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Biomedical subjects

M F Norman

Publications and source records attributed to M F Norman.

12 recordsLinked to original sources
PubMed2001

Development and validation of a telephone questionnaire to characterize lymphedema in women treated for breast cancer.

BACKGROUND AND PURPOSE: Accurate and economical characterization of lymphedema is needed for population-based studies of incidence and risk. The purpose of this study was to develop and validate a telephone questionnaire for characterizing lymphedema. SUBJECTS: Forty-three women who were treated previously for breast cancer and who were recruited from physical therapy practices and a cancer support organization were studied. METHODS: Questionnaire assessment of the presence and degree of lymphedema was compared with physical therapists' diagnoses, based primarily on circumferential measurements. Twenty-five of the 43 subjects were measured independently by 2 physical therapists to assess interobserver agreement. RESULTS: Interobserver agreement on clinical assessments of the presence and degree of lymphedema was high (20/25, weighted kappa=.80); all of the disagreements were between judgments of whether there was no lymphedema or mild lymphedema. For the diagnosis of at least moderate lymphedema (differential in the circumferences of the upper extremities greater than 2 cm), sensitivity of the questionnaire varied from 0.86 to 0.92 and specificity was 0.90. However, sensitivity (varying from 0.93 to 0.96) was higher than specificity (varying from 0.69 to 0.75) for the diagnosis of any lymphedema. DISCUSSION AND CONCLUSION: A few straightforward questions exhibited excellent agreement with physical therapists' assessments for identifying at least moderate lymphedema.

Adult↗
PubMed1992

Monoamines and their metabolites in the amphibian (Ambystoma tigrinum) brain: quantitative changes during metamorphosis and captivity.

1. Monoamine neurotransmitters (epinephrine, norepinephrine, dopamine, serotonin and some of their metabolites (DOPEG, MHPG, DOPAC, 5-HIAA) were measured by HPLC in extracts from telencephalon (TEL) and diencephalon-midbrain (DM) before, during at the end of metamorphosis. 2. During metamorphosis MHPG increased and 5-HIAA decreased in TEL and DM while DOPEG decreased only in DM. 3. Monoamine levels were greater in the TEL and a larger increase in MHPG occurred there. 4. Captivity without metamorphosis also caused a significant depression of 5-HIAA in TEL and depression of DOPEG, MHPG and DOPAC in DM.

Ambystoma↗
PubMed1989

The rat growth hormone gene contains multiple thyroid response elements.

The thyroid hormone receptor exerts transcriptional control over a variety of genes. This report describes four sites that bind this receptor with high affinity within the 5'-flanking DNA of the rat growth hormone gene, approximately centered at -180, -160, -60 and -20 nucleotides from the transcription start site. These sites were defined by gel retardation of short synthetic oligonucleotides using native receptor purified several hundred-fold from rat liver. Binding sites were also defined by methylation interference and methidium-propyl-EDTA footprinting. Alignment of the four binding sites suggests that each contains two purine-rich regions, the more downstream of which, GGGATCGC, is highly conserved. Mutations made within each of the two upstream sites reduce receptor binding affinity. For one mutation, a partial loss of receptor binding strength correlated with a change in electrophoretic mobility, indicating that receptor binding may alter DNA conformation. Mutations at each of the four sites also reduce thyroid hormone responsiveness of the -237/+11 promoter linked to the chloramphenicol acetyltransferase gene coding sequences and transfected into cultured pituitary (GC) cells. These results suggest that several different receptor-binding elements interact to control thyroid hormone responsiveness of the rat growth hormone gene and reveal common sequences that may be important for receptor-DNA recognition.

Animals↗
PubMed1989

Antagonism of thyroid hormone action by amiodarone in rat pituitary tumor cells.

A thyroid hormone antagonist has not been previously described. A number of thyroid hormone analogues have been shown to compete with [125I]triiodothyronine ([125I]T3) for binding to the intranuclear thyroid hormone receptor and to have agonist activity proportional to their affinities for the receptors. We report that the benzofuran amiodarone acts as a competitive antagonist to thyroid hormone action as defined by its dose-dependent ability to (a) bind to the thyroid hormone receptor and (b) inhibit T3-induced increases in growth hormone mRNA levels in a cultured rat pituitary cell line, GC cells. Like T3 itself, amiodarone also decreases transport of [125I]T3 across GC cell membranes. An analysis of the amiodarone structure suggests that this compound has certain similarities to T3. These findings hold promise for the development of other thyroid hormone antagonists for clinical use and for understanding thyroid hormone action.

Amiodarone↗
PubMed1987

Adenohypophysial-thyroid activity of the tiger salamander, Ambystoma tigrinum, as a function of metamorphosis and captivity.

The aim of this study was to determine the timing of adenohypophysial activation during metamorphosis of the tiger salamander, Ambystoma tigrinum. It consisted of two parts: 1) determination of plasma thyroid hormone concentrations and analysis of thyroid gland histology as a function of metamorphic stage and 2) analysis of the time-course of uptake of 125I by the thyroids during metamorphosis as an indicator of endogenous thyrotropin (TSH) levels. Significant increases in both triiodothyronine (T3) and thyroxine (T4) first were evident at the onset of metamorphic climax (stage II). Maximum levels of both hormones were not observed, however, until the completion of gill resorption (stage VII). No changes in thyroid histology were observed that could be unambiguously related to metamorphic transformation. The thyroids accumulated 125I in a slow but linear fashion in premetamorphic larvae (stage I). However, uptake exhibited a rapid peak during early climax (stage II), before maximum concentrations of thyroid hormones were observed. In addition, uptake was maintained above premetamorphic levels at stage VII, in conjunction with maximum levels of T4 and T3. Captivity alone produced a small but significant increase in plasma concentrations of T3. It produced no significant effect on either thyroid histology or uptake of 125I. These results indicate that adenohypophysial activation occurs rapidly and is maximal at the onset of metamorphic climax.

Ambystoma↗
PubMed1987

Effects of metamorphosis and captivity on the in vitro sensitivity of thyroid glands from the tiger salamander, Ambystoma tigrinum, to bovine thyrotropin.

The sensitivity of thyroid glands from the tiger salamander, Ambystoma tigrinum, to bovine thyrotropin (bTSH) was tested in vitro. Thyroids were taken from subjects representing metamorphic stages I (premetamorphic larvae), II (onset of climax), and VII (completion of gill resorption), as well as from captivity control larvae. Exogenous TSH reduced the cumulative uptake of 125I in vitro by thyroids from stage I larvae after 24 and 48 hr. The capacity of thyroids to release thyroxine (T4) in vitro was used subsequently as a measure of their responsiveness to TSH. Baseline levels of T4 release in vitro were variable but did not differ significantly among developmental stages. A low dose of bTSH (5 X 10(-6) IU/ml) did not increase in vitro T4 release compared with that of controls. A larger dose (5 X 10(-4) IU/ml) caused greater increases in T4 release from thyroids of stage II and VII subjects than from those of controls. This dose produced only a small response by thyroids from captivity-control subjects. The results suggest that the thyroids of Ambystoma increase in their capacity to respond to TSH during the process of metamorphosis.

Ambystoma↗
PubMed1985

A practical method for staging metamorphosis in the tiger salamander Ambystoma tigrinum.

The aim of this study was to develop a set of practical metamorphic stages for the tiger salamander Ambystoma tigrinum that would 1) provide an early and quantifiable marker of the onset of metamorphosis and 2) not be dependent on knowledge of maximal values of gill length or tail height. Twenty morphological parameters were obtained from Ambystoma tigrinum larvae as they progressed through laboratory-induced metamorphosis (21 degrees C, continuous light). These parameters included measures of body weight, gill length, and tail height. Initiation or duration of metamorphosis could not be predicted when parameters were expressed relative to the number of days larvae were held in laboratory conditions. Early phases of metamorphosis were characterized by regression of the lower tail fin. Selected morphological parameters were expressed relative to the day on which each subject exhibited complete regression of the lower fin. This technique made it possible to order these parameters into a progressive series of metamorphic phases. Seven stages of metamorphosis were derived from this series, ranging from larvae (stage I) to complete regression of the gills (stage VII). Application of these stages does not require prior knowledge of maximal (initial) values of gill length or tail height.

Ambystoma↗
PubMed1985

Seasonal variations in spermatogenesis, testicular weights, vasa deferentia, and androgen levels in neotenic male tiger salamanders, Ambystoma tigrinum.

Significant seasonal changes were observed in spermatogenesis, testicular weights, vasa deferentia, and cloacal development as well as in plasma androgen levels (testosterone and dihydrotestosterone). Androgen levels were highest in the fall and lowest during the period of spermatogenesis. Low levels of androgens were also observed during the breeding season. Diameter of the vasa deferentia corresponded to presence of stored spermatozoa and not to plasma androgen levels. Testicular weights were independent of androgen levels and stage of spermatogenesis. Maximal testicular weight occurred at the onset of spermiation. Hypertrophy of the epithelial lining of the vasa deferentia and the condition of the cloacal gland complex were correlated closely to plasma androgen levels. Comparison of spermatogenetic events, androgen-dependent sex accessory structures, and plasma androgen levels suggests either differential release of pituitary gonadotropins on a seasonal basis or variable testicular responsiveness to gonadotropins.

Ambystoma↗
PubMed1985

Response of amphibian (Ambystoma tigrinum) oviduct to arginine vasotocin and acetylcholine in vitro: influence of steroid hormone pretreatment in vivo.

Oviducts of the salamander Ambystoma tigrinum contract in vitro in response to stimulation by arginine vasotocin (AVT) and acetylcholine (ACh). Steroid hormone pretreatment significantly affects the responsiveness of the oviductal tissue to AVT and ACh. Oviducts initially pretreated with estradiol, testosterone and saline or a combination of estradiol and testosterone exhibit no response to AVT and only saline or estradiol/testosterone treated oviducts respond to ACh. Secondary pretreatment with progesterone stimulated a significant increase in responsiveness to AVT and ACH in all groups.

Acetylcholine↗
PubMed1977

Error estimate for the diffusion approximation of the Wright--Fisher model.

The Wright--Fisher model and its approximating diffusion model are compared in terms of the expected value of a smooth but arbitrary function of nth-generation gene frequency. In the absence of selection, this expectation is shown to differ in the two models by at most a linear combination (with coefficients depending only on the derivatives of the smooth function involved) of the maximum mutation rate and the reciprocal of the population size.

Genetics↗