Biomedical subjects

Margaret Skinner

Publications and source records attributed to Margaret Skinner.

4 recordsLinked to original sources

PubMed2003

Characterization of Beauveria bassiana and Metarhizium anisopliae isolates for management of tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae).

Selected morphological and physiological characteristics of four Beauveria bassiana (Balsamo) Vuillemin isolates and one Metarhizium anisopliae (Metschnikoff) Sorokin isolate, which are highly pathogenic to Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), were determined. There were significant differences in conidial size, viability, spore production, speed of germination, relative hyphal growth, and temperature sensitivity. Spore viability after incubation for 24h at 20 degrees C ranged from 91.4 to 98.6% for the five isolates tested. Spore production on quarter-strength Sabouraud dextrose agar plus 0.25% (w/v) yeast extract after 10 days incubation at 20 degrees C ranged from 1.6x10(6) to 15.5x10(6)conidia/cm(2). One B. bassiana isolate (ARSEF 1394) produced significantly more conidia than the others. Spore germination was temperature-dependant for both B. bassiana and M. anisopliae. The time required for 50% germination (TG(50)) ranged from 25.0 to 30.9, 14.0 to 16.6, and 14.8 to 18.0h at 15, 22, and 28 degrees C, respectively. Only the M. anisopliae isolate (ARSEF 3540) had significant spore germination at 35 degrees C with a TG(50) of 11.8h. A destructive sampling method was used to measure the relative hyphal growth rate among isolates. Exposure to high temperature (40-50 degrees C) for 10min had a negative effect on conidial viability. The importance of these characteristics in selecting fungal isolates for management of L. lineolaris is discussed.

Animals↗

PubMed2003

The incudostapedial joint angle: implications for stapes surgery prosthesis selection and crimping.

OBJECTIVE: To evaluate the role of the incudostapedial joint (ISJ) angle in stapes prosthesis size selection and crimping. METHODS: The ISJ of 13 cadaveric human temporal bones were photographed, then measured using computer-aided design software. The relationship of ISJ angle to prosthesis length was modeled. A literature review evaluated factors contributing to stapedectomy failure. RESULTS: The mean ISJ angle was 93.0 degrees (SD = 8.3 degrees ) (range, 75.0 degrees -104.0 degrees ). The mean ISJ angle deviation from 90 degrees was 7.35 degrees (SD = 4.45 degrees ) (range, 0.3 degrees -15.0 degrees ). The mean distance along the incus accessible for prosthesis placement was 3.21 mm (SD = 0.55 mm) (range, 2.00-4.00 mm). CONCLUSIONS: Significant deviation of the ISJ angle from 90 degrees was found (P <.0001). The length along the incus accessible for prosthesis placement was sufficient to result in errors in prosthesis size selection and crimping with only small variations in the ISJ angle. Incorrect prosthesis sizing and crimping are frequently associated with stapedectomy failure. Variations in ISJ anatomy should be considered when selecting stapes prostheses lengths and may affect crimping technique.

Culture Techniques↗

PubMed2003

Vestibular dysfunction after cochlear implantation.

OBJECTIVE: To determine the prevalence, symptom characteristics, and potential risk factors for vestibular symptoms after cochlear implantation. STUDY DESIGN: Case-control study design embedded within an ongoing cohort of patients undergoing implantation. SETTING: Academic medical center cochlear implant research program funded by the National Institutes of Health. PATIENTS: Seventy five eligible consecutive patients undergoing cochlear implantation. INTERVENTION: Medical record review. MAIN OUTCOME MEASURE: Recorded symptoms of vestibular symptoms after cochlear implantation. Subjects with vestibular symptoms were considered case subjects; those without vestibular symptoms were considered control subjects. RESULTS: Twenty-nine of 75 (39%) patients experienced dizziness postoperatively. Four patients experienced a single, transient acute vertigo attack occurring less than 24 hours after surgery. The majority, 25 patients, experienced delayed, episodic onset of vertigo. The median (interquartile range) time of delayed onset was 74 (26-377) days after implantation. Delayed dizziness manifested as spontaneous episodic or positional vertigo. Preoperative dizziness, age at implantation, and age at onset of hearing loss were significantly greater in the dizzy group. Preoperative electronystagmography did not differentiate between groups. CONCLUSIONS: Thirty-nine percent (29/75) of subjects with implants were dizzy after implantation. The majority of subjects experienced dizziness in a delayed episodic fashion. Dizziness was not related to implant activation. It seemed that delayed dizziness was not related to immediate surgical intervention but could result from chronic changes occurring in the inner ear; there was some suggestion this could take the form of endolymphatic hydrops.

Acute Disease↗

PubMed2002

Pathogenicity of Beauveria bassiana, Metarhizium anisopliae (Deuteromycotina: Hyphomycetes), and other entomopathogenic fungi against Lygus lineolaris (Hemiptera: Miridae).

The pathogenicity of 32 fungal isolates from the genera of Beauveria, Verticillium, Paecilomyces, Metarhizium, Mariannaea, and Hirsutella to second-instar tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was tested under laboratory conditions. These isolates originated from various insect hosts and substrates from France, Denmark, Austria, Italy, Turkey, Syria, and the United States. A single exposure concentration (1 x 10(7) conidia/ ml) assay for each isolate was first conducted by immersing the insects in 10 ml of a fungal suspension for 5s. These were followed by concentration-mortality assays on five of the most pathogenic isolates using four test concentrations ranging from 2 x 10(4) to 2 x 10(7) conidia/ml. B. bassiana 726 (Bemisia-passaged GHA strain) was used as a standard for comparison in all of the assays. Among the test isolates, three produced mortality not significantly different from the water control. Mortality ranged from 35 to 98% among the other 29 isolates. The LC50 values of the five most pathogenic isolates ranged from 0.8 to 5.0 x 10(5) conidia/ml. The LT50 values for these isolates ranged from 6.0 to 6.9, 3.1 to 5.1, and 2.5 to 4.0 d for concentrations of 2 x 10(5), 2 x 10(6), and 2 x 10(7) conidia/ml, respectively. Two strains of B. bassiana (ARSEF 1394,5665) and one M anisopliae (ARSEF 3540) were more pathogenic to the nymphs than the standard, having significantly lower LC50 and LT50, values. Our results demonstrated that several genera of entomopathogenic fungi have promise as microbial control agents against L. lineolaris.

Animals↗