PubMed Health⌕ Search

Biomedical subjects

C R Stockard

Publications and source records attributed to C R Stockard.

14 recordsLinked to original sources
PubMed2003

Cellular mechanism of thymic involution.

Involution of the thymus and alterations in the development of thymocytes are the most prominent features of age-related immune senescence. We have carried out a comparative analysis of thymocyte and stroma in rapid thymic involution DBA/2 (D2) strain of mice compared with slow involution C57BL/6 (B6) strain of mice. Analysis of mice at 15 months of age suggested an age-related decrease in the thymocyte cell count, a block in the development of T cells and cortical involution in D2 mice compared with 3-month-old mice. TUNEL (terminal-deoxynucleotidyl-transferase-mediated dUTP-digoxigenin nick end labelling) staining and fluorescence-activated cell sorter (FACS) analysis showed that there was a significant increase in apoptotic cells in the cortex region of thymus in 15-month-old D2 mice compared with the same aged B6 mice. The thymocyte proliferation rate, as assessed by bromodeoxyuridine (BrdU) staining and [3H]-thymidine incorporation assay, was lower in 3-month-old D2 mice compared with the same age B6 mice. Immunohistochemical staining showed that the arrangement of MTS (mouse thymus stromal)-10+ epithelial cells and MTS-16+ connective tissue staining pattern had become disorganized in 15-month-old D2 mice but remained intact in B6 mice of the same age. These results suggest that, in D2 mice, both the thymocytes and stromal cells exhibit age-related defects, and that the genetic background of mice plays an important role in determining age-related alterations in thymic involution.

Aging↗
PubMed2001

Effects of time and temperature during attachment of sections to microscope slides on immunohistochemical detection of antigens.

To study the effects of time and temperature on attachment of tissue sections to microscope slides, we examined the intensity of immunohistochemical staining of selected antigens in nine different neoplastic and normal tissues after attaching sections at different times and temperatures. Typically, both the temperature and time are minimized when tissue sections attached to slides; however, suboptimal times and temperatures during attachment may result in either loss of tissue due to poor attachment or the necessity for inconvenient staining regimens. Using standard immunohistochemical techniques, 5 microm tissue sections were attached at 58 degrees C for 1, 4 and 24 hr. In a separate study, 5 microm tissue sections were attached for 16 hr at 58, 68 and 80 degrees C. The intensity of staining decreased slightly when the tissue sections were heated at 80 degrees C for 16 hr, but there was little or no decrease when tissues were heated at 68 degrees C or lower for 16 hr, or at 58 degrees C for up to 24 hr.

Antibodies, Monoclonal↗
PubMed1996

Elevated serum levels of p105(erbB-2) in patients with advanced-stage prostatic adenocarcinoma.

Expression of a truncated or extracellular form (p105erbB-2) of p185erbB-2 has been demonstrated in the sera of breast cancer patients. We examined the levels of p105erbB-2 in the sera of patients with various stages of prostatic adenocarcinoma, in patients with benign prostatic hyperplasia (BPH) and in a series of control male patients hospitalized for illnesses unrelated to the prostate. p105erbB-2 levels did not differ between the controls and BPH patients or between these groups and patients with stage A, B or C adenocarcinomas. In contrast, serum p105erbB-2 levels of patients with stage D adenocarcinomas were significantly elevated when compared with either control or BPH patients. There was no correlation between PSA and p105erbB-2 levels among controls, patients with BPH or patients with prostate cancer. Patients with poorly differentiated tumors (combined Gleason score >7) or moderately differentiated tumors (combined Gleason score 5-7) had higher p105erbB-2 levels as compared to patients with well-differentiated tumors (combined Gleason score <5), though this difference was not statistically significant. There was no correlation between serum p105erbB-2 levels and p185erbB-2 expression in malignant tissue, as determined by immunohistochemistry. However, patients with moderate to strong expression of p185erbB-2 within the adenocarcinomas were approximately 4 times more likely to demonstrate elevated serum p105erbB-2 levels as compared with patients with low expression of p185erbB-2.

Adenocarcinoma↗
PubMed1996

Effects of fixation and tissue processing on immunohistochemical demonstration of specific antigens.

Identification of biomarkers in archival tissues using immunochemistry is becoming increasingly important for determining the diagnosis and prognosis of tumors, for characterizing preinvasive neoplastic changes in glandular tissues such as prostate, for evaluating the response of tumors and preinvasive neoplastic changes to certain therapies (i.e., as a surrogate intermediate end point), for selecting patients who are candidates for specific therapies (e.g., immunotherapy) and for retrospective studies. For detecting specific biomarkers it is important to understand the limitations imposed by the fixation methods and processing of the tissues. This study was designed to determine the effects of fixation on the detection in archival paraffin blocks of selected antigens postulated to be important in tumor biology. We evaluated the antigens TGF alpha, p185erbB-2, broad spectrum keratins, p53, and TAG-72 (B72.3). Fixatives evaluated included standard preparations of neutral buffered formalin, acid formalin, zinc formalin, alcoholic formalin, ethanol, methanol, and Bouin's fixative. We found that in general neutral buffered formalin is the poorest fixative for maintaining antigen recognition by immunohistochemistry and that no single fixative was best for all antigens. The dehydrating (coagulant) fixatives (e.g., ethanol and methanol) preserved immunorecognition of p53 and broad spectrum keratins best while the slow cross-linking fixatives (e.g., unbuffered zinc formalin) were best for demonstrating TGF alpha and p185erbB-2. Fixatives other than neutral buffered formalin produced equivalent recognition of the epitope of TAG-72 by B72.3. In formalin fixed archival tissues, only a portion of the antigen signal can be detected by routine immunohistologic methods.

Antigens, Neoplasm↗
PubMed1995

Extracellular FGF-1 acts as a lens differentiation factor in transgenic mice.

The vertebrate ocular lens undergoes a spatially defined pattern of differentiation which may be regulated by the ocular distribution of proteins from the fibroblast growth factor (FGF) family. The ability of altered FGF-1 (acidic FGF) distribution to disrupt the normal pattern of lens differentiation was evaluated by the production of transgenic mice which express FGF-1 under the control of the lens-specific alpha A-crystallin promoter. Since FGF-1 lacks a classical signal peptide consensus sequence, transgenic mice were also produced with a chimeric construct containing the signal peptide sequence of the FGF-4 gene fused in frame to the coding sequences of the FGF-1 cDNA in order to obtain extracellular expression of the transgene. The presence of transgenic mRNA and protein was confirmed by in situ hybridization, Western analysis and immunohistochemistry. The ocular histology of newborn and young adult transgenic mice expressing FGF-1 without a signal peptide appeared normal. In contrast, mice expressing secreted FGF-1 exhibited lens abnormalities including the elongation of anterior epithelial cells. Epithelial cell elongation was accompanied by expression of the fiber cell differentiation marker, beta-crystallin. These observations provide an in vivo demonstration that FGF-1 can induce anterior lens epithelial cells to express characteristics consistent with the onset of fiber cell differentiation. The transgenic induction of differentiation confirms that normal lens morphology reflects an asymmetric distribution of inductive factors within the eye.

Animals↗
PubMed1994

Tumor associated glycoprotein-72 is highly expressed in prostatic adenocarcinomas.

We examined the expression of two well-characterized oncofetal antigens, the tumor associated glycoprotein-72 (TAG-72) and carcinoembryonic antigen (CEA), in malignant prostatic tissues. Three specific monoclonal antibodies, B72.3, CC49 and CC83, were used to examine the expression of TAG-72. Immunoreactivity was detected in 63% of the malignant specimens using B72.3. CC49 and CC83 were more sensitive than B72.3 in detecting TAG-72 expression. Immunoreactivity was detected in approximately 80% of prostatic adenocarcinomas with CC49 or CC83. The pattern and localization of TAG-72 immunoreactivity were similar for the three antibodies with most immunoreactivity observed within the cytoplasm of malignant cells and within the lumens of malignant glands. TAG-72 immunoreactivity was not detected within benign epithelium or stroma, with the exception of focal epithelial expression in areas of acute prostatitis. The COL-1 antibody to CEA did not detect CEA in benign glands, stroma, or malignant cells of prostate specimens resected for prostatic adenocarcinoma. These results demonstrate that TAG-72, but not CEA, is frequently expressed in prostatic adenocarcinomas.

Adenocarcinoma↗
PubMed1994

Interactions between TGF-beta and adrenocorticotropin in growth regulation of human adrenal fetal zone cells.

The factors that regulate growth and function of the human adrenal gland during intrauterine development and thereafter are ill defined. Whereas others have reported that adrenocorticotropic hormone (ACTH) augments the inhibitory effect of transforming growth factor-beta (TGF-beta) on growth of fetal zone (FZ) cells of the human fetal adrenal, we recently found that ACTH interferes with TGF-beta's inhibition of growth of fetal adrenal neocortex cells. In this study we sought to assess independently the effects of TGF-beta in the absence and presence of ACTH on growth of FZ cells. TGF-beta, in a time- and dose-dependent manner, inhibited growth (i.e., [3H]thymidine incorporation) of FZ cells. ACTH (Cortrosyn), at 90 pM to 90 nM, was found to interfere with the TGF-beta inhibition of FZ growth. ACTH 1-24 and human ACTH 1-39, both from Sigma Chemical, also were found to blunt the response of FZ cells to TGF-beta. Growth inhibition due to TGF-beta action and the reversal by ACTH of TGF-beta effects on FZ cell growth were confirmed by the results of immunohistochemical analyses of 5'-bromo-2'-deoxyuridine incorporation into nuclei of FZ cells and by indirect evaluations of cell numbers. Both forskolin (10 microM) and dibutyryl adenosine 3',5'-cyclic monophosphate (1 mM), but not phorbol 12-myristate 13-acetate (1 or 100 mM), were able to mimic ACTH actions in blunting the inhibitory effects of TGF-beta on DNA synthesis. We conclude that ACTH, possibly via activation of adenylate cyclase, interferes with, rather than augments, the growth-inhibitory effect of TGF-beta on FZ cell growth.

Adrenal Glands↗
PubMed1994

Immunohistochemical localization of dehydroepiandrosterone sulfotransferase in human fetal tissues.

Sulfurylation of many steroid hormones has been found to occur in several tissues of the fetal and adult human. Because the production of prodigious quantities of dehydroepiandrosterone sulfate in the developing fetus is believed to be of signal importance in the hyperestrogenic state that is characteristic of human pregnancy, we sought to define the tissue sites that contain dehydroepiandrosterone sulfotransferase (DST). To this end, antibodies directed against purified human liver DST were employed for the immunohistochemical localization of DST in several fetal tissues. Abundant DST was found in the fetal and neocortical zones of the adrenal cortex, liver, testis, and intestine. Collecting ducts of the kidney were weakly positive for DST. DST immunostaining was not observed in spleen, thymus, lung, brain, heart, stomach, pancreas, or skeletal muscle. The tissue localization of DST immunoreactivity is consistent with the reported localization of enzymatic activity determined during in vitro studies on sulfurylation of C19 and C21 steroids. On the other hand, DST localization does not correspond as well to the sites of estrogen sulfurylation found by others. These data suggest that a single enzyme may be responsible for sulfurylation of C19 and C21 steroids in the developing human.

Fetus↗
PubMed1993

Expression of IGF-II/Man-6-P receptors on rat, rabbit, and human colon epithelial cells.

Previous experiments from this laboratory have established the presence of receptors for insulin and insulin-like growth factor I (IGF-I) on apical membranes prepared from rabbit colon epithelial cells; however, no receptors for multiplication-stimulating activity (MSA), the rat peptide hormone equivalent of human IGF-II, were found in this tissue. In the current studies, radioligand binding assays, covalent cross-linking experiments, and immunoblot analyses using a polyclonal rabbit antiserum that recognizes the IGF-II/mannose 6-phosphate (Man-6-P) receptor, all confirmed the presence of IGF-II/Man-6-P receptors on membranes prepared from rat and human colon epithelial cells. Exposure of rat colon epithelial cell membrane fractions to 5 mM Man-6-P before incubation with 125I-labeled IGF-II increased radioligand binding. Immunoblot analysis indicated that IGF-II/Man-6-P receptors were present in both unfractionated rat colon membranes and fractions enriched with apical membranes. Rabbit and human colon epithelial cells displayed a different pattern of receptor distribution than rat colon epithelial cells, with more insulin receptors but relatively few IGF-II/Man-6-P receptors. Immunohistochemical studies using a rabbit polyclonal antiserum confirmed that IGF-II/Man-6-P receptors were present on both the apical and the basolateral surfaces of colon epithelial cells.

Animals↗
PubMed1989

Receptors for insulin and insulin-like growth factor-I in the human adrenal gland.

Human adrenal glands contain high-affinity receptors for insulin and insulin-like growth factor I (IGF-I). Comparative studies with rat, hamster and human adrenal membranes confirmed that IGF-I receptors are most abundant in rat and hamster adrenals, whereas insulin and IGF-I receptors are present in equivalent numbers in human adrenal glands. Covalent crosslinking studies revealed that the human adrenal gland IGF-I receptor binding subunit migrated on dodecyl sulfate polyacrylamide gels with Mr = 135,000, which is identical to the migration of IGF-I receptor binding subunits isolated from other tissues. Autoradiography of frozen human adrenal slices incubated with [125I]insulin showed prominent, displaceable binding of this radioligand to the zona reticularis, zona glomerulosa, vasculature and medulla; in contrast, [125I]IGF-I binding to human adrenal tissue was most prominent in the zona reticularis and negligible in the medullary region.

Adrenal Glands↗
PubMed1988

Paradoxical organ-specific adaptations to streptozotocin diabetes mellitus in adult rats.

Adult male Fisher rats injected with streptozotocin (Stz) to produce diabetes mellitus demonstrated a significant loss of total body weight associated with adipose and muscle tissue wasting. Paradoxically, intestinal mass and length were increased in Stz-treated rats despite catabolism of other tissues. Concomitant with increased intestinal mass, food and water intake increased significantly in Stz-diabetic animals. Renal weight was not reduced despite the fall in total body weight. It is proposed that the adult Stz-diabetic rat responds to a loss of available insulin by polyphagia, polydipsia, and catabolism of adipose and muscle tissue and that a large percentage of available synthetic fuel is devoted to the production of additional intestinal tissue.

Adaptation, Physiological↗
PubMedDate not supplied

Hormone levels and mammary epithelial cell proliferation in rats treated with a regimen of estradiol and progesterone that mimics the preventive effect of pregnancy against mammary cancer.

Women who bear their first child by their late teens have about half the risk of developing breast cancer relative to nulliparous women. The rat is a good model for studying the role of hormones in breast cancer since, for example, young rats become nearly refractory to mammary carcinogenesis after delivering a litter of pups. Short term administration of estradiol and progesterone (E & P) provides virgin rats protection from mammary carcinogenesis as effectively as pregnancy. The purpose of these studies were twofold: first, to evaluate potential long-term toxicity of the E & P treatments and second, to compare hormone treated rats and pregnant rats with respect to circulating E & P levels as well as mammary epithelial cell proliferation and differentiation. To test for toxicity, rats were treated with E & P (20 micrograms and 4 mg, respectively) or vehicle by s.c. injections 5 times per week for 5 weeks beginning at 40 days of age. The animals were weighed biweekly and sacrificed at 500 days of age when detailed necropsies were performed. No significant difference in weight gain was observed between the two groups nor was any toxicity grossly observable in the hormone-treated rats. Furthermore, there was no increase in the number of spontaneous mammary or pituitary tumors in the E & P treated group relative to controls. To evaluate serum hormone titers and mammary proliferation, rats were treated with steroids or vehicle daily beginning at 65 days of age. At 6 and 24 hours after the 1st, 14th and 35th injection, serum E & P were measured by RIA and mammary epithelial cell proliferation by immunohistochemistry (PCNA). At 6 hours after each injection, E & P levels were 3 to 5 fold those observed late in pregnancy. By 24 hours, however, E & P levels subsided to late pregnancy levels or lower. The mammary epithelial cell proliferation index in either E & P treated or late pregnant rats was 6 to 14%. Histologic sections and wholemounts of mammary glands showed a similar degree of differentiation between rats treated with E & P for 14 days or longer and late pregnant rats. These data further suggest that E & P treatments are a non-toxic means of mimicking the protective effect of pregnancy against mammary cancer and that pregnancy or hormone treatments may achieve this prophylaxis through a differentiation mechanism.

Aging↗