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Biomedical subjects

D H Griffin

Publications and source records attributed to D H Griffin.

16 recordsLinked to original sources
PubMed1981

Hearing loss.

Defective hearing is the most prevalent chronic health problem in the United States, making it a primary concern of the physician. Failure to diagnose, misdiagnose, and delay of diagnosis of hearing loss are common errors that have serious implications. However, they can be avoided. If children exhibiting the symptoms of delayed language, articulation defects, and academic problems (especially with reading or a medical history of certain diseases) are referred for audiological testing, most cases of hearing impairment will be promptly detected. With adults the implications of hearing loss are different, both medically and psychosocially. After 30 years of age the prevalence of hearing defects increases rapidly. Some major causes are noise, otosclerosis, otitis media, and presbycusis. Surgery and amplification are the principle treatments. Management of nonmedical aspects should involve programs such as the Division of Vocational Rehabilitation, state schools for the deaf, and sign language classes.

Adult↗
PubMed1978

Resistance of selected saprobic and zoopathogenic fungi to cycloheximide.

Spore germination was used as an assay to measure the sensitivities of selected fungi (Achlya bisexualis, Cladosporium sp., Trichophyton mentagrophytes and Microsporum gypseum) to cyclohexamide and to determine their abilities to adapt to the drug. Two patterns of response were noted. The saprobes, A. bisexualis and Cladosporium sp., demonstrated acquired resistance. Spores from hyphae previously exposed to cycloheximide either germinated in the presence of concentrations of the drug that completely inhibited spores from unexposed hyphae (Achlya), or germinates with a shorter lag and to a greater extent in the presence of the antibiotic than did spores from unexposed hyphae (Cladosporium). Hyphae of Achlya adapted at concentrations of cycloheximide in which spores did not germinate and hyphae of Cladosporium adapted more rapidly than spores. Achlya adapted to only 12 muM-cycloheximide whereas Cladosporium acquired resistance to 18 mM-cycloheximide. These fungi lost this acquired resistance after a single transfer to media lacking cycloheximide. The zoopathogens, T. mentagrophytes and M. gypseum, had a contrasting response, indicating constitutive resistance. Conidia from unexposed hyphae showed 90 to 100% germination on media containing up to 18 mM-cycloheximide; prior exposure to the drug did not affect their response.

Adaptation, Physiological↗
PubMed1977

Inhibition of DNA synthesis by cycloheximide and blasticidin-S is independent of their effect on protein synthesis.

The effects of cycloheximide and related glutarimide antibiotics on DNA synthesis in Achlya bisexualis Coker and A. Couch were compared to those of other protein synthesis inhibitors, puromycin, p-fluorophenylalanine and blasticidin-S. The inhibitors had no significant effects on intrahyphal pool sizes of dTTP, dCTP, ATP, UTP and CTP, nor on the specific activity of the dTTP pool labelled by [3H] thymidine. DNA was the sole acid-insoluble product of [3H]-thymidine incorporation. Cycloheximide, isocycloheximide, streptimidone and blasticidin-S inhibited DNA synthesis rapidly and completely and anhydrocycloheximide was less effective. Cycloheximide acetate, puromycin and p-fluorophenylalanine did not inhibit DNA synthesis. It is concluded that the effects of the several glutarimide antibiotics and of blasticidin-S on DNA synthesis were independent of their effects on protein synthesis.

Anti-Bacterial Agents↗
PubMed1974

Differential effects of analogs of cycloheximide on protein and RNA synthesis in Achlya.

Analogs of the glutarimide antibiotic cycloheximide were tested for their effect on growth and incorporation of proline and uridine into acid-insoluble material in Achlya bisexualis. Each of the compounds tested had reduced antibiotic activity as compared to cycloheximide. The effects of the antibiotics on protein and RNA synthesis were varied. While cycloheximide inhibited both protein and RNA synthesis immediately, two of the analogs inhibited proline incorporation without effect on uridine incorporation, while three, each representing a modification of the hydroxyl of cycloheximide, stimulated uridine incorporation and either had no effect on or inhibited protein synthesis. These results indicate that the control of RNA synthesis by protein synthesis in Achlya can be released by glutarimide antibiotics.

Antifungal Agents↗
PubMed1973

Protein synthesis during the differentiation of sporangia in the water mold Achlya.

During the synchronous differentiation of sporangia in the absence of added nutrients, the water mold Achlya bisexualis (Coker and Couch) actively synthesized protein. Inhibition of protein synthesis at any time during the sporulation process completely inhibited further differentiation. Large changes in the rate of radioactive amino acid uptake resulted in changes in the specific activity of the cellular amino acid pool. The rate of protein synthesis was calculated from the amino acid pool specific activity and the incorporation of isotope into protein. During the 1st h after induction of the sporulation process, the rate of protein synthesis increased to two times the initial value. The amino acid precursors for this synthesis were supplied by the degradation of preexisting protein. Proteolytic enzyme activity assayed in vitro increased in proportion to the in vivo rates of protein synthesis and degradation. Differentiation was accompanied by a slight decline in dry weight of the mycelium as well as by a decrease in the protein content, whereas the relative size of the amino acid pools remained constant.

Amino Acids↗
PubMed1971

Specific inhibitors of the three RNA polymerases from the aquatic fungus Blastocladiella emersonii.

Specific inhibitors of each of the three RNA polymerases of Blastocladiella emersonii have been found. Cycloheximide specifically inhibited the in vitro activity of the DEAE-fraction I enzyme, alpha-amanitin specifically inhibited the DEAE-fraction II enzyme, and rifampicin specifically inhibited the fraction III enzyme. DNA stimulation and dependency on the four riboside triphosphates were shown to be characteristic of each of the three fractions. Optimum concentrations of magnesium ions required were shown to differ among the three fractions and to be somewhat higher than optimum concentrations of manganese ions. The effect of pH on activity was essentially identical for each of the three fractions. Kinetic experiments and nuclease assays indicated the presence of some interfering substances in the partially purified RNA polymerase fractions.

Biological Assay↗
PubMed1969

Ribonucleic acid synthesis during the differentiation of sporangia in the water mold Achlya.

The role of ribonucleic acid (RNA) synthesis in the development of sporangia in the saprolegniaceous mold Achlya was studied. Methods were developed for growing and treating large populations of mycelia so that the hyphal tips would differentiate into sporangia with considerable synchrony. Under the starvation conditions imposed for the differentiation of sporangia, net RNA, deoxyribonucleic acid (DNA), and protein synthesis ceased. However, incorporation of radioactive precursors into RNA continued at a high rate throughout the period of differentiation, showing that the enzymatic mechanism for RNA synthesis was still in an active state. Actinomycin D inhibited the differentiation of sporangia and the incorporation of labeled precursors into RNA. The level of actinomycin used did not inhibit the normal outgrowth and branching of the mycelia that occurred during differentiation. Thus, DNA-dependent RNA synthesis was required for the differentiation of sporangia. Sucrose gradient analysis of newly synthesized RNA showed that only the ribosomal and soluble fractions of RNA were labeled during vegetative growth. During the differentiation of sporangia, ribosomal and soluble RNA fractions were also labeled, and, in addition, a heterodisperse fraction of labeled RNA which was heavier than ribosomal RNA appeared; this fraction was not evident in the newly synthesized RNA from vegetative mycelia.

Cell Differentiation↗