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Biomedical subjects

G E Hofmann

Publications and source records attributed to G E Hofmann.

65 records · Page 4Linked to original sources
PubMed1985

Cytochrome P-450 activity in human leiomyoma and normal myometrium.

Variations in cytochrome P-450 levels may influence the responsiveness of uterine and breast tissue as well as carcinomas to endocrine therapy and may be of particular importance with agents such as tamoxifen (Nolvadex) where hydroxylation is known to alter therapeutic activities. Therefore, a sensitive spectrophotometric assay of cytochrome P-450 levels in reproductive tissue microsomes was developed to measure cyclohexane hydroxylase activity. Cyclohexane served as a substrate for several forms of cytochrome P-450. Human uterine leiomyomas (uterine fibroid tumor) contained significantly higher (p less than 0.01) cytochrome P-450 activity than adjacent normal myometrium. Specific activities for both leiomyomas (2.87 +/- 0.26 nmol/min/mg) and normal myometrium (1.60 +/- 0.11 nmol/min/mg) were in the range of those observed for untreated rabbit liver microsomes (1 to 3 nmol/min/mg). The contribution of smooth muscle in the specimen, the phase of the menstrual cycle, and the clinical diagnosis did not influence the level of cytochrome P-450 activity.

Adult↗
PubMed1985

Human endometrial prostaglandin E2 binding sites and their profiles during the menstrual cycle and in pathologic states.

Endometrial tissue from uteri of 35 nonpregnant, premenopausal women was assayed for prostaglandin E2 and F2 alpha binding site content as a function of the phase of the menstrual cycle and the pathologic state. For all specimens, tritium-labeled prostaglandin F2 alpha, binding was very low (less than 8 fmol/mg of protein) or undetectable regardless of the phase of the menstrual cycle or pathologic state or in the presence or absence of 10 mumol/L of indomethacin, a prostaglandin synthetase inhibitor. However, tritium-labeled prostaglandin E2 binding was detected in every specimen and was independent of the presence or absence of indomethacin. Binding of tritium-labeled prostaglandin E2, as determined by Scatchard analyses, was biphasic (dissociation constant approximately 1 nmol/L; dissociation constant for low-affinity sites approximately 10 nmol/L) for both proliferative and secretory endometrial tissue. However, the total number of prostaglandin E2 binding sites, determined from Scatchard or single-point analyses, was significantly higher (p less than 0.01) in proliferative endometrium compared to secretory endometrium. In addition, for endometrium from the proliferative phase of the menstrual cycle, the diagnosis of abnormal uterine bleeding was associated with higher (p less than 0.01) tritium-labeled prostaglandin E2 binding than diagnosis of dysmenorrhea, stress urinary incontinence and uterine prolapse, or pelvic inflammatory disease. Endometrial specimens with the last four diagnoses did not differ significantly (p greater than 0.1) from each other.

Adult↗
PubMed1984

High-performance size exclusion chromatography as a rapid method for the separation of steroid hormone receptors.

High-performance size exclusion chromatography ( HPSEC ) on TSK 3000SW molecular sieve columns was used to separate estrogen, progestin, and androgen receptors from several target tissues within 50 min on the basis of size and shape (Stokes radius). Moreover, this system provided for the detection of heterogeneity of receptor species (isoforms) in a manner superior to that observed with sucrose density gradient centrifugation. HPSEC separated various estrogen receptor isoforms having Stokes radii of greater than 61 A, approximately 48 A and 29-32 A. Agents such as potassium chloride and sodium molybdate which alter the distribution of estrogen receptor species on sucrose density gradient centrifugation, promote similar alterations in receptor profiles when HPSEC was employed. Our investigations suggest the use of [125I]iodoestradiol-17 beta and HPSEC allows the sequential analysis of estrogen receptor species providing new insights into receptor composition and structure. It is concluded that HPSEC has a broad application in the field of steroid hormone receptors. This method should be useful in studies ranging from measurements of molecular and kinetic properties to their mode of cellular interaction and regulation.

Animals↗
PubMed1984

Prostaglandin E and F2 alpha receptors in human uterine leiomyomas.

9uman uterine leiomyomas specifically bound less (P less than 0.01) [3H]prostaglandin E1 ([3H]PGE1) and [3H] PGF2 alpha than adjacent normal myometria [leiomyomas: mean [3H]PGE1, 16.4 (range, 11.1-25.2) fmol/mg protein; mean [3H]PGF2 alpha, 4.7 (range, 0.8-12.1) fmol/mg protein; adjacent normal myometria: mean [3H]PGE1, 41.7 (range 27.1-60.7) fmol/mg protein; mean [3H]PGF2 alpha, 7.8 (range, 4.3-16.3) fmol/mg protein]. The lower binding of both [3H]PGs by leiomyomas was due to lower numbers of available high and low affinity sites. Leiomyomas and normal adjacent myometria bound 4-7 times more [3H]PGE1 than [3H]PGF2 alpha, and this appears to be due to high affinity and high numbers of low affinity PGE sites. The smooth muscle content was lower (P less than 0.01) in leiomyomas (mean, 28.0%; range, 9.7-45.5%) than that of adjacent normal myometria (mean, 58.9; range, 51.4-71.2%). In summary, this is the first demonstration of PGE and PGF2 alpha receptors in human uterine leiomyomas. Lower receptor numbers in leiomyomas appear to be due to the lower smooth muscle content of the tissue.

Adult↗
PubMed1984

Binding sites for epidermal growth factor in human uterine tissues and leiomyomas.

There is no published data regarding whether human uterine tissues and leiomyomas contain binding sites for epidermal growth factor (EGF). The present study was undertaken with 33 myometria, 13 leiomyomas, and 4 endometria. All myometria (fundus) and leiomyomas and 3 of 4 endometria specifically bound 125I-labeled mouse EGF (myometria: mean, 1.1; range, 0.1-3.9 fmol/mg protein; leiomyomas: mean, 1.1; range, 0.2-2.6 fmol/mg protein; endometria: mean, 1.0; range, 0.0-3.1 fmol/mg protein). [125I]EGF binding to myometrium was ligand specific in that only unlabeled EGF, but not unlabeled insulin, hCG, human PRL, prostaglandin E1, or prostaglandin F2 alpha, competed with [125I]EGF for binding. The apparent dissociation constants and specific binding capacities for myometrium and leiomyoma were: 0.7 nM, 1.9 fmol/mg protein; and 0.1 and 3.7 nM, 0.1 and 4.4 fmol/mg protein, respectively. While smooth muscle content decreased from the fundus to the cervical end of uteri, [125I]EGF binding did not correspondingly decrease (r = 0.5; n = 4). The binding of [125I]EGF to myometrium did not vary with the phase of the menstrual cycle or the patients' diagnosis before hysterectomy (P greater than 0.1). In summary, these results demonstrate that human uteri and leiomyomas contain specific, high affinity binding sites for EGF, but the binding neither exhibited topographical changes nor varied with the phase of the menstrual cycle or benign pathological state of the tissue.

Adult↗
PubMed1983

Topography of human uterine prostaglandin E and F2 alpha receptors and their profiles during pathological states.

The topography of prostaglandin (PG) E and F2 alpha receptors in uteri of premenopausal women was investigated by dividing uteri into six equal longitudinal strips and further dividing each strip into approximately 1-cm segments. Tissue for determination of smooth muscle content using the Trichrome stain was taken from each section, and the remainder was homogenized for binding studies with 3H-labeled PGs. The [3H] PGE1 binding (mean, 41.5 fmol/mg protein; range, 23.1-58.3) was about 8-fold greater in the fundus than [3H]PGF2 alpha binding (mean, 4.8 fmol/mg protein; range, 1.3-13.0), and this trend was found in most uterine sections. The binding of both 3H-labeled PGs decreased from fundus to cervix, and this decrease was similar to the decrease in smooth muscle content. Scatchard analysis revealed apparent dissociation constants (Kds) of 1.4 and 76 nM and apparent specific binding capacities (Ns) of 25 and 488 fmol/mg protein for [3H]PGE2, and Kd values of 11.5 and 81 nM and Ns values of 19.4 and 58 fmol/mg protein for [3H]PGF2 alpha in the uterine fundus. The Kd values for [3H]PGE2 were similar in other sections of the uterus, but the Ns values were smaller in the lower uterine body and cervical end. While the phase of the menstrual cycle did not influence [3H]PG binding, the diagnosis of abnormal uterine bleeding compared to dysmenorrhea was associated with an increase in [3H]PGE1 binding (P less than 0.05).

Adult↗
PubMed1979

Comparison of van 't Hoff and calorimetrically determined enthalpies of binding of N-phosphonacetyl-L-aspartate to E. coli aspartate transcarbamylase.

A comparison has been made of the values obtained by direct calorimetric measurements and van 't Hoff analysis, under similar conditions, for the enthalpy of binding of the bisubstrate analog N-phosphonacetyl-L-aspartate (PALA) to E. coli aspartate transcarbamylase and its catalytic subunit. In the case of the catalytic subunit, data were obtained at both saturating and non-saturating concentrations of L-Asp, and at two ionic strengths. Despite a 1000-fold difference in protein concentrations, and the obligatory omission of carbamyl phosphate in the calorimetric experiments, the values obtained by the two methods are shown to agree to within 15% when appropriate corrections are made. These results suggest that subunit dissociation is not a significant factor at the low protein concentrations used in the van 't Hoff analysis, and, conversely, that aggregation of the protein is negligible at the high protein concentrations used in the calorimetric experiments. They also imply that, at pH 8.3, the enthalpic difference between the two conformational states of the enzyme which exist in the presence and absence of substrates is less than 2.5 kcal/mol. In addition, the trends in the three sets of data for the catalytic subunit indicate that ionic bonds are involved in binding PALA to the active site, and that non-productive binding by L-Asp is negligible under these experimental conditions.

Aspartate Carbamoyltransferase↗
PubMed1978

EPR investigation of the Mn(II) binding sites in glutamine synthetase (Escherichia coli W). II. Intermediate-affinity binding sites.

The nature of the intermediate-affinity (n2) Mn(II) binding sites in glutamine synthetase [EC 6.3.1.2] has been studied as a function of adenylylation in a variety of enzyme-metal complexes by EPR. In the absence of nucleotide the n2 Mn(II) environment is nearly isotropic, the Mn(II) bonds are highly ionic, and the interaction distance R greater than or equal to 12-14 A. Nucleotide binding at the n2 Mn(II) site renders the n2 Mn(II) signal unobservable and causes a reduction in signal amplitude (approximately 30%) and line broadening (approximately 6 G) at the high-affinity (n1) Mn(II) site. This behavior indicates that nucleotide binding induces a conformational change in the enzyme which brings the previously distant n1 and n2 sites into closer proximity (R less than or equal to 8-11 A), possibly for the purpose of activating the nucleotide for direct phosphoryl transfer to L-glutamate. In line with this suggestion, the broad, unresolved resonances in complexes containing both L-methionine SR-sulfoximine (MSOX) and nucleotide may result from the phosphorylation of MSOX. The n2 Mn(II) site is not affected by adenylylation in all the enzyme-metal complexes studied, which suggests that the regulatory effects of adenylylation may only act at the n1 Mn(II) sites.

Binding Sites↗
PubMedDate not supplied

Common technical errors in hysterosalpingography.

Hysterosalpingograms from 100 consecutive patients referred for in vitro fertilization were reviewed to evaluate the adequacy of visualization of the uterine cavity. In 17 cases the hysterosalpingogram failed to demonstrate the entire uterine cavity. The most common reason for failure was an axial view of the uterus secondary to inadequate traction on the cervix in 82% (14/17) of the cases, followed by obstructed visualization of the lower uterine cavity and endocervical canal by the delivery catheter bulb in 21% (3/17). A speculum left in the vagina obscured visualization of the endocervical canal in 21% (3/17) of the cases. There were no significant differences in the mean number of radiographic exposures between the adequate and inadequate groups (4.7 vs. 5.9). This study suggests that failing (1) to remove the speculum before injecting contrast, (2) to evaluate the lower uterus and endocervix when using an intrauterine catheter, or (3) to place adequate traction on the cervix, may result in inadequate visualization of the uterine cavity and a need to repeat the study.

Diagnostic Errors↗