems suffering from low HDR frequencies, such as mammalian cells or mouse germline transformations.

Targeting double-strand break indel byproducts with secondary guide RNAs improves Cas9 HDR-mediated genome editing efficiencies

Programmable double-strand DNA breaks (DSBs) can be harnessed for precision genome editing through manipulation of the homology-directed repair (HDR) pathway. However, end-joining repair pathways often outcompete HDR and introduce insertions and deletions of bases (indels) at the DSB site, decreasing precision outcomes. It has been shown that indel sequences for a given DSB site are reproducible and can even be predicted. Here, we report a general strategy (the "double tap" method) to improve HDR-mediated precision genome editing efficiencies that takes advantage of the reproducible nature of indel sequences. The method simply involves the use of multiple gRNAs: a primary gRNA that targets the wild-type genomic sequence, and one or more secondary gRNAs that target the most common indel sequence(s), which in effect provides a "second chance" at HDR-mediated editing. This proof-of-principle study presents the double tap method as a simple yet effective option for enhancing precision editing in mammalian cells.

Optimized CRISPR tools and site-directed transgenesis towards gene drive development in Culex quinquefasciatus mosquitoes

Culex mosquitoes are a global vector for multiple human and animal diseases, including West Nile virus, lymphatic filariasis, and avian malaria, posing a constant threat to public health, livestock, companion animals, and endangered birds. While rising insecticide resistance has threatened the control of Culex mosquitoes, advances in CRISPR genome-editing tools have fostered the development of alternative genetic strategies such as gene drive systems to fight disease vectors. However, though gene-drive technology has quickly progressed in other mosquitoes, advances have been lacking in Culex. Here, we develop a Culex-specific Cas9/gRNA expression toolkit and use site-directed homology-based transgenesis to generate and validate a Culex quinquefasciatus Cas9-expressing line. We show that gRNA scaffold variants improve transgenesis efficiency in both Culex quinquefasciatus and Drosophila melanogaster and boost gene-drive performance in the fruit fly. These findings support future technology development to control Culex mosquitoes and provide valuable insight for improving these tools in other species.

Small-Molecule Control of Super-Mendelian Inheritance in Gene Drives

Synthetic CRISPR-based gene-drive systems have tremendous potential in public health and agriculture, such as for fighting vector-borne diseases or suppressing crop pest populations. These elements can rapidly spread in a population by breaching the inheritance limit of 50% dictated by Mendel's law of gene segregation, making them a promising tool for population engineering. However, current technologies lack control over their propagation capacity, and there are important concerns about potential unchecked spreading. Here, we describe a gene-drive system in Drosophila that generates an analog inheritance output that can be tightly and conditionally controlled to between 50% and 100%. This technology uses a modified SpCas9 that responds to a synthetic, orally available small molecule, fine-tuning the inheritance probability. This system opens a new avenue to feasibility studies for spatial and temporal control of gene drives using small molecules.

A transcomplementing gene drive provides a flexible platform for laboratory investigation and potential field deployment

CRISPR-based gene drives can spread through wild populations by biasing their own transmission above the 50% value predicted by Mendelian inheritance. These technologies offer population-engineering solutions for combating vector-borne diseases, managing crop pests, and supporting ecosystem conservation efforts. Current technologies raise safety concerns for unintended gene propagation. Herein, we address such concerns by splitting the drive components, Cas9 and gRNAs, into separate alleles to form a trans-complementing split-gene-drive (tGD) and demonstrate its ability to promote super-Mendelian inheritance of the separate transgenes. This dual-component configuration allows for combinatorial transgene optimization and increases safety by restricting escape concerns to experimentation windows. We employ the tGD and a small-molecule-controlled version to investigate the biology of component inheritance and resistant allele formation, and to study the effects of maternal inheritance and impaired homology on efficiency. Lastly, mathematical modeling of tGD spread within populations reveals potential advantages for improving current gene-drive technologies for field population modification.

Protection of cattle from Culicoides spp. in Australia by shelter and chemical treatments

Trials were conducted in three regions of Australia to investigate the potential for improvised shelters and chemical treatments to reduce feeding by Culicoides on cattle and thereby minimise the risk of bluetongue transmission during transport of cattle to ports. Various designs and combinations of roofs and walls were placed around penned cattle. Chemical treatments were applied to other penned cattle. Culicoides were collected from the cattle by vacuum samplers or by light traps in the pens. Roofs alone did not consistently reduce the numbers of Culicoides brevitarsis or C. fulvus and increased the numbers of C. actoni collected. Walls alone reduced the numbers of C. wadai but not C. brevitarsis. Roofs and walls in combination reduced the numbers of C. brevitarsis and C. wadai. The chemical treatments 'Flyaway' (a blend of repellents) and fenvalerate reduced the numbers of C. brevitarsis and C. wadai up to 52 h post treatment.

Factors affecting the spread of Culicoides brevitarsis at the southern limit of distribution in eastern Australia

Culicoides brevitarsis Kieffer is the main vector of bluetongue and Akabane viruses in Australia. Its threat to animal health and livestock exports requires that areas free of the vector and viruses be defined clearly. In New South Wales, survival of the vector over winter is limited to the northern coastal plains. C. brevitarsis therefore has to reinfest areas outside the endemic area each year. Models have been developed to predict the extent and nature of its movements. It can move at different rates and this is partly due to significant delays of movement due to the barrier formed by the altitude of the Great Dividing Range. C. brevitarsis subsequently retains a coastal distribution in most years. At the end of the season, the times when activity would effectively cease can be estimated from temperature data. These data allow evidenced-based conclusions on zonal and seasonal freedom to be made in combination with light trap monitoring.

Improving light-trap efficiency for Culicoides spp. with light-emitting diodes

The robustness of light traps used to monitor Culicoides spp. throughout Australia was improved with stainless steel and heavy duty plastic fittings. Printed circuit boards and light-dependent resistors were modified to be compatible with recent advances in electronics. In experiments with light-emitting diodes (LEDs), C. brevitarsis Kieffer was significantly attracted to green light. This species is the major vector of Akabane and bluetongue viruses in Australia and is the main target of a national monitoring programme using light traps. This response was significantly greater than the response to the incandescent lights currently used in the light traps. Catches of C. brevitarsis were also related to the intensity of the green LEDs. These were more effective than the currently used incandescent globes at intensities between 46% and 142% of the incandescent intensity. The response of seven other Culicoides spp. to the LEDs was also determined.

Models for the dispersal in Australia of the arbovirus vector, Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae)

Culicoides brevitarsis is the main biting midge responsible for the transmission of bluetongue and Akabane viruses to livestock in Australia. Models are given for its dispersal after winter from endemic areas at the southern limit of its distribution in New South Wales (NSW); the models might also be applicable elsewhere. Model 1 shows that dispersal can be explained by distance from a key point just outside the endemic area in mid-northern/northern coastal NSW. The model provides probability data for times of first occurrence at sites within regions down the southern coastal plain or up the Hunter Valley towards (but rarely reaching) the western slopes and tablelands. Model 2 shows that the movement depends on temperature and wind speed from northerly and easterly directions. Preliminary data also are given to suggest a relationship between density in the endemic area and the maximum distance that C. brevitarsis can travel in a given year. The models can be linked to other information which in combination can provide probabilities for winter survival outside the endemic area, times of occurrence at sites where it cannot survive winter and times when activity ceases naturally at these sites at the end of the season. This information can be used to predict the potential for virus transmission and indicate zones of seasonal freedom from both vector and virus for the export of livestock.

Rho GTPases and their effector proteins

Rho GTPases are molecular switches that regulate many essential cellular processes, including actin dynamics, gene transcription, cell-cycle progression and cell adhesion. About 30 potential effector proteins have been identified that interact with members of the Rho family, but it is still unclear which of these are responsible for the diverse biological effects of Rho GTPases. This review will discuss how Rho GTPases physically interact with, and regulate the activity of, multiple effector proteins and how specific effector proteins contribute to cellular responses. To date most progress has been made in the cytoskeleton field, and several biochemical links have now been established between GTPases and the assembly of filamentous actin. The main focus of this review will be Rho, Rac and Cdc42, the three best characterized mammalian Rho GTPases, though the genetic analysis of Rho GTPases in lower eukaryotes is making increasingly important contributions to this field.

Epidemic of blindness in kangaroos--evidence of a viral aetiology

OBJECTIVE

To determine the cause of an epidemic of blindness in kangaroos.

DESIGN AND PROCEDURES

Laboratory examinations were made of eyes and brains of a large number of kangaroos using serological, virological, histopathological, electron microscopical, immunohistochemical methods, and PCR with cDNA sequencing. In addition, potential insect viral vectors identified during the disease outbreak were examined for specific viral genomic sequences.

SAMPLE POPULATION

For histopathological analysis, 55 apparently blind and 18 apparently normal wild kangaroos and wallabies were obtained from New South Wales, Victoria, South Australia, and Western Australia. A total of 437 wild kangaroos and wallabies (including 23 animals with apparent blindness) were examined serologically.

RESULTS

Orbiviruses of the Wallal and Warrego serogroups were isolated from kangaroos affected with blindness in a major epidemic in south-eastern Australia in 1994 and 1995 and extending to Western Australia in 1995/96. Histopathological examinations showed severe degeneration and inflammation in the eyes, and mild inflammation in the brains. In affected retinas, Wallal virus antigen was detected by immunohistochemical analysis and orbiviruses were seen in electron microscopy. There was serological variation in the newly isolated Wallal virus from archival Wallal virus that had been isolated in northern Australia. There were also variations of up to 20% in genotype sequence from the reference archival virus. Polymerase chain reactions showed that Wallal virus was present during the epidemic in three species of midges, Culicoides austropalpalis, C dycei and C marksi. Wallal virus nucleic acid was also detected by PCR in a paraffin-embedded retina taken from a blind kangaroo in 1975.

CONCLUSION

Wallal virus and perhaps also Warrego virus are the cause of the outbreak of blindness in kangaroos. Other viruses may also be involved, but the evidence in this paper indicates a variant of Wallal virus, an orbivirus transmitted by midges, has the strongest aetiological association, and immunohistochemical analysis implicates it as the most damaging factor in the affected eyes.

Mapping of a yeast G protein betagamma signaling interaction

The mating pathway of Saccharomyces cerevisiae is widely used as a model system for G protein-coupled receptor-mediated signal transduction. Following receptor activation by the binding of mating pheromones, G protein betagamma subunits transmit the signal to a MAP kinase cascade, which involves interaction of Gbeta (Ste4p) with the MAP kinase scaffold protein Ste5p. Here, we identify residues in Ste4p required for the interaction with Ste5p. These residues define a new signaling interface close to the Ste20p binding site within the Gbetagamma coiled-coil. Ste4p mutants defective in the Ste5p interaction interact efficiently with Gpa1p (Galpha) and Ste18p (Ggamma) but cannot function in signal transduction because cells expressing these mutants are sterile. Ste4 L65S is temperature-sensitive for its interaction with Ste5p, and also for signaling. We have identified a Ste5p mutant (L196A) that displays a synthetic interaction defect with Ste4 L65S, providing strong evidence that Ste4p and Ste5p interact directly in vivo through an interface that involves hydrophobic residues. The correlation between disruption of the Ste4p-Ste5p interaction and sterility confirms the importance of this interaction in signal transduction. Identification of the Gbetagamma coiled-coil in Ste5p binding may set a precedent for Gbetagamma-effector interactions in more complex organisms.

Characteristics predicting incorrect metered-dose inhaler technique in older subjects

OBJECTIVE

To determine whether cognitive status, hand strength, and demographic variables are predictive of correct use of metered-dose inhalers by older subjects.

METHODS

Clinic patients (n = 29) and healthy volunteers (n = 42) older than 50 years with no previous or limited metered-dose inhaler use were enrolled. After cognitive (Mini-Mental State Examination) and hand strength assessments, subjects received extensive instruction in proper metered-dose inhaler technique. Technique was independently assessed by two evaluators immediately after instruction and 1 week later. Correct technique was defined as (1) activating the canister in the first half of inhalation, (2) continuing to inhale slowly and deeply, and (3) holding breath at full inspiration (5 seconds). Data for the two subject groups were pooled for analyses.

RESULTS

The mean age of the subjects was 69.7 years. Forty subjects (56%) demonstrated correct metered-dose inhaler technique at 1 week. Logistic regression showed that hand strength measurement (odds ratio, 0.68; 95% confidence interval, 0.55 to 0.84), Mini-Mental State Examination score less than 24 (odds ratio, 3.66; 95% confidence interval, 1.07 to 12.4), and male gender (odds ratio, 5.01; 95% confidence interval, 1.07 to 23.5) were significant predictors of incorrect inhaler use. Correct use of the metered-dose inhaler was unrelated to age, education, or subject status.

CONCLUSIONS

Clinicians should consider cognitive status and hand strength when metered-dose inhaler therapy is initiated for an older adult. Patients with cognitive impairment and hand strength deficits may require more extensive training, frequent follow-up, or alternative dosage forms.

The dispersal of Culicoides brevitarsis in eastern New South Wales and associations with the occurrences of arbovirus infections in cattle

Distributions of the vector Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae) (determined from light trap data) and 2 arboviruses (determined from seroconversions in sentinel cattle) were studied in eastern New South Wales in 1993-94. C brevitarsis was recorded progressively from endemic areas on the north coast, to Nowra on the south coast, and westward to Scone, in the Hunter Valley. C brevitarsis also survived through winter at Paterson, in the Hunter Valley. Its apparently focal reappearance in this marginal area had no obvious effect on the broad pattern of its progression or the dispersal of Akabane and bluetongue viruses. These viruses were first recorded from foci near Coffs Harbour, on the mid-north coast. Their first occurrences at different locations were associated with those of C brevitarsis, but not with each other. The viruses were found only within the recorded limits of the vector's distribution. Delays between the initial occurrence of C brevitarsis and first evidence of virus transmissions at locations ranged from 2 to 7 months. The delays decreased away from the points of focus and were negatively associated with the time of initial occurrence of the vector. Seroconversions to the viruses were related to the presence of C brevitarsis. However, the densities of C brevitarsis had no apparent effect on the initial numbers of cattle seroconverting to either virus. The results support the conclusion that the progressions of C brevitarsis and Akabane and bluetongue viruses were the result of gradual movements by the vector.

Albuterol aerosol versus albuterol Rotacaps in exercise-induced bronchospasm in children

The purpose of this study was to determine the safety and effectiveness of albuterol aerosol 180 micrograms and albuterol powder 200 micrograms in the prevention of exercise-induced bronchospasm in children. Forty-six patients aged 4-11 years with asthma and exercise-induced bronchospasm were enrolled in this randomized, double-blind, single-dose, three-way crossover study comparing albuterol aerosol, albuterol powder, and placebo. Exercise challenge was performed at the screening visit for qualifying and baseline determinations of pulmonary function and then 15 min after drug administration at each of three visits. Prevention of exercise-induced bronchospasm was assessed by comparing across all treatment groups the percentage change in FEV1 from pre- to postexercise, the percentage of patients protected by treatment, postexercise minimum FEV1, and postexercise change in FEV1. Safety was assessed by observation of clinical adverse events, laboratory tests, physical examination, electrocardiogram and rhythm strips, vital signs, and pulmonary auscultation. Forty-four patients completed the study. Mean postexercise FEV1 decreased 6% from preexercise values when patients were treated with either albuterol formulation; FEV1 decreased 23% when patients were treated with placebo. Exercise-induced bronchospasm was prevented in 95% of patients when treated with albuterol powder, in 91% treated with albuterol aerosol, and in 57% treated with placebo. Patients maintained significantly higher mean minimum FEV1 values after treatment with albuterol powder and albuterol aerosol than when treated with placebo. Treatment with either albuterol formulation produced a significantly smaller decrease in mean FEV1 from pre- to postexercise than treatment with placebo. No drug-related adverse events were reported, and safety assessments were within normal limits.(ABSTRACT TRUNCATED AT 250 WORDS)

The Effects of Habitat on the Distribution of Culicoides Brevitarsis Kieffer (Diptera, Ceratopogonidae) During Its Resting Phase

Culicoides brevitarsis is a biting midge and a vector of several arboviruses affecting livestock in Australia. The effect of habitat on adults during their resting phase in pasture was studied in the Hunter Valley during 1994 and 1995. C. brevitarsis was 21 times more abundant in grass tussocks (Pea sp.) than in pasture grass and its numbers were related positively to the increasing size of these tussocks. High numbers were also found in reed tussocks (Juncus sp.) and grass along the margins of dams. When tussocks were absent in pasture, numbers of C. brevitarsis varied within the pasture grass during the day. More C. brevitarsis were found in grass when no cattle were present. The presence of cattle affected the parous ratio, with 85% of females being parous when cattle were absent and only 38% being parous when cattle were present. Counts in tussocks and grass were lowest and counts in the the air above tussocks were highest 1 h before sunset. After sunset, numbers increased on pasture grass more than in reed tussocks. Numbers in reed tussocks were again high after the morning flight peak the next day. Relationships with weather variables were weak.

Cilicoides Brevitarsis Kieffer (Diptera, Ceratopogonidae) in Different Farm Habitats

In a study of Culicoides brevitarsis in different farm habitats it was found that adults rested on vegetation in 'open' conditions but were more abundant in areas of higher humidity (dam margins). Numbers caught in light traps were highest in open and wooded pasture while levels of oviposition were highest in open pasture and along dam margins. The distributions and behaviours of C. brevitarsis and its cattle hosts in different habitats maintained contact between the two species, although the resting and oviposition phases of the insect did not require cattle to be constantly close by. Differences due to habitat should be considered when designing sampling/monitoring procedures and in the interpretation of survey, research and predictive data.

Efferent terminals in the cochlea of the mustached bat: quantitative data

Efferent terminals in the cochlea of the mustached bat were stained for acetylcholinesterase (AChE) and quantitative data were obtained for the number and size of the endings on the outer hair cells (OHCs) in each row, from base to apex. From TEM micrographs and AChE-stained, surface preparations it was determined that every OHC had a single, large terminal. The mean size of the terminals was significantly different in each row, with the largest occurring in the first row (7.1 microns 2); the mean size in the second and third rows was 5.7 and 5.0 microns 2 respectively. In specific frequency processing regions, the largest mean size (8.4 microns 2) for first row OHCs was consistently found in the distal densely innervated (DDI) area. This region has afferent neurons that are sharply tuned to the second harmonic, constant frequency component of the bat's biosonar signals. Sudden changes in the size of the terminals were observed exactly at the boundaries of the DDI with adjacent sparsely innervated regions. Similar, but less striking, size changes also occurred in and adjacent to the proximal densely innervated (PDI) region, a harmonically related, sharply tuned region, which processes the bat's 91.5 kHz, third harmonic, constant frequency signals. The region of the cochlea with the smallest first row terminals (mean 5.3 microns 2) was the large, sparsely innervated region of the basal turn, a region that does not appear to process biosonar signals. Although the significance of differences in efferent terminal size is not known, the data suggest a possible correlation between OHC stimulation and sharp tuning. The potentially greater influence of the efferent fibers on the first row of OHCs, compared to other rows, is consistent with observations made on other mammals; in the latter, however, the greater influence has been suggested more by number than size. Unlike other mammals, the OHC efferents in the mustached bat have no clear base-to-apex gradient in the number or size of the efferent terminals. It is suggested that this might reflect the high frequency nature of the ear (6-120 kHz) and absence of low frequency hearing.

Twenty-four-hour intragastric pH patterns in ICU patients on ranitidine

Thirty critically ill patients with mixed diagnoses underwent continuous intragastric pH monitoring for 72 hr while confined to a shock/trauma intensive care unit. The first 24 hr were monitored under no specific acid-suppressing therapy (placebo control). During the second and third consecutive 24-hr periods, patients received continuous infusion of intravenous ranitidine in the dose of 6.25 mg/hr and 12.5 mg/hr, respectively. Results of the placebo-control 24-hr study revealed that one third (N = 10) of the patients were gastric acid hyposecretors (24-hr median intragastric pH values above pH 4.0). In the normosecreting group (N = 20), both ranitidine schedules significantly elevated 24-hr median pH values, when compared to placebo (placebo 24-hr median intragastric pH 1.75; ranitidine 6.25 mg/hr 24-hr median intragastric pH 4.625, P < 0.0001; ranitidine 12.5 mg/hr 24-hr median intragastric pH 6.29, P = 0.0099). Five patients (18%) failed to adequately respond to the ranitidine 12.5 mg/hr dose (24-hr median intragastric pH < 4.0). These findings suggest that a significant percentage of intensive care unit patients are not in need of acid-suppressing therapy as prophylaxis against stress-induced ulceration. Conversely, other patients may require more intensive acid-suppressing regimens because of failure to respond to high dose H2-antagonist therapy.

Short- and long-term retention of a nursing home education program on metered-dose inhaler technique

OBJECTIVE

To evaluate an education program on metered-dose inhaler (MDI) technique designed for nurses and trained medication aides (TMAs).

DESIGN

The education program included a handout, a lecture incorporating a videotape on correct inhaler and device technique, and hands-on experience with placebo inhalers. The participants' ability to verbalize and demonstrate correct MDI technique was assessed by the same two-person teams before, immediately after, and two months after the program.

SETTING

Five nursing homes.

PARTICIPANTS

Fifty-six nurses and TMAs practicing in nursing homes.

MAIN OUTCOME MEASURES

Learning and retention.

RESULTS

The participants' mean (+/- SD) verbal and demonstration scores increased immediately after the program by 68 +/- 18 points for verbalization and 47 +/- 16 points for demonstration. The participants were always better at demonstrating than verbalizing MDI technique. The participants' baseline verbal and demonstration scores correlated with the amount learned. Learning was influenced by the individual nursing home (verbal and demonstration) and personal use (demonstration only), but not by academic degree, previous training, past instruction of a patient, or current care of a patient who was receiving inhaler therapy. After two months, the scores were lower than immediately after the program test by 0-92 points for verbalization and 10-80 points for demonstration; however, the mean scores were still significantly greater (p less than 0.05) than the baseline scores. Retention of knowledge on the correct technique was greater for the demonstration component. Retention was influenced only by the nursing home in which the participant worked, and not any of the other variables.

CONCLUSIONS

Our structured education program significantly improved inhaler technique; however, to maintain retention of the material, the program should be frequently repeated.

Pharmacokinetics and pharmacodynamics of ranitidine after burn injury

The pharmacokinetics and pharmacodynamics of ranitidine were studied in 10 hypermetabolic burned patients with normal creatinine clearance and compared with healthy volunteers. Ranitidine was administered as a single 50 mg intravenous bolus and multiple blood samples were obtained up to 10 hours after the dose for determination of plasma ranitidine concentrations. Gastric pH in burned patients was monitored by way of a nasogastric tube. Burned patients exhibited significantly higher (p less than 0.01) ranitidine clearance (mean +/- SD; 10.80 +/- 2.38 versus 7.53 +/- 1.71 ml/min/kg) and steady-state distribution volume (1.63 +/- 0.13 versus 1.16 +/- 0.33 L/kg). Within an hour of administration of drug the gastric pH was greater than or equal to 4.0 in all but one patient. This pH was maintained for at least 6 hours. In five patients the pH was greater than or equal to 4.0 throughout the 10-hour study. Thus, despite increased ranitidine clearance, the recommended dose of ranitidine maintained gastric pH greater than or equal to 4.0 throughout the normal dosing interval in the majority of patients. Dosage adjustment reported for many other drugs after burn injury may not be necessary for ranitidine.

Intragastric pH and pharmacokinetics of intravenous ranitidine during sinusoidal and constant-rate infusions

Six patients with healed duodenal ulcer completed two treatment periods with continuous i.v. infusion ranitidine. A 25-mg i.v. bolus was followed by a constant infusion at 6.25 mg/h or a sinusoidal infusion with infusion rates ranging from 3.125 to 9.375 mg/h. The sinusoidal infusion rate was designed to match the previously observed circadian changes in basal acid secretion. The peak infusion rate occurred at 19:30 h. A pharmacokinetic method was designed to predict the resultant plasma concentrations of ranitidine. Intragastric pH and plasma ranitidine concentration data were fit to a cosine function to evaluate circadian and ultradian rhythms. Plasma concentrations during the sinusoidal infusion exhibited a circadian rhythm according to model predictions. Cosinor analyses of the mean ranitidine plasma concentration data showed a mesor concentration of 237 ng/mL and amplitude of 76 ng/mL (coefficient of determination [CD] = 0.98). The acrophase in plasma concentration occurred at 2223 h, a delay of approximately 2.9 hours from the peak in the infusion rate. The constant-rate infusion resulted in a mean plasma concentration of 222 +/- 32 ng/mL. The 24-h mean intragastric pH values for the sinusoidal and constant regimens were 5.4 and 5.1, respectively (p = 0.170). The intragastric pH during the constant-rate infusion exhibited a significant circadian rhythm (CD = 0.52). The minimum pH (bathy-phase) occurred at 2031 h. No circadian rhythm was present during the sinusoidal-rate infusion (CD = 0.08). At the approximate time of the peak basal acid secretion, between 21:00 hours and midnight, the mean pH for the sinusoidal infusion was 5.77 versus 4.5 for the constant-rate infusion (p = 0.112). Sinusoidal infusions or alternate methods of increased doses at the times of peak acid output may improve around-the-clock control of intragastric pH.

Use of Ti Plasmid DNA Probes for Determining Tumorigenicity of Agrobacterium Strains

Probes consisting of T-DNA genes from the Ti plasmid of Agrobacterium tumefaciens were used for determining tumorigenicity of strains. Two 32 P-labeled probes hybridized with 28 of 28 tumorigenic strains of the pathogen but not with 20 of 22 nontumorigenic strains. One probe, pTHE17, consists of all but the far left portion of the T-DNA of strain C58. Probe Sma I7 consists of Sma I fragment 7 of pTiC58, including onc genes 1, 4, and 6a and most of 2. Another probe, pAL4044, consisting of the vir region of strain Ach-5, hybridized with several nontumorigenic as well as tumorigenic strains. Colony hybridizations were done with 28 tumorigenic and 22 nontumorigenic Agrobacterium strains. About 10 6 CFU of the different tumorigenic strains were detectable with this method. Southern analyses confirmed the presence or absence of Ti plasmids in strains for which tumorigenicity was questioned. Colony hybridization with the T-DNA probes provides a rapid and sensitive means for determining the tumorigenic nature of Agrobacterium strains.

Pharmacodynamics of intravenous ranitidine after bolus and continuous infusion in patients with healed duodenal ulcers

Fifteen adult men who had histories of duodenal ulcer disease were studied for 24 hours during treatment with varying intravenous doses of ranitidine (50 mg every 8 hours, 100 mg every 12 hours, 6.25 mg/hr continuous infusion, and 10 mg/hr continuous infusion) and placebo. Gastric pH was monitored under fasting conditions by means of an indwelling pH sensitive electrode. The continuous infusion regimens provided the most constant level of acid suppression. A "breakthrough" decrease in gastric pH began at approximately 6 PM at the 6.25 mg/hr dose level. The drop in pH at the 10 mg/hr dose level was less impressive. Ranitidine, 100 mg every 12 hours, resulted in better acid suppression than the regimen of 50 mg every 8 hours. A gastric pH greater than or equal to 4 was achieved 35 to 50 minutes after the start of administration for all regimens. The median effective concentration (EC50) of ranitidine was approximately 45 ng/ml. Continuous infusion regimens, with a dosage adjustment for the time of day, may be the optimal dosage regimen for patients requiring continuous protection from gastric damage by hydrochloric acid. Bolus loading doses are not required to speed the onset of effect in the clinical setting.

The efferent cochlear projections of the superior olivary complex in the mustached bat

Following the placement of horseradish peroxidase in the scala tympani, labeled neurons were found in the ipsilateral interstitial nucleus (INT) and throughout the ipsilateral and contralateral dorsomedial periolivary nuclei (DMPO). The neurons in the INT were morphologically distinct from those in the DMPO. The INT neurons formed a thin shell over the lateral superior olivary nucleus (LSO) and their dendrites extended into the body and hilar region. The DMPO neurons had long, tapering dendrites that extended in every direction. Data indicate that the crossed fibers in the floor of the ventricle arise entirely from the DMPO while uncrossed olivocochlear fibers originate in the INT and DMPO. It was estimated that 75% of the efferent fibers arise from the INT and 25% from the DMPO. Approximately 70% of the efferent neurons in each DMPO project to the contralateral cochlea via the crossed olivocochlear bundle. The number of olivocochlear neurons associated with each ear was determined to be approximately 1585. This number is similar to that found in cats and guinea pigs, but the number of neurons per unit length of the basilar membrane is considerably higher in the mustached bat than in other species examined to date. The compact, restricted locations of the neurons in the INT and DMPO in the mustached bat are different from those described for most other mammals and the arrangement in the mustached bat offers advantages over other species for future anatomical and physiological studies.

Echo intensity compensation by echolocating bats

When mounted on a swinging pendulum, mustache bats, Pteronotus p. parnellii, emit ultrasonic pulses as they move toward and away from fixed targets. During forward swings they systematically decrease the intensity of their emitted pulses and during backward swings they increase the intensity. In this way, echo strength is continuously adjusted and apparently optimized for signal analysis. We have called this behavior echo intensity compensation. Pteronotus simultaneously Doppler and echo intensity compensate during forward swings of the pendulum but during backward swings they only echo intensity compensate. Pteronotus can regulate the intensity of both the constant frequency and frequency modulated components of their pulses; this regulation is independent of vestibular cues, pulse repetition rates, pulse durations and pulse-echo intervals.

The Spatial Dispersion of Spiders in a Cotton Ecosystem

In a cotton field in south-eastern Queensland, the spider species Cheiracanthium mordax L. Koch (diversum L. Koch), Archaearanea veruculata (Urquhart) and Lycosa sp. were equally distributed in the outer, middle and inner portions. However, A. veruculata was more abundant in the western side of the field late in the season, apparently in response to a more favourable habitat. In sampling, the variance was greater than the mean and overdispersion was apparent. C. mordax and A. veruculata were most abundant in the top one-third of plants, and Oxyopes mundulus L. Koch was evenly distributed over plants. The consistency with which these spiders were recorded in levels of vertical strata was enhanced by the formation of the crop canopy, and the eventual vertical distribution of C. mordax was apparently influenced by rainfall. Among crop spacings, most spiders of 4 species preferred the highest density (12 plants/m). The ecological consequences of the distribution characteristics are discussed in relation to current sequential decision plans for the management of cotton pests and beneficial species in the region.

Arthropod Ground Strata Composition of the Cotton Ecosystem in South-Eastern Queensland, and the Effect of Some Control Strategies

A record is provided of 23 arthropod species inhabiting the ground strata of cotton fields in south-eastern Queensland. The Coleoptera were the most diverse group (14 species) and Labidura riparia truncata Kirby, and Nala lividipes (Dufour) (both Labiduridae : Dermaptera) were the most abundant species caught in pitfall traps. Changes in the ecosystem in response to different pest control strategies were considered; broad-spectrum insecticide use resulted in the suppression of most species. Resurgence of L. riparia was evident in fields treated with DDT-toxaphene. Possible resurgence of four other species was observed after the removal of insecticide pressure. Several of these species may be of importance because of their predatory function.

Management of Acyrthosiphon kondoi Shinji, blue-green aphid, and Therioaphis trifolii (Monell) f. maculata, spotted alfalfa aphid, by grazing and cutting lucerne

Three experiments were carried out in New South Wales to assess the effects of grazing, forage harvesting and haymaking on populations of blue-green aphid (BGA) and spotted alfalfa aphid (SAA) and some of their predators. In experiment 1, at Tamworth, grazing by sheep at light, medium and heavy intensities reduced BGA numbers after 10 days by 52%, 74% and 93%, respectively, from the ungrazed control in dryland Hunter River lucerne. Grazing had no significant effect on the numbers of SAA and had little direct effect on the small numbers of predators present. A resurgence of both aphid species resulted in numbers significantly higher on regrowth in grazed areas than in the area left ungrazed. In experiment 2, at Tocal, grazing cattle on irrigated CUF101 at light, medium and heavy rates initially reduced BGA numbers by 30%, 53% and 75%, respectively, from their untreated levels. Grazing had little direct effect on the low number of predators present. In experiment 3, forage harvesting and mowing for hay reduced BGA and its predators more than did grazing at normal rates. It was concluded that while grazing or harvesting may reduce aphid numbers and damage initially, problems may result on regrowth.

The Composition and Abundance of the Spider Fauna in South-East Queensland Cotton

In unsprayed cotton grown in 2 regions of south-eastern Queensland in 1973-77, 10 families, 19 genera and 25 species of spiders were represented. Of these, Cheiracanthium mordax L. Koch (diversum L. Koch), Achaearanea veruculata (Urquhart) and Theridion sp. made up 80-86%. Comparisons of population abundances, stage and sex ratios were made, and although some differences were recorded there were similarities between successive seasons. The seasonal distributions of the most abundant species are given, and their relation to the average crop phenology is discussed.

The potential of Campylomma livida Reuter, and Megacoelum modestum Distant, (Hemiptera: Miridae) to damage cotton in Queensland

The damage potential of Campylomma livida Reuter, and Megacoelum modestum Distant, (Hemiptera : Miridae) on cotton in Queensland was investigated in the seasons 1976-77 and 1977-78. In field trials, 54% and 35% fewer squares on untreated plants compared with those protected with DDTtoxaphene were related to mirid presence, in the first and second seasons, respectively. In glasshouse experiments M. modestum was the more important of the two species, causing 70% reductions in the number of squares on infested plants compared with uninfested plants. C. livida caused 20% of squares to be shed. Mirid presence may coincide with Heliothis spp, activity, so techniques for the control of mirids would have to complement current Heliothis spp. management.

Temporal Distribution and Abundance of the Coccinellid Complex as Related to Aphid Populations on Cotton in South-East Queensland

Population abundance data are given for coccinellid species as related to aphid presence on cotton in south-east Queensland. Coccinellids (and other aphidophagous species) have been observed to effectively maintain aphid numbers below crop-damaging levels in unsprayed cotton for three consecutive cotton seasons, two of which are reported here. Six species were recorded, forming a continuous and generally uniformly distributed species-complex which exhibited several functional characteristics necessary for successful aphidophagous predation in agricultural ecosystems. Five of these species responded to aphid presence by producing offspring. Insecticidal treatments for aphid control under similar circumstances in commercially grown cotton fields would be unwarranted.

The distribution of cotton looper (Anomis flava Fabr.) larvae and larval damage on cotton and its relationship to the photosynthetic potential of cotton leaves at the attack sites

Data are given for the distribution of larvae and larval damage of the cotton looper, Anomis flava Fabr., during periods of natural attack on cotton in the south-east Queensland region. A distinct distributional pattern developed in which larvae and major damage to leaves were centrally located on both the horizontal and vertical axes of the plant. The distribution and damage potential of the larval population was subsequently greatly modified by a nucleopolyhedrosis virus epizootic disease commonly recorded in cotton looper populations in the region. Major damage was caused to leaves 14–21 days old which were approximately midway through their photosynthetic capacity range and continuing to decline in photosynthetic importance. The data are considered relative to the inclusion of loopers in a complete pest management program currently being developed for cotton in the south-east Queensland region.

Temporal Distribution, Biology and Life History of the Cotton Tipworm, Crocidosema Plebiana Zeller, on Cotton in the South-Eastern Queensland Region

Data are presented from a three-season study of the seasonal abundance, biology and life history of C. plebeiana, which affects cotton during its establishment and early fruiting phases in the south-east Queensland region. Results suggest that if insecticidal control of tipworm is necessary it should be initiated during the egg stage.

Effect of damaging main stem terminals at various stages of flowering, on yield of cotton in south-east Queensland

Damage by the cotton tipworm, Crocidosema plebeiana Zeller, was simulated in field trials by the removal of terminal buds (tipping) at different phenological stages coinciding with tipworm presence on cotton grown in south-eastern Queensland. The effect of this damage was considered in relation to the induced changes in crop morphology, fruit production, yield and harvestability of cotton grown under field conditions. No significant differences in fruit formation and yield were established. There were significant delays in times to 50 per cent flowering and boll opening in plants tipped before squaring had commenced. Changes in the location of monopodial branches arising from the main stem were induced in plants tipped pre-squaring but this did not significantly affect the harvestability.