PubMed Health⌕ Search

Biomedical subjects

B K Mitchell

Publications and source records attributed to B K Mitchell.

17 recordsLinked to original sources
PubMed2001

Olfaction in the Colorado potato beetle: ultrastructure of antennal sensilla in Leptinotarsa sp.

Sensillae on the antennae of the Colorado potato beetle, Leptinotarsa decemlineata are described using scanning (SEM) and transmission (TEM) electron microscopy and compared with SEM observations of antennal sensilla in L. haldemani and L. texana. In all the three species, 13 distinct sensillar types were identified with a higher density of sensilla in the more polyphagous species, L. decemlineata than in the moderately host specific L. haldemani and the highly host specific L. texana. Cuticular specializations and the predominance of olfactory sensilla are discussed in relation to host specificity in the three species.

Animals↗
PubMed2000

Oviposition by Plutella xylostella (Lepidoptera: Plutellidae) and effects of phylloplane waxiness.

Three approaches were used to investigate effects of host plant epicuticular waxes on oviposition site selection by Plutella xylostella (L.). In the first approach, oviposition on canola (Brassica napus L.) that had epicuticular wax reduced by application of a carbamate herbicide (S-ethyl dipropylthiocarbamate) was compared with oviposition on untreated control plants. A second approach compared oviposition on sibling strains of B. napus with different wax blooms (glossy and waxy), and a third approach compared oviposition by P. xylostella on parafilm that had been applied to glossy and waxy B. napus strains for transfer of leaf components. Significantly more eggs were deposited on herbicide-treated plants (with reduced epicuticular wax) than on untreated controls. Similarly, more eggs were deposited on glossy than on waxy sibling strains of B. napus. In parafilm assays significantly more eggs were deposited on treated than on untreated parafilm. Several mechanisms could explain the differences in attractiveness of surfaces with varying wax content as oviposition sites for P. xylostella, including visual, chemical, and tactile differences between substrates. These mechanisms are discussed.

Animals↗
PubMed1999

Peripheral and central structures involved in insect gustation.

Studies in insect gustation have a long history in general physiology, particularly with work on fly labellar and tarsal sensilla and in the general field of insect-plant interactions, where work on immature Lepidoptera and chrysomelid beetles has been prominent. Much more emphasis has been placed on the physiological characteristics of the sensory cells than on the central cellular mechanisms of taste processing. This is due to the fairly direct access for physiological experimentation presented by many taste sensilla and to the obvious importance of tastants in insect feeding and oviposition behaviour. In some of the insect models used for gustatory studies, advances have been made in understanding the basic morphology of the central neuropils involved in the first stages of taste processing. There is much less known about the physiology of interneurons involved. In this review, we concentrate on four insect models (Manduca sexta, Drosophila melanogaster, Neobellieria bullata (and other large flies), and Apis mellifera) to summarize morphological knowledge of peripheral and central aspects of insect gustation. Our views of current interpretations of available data are discussed and some important areas for future research are highlighted.

Animals↗
PubMed1996

Mechanism of technetium 99m sestamibi parathyroid imaging and the possible role of p-glycoprotein.

BACKGROUND: Localization of parathyroid glands is critical in the treatment of recurrent or persistent hyperparathyroidism. Technetium sestamibi imaging may improve localization; however, the mechanism of visualization of parathyroid tissue remains unclear. On the basis of the chemical structure of sestamibi it has been suggested that p-glycoprotein is involved in the transport of sestamibi across cell membranes. This study was designed to examine sestamibi uptake and retention and p-glycoprotein expression in normal and abnormal parathyroid tissue. METHODS: Thirty-two consecutive patients underwent 2-methoxy-isobutyl-isonitrile imaging immediately before parathyroid exploration. Tissue was obtained from normal and abnormal parathyroids and from the thyroid gland. Touch preparations gave rapid confirmation of tissue origin. Specimens were trimmed and weighed, and gamma-emission was counted. Percentage injected dose per gram of tissue was calculated. Immunohistochemistry was obtained with a battery of monoclonal antibodies to identify p-glycoprotein in parathyroid tissue submitted for permanent histologic examination. Slides were graded by a pathologist familiar with immunohistochemistry. RESULTS: Abnormal parathyroid tissue had a higher mean retention of injected dose per gram than did normal thyroid and parathyroid tissue. Immunohistochemistry revealed that abnormal parathyroid tissue expresses less p-glycoprotein. CONCLUSIONS: These results suggest that size is not the single determinant of parathyroid visualization and that p-glycoprotein expression may be involved in the mechanism of parathyroid imaging.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Localization studies in patients with hyperparathyroidism.

Patients with hyperparathyroidism who have not had previous neck surgery do not require preoperative localization because of the high success rate of cervical exploration (95%) and the limited sensitivity and specificity of all imaging modalities currently in use. Successful parathyroid exploration requires knowledge of the normal and frequently encountered variations in parathyroid anatomy (Fig. 4). Experience permits recognition of often subtle multiple gland disease. In skilled surgical hands, results are excellent with minimal morbidity. When recurrent or persistent disease or previously operated patients are encountered, confirmation of the diagnosis and attempts at localization should precede operation. Technetium sestamibi SPECT imaging and ultrasonography with FNA of suspicious glands are complementary tests that are readily available, inexpensive, and well tolerated by patients. If these tests are unsuccessful, MRI, CT, and invasive procedures should be pursued until the gland is localized.

Biopsy, Needle↗
PubMed1994

Prehospital recognition of AMI using independent nurse/paramedic 12-lead ECG evaluation: impact on in-hospital times to thrombolysis in a rural community hospital.

Because the benefits from thrombolytic therapy in acute myocardial infarction (AMI) are time dependent, multiple strategies have been devised to speed therapy. This study sought to determine whether hospital-based nurse and paramedic advanced life support (ALS) providers could be trained to independently evaluate (sight read) a prehospital 12-lead electrocardiogram (ECG) for the presence of AMI as part of a protocol designed to speed in-hospital administration of thrombolytic agents. Providers were required to determine on the basis of a protocol (1) whether or not AMI was present, and (2) whether or not thrombolytic therapy was indicated. Providers then radioed their impression to the emergency department (ED) and initiated a protocol to prepare identified candidates for thrombolysis. The final decision to initiate thrombolytic therapy was made by the ED physician after patient arrival at the hospital. One hundred fifty-five patients with chest pain were studied. Twenty-one (13.5%) were ultimately proven in-hospital to have AMI. Providers were able to recognize AMI in 17 of 21. Four of 21 did not meet ECG criteria for AMI on the field ECG, but were categorized as having a high index of suspicion for AMI by providers. There were no false-positive diagnoses. Fourteen patients (9%) received thrombolytic therapy. In-hospital times to administration of thrombolytic therapy decreased to an average of 22 +/- 13.8 minutes in the studied group compared with a historical control group average of 51 +/- 50 minutes. It is concluded that hospital-based paramedics and nurses can successfully be taught to evaluate (ie, sight read) a prehospital ECG for the presence of AMI with accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Protocols↗
PubMed1992

Interneurons of the subesophageal ganglion of Sarcophaga bullata responding to gustatory and mechanosensory stimuli.

Intracellular recordings were made from interneurons in the subesophageal ganglion (SEG) of Sarcophaga bullata while stimulating the labellar lobes with solutions of sucrose, NaCl and with distilled water. Neurons that responded to sucrose did not respond to NaCl and vice versa, while sucrose-sensitive neurons often responded weakly to water. Several of the recorded neurons were filled with Lucifer Yellow, and their morphology was reconstructed. Most showed extensive arborizations within the SEG, suggesting that they were local interneurons involved in the early stages of gustatory processing. Some of the filled neurons had extensive projections to the brain, in addition to arborizations in the SEG. This is the first published record of gustatory interneurons in the higher flies.

Animals↗
PubMed1985

Properties of an Escherichia coli mutant deficient in phosphoenolpyruvate carboxylase catalytic activity.

A mutant Escherichia coli (Ppcc-) which was unable to grow on glucose as a sole carbon source was isolated. This mutant had very low levels of phosphoenolpyruvate carboxylase activity (approximately 5% of the wild type). Goat immunoglobulin G prepared against wild-type phosphoenolypyruvate carboxylase cross-reacted with the Ppcc- enzyme. The amount of enzyme protein in the mutant cells was similar to that found in wild-type cells, but it had greatly diminished specific activity. The catalytically less active mutant enzyme retained the ability to interact with fructose 1,6-bisphosphate, but did not exhibit stabilization of the tetrameric form by aspartate. The pI of the mutant protein was lower (4.9) than that of the wild-type protein (5.1). After electrophoresis and immunoblotting of the partially purified protein, several immunostaining bands were seen in addition to the main enzyme band. A novel method for showing that these bands represented proteolytic fragments of phosphoenolpyruvate carboxylase was developed.

Antibodies, Bacterial↗
PubMed1976

Physiology of an ATP receptor in labellar sensilla of the tsetse fly Glossina morsitans morsitans Westw. (Diptera: Glossinidae).

Electrophysiological recordings have been made from cells in the eight large, labellar sensilla of g. morsitans. One of these cells in each sensillum was shown to respond to ATP over a concentration range of 10(-6)-10(-3) M. It was also sensitive to several other adenosine phophates, but much less sensitive to CTP, GTP and ITP. The activity of the receptor was depressed below pH 7, and sometimes considerably increased above pH 9. These aspects the receptor's physiology support the results of behavioural studies. It is concluded that the eight receptors mediate the flies' behavioural response to ATP.

Action Potentials↗