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Biomedical subjects

L M Field

Publications and source records attributed to L M Field.

At least 55 records · Page 3Linked to original sources
PubMed1998

Evidence that the E4 and FE4 esterase genes responsible for insecticide resistance in the aphid Myzus persicae (Sulzer) are part of a gene family.

The amplification of genes encoding the esterases E4 and FE4 is a widespread mechanism of insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer). We present evidence that in susceptible aphids the two genes are adjacent to each other in a head-to-tail arrangement with E4 upstream of FE4 and with approx. 19 kb of intervening sequence. There are also at least two other closely related sequences which might come from other members of an esterase gene family, in line with reports of other insect gene families encoding detoxifying enzymes. The close identity between E4 and FE4 genes indicates a recent duplication and divergence. The subsequent amplifications giving multiple copies of either E4 or FE4 must have involved two separate events, each probably occurring once and then being selected by insecticide exposure and spread by migration. The cloning of sequences upstream of the FE4 gene suggest, by comparison with E4, that the two genes are regulated in different ways. FE4 has sequences corresponding to a conventional promoter (TATA box and CAP site) that are not present in E4; on the other hand, FE4 lacks the CpG island present 5' of E4 genes that may control expression through changes in DNA methylation. The differences are likely to have occurred by the duplication event that gave rise to E4 and FE4 leading to different 5' sequences.

Animals↗
PubMed1997

Structure and organization of amplicons containing the E4 esterase genes responsible for insecticide resistance in the aphid Myzus persicae (Sulzer).

Insecticide resistance in the aphid Myzus persicae results primarily from the amplification of genes encoding the insecticide-detoxifying esterase, E4. Here we report the analysis of flanking DNA co-amplified with the E4 gene. The 5' end of this gene has an untranslated leader sequence interspersed by two introns, and the promoter region lacks TATA and CAAT boxes. The DNA breakpoint involved in the generation of the amplification is just upstream (approx. 250 bp) of the putative E4 transcription start site; thus the E4 gene is very close to the 5' end of the approx. 24 kb amplicon. PCR primers specific to the 'novel joint' generated during the amplification have been used to show that a wide range of aphid clones have the same amplicons, arranged as a series of head-to-tail direct repeats. Long-distance mapping has revealed the structure of these repeats. This has important implications for understanding both the generation of the amplified genes and the origin and spread of insecticide resistance in M. persicae.

Animals↗
PubMed1997

Bilevel tumescent anesthetic infiltration for hair transplantation.

BACKGROUND: A dual level of tumescent anesthetic infiltration has been found to expedite hair graft or strip harvesting for hair transplantation, reducing bleeding, and increasing the exit angle of the hairs, thereby promoting increased survivorship of hair shafts and bulbs. OBJECTIVE: To acquaint the readership with this variation of anesthetic tumescent technique in hair transplantation. METHODS: Patients were utilized for this study during international teaching exchanges. Larger multiport infiltrators were used for the deep infiltration; smaller and more narrow infiltrators were used for the more superficial anesthetic administration. RESULTS: Subcutaneous compression and a bilevel vasoconstriction in both donor and recipient sites resulted in an increased upwardly angled exit angle of the hairs to be harvested, an increased separation of individual hair shafts, and reduced bleeding. Placement of the correct incisional angle of instruments inserted into the donor site was facilitated. CONCLUSION: Utilization of a bilevel tumescent anesthetic infiltration technique is a superior method of anesthesia for hair transplant harvesting and transplanting. Bleeding at both occipital donor and frontal recipient sites was negligible.

Anesthesia, Local↗