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J Chappell

Publications and source records attributed to J Chappell.

7 recordsLinked to original sources
PubMed1992

Gene family for an elicitor-induced sesquiterpene cyclase in tobacco.

The initial step in the conversion of the isoprenoid intermediate farnesyl diphosphate to the sesquiterpenoid phytoalexin capsidiol in elicitor-treated tobacco tissues is catalyzed by an inducible sesquiterpene cyclase [5-epi-aristolochene synthase (EAS)]. Two independent cDNA clones (cEAS1 and cEAS2) encoding EAS were isolated from an elicitor-induced tobacco cDNA library by differential hybridization and subsequently were characterized by hybrid selection--in vitro translation. Insertion of cEAS1, a partial cDNA clone encoding 175 C-terminal amino acids, into an Escherichia coli expression vector resulted in accumulation of a fusion protein immunodetectable with EAS-specific polyclonal antibodies. The cDNA clones were used to isolate two full-length EAS genes that mapped 5 kilobases (kb) apart on one 15-kb genomic clone. The nucleotide sequences of the structural gene components were identical from 388 base pairs (bp) upstream of the transcription initiation site to 40 bp downstream of the translation termination codon, suggesting a relatively recent duplication event. The genes consist of 1479-bp open reading frames, each containing five introns and specifying 56,828-Da proteins. The N-terminal amino acid sequence deduced from the genomic clones was identical to the first 16 amino acids of the EAS protein identifiable by Edman degradation. RNA blot hybridization with cEAS1 demonstrated a mRNA induction time course consistent with the induction of the EAS mRNA translational activity with maximum levels 4-6 h after elicitation. EAS mRNA was not detected in control cells. DNA blot-hybridization analysis of genomic DNA revealed a copy number of approximately 12-15 for EAS-like genes in the tetraploid tobacco genome. The conservation of a putative allelic prenyl diphosphate binding motif is also discussed.

Alkyl and Aryl Transferases↗
PubMed1991

Inhibition of a plant sesquiterpene cyclase by mevinolin.

The specificity of mevinolin as an inhibitor of sterol and sesquiterpene metabolism in tobacco cell suspension cultures was examined. Exogenous mevinolin inhibited [14C]acetate, but not [3H]mevalonate incorporation into free sterols. In contrast, mevinolin inhibited the incorporation of both [14C]acetate and [3H]mevalonate into capsidiol, an extracellular sesquiterpene. Microsomal 3-hydroxy-3-methylglutaryl Coenzyme A reductase was inhibited greater than 90% by microM mevinolin, while squalene synthetase was insensitive to even 600 microM mevinolin. Sesquiterpene cyclase, the first branch point enzyme specific for sesquiterpene biosynthesis, was inhibited in a dose-dependent manner by mevinolin with a 50% reduction in activity at 100 microM. Kinetic analysis indicated that the mechanism for inhibition was complex with mevinolin acting as both a competitive and noncompetitive inhibitor. The results suggest that the mevinolin inhibition of [3H]mevalonate incorporation into extracellular sesquiterpenes can, in part, be attributed to a secondary, but specific, site of inhibition, the sesquiterpene cyclase.

Acetates↗
PubMed1979

Congenital euryblepharon.

Three cases of congenital euryblepharon are presented. In these cases, horizontal width of the eyelid margin is abnormally increased in comparison to the globe and orbit. The 3 cases were all different. One case had involvement of all 4 lids. Another had unilateral involvement of upper and lower eyelids. A third case had bilateral lower lid involvement associated with other anomalies. The additional anomalies which have not been previously reported include a double row of meibomian gland orifices and an extreme lateral displacement of the lower canaliculus and punctum. All cases had varying degrees of vertical shortage of skin in the involved lids leading to lagophthalmos with a mild to moderate exposure keratitis. A review of previously reported cases of euryblepharon is made. The types of surgical procedures used to correct the deformities are discussed.

Child↗
PubMedDate not supplied

Augmenting the critical care data base of junior medical students with an emergency medicine lecture curriculum: a controlled study.

A mandatory lecture course in emergency medicine, consisting of 13 lectures, was given to junior medical students over 3 years at Texas Tech University Regional Academic Health Center--El Paso. The performance of the students on a 25-question pretest and posttest was compared to a statistically similar group of their classmates on geographically separate campuses of Texas Tech University School of Medicine undergoing an otherwise comparable junior year clinical curriculum. Both groups exhibited improvement in posttest scores from pretest score values; additionally, students exposed to the lecture series at Texas Tech--El Paso performed significantly higher on the posttest, compared to the other campuses. We conclude that some emergency medicine material is successfully learned by junior medical students during their required third year clerkships; however, important learning objectives within the domain of emergency medicine can be most successfully taught if a mandatory junior year lecture course in emergency medicine is also incorporated into the third year curriculum.

Critical Care↗
PubMedDate not supplied

A 40,000 year-old human occupation site at Huon Peninsula, Papua New Guinea.

The geographical position of the island of New Guinea suggests that it may have been an early staging post in the Pleistocene settlement of Australia from the Indonesia-Indochina region. Previous data have not supported this, as archaeological sites 35,000 to 40,000 years old occur in southern Australia, whereas the earliest previously known in Papua New Guinea is 26,000 years old. We now report evidence that the north coast of Papua New Guinea was occupied at least 40,000 years ago. Sahuland, which is the greater land area of Australia and New Guinea plus their connecting continental shelf exposed as land when Pleistocene sea levels were lower than now, was occupied by humans in several widely separated areas at that time. A distinctive 'waisted axe' culture appears to have existed in New Guinea and probably in Australia in the Late Pleistocene, but antecedents are not yet known from east and southeast Asia. There is evidence for hafting of these tools at a date which is earlier than known elsewhere in the world.

Animals↗