Effect of cabergoline, a dopamine agonist, on estrogen-induced rat pituitary tumors: in vitro culture studies

Cabergoline (CG) is a dopamine agonist that inhibits secretion of prolactin (PRL) and growth hormone. The purpose of this study was to investigate the PRL-lowering effect and antitumor effect of CG on estradiol-induced rat pituitary tumors in vitro and to elucidate these mechanisms. We compared the effects of CG with those of bromocriptine (BC) in terms of the inhibition of hormone secretion as well as antitumor effects on rat pituitary tumors. Primary cultures of dissociated pituitary tumor cells were used in these studies. A significant inhibition of prolactin (PRL) secretion was observed for both drugs within 12 h after treatment, and the inhibitory effects of CG and BC were antagonized by sulpiride or haloperidol. Inhibitory effect on PRL secretion after 12-h BC or CG pretreatment was more pronounced with CG than BC treatment at all time points. PRL secretion in group pretreated with CG was significantly suppressed at 72 h when compared to that of vehicle. Inhibition of de novo PRL synthesis was better demonstrated in the CG group. These findings suggest that CG has a higher affinity for the D2 receptor of pituitary cells as compared to BC and may preferentially inhibit PRL secretion rather than PRL production. An antitumor effect of CG has been confirmed at a lower dosage than that of BC.

Effects of L-arginine analogues on vasomotion of isolated porcine coronary arteries

L-Arginine analogues have been widely used to examine the role of endothelium-derived nitric oxide (NO) in vascular responses; however, the effects of the agents on coronary vasomotion are not fully understood. In this study, we examined the effects of the analogues on vasomotion of isolated porcine coronary arteries. Strips of the porcine coronary artery were suspended for isometric tension recording in Krebs-Henseleit solution. L-Arginine analogues, N omega-nitro-L-arginine methyl ester (L-NAME, 10(-9)-10(-3) M), NG-monomethyl-L-arginine (L-NMMA, 10(-9)-10(-3) M), and NG-nitro-L-arginine (L-NNA, 10(-9)-10(-3) M), caused dose-dependent contractions, which were greater in strips with than in those without endothelium. Those endothelium-dependent contractions were almost abolished by indomethacin (10(-5) M) and FeCl2 (10(-3) M). The latter reduces prostaglandin H2 to 12-heptadecatrienoic acid, which has no vasoconstrictor effect. These results indicate that the L-arginine analogues cause endothelium-dependent contractions that are mediated by prostaglandin endoperoxides and suggest that they have properties other than simple inhibition of NO synthesis in porcine coronary arteries.

Effect of topical application of nitroglycerin on cochlear blood flow

PURPOSE

To investigate whether topical application of the vasodilator nitroglycerin would increase cochlear blood flow without adversely affecting inner ear function.

MATERIALS AND METHODS

The effect of topical application of nitroglycerin to the round window membrane on cochlear blood flow was measured in 33 guinea pigs with a laser Doppler flowmeter. Endocochlear potential, as an indicator of inner ear function, was recorded by a glass microelectrode inserted through the round window membrane in a second series of 27 guinea pigs. Blood pressure was also monitored in both experiments.

RESULTS

Low doses (0.0001 to 1 microgram) of nitroglycerin induced an increase in cochlear blood flow with no change in blood pressure. The cochlear blood flow was maximally increased by approximately 50%. A high dose (50 micrograms) of nitroglycerin induced a significant decrease in blood pressure but did not significantly affect endocochlear potential.

CONCLUSIONS

Topical application of nitroglycerin may be useful in increasing cochlear blood flow in various inner ear diseases.

Enhanced expression of CD34 messenger RNA by developing endothelial cells of mice

BACKGROUND

Immunohistochemical studies have demonstrated that CD34 antigen is present on the surface of vascular endothelial cells and hematopoietic cells. Roles of CD34 for angiogenesis and its function as a homophilic adhesion molecule between endothelial and hematopoietic cells have been speculated.

EXPERIMENTAL DESIGN

Northern blotting was used to examine the expression levels of CD34 mRNA, and in situ hybridization was used to localize CD34 mRNA. First, we investigated changes in CD34 mRNA expression in developmental processes of mice. Second, we investigated the changes in skin tissues of adult mice in the process of wound healing and tumor growth.

RESULTS

CD34 mRNA was strongly expressed by most of the vascular endothelial cells in developing organs. The magnitude of the expression decreased after birth but increased again in the process of wound healing and tumor growth. Although CD34 mRNA signals were observed in hematopoietic cells in the yolk sac and fetal liver, the endothelial cells of these tissues did not express CD34 mRNA signals. CD34 mRNA signals were detectable in neither hematopoietic nor endothelial cells of the bone marrow. In tissues other than hematopoietic ones, however, blood cells within the vessels did not express CD34 mRNA, although the endothelial cells expressed CD34 mRNA.

CONCLUSIONS

The expression pattern of CD34 mRNA suggested its significant role in development of blood vessels not only in embryos but also in adults. Although CD34 mRNA was expressed both by endothelial cells and hematopoietic cells, the expression did not occur within the same organ, suggesting that the CD34 molecule may not be used as a homophilic adhesion molecule between endothelial and hematopoietic cells.

Co-culture of human breast adenocarcinoma MCF-7 cells and human dermal fibroblasts enhances the production of matrix metalloproteinases 1, 2 and 3 in fibroblasts

No measurable amounts of matrix metalloproteinases (MMPs) were produced by human breast adenocarcinoma cell lines MCF-7 and BT-20 in culture. When MCF-7 cells were co-cultured with human dermal fibroblasts enhanced production of precursors of MMP-1 (interstitial collagenase), MMP-2 (gelatinase A), MMP-3 (stromelysin 1) and tissue inhibitor of metalloproteinase type 1 (TIMP-1) was observed. Immunohistochemical studies indicated that these pro-MMPs originated primarily from the fibroblasts, suggesting that MCF-7 cells have a stimulatory effect on stromal cells to produce at least three pro-MMPs and TIMP-1. BT-20 cells also enhanced the production of pro-MMP-2 and TIMP-1 in the dermal fibroblasts, but not of pro-MMP-1 and pro-MMP-3. Normal mammary epithelial cells promoted only TIMP-1 production. To investigate further the stimulatory factors from MCF-7 cells, the conditioned medium and the cell membrane were prepared and examined. The cell membrane fraction enhanced the production of pro-MMP-1 and -3 and TIMP-1, but not of pro-MMP-2. The conditioned medium, on the other hand, augmented the production of all four proteins in the fibroblasts. These observations suggest that breast adenocarcinoma MCF-7 cells in culture produce both soluble and membrane-bound factor(s) which stimulate the production of pro-MMPs and TIMP-1 in neighbouring stromal cells, but the factor(s) released into the medium and that associated with cell membranes are probably different. Such communication between the normal and malignant cell types may, in part, assist the cancer cells to invade and metastasise.

In vivo effect of cabergoline, a dopamine agonist, on estrogen-induced rat pituitary tumors

Cabergoline (CG) is a dopamine agonist that inhibits the secretion of prolactin (PRL) and growth hormone. In the present study, we evaluated the in vivo effect of CG on PRL secretion and the pituitary tumor induced by estrogen. Estrogen was administered by subcutaneous injection to 4-week-old Fischer 344 rats weekly for 10 weeks to induce tumors. On the last day of estrogen administration, doses of either CG or bromocriptine (BC), 0.6 mg/kg, were administered as a single oral route or chronically, given every third day. Sera and pituitary tumors were sampled on each treatment schedule. Serum levels of PRL were measured and the pituitary glands were weighed. Immunohistological evaluation was performed by optical and electron microscopy. A single dose of CG significantly inhibited the serum levels of PRL for 6 days. Following a single dose of BC, the PRL level was significantly inhibited only at 6 hours' postadministration. The continued oral administration of CG significantly reduced both the serum PRL level and the weight of the pituitary during 15 to 60 days of treatment as compared with BC. Morphologic studies revealed that CG reduced the size of the cells and of the granules, and increased the number of granules per unit area of the cytoplasm. These findings suggest that CG inhibits the maturation of PRL secretory granules and the secretion of PRL more than its synthesis. Thus, CG induced a prolonged lowering of PRL and had a good antitumor effect on rat pituitary tumors induced by estrogen.

Dietary high-linoleate safflower oil is not hypocholesterolemic in aged mice after a long-term feeding--comparison with lard, perilla oil and fish oil

Aged mice (6 months of age) fed a conventional diet were shifted to diets containing 10% lard, high-linoleate safflower seed oil, high alpha-linolenate perilla seed oil or high-docosahexaenoate fish oil. A significant increase in whole body cholesterol (/g wt) was seen within 30 d after the shift (rapid response), followed by a gradual decrease in 60 to 120 d (slow response); similar changes occurred in all the dietary groups. Shortly after the shift, the serum cholesterol concentrations increased to higher levels in the lard and safflower oil groups than in the other groups, and the levels at 120 d were in the group order of safflower oil > lard > perilla oil > fish oil. Rapid and slow responses to dietary shifts were also seen in hepatic cholesterol levels (/g wt), which were higher in the lard group than in the other groups at 120 d. The arterial cholesterol contents of the fish oil group tended to be less than in the other groups at 120 d. Thus in aged mice after a relatively long-term feeding (> one tenth of the life-span), safflower oil was not hypocholesterolemic as compared with lard and other omega 3-rich oils. Long-term feeding of fish oil maintained serum cholesterol concentrations at lower levels than feeding with safflower oil or lard and without accumulating cholesterol in the aorta, liver or whole body; perilla oil was also hypocholesterolemic but to a lesser degree than fish oil.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple method for collecting eggs of taeniid cestodes from fresh, frozen or ethanol-fixed segments

A simple method was devised for collecting eggs of Taenia taeniaeformis and T. saginata. All gravid segments, either fresh or frozen or 70% ethanol-fixed, were gently scraped using a pestle on a 150 mesh stainless steel sieve. Eggs and tissue debris were washed out all together with mouse tonicity phosphate buffered saline (MTPBS) through the 150 mesh sieve into a glass beaker. Egg suspension with a huge amount of tissue debris in MTPBS was centrifuged 5 min at 3000 r.p.m. (x 1600 g) and the pellet of eggs and tissue debris was resuspended with 1 vol. of MTPBS and 2 vol. of Percoll (Pharmacia) and centrifuged 60 min at 3000 r.p.m. More than 90% of eggs sedimented in the pellet. The supernatant covered with tissue debris was decanted, and the egg pellet was resuspended and centrifuged several times with MTPBS to remove Percoll. It is suggested that this simple method may prove useful for preparation of eggs of biohazardous taeniid cestodes, such as Taenia solium and Echinococcus spp.

Characteristics of prolactin secretion in normal and estrogen-treated pituitaries of rats at the single cell level: analysis by reverse hemolytic plaque assay

We studied PRL release from individual pituitary cells in normal and estrogen (E2)-treated female Fischer 344 rats by means of a reverse hemolytic plaque assay. In this assay, the area of the hemolytic plaque around a pituitary cell is proportional to the amount of hormone secreted from the cell. Multimodal distribution of the plaque area was observed in normal pituitary cells, and was unchanged in the course of aging. In E2-treated pituitary cells, bimodal distribution was found. The heterogeneity of the distribution pattern (functional heterogeneity) and PRL secretion from a single pituitary cell decreased in association with the length of E2 treatment. The mean plaque area for the E2-treated pituitary cells was smaller than that for the normal pituitary cells. These results suggest that in E2-treated pituitary cells, the functional heterogeneity and PRL release from a single cell decrease as tumorigenesis progresses.

Rumen ciliates of Tokara native goat in Kagoshima, Japan

The composition of rumen ciliate protozoa was surveyed in 15 Tokara native goats, Capra hircus domesticus, inhibiting Kagoshima, Japan. As a result, of 11 species with 3 forms under 5 genera detected, Entodinium simplex, E. nanellum and E. rectangulatum were found in all the animals examined. The large ophryoscolecid ciliates detected were Polyplastron multivesiculatum and Metadinium affine alone, which have been regarded as the typical members of Type A composition proposed by Eadie. Since Tokara native goats have been bred isolated in a small islet for a long time, native goats that had been kept in south Japan might possess Type A fauna. Average ciliate density was 43.9 x 10(4) per 1 ml of rumen fluid. The number of species per host was 8.3 on average. Diversity index was 1.412 on average.

The minimum effective dose of praziquantel in treatment of Hymenolepis diminuta in rats

To determine the minimum effective dose of praziquantel against Hymenolepis diminuta in rats, 5.0 mg/kg, 2.5 mg/kg, 1.0 mg/kg, 0.5 mg/kg, 0.1 mg/kg, or 0.05 mg/kg praziquantel were given to each of five experimentally infected rats in six groups. Faecal samples from each rat were examined on ten consecutive days following treatment. The rats were killed and examined for worms on day 10. Based on the results of faecal examination and autopsy, the minimum effective dose of praziquantel against Hymenolepis diminuta in rats was determined to be 0.5 mg/kg.

Cyclooxygenase inhibitors augment the production of pro-matrix metalloproteinase 9 (progelatinase B) in rabbit articular chondrocytes

Matrix metalloproteinase 9 (MMP-9/gelatinase B) has recently been proposed to participate in the destruction of articular cartilage. Here, we report that interleukin 1 (IL-1) enhances the production of the precursor of MMP-9 in rabbit articular chondrocytes in primary culture, and this IL-1-mediated production of proMMP-9 is greatly augmented by cyclooxygenase inhibitors such as diclofenac and indomethacin, whereas the constitutive production of proMMP-2 (progelatinase A) is not modulated by IL-1 and/or cyclooxygenase inhibitors. Exogenous prostaglandin (PG) E1 and PGE2 suppress the proMMP-9 production in a dose-dependent manner. Similar results are also obtained with cultured rabbit synoviocytes. These results provide the first evidence that PGE down-regulates the production of proMMP-9 in chondrocytes and synoviocytes. Thus, cyclooxygenase inhibitors probably exert undesirable catabolic actions on the maintenance of articular cartilage under inflammatory conditions.

Differential effects of hypoxia on ligand binding properties of nicotinic and muscarinic acetylcholine receptors on cultured bovine adrenal chromaffin cells

Hypoxia is known to disturb neuronal signal transmission at the synapse. Presynaptically, hypoxia is reported to suppress the release of neurotransmitters, but its postsynaptic effects, especially on the function of neurotransmitter receptors, have not yet been elucidated. To clarify the postsynaptic effects, we used cultured bovine adrenal chromaffin cells as a model of postsynaptic neurons and examined specific binding of L-[3H]nicotine (an agonist for nicotinic acetylcholine receptors: nAChRs) and 22Na+ flux under control and hypoxic conditions. Experiments were performed in media preequilibrated with a gas mixture of either 21% O2/79% N2 (control) or 100% N2 (hypoxia). Scatchard analysis of the specific binding to the cells revealed that the KD under hypoxic conditions was twice as large as that under control conditions, whereas the Bmax was unchanged. When the specific [3H]nicotine binding was kinetically analyzed, the association constant (k1) but not the dissociation constant (k-1) was decreased to 40% of the control value by hypoxia. When the binding assay was performed using the membrane fraction, these changes were not observed. Nicotine-evoked 22Na+ flux into the cells was suppressed by hypoxia. In contrast, specific [3H]quinuclidinyl benzilate binding to the intact cells was unaffected by hypoxia. These results demonstrate that hypoxia specifically suppresses the function of nAChRs (and hence, neuronal signal transmission through nAChRs), primarily by acting intracellularly.

Intraspecific variation of isoenzymes in Taenia taeniaeformis

The technique of isoenzyme electrophoresis was applied to Japanese wild populations of Taenia taeniaeformis (isolated from Norway rats) and three laboratory reared isolates (KRN isolated from a Malaysian Norway rat, BMM from a Belgian house mouse and ACR from a Japanese gray red-backed vole). The average heterozygosities of Japanese wild populations were fairly small and total genetic variability was 0.0499. The genetic make-up of T. taeniaeformis in Norway rats was rather uniform in the whole of Japan. In KRN isolate, each of all 10 loci examined possessed the allele which was predominant in Japanese wild populations. Similarly, each of 9 loci in BMM isolate possessed the same alleles, but one of 2 alleles at HK locus was different from that in the others. T. taeniaeformis parasitizing house mice and rats were considered to be genetically closely related to each other. In ACR isolate, 7 out of 10 loci possessed different alleles from those in the other populations. It was considered that ACR isolate was genetically distant and its phylogenetic origin in Japan should be different from worms parasitizing Norway rats.

Plasma (1-->3)-beta-D-glucan measurement in diagnosis of invasive deep mycosis and fungal febrile episodes

(1-->3)-beta-D-glucan is a characteristic fungal cell-wall constituent. To assess the clinical usefulness of this glucan in screening for invasive fungal infection or fungal febrile episodes, we measured the plasma concentration at the time of routine blood culture in 202 febrile episodes by means of factor G, a horseshoe-crab coagulation enzyme that is extremely sensitive to this polysaccharide. With a plasma cut-off value of 20 pg/mL, 37 of 41 episodes of definite fungal infections (confirmed at necropsy or by microbiology) had positive results (sensitivity 90%). All of 59 episodes of non-fungal infections, tumour fever, or collagen diseases had concentrations below the cut-off value (specificity 100%). Of 102 episodes of fever of unknown origin, 26 had plasma glucan concentrations of more than 20 pg/mL. With those 102 cases taken as non-fungal infections, the positive predictive value of the test was estimated as 59% (37/63), the negative predictive value as 97% (135/139), and the efficiency as 85% (172/202). The positive predictive value should improve if there were a sensitive gold standard that could discriminate fungal from non-fungal infections. Causative fungi included candida, aspergillus, cryptococcus, and trichosporon. Determination of plasma (1-->3)-beta-D-glucan with factor G is a highly sensitive and specific test for invasive deep mycosis and fungal febrile episodes, and will substantially benefit immunocompromised patients.

Em18, a new serodiagnostic marker for differentiation of active and inactive cases of alveolar hydatid disease

We determined whether detection of antibody response against a newly detected epitope, designated Em18, among Echinococcus multilocularis antigens could be a reliable marker for differentiation of active cases of alveolar hydatid disease (AHD) from inactive cases. Fifteen Alaskan patients with either active or inactive lesions of AHD previously confirmed clinically, pathologically, and serologically by the Em2-enzyme-linked immunosorbent assay (ELISA) were used for a blind test by Western blotting. Ten and five cases were considered to be active and inactive cases, respectively. One of the 10 cases classified serologically as active was judged to be inactive based on clinical and pathologic criteria; the patient had a recognizable parasitic lesion, and following short-term treatment with albendazole, a biopsy of the liver showed a degenerated lesion that did not grow in rodents. The five cases judged to be inactive included two confirmed inactive cases with cicatrized lesions and three active cases that showed the weakest values in the Em2-ELISA. The most predominant IgG subclass responding to Em18 was IgG4. In general, there were good correlations between 1) the antibody response against Em18 and the presence of active lesions and 2) the antibody response against Em18 and the Em2-ELISA values.