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Biomedical subjects

J Schechter

Publications and source records attributed to J Schechter.

At least 19 recordsLinked to original sources
PubMed2001

Levonorgestrel concentrations during 7 years of continuous use of Jadelle contraceptive implants.

Serum levonorgestrel concentrations were assayed in a multicenter, 7-year study of 199 users of Jadelle rod implants. We examined drug levels, patterns of changes, factors affecting drug levels, and concentrations at which pregnancies occurred. Mean levonorgestrel concentrations declined from 435 pg/mL at 1 month of use to 64% of that value (280 pg/mL) at the end of 3 years. Between the end of the third and fifth years neither mean nor median serum levels varied markedly. At 5 years the mean concentration was again 64% of the first month's mean. Declining levels were observed thereafter through the end of 7 years when the mean, 224 pg/mL, was 52% of the 1-month value. Last measured drug concentrations of women who became pregnant during Jadelle use had mean and median values of 152 and 144 pg/mL, respectively, and a maximum value of 180 pg/mL. Analyses indicated ponderal index, body weight, duration of use, and a single clinical center were the most important variables affecting measured levonorgestrel levels. Approximately one-third of assays in the sixth and seventh years were found to be below 180 pg/mL, suggesting that Jadelle levonorgestrel implants would not maintain sufficiently high levels of effectiveness against pregnancy after 5 years and that heavier women would then be at greater risk of pregnancy.

Adolescent↗
PubMed2000

Corneal insult affects the production and distribution of FGF-2 within the lacrimal gland.

The purpose of this study was to determine the distribution of FGF-2 within rabbit lacrimal glands and to determine whether corneal insult affects that distribution. The scarified corneas of experimental animals were inoculated either with adenovirus type 5 or buffer. Control animals were either untreated, or animals whose corneas were scarified. Twenty-one days later all animals were killed and the lacrimal glands were studied by immunocytochemistry and Western blotting to detect FGF-2. In untreated control animals, FGF-2 was immunolocalized predominantly within a population of elongated cells in the basal epithelium of ducts, and to a lesser degree in the basal epithelium of the acini. The elongated immunopositive cells appear to be myoepithelial cells known to be present at these sites. Interstitial cells around ducts and acini, and the basement membranes of the ducts and acini, were also immunopositive for FGF-2. Twenty-one days after adenovirus inoculation and scarification of the cornea, immunopositivity for FGF-2 was dramatically decreased in basement membranes, but increased within myoepithelial cells of the duct epithelium. These myoepithelial cells were frequently enlarged, bulging toward the duct lumen. In animals whose corneas were inoculated with buffer and scarified, or animals whose corneas were simply scarified, the changes in the lacrimal gland were similar, but somewhat less pronounced, to those of adenovirus-inoculated animals. Western blots confirmed the presence of FGF-2 immunoreactivity in all groups. The major band in untreated controls was at 24 kD, whereas all animals with corneal scarification had major bands at 38 kD. Densitometry of Western blots demonstrated that the amount of 24 kD FGF-2 present within the lacrimal gland after corneal scarification was at least 50% less than in untreated controls, whereas 38 kD FGF-2 was at least ten-fold greater. Our findings indicate that corneal scarification results in an altered distribution of FGF-2 within the lacrimal gland, which involves a decrease in low molecular weight FGF-2 and a dramatic increase in a higher molecular weight isoform of FGF-2. FGF-2 may be released from myoepithelial cells apically (exocrine) into the tear fluid and basally (autocrine/paracrine) into the connective tissue, as well as from extracellular complexes within basal laminae.

Adenoviridae Infections↗
PubMed2000

Distribution of growth factors and immune cells are altered in the lacrimal gland during pregnancy and lactation.

We have undertaken a series of studies to elucidate the roles of growth factors (FGF-2, EGF, TGF-beta1) and prolactin (PRL) in lacrimal gland function during pregnancy and lactation, and to better understand the status of the immune system within the lacrimal gland during those physiological states. In this initial study, lacrimal glands of pregnant (d15, d29), lactating (9d, 22d), and adult female control rabbits, were evaluated by immunohistochemistry, Western blotting and image analysis. In control rabbits EGF, TGF-beta1, and PRL, were immunolocalized primarily in the apical cytoplasm of intralobular ductal epithelial cells, and acini demonstrated a basement membrane-associated immunopositivity for TGF-beta1. FGF-2 immunolocalized in myoepithelial cells in the basal ductal epithelium and complexed to the basement membrane enclosing ducts and acini. Cells immunopositive for immune cell markers (RTLA and CD18) were apparent primarily around interlobular ducts. In d29 pregnant rabbits immunopositivity for EGF and TGF-beta1 was increased within intralobular ducts, both apically and basally, and within some interlobular ductal epithelial cells. Immunopositivity for PRL was strongest in d29 pregnant rabbits within the apical and basal cytoplasm of intralobular ductal epithelial cells. Immunopositivity for FGF-2 in myoepithelial cells was strong in d15 and d29 pregnant rabbits, although basement membrane-associated immunopositivity around acini was often decreased. Immunostaining for EGF and TGF-beta1 in lactating rabbits was similar to that in d29 pregnant rabbits, although basement membrane-associated immunopositivity around acini was more comparable to controls. By 22d lactation immunopositivity for FGF-2 closely resembled that in controls. Image analysis of pregnant and lactating rabbits demonstrated that cells immunopositive for RTLA and CD18 were less abundant around ducts and more abundant between acini, although in 22d lactating rabbits the size of periductal foci was increased to nearly that of controls. Western blots correlated well with the immunohistochemistry. Our findings demonstrate that pregnancy and lactation are accompanied by a shift in the distributions of growth factors and PRL, suggestive of increased release both apically into the lacrimal fluid and basally into the interstitium. Additional shifts in the distributions of cells of the immune system from periductal foci to interacinar sites suggest that there is a recruitment of immune cells away from ducts and toward the connective tissue interstitium surrounding the acini, possibly as part of a heightened state of immune readiness during pregnancy and lactation.

Animals↗
PubMed2000

Prolonged effectiveness of Norplant(R) capsule implants: a 7-year study.

Soft tubing Norplant(R) contraceptive implants were studied in 1210 women for 7 years to measure the duration of effectiveness and the magnitude of the pregnancy rates over that time. Mean age at enrollment was 27.4 years. Of the enrollees, 42% were US residents. One-sixth (16.1%) weighed >/=70 kg at the time of implant placement. At the end of 5 years, the cumulative pregnancy rate was 1.1/100; at the end of 7 years, it was 1.9/100. No pregnancies occurred to any of the 400 women who enrolled in the study at age >/=30 years and who weighed <100 kg. Among women aged 18-33 years, the 7-year Norplant pregnancy rates are comparable to the median pregnancy rates of tubal sterilization methods for women of the same age and duration of use. For women aged >/=34 years, without regard to weight at admission, the 7-year effectiveness of soft tubing Norplant equals or surpasses that of tubal sterilization. For continuing implant users, annual pregnancy rates <1.0/100 in years 6 and 7, together with low cumulative pregnancy rates, testify that Norplant capsule implants remain highly effective for 7 years.

Adolescent↗
PubMed1999

Role of radiation therapy in the management of cutaneous malignant melanoma.

Traditionally, cutaneous malignant melanoma is regarded as a radioresistant tumor. Recently, however, an increasing number of clinical studies have refuted this notion. The authors examined the role of radiation therapy in the palliative and/or adjuvant treatment of cutaneous malignant melanoma. The records of 69 patients with cutaneous malignant melanoma were reviewed. Twenty-five patients with extensive regional lymph node involvement received adjuvant radiation therapy after primary surgical treatment, and the remainder received palliative radiation therapy. The therapeutic significance of fraction size was analyzed. In the palliative radiation therapy group, the response rate was 52% with a fraction size < or = 300 cGy and 35% with a larger fraction size (p > 0.05, NS). Local regional control rates after adjuvant radiation therapy using conventional fractionation and larger fraction size were 87% and 82%, respectively (p > 0.05, NS). Radiation therapy is effective in the management of cutaneous malignant melanoma. It plays an important role in the palliation of metastatic disease and as an adjuvant treatment. No advantage in using a large fraction size over conventional dose schedules was found.

Adult↗
PubMed1996

Basic fibroblast growth factor within endothelial cells during vascularization of the anterior pituitary.

BACKGROUND: Basic fibroblast growth factor (FGF-2), a potent angiogenic peptide, is known to be present in gonadotropes of the anterior pituitary parenchyma of rats and mice, and has been isolated from endothelial cells of many organs. Its localization within endothelial cells has not been determined, nor the mechanisms by which it might be released from endothelial cells during normal organogenesis. METHODS: Localization of FGF within endothelial cells of the anterior pituitary was accomplished by immunocytochemistry and studied by light- and electron microscopy. Capillaries within the anterior pituitary were studied in fetal rats from day 15 to term, and in adult rats. RESULTS: At the onset stages of vascularization (15-18 days fetal), the cytoplasm of the endothelial cells of many of the invading, immature capillaries (thick-walled with few or no fenestrations) was intensely immunopositive for FGF. Immunoprecipitate-filled blebs and slender cytoplasmic processes projected from the endothelial cells into the presumptive pericapillary space and toward the parenchymal cells. As gestation progressed (19-20 day fetal), and an increasing number of capillaries acquired the features characteristic of capillaries in the anterior pituitary of adult animals, i.e., thin-walled and fenestrated, there were fewer capillaries demonstrating immunopositivity for FGF. Foci of released FGF, i.e., extracellular, were occasionally evident within the presumptive pericapillary spaces throughout gestation. By comparison, capillaries of the anterior pituitary of adult rats did not contain immunostainable FGF in their cytoplasm, nor were any blebs and/or processes filled with immunoprecipitate evident. However capillaries did reveal an immunopositive enhancement of their lumenal and ablumenal surfaces. CONCLUSIONS: During vascularization of the anterior pituitary, FGF within the cytoplasm of endothelial cells is released from blebs and/or processes of endothelial cells, and after the capillary bed is stabilized postnatally, these characteristics of vascularization are absent.

Animals↗
PubMed1995

Basic fibroblast growth factor: the neurotrophic factor influencing the ingrowth of neural tissue into the anterior pituitary of alpha-T7 transgenic mice?

alpha-T7 mice are a transgenic line which carries a hybrid transgene composed of the 5' flanking region of the human glycoprotein hormone alpha-subunit gene (1.8 kb) linked to the coding region of the oncogene SV40 T-antigen. Large, hemorrhagic, pituitary tumors form in these mice and contain giant, transformed gonadotropes (immunopositive for T-antigen), in addition to normal-appearing gonadotropes (also immunopositive for T-antigen). An additional feature of these tumors is an abundance of neural tissue proliferating throughout the anterior pituitary, concentrated around the giant gonadotropes, and forming synaptoid contacts upon them. Continued study of these mice has demonstrated that the giant gonadotropes contain immunostainable basic fibroblast growth factor (FGF-2), and apparently release the FGF by focal cellular disruption and/or cytoplasmic blebbing. Normal gonadotropes, in control and transgenic mice, were strongly immunopositive for FGF, and appeared intact. In 8- to 13-month-old transgenic mice most of the giant cells were intact, and were surrounded by well-differentiated neural tissue. These giant cells were lightly immunopositive for FGF. Disrupted, giant gonadotropes were more frequent in 2- to 7-month-old transgenic mice, and also were surrounded by well-differentiated neural tissue with many synaptoid contacts. These cells generally were moderately immunopositive for FGF. In neonatal mice, 1-8 days old, precursors of the giant, transformed gonadotropes were identified, primarily, but not exclusively, near the periphery of the anterior pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗