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Biomedical subjects

F M Davis

Publications and source records attributed to F M Davis.

At least 19 recordsLinked to original sources
PubMed2003

Impact of a novel species of Nosema on the southwestern corn borer (Lepidoptera: Crambidae).

A study was undertaken to elucidate the impact of an undescribed Nosema sp. on the southwestern corn borer (SWCB; Diatraea grandiosella Dyar). The Nosema sp. (isolate 506) included in the study was isolated from an overwintering SWCB larva in Mississippi. It was highly infectious per os, with a median infective dose of 2.0 x 10(3) spores per larva. Even at the highest dosage tested (10(7) spores per larva), minimal mortality (< or = 3%) was observed in infected larvae, pupae, and adults reared in the laboratory on an artificial diet. However, infected pupae (0- and 7-d-old) were smaller, and the time to adult eclosion from pupation was slightly increased. Furthermore, the number of eggs produced by infected SWCB female moths substantially decreased (32%), and this effect was most pronounced on day 2, when the greatest number of eggs were oviposited by infected and noninfected moths. For eggs produced by infected females mated with infected males, hatch was slightly decreased by 16 and 15% for eggs laid on days 2 and 3, respectively. In addition, egg hatch was reduced in eggs oviposited by noninfected females mated with infected males on day 3. A low prevalence of infection (< 6%) was observed in the F1 generation originating from infected females mating with noninfected males, from noninfected females mating with infected males, and from infected females mating with infected males. Nosema 506 spores were observed in the proximity of reproductive tissues of infected female and male moths. Spores also were detected on the chorion surface and within eggs laid by infected females. Furthermore, 1-11% of larvae hatching from surface-sterilized eggs were infected by Nosema 506 indicating a transovarial mechanism of transmission.

Animals↗
PubMed2001

Impact of Bt cottons expressing one or two insecticidal proteins of Bacillus thuringiensis Berliner on growth and survival of noctuid (Lepidoptera) larvae.

A series of laboratory assays were performed to compare the relative impact of commercial and experimental cultivars of cotton, Gossypium hirsutum (L.), expressing zero, one, or two insecticidal proteins of Bacillus thuringiensis Berliner, on several lepidopteran pests. Assays in which larvae were fed fresh plant tissue indicated that dual-toxin B. thuringiensis (Bt) cultivars, expressing both Cry1Ac and Cry2Ab endotoxins of B. thuringiensis, were more toxic to bollworms, Helicoverpa zea (Boddie), fall armyworms, Spodoptera frugiperda (J. E. Smith), and beet armyworms, Spodoptera exigua (Hubner), than single-toxin cultivars expressing Cry1Ac. Assays in which lyophilized plant tissue was incorporated into artificial diet also indicated improved activity of the dual-toxin Bt cultivar compared with single-toxin plants. Both bollworm and tobacco budworm, Heliothis virescens (F.), growth was reduced by Bt cotton, particularly the dual-toxin cultivar. Although assays with lyophilized tissues were done using largely sublethal doses, bollworm survival was reduced by the dual-toxin cultivar. It appears that this newly developed Bt cotton expressing two toxins will be more effective and have a wider range of activity on these lepidopteran pests.

Animals↗
PubMed2000

A unique 33-kD cysteine proteinase accumulates in response to larval feeding in maize genotypes resistant to fall armyworm and other Lepidoptera.

Plants respond to insect feeding with a number of defense mechanisms. Using maize genotypes derived from Antiquan germ plasm that are resistant to Lepidoptera, we have demonstrated that a unique 33-kD cysteine proteinase accumulates in the whorl in response to larval feeding. The abundance of the proteinase increased dramatically at the site of larval feeding after 1 hr of infestation and continued to accumulate for as long as 7 days. The 33-kD cysteine proteinase was most abundant in the yellow-green portion of the whorl-the normal site of larval feeding and the tissue that has the greatest inhibitory effect on larval growth in bioassays. The proteinase was expressed in response to wounding and was found in senescent leaves. It may be a marker of programmed cell death. The gene coding for the proteinase, mir1, has been transformed into Black Mexican Sweet callus. When larvae were reared on callus expressing the proteinase, their growth was inhibited approximately 60 to 80%. The expression of a cysteine proteinase, instead of a cysteine proteinase inhibitor, may be a novel insect defense mechanism in plants.

Animals↗
PubMed2000

Influence of whorl region from resistant and susceptible corn genotypes on fall armyworm (Lepidoptera: Noctuidae) growth and development.

The effect of diets prepared from whorl tissue of resistant and susceptible corn genotypes, Zea mays L., on the larval growth, development, and physiology of fall armyworm, Spodoptera frugiperda (J. E. Smith), was analyzed. Larvae reared on an optimized artificial diet had a higher growth rate and developed faster than those reared on lyophilized whorl tissue from resistant and susceptible genotypes. Larvae reared on the resistant material were smaller and had a longer developmental period. Larvae reared on yellow-green and green whorl sections from resistant plants were significantly smaller than those reared on the same sections of susceptible plants. There was no significant difference in weight when larvae were reared on the yellow whorl regions from either resistant or susceptible lines. Physiological indices were determined for larvae fed resistant and susceptible lyophilized and fresh whorl material. Larvae fed resistant lyophilized material had significantly lower growth rate (GW) and efficiency of conversion of ingested food to body substance (ECI) than those reared on artificial diet or susceptible material. However, there were no significant differences in consumption index (CI), approximate digestibility (AD) and efficiency of conversion of digested food to body substance (ECD) between larvae reared on lyophilized tissue from resistant and susceptible genotypes. Larvae reared on fresh yellow-green whorl sections from resistant plants had significantly lower GW, ECI, and ECD than those reared on susceptible material. In contrast, no significant differences in any of the estimated food consumption and utilization indices were observed between larvae reared on fresh yellow whorl sections from resistant or susceptible plants. These results suggest that some components of whorls from resistant plants, especially the yellow-green region, inhibit food utilization in fall armyworm larvae.

Animals↗
PubMed2000

Conventional resistance of experimental maize lines to corn earworm (Lepidoptera: Noctuidae), fall armyworm (Lepidoptera: Noctuidae), southwestern corn borer (Lepidoptera: Crambidae), and sugarcane borer (Lepidoptera: Crambidae).

Plant resistance is a useful component of integrated pest management for several insects that are economically damaging to maize, Zea mays L. In this study, 15 experimental lines of maize derived from a backcross breeding program were evaluated for resistance to corn earworm, Helicoverpa zea (Boddie); fall armyworm, Spodoptera frugiperda (J. E. Smith); southwestern corn borer, Diatraea grandiosella Dyar; and sugarcane borer, Diatraea saccharalis (F.). Experimental line 100-R-3 was resistant in the field to leaf feeding by fall armyworm and line 116-B-10 was resistant in the field to leaf feeding by fall armyworm and leaf and stalk feeding by southwestern corn borer. When corn earworm larvae were fed field harvested silks from experimental line 81-9-B in the laboratory, their pupal weights were significantly lower than the pupal weights of larvae that were fed silks from the resistant control, Zapalote Chico. Maysin levels lower than those commonly associated with corn earworm resistance were present in the resistant experimental line, 107-8-7, indicating a new basis confers resistance to corn earworm in this line. These resistant experimental lines will provide plant breeders with new sources of resistance to lepidopterous insects for the development of improved maize breeding populations.

Animals↗
PubMed2000

Pathogens associated with southwestern corn borers and southern corn stalk borers (Lepidoptera: Crambidae).

A study was undertaken to isolate entomopathogens of southwestern corn borer, Diatraea grandiosella Dyer, and southern corn stalk borer, Diatraea crambidoides (Grote). Field-collected diapausing larvae of southwestern corn borer (three sites in Mississippi) and southern corn stalk borer (one site in North Carolina), and a laboratory strain of D. grandiosella in the diapause state were maintained in a simulated winter followed by a simulated spring environnent. Few larvae (< or = 6%) collected from any of the field sites died in the winter environment, and most insect mortality (11-25%) occurred after transfer of the larvae to the simulated spring environment. Mortality during the simulated spring period differed among the collection sites, and the highest mortality was recorded for southwestern corn borers from Washington County (25%), followed by Marshall (16%) and Oktibbeha (11%) Counties. A high level of mortality was also observed in southern corn stalk borers during the simulated spring period (27%). No viruses were observed, but a number of bacteria, microsporidia, and fungi were isolated from both southwestern corn borer and southern corn stalk borer larvae and pupae. In most instances, numerous bacterial taxa were isolated from cadavers, but on some occasions a single taxon predominated. The most prevalent bacterial taxon from larval and pupal cadavers was Enterococcus faecalis (Andrewes & Horder) Schleifer & Kilppel-Balz, but Bacillus spp., Pseudomonas aeruginosa (Schroeter) Migula, and Serratia marcescens Bizio were frequently isolated as well. Few fungi (1-7%) were recovered from southwestern corn borer and southern corn stalk borer larvae and pupae. The most common entomopathogenic taxon isolated was Beauveria bassiana (Balsamo) Vuillemin from southern corn stalk borer larvae. Microsporidia were not isolated from southern corn stalk borers. However, Nosema spp. were isolated from southwestern corn borer cadavers from Washington (15%), Marshall (1%), and Oktibbeha (3%) Counties in Mississippi. In addition, we observed parasitism of southern corn stalk borer larvae by Macrocentrus cingulum Reinhard (Hymenoptera: Braconidae). No parasitism of southwestern corn borers was observed. Isolates of Bacillus, Beauveria, Entercoccus, Nosema, Pseudomonas and Serratia were all pathogenic to southwestern corn borer larvae under controlled environmental conditions, and with the exception of B. bassiana, these are novel pathogens of Diatraea corn borers.

Animals↗
PubMed1999

Subsequent general anaesthesia in patients with a history of previous anaphylactoid/anaphylactic reaction to muscle relaxant.

Of 151 patients with a possible anaphylactoid/anaphylactic reaction to a muscle relaxant investigated over a 20-year period, follow-up for any subsequent general anaesthesia was complete in 145 (96%). One hundred and twenty-two anaesthetics in 72 patients were documented. There were no anaesthetic-related deaths. No subsequent reactions were seen if muscle relaxants were not used in the subsequent anaesthetic, nor were they in patients with severe reactions if the original intradermal test had been equivocal or negative. In the patients with a severe reaction and a positive intradermal test to one or more muscle relaxants, six out of 40 later anaesthetics using muscle relaxants were associated with clinical problems, three being probable anaphylactic reactions, whilst three were minor. Intradermal testing should be performed prior to surgery in this group of patients for the muscle relaxant(s) planned, or an anaesthetic technique which avoids relaxants should be used. This review should encourage other centres to undertake similar follow-up.

Adult↗
PubMed1998

In vitro regulation of FcepsilonRIalpha expression on human basophils by IgE antibody.

In vivo studies suggested the possibility of an IgE-dependent regulation of high-affinity (FcepsilonRI) IgE receptor expression on basophils. The current studies extend these observations to in vitro cultures of human basophils. Incubation of basophils for 3 to 4 weeks resulted in a slow dissociation of IgE antibody, during which time FcepsilonRI expression decreased, as measured by flow cytometry using the anti-FcepsilonRIalpha monoclonal antibody, 22E7, or by measuring FcRIalpha mass by Western blotting of whole-cell lysates. Culture of basophils with IgE resulted in upregulation of FcepsilonRIalpha expression by both flow cytometry and Western blotting of whole-cell lysates. Upregulation followed a linear time course during 2 weeks of culture. The relative increase in FcepsilonRIalpha density depended on the starting density; with starting densities of FcepsilonRIalpha of 10,000 to 170,000 per basophil, the upregulation varied 20- to 1.1-fold, respectively. Upregulation occurred in high-purity basophils, was not influenced by IgG at concentrations up to 1 mg/mL, and was inhibited by dimeric IgE. Heat-inactivated IgE was less effective and the monoclonal antibody CGP51901 that prevents IgE binding to FcepsilonRIalpha blocked the ability of IgE to induce upregulation. The dose-response curve for IgE-induced upregulation had an effective concentration50 of 230 ng/mL. Although the receptor through which IgE induces this upregulation is not yet known, several characteristics suggest that the upregulation is mediated by IgE interacting through FcepsilonRIalpha itself.

Antibodies, Monoclonal↗
PubMed1997

Dermal and airway responses to monoclonal antibodies specific for canine IgE.

In order to understand mechanisms underlying variability of IgE-mediated responses in vivo, we compared effects of different monoclonal antibodies of IgE on dermal and airway responses in a group of atopic dogs. Using intradermal testing, fourteen antibodies were screened in Basenji-Greyhound dogs. For further comparisons between dermal and airway responses, we selected the two antibodies that stimulated the greatest and least dermal responses, respectively. These antibodies bound to IgE with similar affinities (4.1 +/- 0.2 x 10(9) and 1.5 +/- 0.2 x 10(10) M-1). Dose-response curves to intradermal testing were constructed for these two antibodies. On a separate occasion, peripheral airway resistance (Rp) was determined before and after aerosol challenge with an antibody or saline in the same dogs. For one antibody (affinity 4.1 +/- 0.2 x 10(9) M-1), Rp reached a maximum (407 +/- 142% above baseline; mean +/- SE, n = 6) 10 to 15 min after challenge, while maximum responses to saline (62 +/- 16% above baseline, p < 0.01) occurred immediately after aerosol delivery. Responses to the other antibody were similar (p = 0.068) to responses to saline. The magnitude of skin responses did not predict the magnitude of airway responses. These findings suggest that differences in affinities, alone, do not predict magnitude of responsiveness to the anti-IgE antibody and that mechanisms underlying skin and airway responses may differ qualitatively and/or quantitatively.

Airway Resistance↗
PubMed1997

Efficacy, pharmacodynamics, and pharmacokinetics of CGP 51901, an anti-immunoglobulin E chimeric monoclonal antibody, in patients with seasonal allergic rhinitis.

The efficacy, pharmacodynamics, and pharmacokinetics of CGP 51901, a recombinant monoclonal mouse-human chimeric anti-human immunoglobulin E (IgE) antibody were evaluated for 153 patients with seasonal allergic rhinitis treated with placebo or with 15, 30, or 60 mg CGP 51901 in six biweekly doses. Seasonal allergic rhinitis was chosen to validate the concept of anti-IgE therapy because the causal and temporal relation between allergen confrontation and IgE-mediated evocation of symptoms is firmly established. A sustained 85% or greater reduction of serum free IgE levels was shown to be effective in improving clinical symptoms. The concentration of CGP 51901 needed to maintain 85% or greater reduction of IgE was estimated to be about 5000 ng/ml. Baseline IgE levels and body weights of the patients greatly influenced the pharmacokinetic and pharmacodynamic profiles of CGP 51901. A population model was developed and refined to take into account patient baseline IgE level and body weight. The model was able to help predict multiple-dose pharmacokinetic and pharmacodynamic profiles on the basis of single-dose pharmacokinetic and pharmacodynamic measurements in the therapeutically effective dose range.

Adult↗
PubMed1996

Structural features of the extracellular portion of membrane-anchoring peptides on membrane-bound immunoglobulins.

Membrane-bound immunoglobulins, mIgs, are displayed as transmembrane proteins on the surface of B cells, where they serve as antigen receptors. The mIgs are anchored to the membrane through a carboxy-terminal extension of the immunoglobulin heavy chain. Three distinct structural regions of these membrane-anchor peptides, of mouse and human mIgs, have been delineated: (1) a central conserved stretch of 25 hydrophobic, unchanged amino acid residues, which spans the membrane lipid bilayer; (2) a C-terminal hydrophilic region of 3-28 amino acids, which is intracytoplasmic; and (3) an N-terminal extracellular hydrophilic region of 13-67 amino acids, which is isotype-specific. Here we report predicted secondary and tertiary structures of the third structural region of the membrane anchoring peptide along with corroborating experimental evidence. The predictions of secondary and tertiary structure indicate that most of these regions can assume an chi-helical conformation. Circular dichroism spectroscopy of corresponding synthetic peptide confirms this essential feature. The choice of solvent and pH have dramatic effects on peptide helicity; solvent conditions consistent with a membrane-proximal environment promote helicity. Additional studies suggest that the two adjacent extracellular peptides may be stabilized through coiled-coil interactions similar to those described for some other transmembrane proteins.

Amino Acid Sequence↗
PubMed1996

Physical aspects of total-body irradiation at the Middlesex Hospital (UCL group of hospitals), London 1988-1993: I. Phantom measurements and planning methods.

This paper, which is divided into parts I and II, describes the physical aspects of work on total-body irradiation (TBI) at the Middlesex Hospital, London, from 1988 to 1993. Irradiation is fractionated and bi-lateral with horizontal accelerator photon beams of 8 MV (1988-1992) at a source-surface distance (SSD) of 3.36 m and 10 MV (1992-1993) at an SSD of 4.62 m. The main aims were maximum patient comfort, a simple, accurate set-up with overall times per fraction of 30 min or less, dose homogeneity throughout the body within +/- 10 to +/- 15%, pre-irradiation treatment planning on nine CT slices using our commercial IGE RTplan (1988-1992) and Target 2 (1992-1993) treatment planning systems and, most important, verification of the plans by in vivo dosimetry to within +/- 5%. Verification of the planned lung doses, which are distributed over five CT slices, was given special attention. In part I of this paper we describe the preliminary work, most of which was done prior to patient treatment. This consisted of standard dosimetric measurements (central axis depth doses, beam profiles at several depths, build-up and build-down curves, beam output calibrations, effect of body compensators, etc), in evaluating silicon diode dosimeters for in vivo dosimetry and of adapting and verifying the methods of treatment planning for TBI conditions. The results obtained with phantoms, including a Rando body phantom, showed that, in principle, our aims could be achieved. The final proof depended, however, on an analysis of the results of the in vivo work and this forms the subject of part II of this paper.

Algorithms↗
PubMed1996

Physical aspects of total-body irradiation at the Middlesex Hospital (UCL group of hospitals), London 1988-1993: II. In vivo planning and dosimetry.

Part II of this paper gives the results of applying the TBI methods described in part I, to in vivo patient planning and dosimetry. Patients are planned on nine CT based body slices, five of which pass through the lungs. Planned doses are verified with ten silicon diodes applied bi-laterally to five body sites, at each treatment. LiF TLDs are applied to seven other body sites at the first treatment only. For 84 patients and at least 1016 measurements per body site with the diodes, the mean measured total doses agreed with planned doses within at most 2% except at lung levels, where the mean measured dose was 3% too low. Standard deviations of the measurements about the mean were between 2.4 and 3.1%. For the LiF TLDs, the mean measured doses for all seven body sites were with in +/- 5% of planned doses. A separate assessment of measured entrance and transmitted doses showed that the former agreed well with planned doses, but that the latter tended to be low, especially over the lungs, and that they had a wider dispersion. Possible reasons for this are discussed. These results show measurement uncertainties similar to those for non-TBI treatments of Nilsson et al, Leunens et al and Essers et al. An analysis of the treatment plans showed a mean dose inhomogeneity in the body (75 patients, nine slices) of 19 +/- 6.0% (1 s.d.) and in the lungs (40 patients, five slices) of 9.2 +/- 2.85% (1 s.d.). The conclusions are that, overall, the methods are reasonably satisfactory but that, with an extra effort, even closer agreement between measured and planned doses and a further limited reduction in the body dose inhomogeneity could be obtained. However, if it were thought desirable to make a substantial reduction in the dose inhomogeneity in the body and lungs, this could only be achieved with the available equipment by changing from lateral to anterior-posterior irradiation and any potential advantages of this change would have to be balanced against a likely deterioration in patient comfort and an increase in treatment set-up times.

Age Factors↗
PubMed1995

Management of scales and other insect debris: occupational health hazard in a lepidopterous rearing facility.

Scales and other body parts of Lepidoptera are known allergens and pose a serious health hazard for workers in rearing programs. Researchers of the Crop Science Research Laboratory (USDA-ARS), located at Mississippi State, MS, have reared lepidopterous insects since the late 1960s. Efforts have been made by them to continuously improve management of the moth scale problem and reduce allergic reactions suffered by workers. We developed strategy that requires a separate facility for housing the moth colonies, oviposition cages that facilitate exit of scales and other debris, an improved air filtration system, and sanitation procedures. The strategy used currently (coined ALERT for Advanced Lepidoptera Environmental Rearing Technology) for scale management efficiently minimizes this serious occupational hazard.

Air Pollutants, Occupational↗
PubMed1993

Can anti-IgE be used to treat allergy?

A summary of the properties of CGP 51901 is shown in Table 3. On the basis of its binding to IgE and IgE-secreting cells and its activity in vitro and in vivo, CGP 51901 is expected to be able to decrease serum IgE by direct clearance of IgE and by reduction of the numbers and productivity of IgE-secreting cells. The end result of reduction of IgE in the circulation and on mast cells is expected to be the attenuation of IgE-mediated reactions and the improvement in allergy symptoms. The effective serum concentration of CGP 51901 is expected to be in the range 1-10 micrograms/ml. Because CGP 51901 is an antibody specific for IgE, it is expected to be highly selective in its activity. Because IgE does not appear to be essential and because CGP 51901 has been rigorously tested to confirm its non-anaphylactic nature, this treatment is not expected to have any adverse effects. Therefore, CGP 51901 is expected to be safe and to have a good probability of being effective when it is tested in human clinical trials.

Animals↗
PubMed1992

A new isoform of human membrane-bound IgE.

The epsilon-chain of membrane-bound IgE on the surface of B lymphocytes is known to contain a membrane-anchoring peptide segment that is encoded by two membrane exons, me.1 and me.2. In analyzing pertinent segments in mRNA from human IgE-expressing B cells by using PCR methods and Northern blotting analyses, we have identified three species of mRNA of epsilon-chain with variations in the splicing of the membrane exons. The conventional species (m/s) contains the predicted me.1 and me.2; species m/1 harbors 156 extra nucleotides 5' of me.1 with unaltered reading frame; species s/t lacks me.1 and hence the segment encoding the hydrophobic transmembrane stretch and contains a shifted me.2 reading frame. Rabbit antibodies, which were prepared by immunization using a peptide of 36 amino acid residues representing an encoded segment unique to mRNA species m/l, could specifically bind to human IgE-expressing B cell lines and react with an epsilon-chain on Western immunoblots. These results indicate that there exists a previously unidentified isoform of human membrane-bound IgE.

Amino Acid Sequence↗