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Biomedical subjects

W A Johnson

Publications and source records attributed to W A Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Internal ophthalmomyiasis and treatment by laser photocoagulation: a case report.

The clinical diagnosis, treatment management, and epidemiology of a case of unilateral posterior ophthalmomyiasis in a university farm manager are reported. Subretinal tracking was prominent, leading to vision abnormalities, which initially prompted the patient to seek medical evaluation. Identification of the organism based on study of photographs was judged to be a first-instar larva of a Cuterebra (rodent bot fly), although identification of first-instar (stage) myiasis-producing fly larvae is impossible. Inasmuch as the patient was a herdsman, it is likely that the larva is of the genus Hypoderma (cattle grub) or possibly Gasterophilus (horse bot). Laser treatment was effectively used to destroy and immobilize the organism. Subsequently, the patient's health remains satisfactory, and his vision has improved. This case is reported to confirm increasing frequency of ophthalmomyiasis and to improve awareness of its features. Early recognition of this condition, when tumors and other conditions remain suspect, would preclude unnecessarily invasive surgical procedures, including enucleation.

Eye Infections, Parasitic↗
PubMed1994

Measurement of pharmacodynamic effects of dexamethasone on epidermis by phosphorus nuclear magnetic resonance spectroscopy in vitro.

An intact, viable epidermal preparation was perfused and phosphoenergetic and phospholipid metabolite levels were measured by 31P NMR. The preparation was stable in the NMR perfusion apparatus for 24 h. The effects of inclusion of ethanolamine and dexamethasone-21-acetate in the perfusion media on phosphorus-containing metabolites was assessed by examination of serial 31P NMR spectra. Phosphomonoesters increased significantly during the fourth hour of perfusion with ethanolamine (3 mM) and remained elevated. A corresponding decrease in nucleotide triphosphates was noted, but phosphocreatine (PCr) remained unchanged. Dexamethasone perfusion resulted in a biphasic effect on phosphomonoester metabolism and a dose-dependent decrease in PCr and nucleotide triphosphate levels. A log-linear relationship was observed between dexamethasone dose in the 1-100-nM range and a decrease in PCr. These techniques with an isolated intact epidermal preparation are useful for elucidating mechanisms of corticosteroid action on the skin and serve as a basis for developing a mechanistically relevant topical corticosteroid bioequivalence technique.

Animals↗
PubMed1990

Binding of a Drosophila POU-domain protein to a sequence element regulating gene expression in specific dopaminergic neurons.

Several genes have been identified that affect the specification of unique neuronal identities during development of the Drosophila central nervous system. At least two of these genes, fushi tarazu (ftz) and even-skipped (eve) share a common structural motif, the homoeobox, which encodes a sequence-specific DNA-binding domain (homoeodomain). A family of related proteins has been recently characterized in mammals and nematodes that contain a diverged homoedomain as part of a structure referred to as a POU domain. Mammalian genes encoding POU domains have region-specific patterns of expression in the central nervous system, indicating a potential role for them in the regulation of neuronal development. The nematode POU-domain gene, unc-86, is involved in the determination of neuroblast lineages leading to serotonergic and dopaminergic neurons. We have now identified a Drosophila gene, Cfla, encoding a sequence-specific DNA-binding protein containing a highly conserved POU domain. The Cfla gene product binds to a DNA element required for expression of the dopa decarboxylase gene (Ddc) in selected dopaminergic neurons, implying that it functions as a neuron-specific transcription factor.

Amino Acid Sequence↗
PubMed1989

A neuron-specific enhancer of the Drosophila dopa decarboxylase gene.

At least two cis-regulatory elements are necessary for correct neuron-specific expression of the Drosophila melanogaster dopa decarboxylase gene, Ddc. In addition to a previously described proximal element located approximately 60 bp upstream of the mRNA start site, we have now characterized a distal approximately 600-bp DNA fragment, extending from -1019 to -1623 bp, which possesses enhancer-like properties and is essential for normal neuron-specific expression. Immunofluorescent labeling of neurons expressing deleted Ddc genes indicates that this region contains both general neuronal regulatory elements and cell-specific elements that selectively affect Ddc expression in either dopaminergic or serotonergic neurons. These selective effects can be correlated with the removal of sequence elements that are protected from DNase digestion by factors present in embryonic nuclear extracts. Several of these elements are also homologous to sequences located upstream of the evolutionarily diverged Ddc gene of Drosophila virilis. These results suggest that the neuron-specific expression of Ddc results from the combined action of several factors binding within this distal enhancer region.

Animals↗
PubMed1989

Influence of exogenous prostaglandin E2 and stress on circulating corticosterone concentrations in Coturnix.

The effects of exogenous prostaglandin E2 (PGE2) injections and stress on circulating corticosterone (B) levels in Coturnix were determined. Adult Japanese quail (Coturnix coturnix japonica) were subjected to one of four treatments: 1) injected with vehicle; 2) injected with PGE2; 3) immobilized for 10 min, followed by vehicle injection; or, 4) immobilized for 10 min, followed by PGE2 injection. Injections were given intraperitoneally, and blood samples were collected by cardiac stab at 15-min postinjection treatment. Plasma B concentrations were quantified by radioimmunoassay. Immobilized, vehicle injected quail had higher plasma B levels than unstressed, vehicle-injected quail. Plasma B levels were significantly greater in unstressed, PGE2-injected quail than in unstressed, vehicle injected quail or in stressed, vehicle injected quail. The effects of immobilization stress and PGE2 injection on B secretion were additive; stressed PGE2-injected quail had significantly higher plasma B levels than unstressed, PGE2-injected quail. It is concluded that, as in mammals, PGE2 is a potent stimulator of adrenal B release in quail.

Analysis of Variance↗
PubMed1989

Using the amniotic cavity of the developing chick embryo for the in vivo culture of early-stage mammalian embryos.

The fertile chicken egg may provide an effective, inexpensive method for promoting the development of early-stage embryos from other species. Presently, the loss of viability associated with the in vitro culture of mammalian embryos is hindering the use of in vitro fertilization with farm animals. Consequently, alternative in vitro laboratory methods are needed for the culture of mammalian embryos. A new method has been developed that involves the culture of mammalian embryos in the amniotic cavity of a developing chick embryo. Chick embryos were placed into shell-less incubation (37 C) at the 72-h developmental stage. After 24 h of shell-less incubation, agarose-embedded mammalian embryos were injected into the amniotic cavity of the chick embryo. The mammalian embryos were first placed into a drop of liquid agarose. One to four embryos were then aspirated into a beveled injection pipette and cooled, allowing the agarose to harden. Following penetration of the amnion with the beveled pipette, the agarose cylinder containing the embryos was expelled into the amniotic cavity. The shell-less culture system was then returned to incubation at 37 C for an additional 72 to 96 h. Following incubation, the amniotic cavity containing both chick and mammalian embryos was isolated and the agarose-embedded mammalian embryos were harvested. Significantly more embryos developed in the chick embryo amnion than in the control medium alone. Results obtained using this method on laboratory animals (mice) and on domestic mammals (goats and cattle) indicate that the chick-embryo amnion can support the development of early-stage, mammalian embryos to the blastocyst stage of development.(ABSTRACT TRUNCATED AT 250 WORDS)

Amnion↗
PubMed1988

A cis-acting element and associated binding factor required for CNS expression of the Drosophila melanogaster dopa decarboxylase gene.

A cis-acting sequence from the Drosophila melanogaster dopa decarboxylase (Ddc) gene is selectively required for Ddc expression in the central nervous system. We analyze several parameters influencing the function of the sequence element and describe a factor which interacts with it and mediates CNS expression of Ddc. The element, element I, can function in vivo when included on a synthetic oligonucleotide inserted near its normal location, or closer to the RNA startpoint. It displays partial activity when inverted. Two different 2-bp mutations in element I abolish its ability to stimulate neuronal Ddc expression in the CNS. A factor present in embryonic nuclear extracts specifically protects element I in DNase I footprinting assays. The binding affinity of this factor is reduced by each alteration of element I that inhibits neuronal expression, indicating a role in mediating CNS expression of Ddc. Element I alone has no detectable activity when placed adjacent to a heterologous promoter, although 2.2 kb of 5' Ddc sequences direct correct cell-specific expression of a heterologous promoter.

Animals↗
PubMed1988

Selection of Japanese quail for contrasting blood corticosterone response to immobilization.

Japanese quail (Coturnix coturnix japonica) were divergently selected for 12 generations for increased (high stress, HS) and decreased (low stress, LS) blood corticosterone (B) response to unfamiliar environments. Response lines were selected initially on the basis of wild-type quail B response to albino (ALB) quail intrusion (S1 to S3) and subsequently on B response to immobilization (IMB) (S4 to S12). Using ALB intruders as stressors proved unsuccessful, therefore the practice was abandoned in favor of using IMB, which proved successful. Across nine generations of selection, using the IMB stressor, the HS line exhibited a mean serum B response that was approximately 58% greater than that of the random-bred (control stress, CS) line, whereas the LS line had a mean response approximately 23% less than that of the CS line. Selection differentials were approximately three-fold greater in the HS than in the LS line whereas realized heritabilities (h2) were approximately two-fold greater in the HS than in the LS line.

Animals↗
PubMed1986

Regulated splicing produces different forms of dopa decarboxylase in the central nervous system and hypoderm of Drosophila melanogaster.

The dopa decarboxylase gene (Ddc) of Drosophila melanogaster is expressed in the hypoderm and the nervous system and promoter elements mediating differential expression in these tissues have been identified (Scholnick et al., 1986). Here we report an additional mode of regulation; the unique primary transcript of the Ddc gene is spliced to form mRNAs in these two tissues which differ by a single internal exon. In vitro mutagenesis and P-element-mediated transformation were employed to manipulate the tissue-specific expression of these RNAs. This approach demonstrated that regulated splicing rather than differential stability causes the tissue-specific expression of these RNAs and allowed the identification of Ddc enzyme isoforms encoded by each mRNA. The Ddc enzyme in the central nervous system differs from the hypodermal Ddc protein by the addition of 33-35 amino acids on the N terminus.

Animals↗
PubMed1984

Solubilization and characterization of thyrotropin-releasing hormone receptors from rat brain.

The thyrotropin-releasing hormone receptor from rat brain was solubilized in a stable unbound form. The natural glycoside digitonin was the only detergent of a variety tested capable of solubilizing the active receptor. The digitonin-solubilized receptor exhibited binding kinetics for 3-[3H]methylhistidine thyrotropin-releasing hormone virtually identical to membrane preparations and responded with a similar order of potency to a series of thyrotropin-releasing hormone analogues that inhibit binding of the labeled ligand. Gel filtration analysis and sucrose density gradient centrifugation indicated a Stokes radius of 5.2 nm, a sedimentation coefficient of 11.2 s, and a corresponding calculated molecular weight of 244,000 for the detergent-receptor complex. The soluble receptor shows a gradual loss of binding activity over 48 to 72 hr when kept at 4 degrees C. However, the preparation may be frozen at -20 degrees C with no significant loss of activity.

Animals↗
PubMed1984

Influence of noon meal on nutrient intakes and meal patterns of selected fifth-grade children.

Fifth-grade students were subjects in a study designed to determine adequacy of dietary intakes and the contribution of the school lunch to diet adequacy. Seven-day food records and 24-hour food recall data showed that only protein and riboflavin were consumed in adequate quantities. There were wide individual variations in consumption of calcium, iron, thiamin, niacin, vitamin A, and ascorbic acid. Vitamin A and ascorbic acid intakes were not significantly related to family income or the mother's education, but fat consumption correlated positively with family income. School lunches as served must provide at least one-third of the RDAs. Meals served in this study contained from 110% to 295% of the nutrients included in the Type A lunch. Even though less than 65% of the available iron, vitamin A, thiamin, riboflavin, and niacin served was consumed, the average intakes met the goal for most of the nutrients. School lunches and noon meals consumed at home were nutritionally superior to bag lunches from home. No significant differences were noted between school and home lunches.

Child↗
PubMed1983

The effects of forced molt treatment on blood biochemicals in hens.

A study was conducted to determine the effects of an environmentally induced force molt treatment on concentrations and daily variations of selected serum biochemicals during early molt. Laying hens were placed into two environmental control chambers. In one chamber, control (Con) laying hens were maintained on long photoperiods of 19 hr of light daily to maintain egg production. In the other chamber, early molt (EM) hens were exposed to short photoperiods of 6 hr of light daily to decrease egg production. After 2 weeks in the chambers, feed was withdrawn from EM hens for 2 days to initiate molt. Three days after feed was restored, hens from both groups were blood sampled every 2 hr for 2 days for selected serum biochemical analyses. Serum concentrations of calcium (Ca), inorganic phosphate (P), glutamic pyruvic transaminase (GPT), and albumin (Alb) were depressed in EM hens. Serum concentrations of alkaline phosphatase (Alk P), lactic acid dehydrogenase (LDH), glutamic oxaloacetic transaminase (GOT), glucose (Glu), cholesterol (Chol), and globulin (Glob) were elevated in EM hens. Daily temporal rhythms of Ca, Glu, total protein (TP), and Alb were found in both hen groups. These temporal changes were independent of force molt treatment. Serum GOT was positively correlated with nuclei free liver corticosteroids (LCS) and negatively associated with plasma corticosterone in Con hens. Serum GOT was positively correlated with nuclei free LCS in EM hens.

Alanine Transaminase↗
PubMed1982

Effects of ischemia on metabolite concentrations in dog renal cortex.

To investigate the effects of ischemia on renal metabolites, sequential slices of renal cortex were removed during 5 min of renal artery occlusion and for 5 min after release of occlusion. ATP concentrations rapidly fell during ischemia and rose during the postischemic period. Based on the rate of decline of ATP concentrations, the rate of ATP production was estimated to be 0.5 mumol ATP/g/min. This is considerably less than the rate of ATP production estimated from renal O2 consumption. During ischemia, AMP concentrations rose, confirming the activity of adenylate kinase. The control lactate/pyruvate ratio suggested that dog kidney cytosol is more reduced than the cytosol of rat liver and kidney. During ischemia, the lactate concentrations and the lactate/pyruvate ratio of dog renal cortex increased as expected, and fell after restoration of blood flow. beta-Hydroxybutyrate concentrations are considerably lower than those previously reported for rat liver and kidney. The beta-hydroxybutyrate/acetoacetate ratio was not measurable during ischemia. However, the mitochondrial redox state, calculated from the glutamate/alpha-ketoglutarate . NH+4 ratio, was similar to previous reports and this ratio appropriately changed during the ischemic and post-ischemic period.

3-Hydroxybutyric Acid↗
PubMed1982

Effects of blood sampling by cardiac puncture on subsequent body weights of broilers.

The effects of blood sampling via cardiac puncture in broiler chicks 2 to 4 weeks of age on subsequent body weights were examined in three experiments. No differences were found in chicks bled or stabbed with 18, 22, or 25-gauge needles when compared to chicks not blood sampled. However, male chicks bled at both 2 and 3 weeks of age with a 25-gauge needle demonstrated elevated body weights at 8 weeks of age when compared to chicks not blood sampled.

Animals↗
PubMed1981

Effects of low intensity red light on testicular recrudescence in Japanese quail.

Experiments were conducted to determine if sighted and blind plumage color mutants of Japanese quail elicit comparable testicular recrudescence when exposed to long daily photoperiods of low intensity red light. Quail exhibiting testicular regression after exposure to 8 hr of light daily for several weeks were blinded via bilateral ocular enucleation. A control group was not enucleated. Two light intensities, 1.4 and 2.8 lx, were applied to half of the birds in each group during a 16 hr daily photoperiod for several weeks. Enucleated birds and birds under the 2.8 lx intensity had greater testis weights than the controls. Birds were also blinded by optic tract sectioning, and a .7 lx red light intensity treatment was included. Greater testis weights were found in birds under higher light intensities. Three plumage pigmentation mutants, sex linked incomplete albino, white and wild-type, were exposed to 8 hr of light daily for either 4 or 8 weeks to induce testicular regression. They were then exposed to the three light intensities for 3 weeks. Higher intensities and albinism resulted in greater testicular recrudescence only when the regression interval was 8 weeks, even though testicular regression appeared after 4 weeks. The absence of eyes or plumage pigmentation, resulting in an increased exposure of the encephalon for extraretinal light reception, may have effected greater testicular recrudescence. Severed optic tracts with tract eyes did not produce this response to light, indicating that the eyes may play a role in mediating the photosexual reflex in quail. Lower intensities may have resulted in reduced tissue penetration and testicular growth. A definite threshold intensity necessary to elicit testis growth was not found.

Animals↗
PubMed1981

Circulating levels of corticosterone in the serum of developing chick embryos and newly hatched chicks.

Circulating levels of corticosterone were determined in chick embryos from 10 to 21 days of incubation using eggs from a Leghorn breeder flock. In Experiment 1, eggs were incubated from 10 to 20 days for daily embryonic blood collection. To verify stage of development with day of incubation, embryo right middle toe lengths were measured concurrent with blood sampling. Serum from three embryos was pooled into one sample and the corticosterone content of 10 samples per day of incubation was determined using a radioimmunoassay procedure. The levels of corticosterone from day 10 to 14 fluctuated slightly and then increased rapidly until 16 days of incubation. At this time serum corticosterone remained relatively constant through day 18 with an apparent increasing trend up to day 20. The use of toe lengths to assure no day-to-day overlap in embryonic development proved effective. In Experiment 2, newly hatched (day 21) chicks were sorted into four 3-hr periods ranging from early to late hatching. Blood samples were collected from five individual chicks during four 15-min sampling periods for each of the four hatch times. Serum corticosterone levels were not affected by sampling periods or hatch times.

Animals↗