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Biomedical subjects

J Y Bradfield

Publications and source records attributed to J Y Bradfield.

13 recordsLinked to original sources
PubMed1999

Juvenile hormone inhibition of gene expression for cytochrome P4504C1 in adult females of the cockroach, Blaberus discoidalis.

The regulation and pattern of gene expression for cytochrome P4504C1 was measured in the fat body of adult females of the cockroach, Blaberus discoidalis. The level of CYP4C1-mRNA was high at adult emergence but disappeared after 4 days of adult life. In starved females, CYP4C1-mRNA levels declined by day 4 but increased steadily thereafter; by 25 days, the levels were nearly twice those observed at eclosion. Both the rapid early disappearance of the transcript and the starvation-related increase failed to occur following decapitation. Allatectomy also prevented the disappearance of CYP4C1-mRNA at day 4, and treatment of decapitated females with methoprene (JHA) stimulated a 70% decrease in transcript within 24 h. Injection of synthetic Blaberus hypertrehalosemic hormone (HTH) increased CYP4C1-mRNA by six-fold in the fat body of both intact and decapitated females. CYP4C1-mRNA in the fat body of males did not respond to JHA treatment. The dynamics of CYP4C1-mRNA in the fat body of females could be explained based on an inhibition of CYP4C1 expression by JH that was overcome by HTH.

Age Factors↗
PubMed1998

Juvenile hormone acid: evidence for a hormonal function in induction of vitellogenin in larvae of Manduca sexta.

In the tobacco hornworm (Manduca sexta), vitellogenin (Vg), the major yolk protein precursor, and its mRNA are first detectable in the prepupal stage; and production of both can be enhanced by methoprene, a juvenile hormone (JH) analog. Competence to respond to methoprene is acquired after ecdysteroid-initiated commitment for metamorphosis. Here we show that acquisition of competence requires prior exposure to JH-II acid in addition to ecdysteroid. Application of 20-hydroxyecdysone or RH5992, an ecdysteroid analog, to isolated abdomens from feeding larvae (precommitment) results in exposure of the dorsal vessel (EDV), a sign of metamorphic commitment--but such abdomens do not make Vg in response to methoprene. However, injection of JH-II acid along with 20-hydroxyecdysone into isolated abdomens causes Vg production in response to methoprene. Methoprene acid similarly induces competence to respond to methoprene. Northern blot analysis confirmed that Vg transcripts are present in fat body only if isolated abdomens were pretreated with both ecdysteroid, and JH-II acid or methoprene acid. The latter two can induce competence even in precocious prepupae resulting from removal of the corpora allata (the glands that produce JH) from early penultimate larvae. JH-III acid and related metabolites such as farnesol, farnesoic acid, and methyl farnesoate do not induce competence. Hitherto, JH acids have been regarded as precursors or catabolites of JHs. Here we show for the first time that JH acid has a hormonal function that cannot be performed by JH itself.

Abdomen↗
PubMed1997

Hypertrehalosemic hormone in a cockroach: molecular cloning and expression.

Hypertrehalosemic hormone (HTH) is a neuropeptide in the adipokinetic hormone/red pigment-concentrating hormone (AKH/RPCH) family that stimulates the synthesis of trehalose, the main blood sugar of many insects. The preproHTH of the cockroach Blaberus discoidalis was cloned from the corpora cardiaca (CC), the endocrine source for HTH, and the deduced sequence and organization of preproHTH were compared with other AKH/RPCH precursors. PreproHTH mRNA was determined to be approximately 0.5 kb in length as predicted by DNA sequence analysis. Northern blot analysis of the CC, ventral nerve cord, brain and fat body detected HTH-mRNA only in the CC. Levels of the HTH transcript in the CC were determined according to age, gender and mating. The HTH message was most abundant in the CC during the first several days of adult life in both sexes, then declined by 50% and were stable. HTH-mRNA levels in the CC did not respond to mating.

Aging↗
PubMed1993

Transferrin in a cockroach: molecular cloning, characterization, and suppression by juvenile hormone.

In a study of juvenile hormone-regulated gene expression, we isolated an anonymous cDNA representing a message that was strongly suppressed by juvenile hormone in the fat body of the cockroach Blaberus discoidalis. The protein deduced from the cDNA sequence showed compelling resemblance in sequence to the transferrins, a superfamily of internally duplicated, 80-kDa iron-binding/transport proteins characterized from several vertebrates and, to date, one insect (the tobacco hornworm, Manduca sexta). We isolated a 78-kDa protein from cockroach hemolymph, verified its congruence with the cloned cDNA, and found that it did bind iron. The cockroach protein is a member of the transferrin superfamily based on several features, including 32-46% amino acid positional identity with transferrins whose sequences are known, internal homology, positioning of cysteine residues, and iron binding. Whereas the previously characterized insect transferrin binds one atom of iron per protein molecule, B. discoidalis transferrin binds two iron atoms as do the vertebrate transferrins. The diferric property of cockroach transferrin is consistent with presence of two sets of residues positioned appropriately for iron binding. Juvenile hormone suppressed transferrin mRNA levels drastically in the adult female cockroach.

Adipose Tissue↗
PubMed1991

Cytochrome P450 family 4 in a cockroach: molecular cloning and regulation by regulation by hypertrehalosemic hormone.

Hypertrehalosemic hormone (a carbohydrate-mobilizing neuroendocrine decapeptide) and starvation markedly increased levels of a cockroach (Blaberus discoidalis) fat body cytochrome P450 message. The gene represented by the cloned P450 cDNA has been named CYP4C1 (cytochrome P450 family 4, subfamily C, gene 1), a newly identified member of the ubiquitous cytochrome P450 monooxygenase gene superfamily. Blaberus CYP4C1 (511 amino acids, Mr = 58,485) has a hydrophobic NH2 terminus and a sequence near the COOH terminus that is homologous to the cysteine-containing heme-binding region definitive of cytochromes P450. The cockroach sequence is 32-36% identical to mammalian family 4A and 4B enzymes. It contains a 13-residue sequence characteristic of family 4 but not other P450s. This study suggests that CYP4C1 is hormonally regulated in association with energy substrate mobilization and supports the idea that family 4 is an old and widespread gene family.

Amino Acid Sequence↗
PubMed1989

Adipokinetic hormone gene sequence from Manduca sexta.

A gene sequence encoding the neuropeptide adipokinetic hormone (AKH) was isolated from a genomic library of the tobacco hornworm, Manduca sexta. 2.5 x 10(5) recombinant plaques were screened with a 29-mer oligonucleotide substituted with deoxyinosine at six ambiguous codon positions. One clone was obtained from which we deduced an intronless gene encoding the AKH precursor (prepro-AKH). From NH2 to COOH terminus, prepro-AKH consists of a signal peptide, a single AKH peptide block followed by a Gly-Lys-Arg processing site, and a 34-residue sequence that appears unrelated to known peptides. The cloned AKH gene sequence hybridized to one transcript from the adult corpus cardiacum/corpus allatum complex. The Manduca genome appears to contain one copy of the AKH gene. These studies are a basis for explaining synthesis of a representative from a widespread, physiologically important family of arthropod neuropeptides.

Amino Acid Sequence↗
PubMed1988

Neuroendocrine and juvenile hormone effects on fat body protein synthesis during the reproductive cycle in female Blaberus discoidalis cockroaches.

Ovarian protein content and fat body protein synthesis were measured during the first gonotrophic cycle in virgin female Blaberus discoidalis cockroaches. Protein synthesis was measured for in vitro fat bodies from animals treated with combinations of a juvenile hormone analog (JHA = methoprene) and corpora cardiaca (CC) extracts. Ovarian protein content began to increase on Day 5 of adult life and reached its maximum at Days 20-22. Synthesis of proteins secreted by the in vitro fat body increased by 12-fold between emergence and its maximum on Day 18, then declined to nearly its original level by Day 33. Synthesis of nonsecreted, fat body proteins increased by 4-fold between emergence and a maximum on Day 21, then declined. CC extracts and JHA were administered to decapitated females to determine their regulative effects on fat body protein synthesis. The synthesis by the fat body of nonsecreted proteins was increased by both JHA and CC extracts. In contrast, synthesis of secreted proteins increased only in the presence of JHA. CC extracts, alone, had no effects on the synthesis of secreted proteins, but administration of CC extracts in combination with JHA increased the synthesis of the secreted proteins by 55% above that observed with JHA alone. SDS-PAGE of proteins secreted into the medium by the in vitro fat body demonstrated that JHA stimulated the synthesis of specific polypeptides, whereas CC extracts did not affect the synthesis of specific-secreted polypeptides. These results suggest that JH regulates specific protein synthesis by the fat body of B. discoidalis; neurohormones elevate the general capacity of the fat body for protein synthesis and amplify the specific effects of JH.

Age Factors↗
PubMed1985

An ubiquitous interspersed DNA sequence family in an insect.

The genome of the African migratory locust, Locusta migratoria (Class Insecta, Order Orthoptera, Family Acrididae) contains an interspersed DNA sequence family, designated the Lm1 family. This family consists of short (approximately 195-bp), widely dispersed, highly reiterated (approximately 6 X 10(5) copies/haploid genome) repeat units, which account for about 2% of the locust genome. Lm1 repeats contain regions that closely resemble internal promoter sequences for RNA polymerase III, and they are structurally very similar to RNA polymerase III templates. Family members are flanked by short direct repeats, and are closely linked to structural genes. These features are reminiscent of the Alu family of man and other repeat sequence families, until now documented only in higher vertebrates.

Animals↗
PubMed1977

AME seminar program in the United States: genesis, goals, and cost-benefit reflections.

The practicing physician's requirement for continuing postgraduate medical education is generally accepted and has generated a number of postgraduate education programs. In 1960, the FAA inaugurated a seminar program to serve the special educational needs of its approximately 7,500 designated Aviation Medical Examiners. These doctors, the majority of whom are civilian physicians representing almost every specialty, are charged with issuing or withholding the pilot's medical license to fly. Under the administration of coauthor Harris, the AME Seminar Program undergoes modification and change as improvements are suggested by accrued experience. Evaluation of data acquired from a variety of sources indicates that the AME does, in fact, need refresher training in civil aviation medicine. In helping fulfill that need, the AME Seminar Program is working effectively.

Aerospace Medicine↗
PubMedDate not supplied

Mitochondrial DNA sequences in the nuclear genome of a locust.

The endosymbiotic theory of the origin of mitochondria is widely accepted, and implies that loss of genes from the mitochondria to the nucleus of eukaryotic cells has occurred over evolutionary time. However, evidence at the DNA sequence level for gene transfer between these organelles has so far been limited to a single example, the demonstration that a mitochondrial ATPase subunit gene of Neurospora crassa has an homologous partner in the nuclear genome. From a gene library of the insect, Locusta migratoria, we have now isolated two clones, representing separate fragments of nuclear DNA, which contain sequences homologous to the mitochondrial genes for ribosomal RNA, as well as regions of homology with highly repeated nuclear sequences. The results suggest the transfer of sequences between mitochondrial and nuclear genomes, followed by evolutionary divergence.

Animals↗