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Biomedical subjects

B L Brown

Publications and source records attributed to B L Brown.

At least 19 recordsLinked to original sources
PubMed1992

Bradykinin stimulates the production of prostaglandin E2 and interleukin-6 in human osteoblast-like cells.

The effect of bradykinin (BK) on proteinase activity, prostaglandin synthesis, and the production of interleukin-6 (IL-6) was investigated in cultures of human osteoblast-like cells. Bradykinin had no effect on stromelysin activity and plasminogen activator activity produced by human osteoblast-like cells. However, BK stimulated the production of prostaglandin E2, an effect that was markedly enhanced by pre-incubation with recombinant interleukin-1 alpha (rhIL-1 alpha), but was apparently unaffected by BK receptor antagonists types 1 and 2. Bradykinin stimulated the intracellular accumulation of total inositol phosphates suggesting that its effects were mediated by stimulation of phosphoinositide metabolism. Bradykinin within the dose range of 10(-11)-10(-5) M also significantly stimulated the production of IL-6. Bradykinin may, therefore, mediate a variety of responses in bone under both physiological and pathological conditions.

Bradykinin↗
PubMed1992

The regulation of connective tissue metabolism by vasoactive intestinal polypeptide.

Immunohistochemical studies have confirmed the innervation of bone with neuropeptidergic neurons containing vasoactive intestinal polypeptide (VIP), substance P (SP) and calcitonin gene-related peptide (CGRP). In this study, we report effects of VIP on connective tissue cell metabolism. VIP stimulated PGE2 production in human articular chondrocytes, human osteoblast-like cells and human synovial cells, however, stromelysin production was unaffected. VIP also stimulated cAMP production in human osteoblast-like cells, but not in human articular chondrocytes or synovial cells. These findings are suggestive of a role of VIP in connective tissue cell metabolism which may contribute to the inflammatory processes of arthritis.

Cartilage, Articular↗
PubMed1992

Effect of the GABAA agonist muscimol on prolactin secretion from human prolactin-secreting adenomas and GH3 rat pituitary tumour cells.

The effect of muscimol, a specific potent GABAA receptor agonist, on prolactin release from human prolactin-secreting tissue was investigated using a perifusion system. Perifusion studies on normal rat anterior pituitary tissue, which has identical GABA receptors to those found in normal human pituitary glands, show that muscimol has a specific biphasic effect on prolactin release. This is characterized by an initial transient stimulation (222.3 +/- 21.6% of basal) lasting for 5-10 min followed by a more prolonged inhibitory phase (63.9 +/- 3.1% inhibition of basal). Five human prolactin-secreting adenomas were studied, and in none of the tumours could a biphasic response be demonstrated. One of the prolactin-secreting adenomas had a blunted inhibitory response, but the other 4 showed no inhibitory effect of muscimol on prolactin release. Muscimol had no significant effect on basal or thyrotropin-releasing-hormone (TRH)-stimulated prolactin secretion from GH3 rat pituitary tumour cells. These studies suggest that the GABAergic effect on prolactin secretion is absent or altered in both rat and human prolactin-secreting tumour cells.

Adult↗
PubMed1992

Maxillary removal and reinsertion for improved access to anterior cranial base tumors.

Portions or all of the maxillae are oftentimes removed solely to provide access to certain cranial base tumors rather than because they are involved directly with disease. The purpose of this report is to describe an approach that involves removal of one or both maxillae to improve tumor exposure with subsequent reinsertion as free bone grafts which are stabilized with titanium craniofacial fixation plates. The titanium permits postoperative imaging studies and radiotherapy. Eleven patients ranging from 10 to 69 years of age have undergone 12 operations using this technique for resection of 4 benign and 8 malignant tumors at The Ohio State University. Seven of the 8 patients with malignancies underwent postoperative radiation therapy. There have been no permanent complications and no evidence of bone resorption in this group after follow-up of up to 15 months.

Adolescent↗
PubMed1992

Behavioral contrast: Pavlovian effects and anticipatory contrast.

Two sources of behavioral contrast have been identified previously: Pavlovian stimulus-reinforcer relations and component sequence effects (anticipatory contrast). This study sought to isolate these sources of control procedurally in a four-ply multiple schedule composed of two fixed two-component sequences. Different cues were associated with the first component of each sequence, and contrast effects were studied in these target components. In Experiment 1, differential cuing of Component 2 between sequences and availability of reinforcement during target components were varied across three groups of pigeons; the stimulus-reinforcer relation between target-component cues and schedule of reinforcement in Component 2 was varied within subjects. Control by the Pavlovian relation was demonstrated under all conditions, and anticipatory contrast was not observed. In Experiment 2, target-component duration was systematically varied in the three groups of Experiment 1. Control by the Pavlovian relation was reliably obtained only when target-component behavior was unreinforced, and diminished with increases in component duration. Anticipatory contrast emerged in the two groups for which target-component reinforcement was available. These and other data indicate that Pavlovian effects in multiple schedules may be obscured when the requisite conditions for anticipatory contrast are present.

Animals↗
PubMed1991

Measurement of intracellular mediators in enterocytes isolated from jejunal biopsy specimens of control and cystic fibrosis patients.

A method that maximises the yield of viable enterocytes has been developed for the isolation of enterocytes from human jejunal biopsy specimens. These enterocytes have been used to study the values of intracellular free calcium and the rises in adenosine 3'5'-cyclic monophosphate (cAMP) induced by secretagogues in normal and cystic fibrosis cells. Basal intracellular free calcium of cystic fibrosis enterocytes, measured fluorimetrically with fura-2, was within the range of the basal intracellular free calcium of non-cystic fibrosis enterocytes (cystic fibrosis 263 nmol/l; non-cystic fibrosis 287 nmol/l). Changes in intracellular free calcium were observed after exposure to ionomycin: a 100 nmol/l solution induced a 2.5 fold increase in intracellular free calcium in the cystic fibrosis enterocytes and a 2.2 fold increase in the intracellular free calcium concentration of the non-cystic fibrosis enterocytes. Basal cAMP values were not significantly different between cystic fibrosis and non-cystic fibrosis enterocytes (cystic fibrosis 575 fmol/100,000 cells; non-cystic fibrosis 716 fmol/100,000 cells, p greater than 0.05) and the enterocyte cAMP value increased in response to stimulation with prostaglandin E2 (7 mumol/l) (cystic fibrosis 2.2 fold increase over basal, p less than 0.05; non-cystic fibrosis 1.9 fold stimulation over basal, p less than 0.05) and vasoactive intestinal polypeptide (100 nmol/l) (cystic fibrosis 7.1 fold increase over basal, p less than 0.05; non-cystic fibrosis 5.8 fold increase over basal, p less than 0.05). There was no significant difference in the magnitude of the response between cystic fibrosis and non-cystic fibrosis enterocytes (p greater than 0.05). These results indicate that the cystic fibrosis defect in the small intestine, as in other affected epithelia, seems to be distal to the production of second messengers. The small intestine is therefore an appropriate model in which to study the biochemical defect in cystic fibrosis.

Animals↗
PubMed1991

Kallidin stimulates prolactin secretion from individual rat anterior pituitary cells.

Kinins are localized within the adenohypophysis where they have been shown to stimulate the release of pituitary hormones. In the present study we have investigated the effect of [Lys]-bradykinin (kallidin) on prolactin secretion at the single cell level from cultured male rat anterior pituitary cells. This was assessed by use of a reverse haemolytic plaque assay which permits quantitative evaluation of the proportion of all pituitary cells which are secreting prolactin, and the amount of prolactin secreted per lactotroph (plaque area). The rate of plaque development was used as an index of the rate of hormone secretion in time-course studies. Kallidin induced a dose-dependent increase in both the percentage of plaque-forming cells and the median plaque area during the first 2 and 3 h of incubation respectively. The threshold concentration of kallidin was 10 nmol/l. After 4 h of kallidin stimulation there was no difference between treated and control monolayers with respect to median plaque area and the total secretion index. Although recruitment of additional cells into the secretory pool cannot be excluded, this seems unlikely since at 3 and 4 h little or no difference was observed in the number of plaque-forming cells. The data suggest that initially kallidin accelerated the rate of prolactin secretion primarily by inducing an increase in the number of cells secreting prolactin, and subsequently by increasing the amount of hormone secreted per lactotroph. The results presented here are consistent with the proposed role of the kallikrein-kinin system in the paracrine or autocrine control of prolactin release from the pituitary gland.

Animals↗
PubMed1991

The effect of retinoic acid on parathyroid hormone- and parathyroid hormone-related peptide-induced intracellular calcium in a rat osteosarcoma cell line, UMR106.

We have examined the effects of parathyroid hormone (PTH) and PTH-related peptide (PTH-rP) on intracellular calcium (Ca2+i) in a rat osteogenic sarcoma cell line, UMR106. Synthetic bovine (b)PTH(1-34) caused a small inconsistent rise in Ca2+i in UMR106 cells, whilst cells pretreated with retinoic acid (RA, 1 mumol/l) for 18 h exhibited reproducible, significant and dose-dependent increases in Ca2+i levels in response to bPTH. The effect of RA on PTH-induced changes in Ca2+i were dependent upon both dose and time. Purified human (h)PTH-rP(1-34) increased Ca2+i in the absence of RA in the same cells. However, RA increased the magnitude of PTH-rP-stimulated changes in Ca2+i without affecting the concentration required for a maximal response. RA also prolonged the delay before the Ca2+i response was observed. Maximal responses to PTH-rP were greater in magnitude than those to PTH. These changes appeared not to be due to cyclic AMP (cAMP), since neither dibutyryl cAMP (1 mmol/l) nor forskolin (15 mumol/l) affected Ca2+i. PTH- and PTH-rP-mediated Ca2+i transients were not completely abolished by the absence of extracellular calcium, and both peptides increased basal levels of inositol trisphosphate. PTH and PTH-rP were subject to mutual desensitization, but were not desensitized by prostaglandin E2. PTH(7-34) antagonized PTH- but not PTH-rP-mediated Ca2+i transients. We conclude that there may be some important differences in the mechanism of action of PTH and PTH-rP.

Animals↗
PubMed1990

Interleukin-1 stimulates diglyceride accumulation in the absence of protein kinase C activation.

Despite advances in the knowledge of the intracellular signalling in response to extracellular messengers, the mechanism of action of interleukin-1 (IL-1) has remained an enigma. In the present study, we have employed human dermal fibroblasts (Detroit 532 cells) to investigate IL-1 beta-induced changes in intracellular signals. Both recombinant human IL-1 beta and a native preparation purified from human placental tissue were employed. Cyclic AMP levels in cell monolayers were unaltered by IL-1 beta. Also, IL-1 beta did not influence significantly the levels of phosphatidylinositol, phosphatidylinositol 4-monophosphate, and phosphatidylinositol 4,5-bisphosphate in the membrane, nor the water-soluble inositol phosphates, inositol monophosphate, inositol bisphosphate and inositol trisphosphate, in cells prelabelled with myo-[3H]inositol. In addition, intracellular calcium as measured by Quin2 was unaffected by interleukin-1. However, in cells labelled with [3H]glycerol or [3H]arachidonic acid, IL-1 beta caused an immediate rise in diglyceride (DG) accumulation. As the effects of IL-1 beta have been reported to be mimicked by tumour-promoting phorbol esters, this rise in DG suggested the involvement of protein kinase C (PKC). However, repeated experiments failed to reveal any acute effect of IL-1 beta on the activity of this enzyme. Furthermore, IL-1 beta did not cause the translocation of PKC between the membrane and the cytosol as has been found in response to other extracellular signals. Rather, IL-1 beta appeared to increase the synthesis of PKC in both membrane and cytosol preparations, an effect which could be prevented by coincubation with cycloheximide. These findings suggest that the diglyceride formed in response to IL-1 beta does not activate protein kinase C.

Calcium↗
PubMed1990

Interactive regulation of signalling pathways in bone cells: possible modulation of PGE2-stimulated adenylyl cyclase activity by protein kinase C.

We have reported previously that tumour-promoting phorbol esters modulate both basal and vasoactive intestinal polypeptide (VIP)-stimulated adenylyl cyclase activity in GH3 (an established pituitary cell line). Here, we probe the receptor and cell specificity of this response. Experiments were performed in the presence of isobutylmethylxanthine. Unlike the response in GH3 cells, the tumour-promoting phorbol ester (tetradecanoyl phorbol acetate (TPA] did not affect either basal adenylyl cyclase activity nor VIP-stimulated activity in the rat osteosarcoma subclones UMR 106-01 and UMR 106-06. In addition, the cyclase responses to parathyroid hormone (PTH), and, in the case of UMR 106-06, to calcitonin were unaffected by tumour-promoting phorbol ester. However, prostaglandin E2-stimulated cyclase activity in both of these subclones was attenuated in a dose-dependent manner.

Adenylyl Cyclases↗
PubMed1990

Flurbiprofen versus diclofenac for the treatment of osteoarthritis of the knee.

Seventy-four patients were enrolled in this double-blind, randomized single-center study to evaluate the therapeutic effectiveness of 50 mg tid regimens of flurbiprofen or diclofenac sodium in patients with osteoarthritis of the knee. By chance, the flurbiprofen patients had a significantly more advanced disease status at baseline than their diclofenac-treated counterparts. However, at subsequent follow-up evaluations, both treatment groups experienced a significant reduction in disease severity regardless of the baseline differences. No serious safety problems were associated with either investigational therapy. The frequency of reported medical events were distributed equally between the flurbiprofen and diclofenac groups. Although the imbalance in disease severity between treatment groups made a rigorous statistical interpretation of the results very difficult, the data from this clinical trial tend to support the equiefficacy of 50 mg tid regimens of flurbiprofen versus diclofenac for treating osteoarthritis of the knee.

Adult↗
PubMed1990

Kallidin-induced stimulation of inositol phosphate production and prolactin release in rat anterior pituitary cells.

The effect of the kinin, kallidin (lysyl-bradykinin) on phosphoinositide metabolism and prolactin secretion was examined in male rat anterior pituitary cells in primary culture. Kallidin was found to stimulate both total inositol phosphate production and prolactin release. The stimulation of inositol phosphate was biphasic in nature, similar to that previously reported for bradykinin, although kallidin was approximately 10-fold more potent. Kallidin also stimulated prolactin secretion provoking a maximal stimulation of 193.0 +/- 11.1 (sem)% at 1 mumol/l. These findings suggest that kallidin-induced prolactin secretion may be mediated intracellularly by activation of phosphoinositide metabolism. The B2 receptor antagonists had no significant inhibitory effects on kallidin-stimulated phosphoinositide metabolism or prolactin release. The B1 agonist des-Arg9-bradykinin has previously been shown to have no effect on either parameter. As the effects of kinins on anterior pituitary cells do not appear to be mediated by either of the known kinin receptors, they may, therefore, act via a hitherto unrecognised kinin receptor.

Animals↗
PubMed1989

Agents affecting adenylate cyclase activity modulate the stimulatory action of 1,25-dihydroxyvitamin D3 on the production of osteocalcin by human bone cells.

The stimulation of osteocalcin synthesis by human osteoblast-like cells in response to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is antagonised by several bone regulatory agents. We have shown that agents which activate adenylate cyclase inhibit this action of 1,25(OH)2D3 on human osteoblast-like cells. Activation of adenylate cyclase, either via the stimulatory GTP-binding protein using cholera toxin, or directly at the catalytic via the stimulatory GTP-binding protein using cholera toxin, or directly at the catalytic subunit using forskolin, results in a suppression of osteocalcin synthesis. Whilst the activation of adenylate cyclase induces this inhibitory response, neither exogenous dibutyryl cyclic AMP nor the phosphodiesterase inhibitor, IBMX, exerted any apparent effect on the production of osteocalcin. The tumour promoting phorbol ester, 4 beta-phorbol 12,13-dibutyrate, also inhibited 1,25(OH)2D3-stimulated osteocalcin production. This was not apparent in response to the non-tumour promoting phorbol ester 4 beta-phorbol suggesting the involvement of protein kinase C.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Regulation of GH3 pituitary tumour-cell adenylate cyclase activity by activators of protein kinase C.

The influence of protein kinase C (PKC) activation on cyclic AMP production in GH3 cells has been studied. The stimulation of cyclic AMP accumulation induced by forskolin and cholera toxin was potentiated by 4 beta-phorbol 12,13-dibutyrate (PDBu). Moreover, PDBu, which causes attenuation of the maximal response to vasoactive intestinal polypeptide (VIP), also induced a small right shift in the dose-response curve for VIP-induced cyclic AMP accumulation. PDBu-stimulated cyclic AMP accumulation was unaffected by pretreatment of cells with pertussis toxin or the inhibitory muscarinic agonist, oxotremorine. PDBu stimulation of adenylate cyclase activity required the presence of a cytosolic factor which appeared to translocate to the plasma membrane in response to the phorbol ester. The diacylglycerol-generating agents thyroliberin, bombesin and bacterial phospholipase C each stimulated cyclic AMP accumulation, but, unlike PDBu, did not attenuate the stimulation induced by VIP. These results suggest that PKC affects at least two components of the adenylate cyclase complex. Stimulation of cyclic AMP accumulation is probably due to modification of the catalytic subunit, whereas attenuation of VIP-stimulated cyclic AMP accumulation appears to be due to the phosphorylation of a different site, which may be the VIP receptor.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Two methods to detect DNA fragments produced by restriction enzymes.

This report summarizes two methods for detecting limited amounts of DNA from restriction endonuclease digests. The first is a photographic system for visualizing ethidium bromide-stained DNA fragments in agarose gels which can detect as little as 50-100 pg DNA per band. The second technique is direct sulfonation of DNA fragments bound to nylon membranes followed by visualization of the fragments by nonradioactive immunoblot methods. The immunohistochemical staining can detect 10 pg DNA per band. The direct sulfonation technique is not intended to identify specific DNA sequences; DNA-DNA hybridization with sulfonated probes has previously been described (P. Lebacq, D. Squalli, M. Duchenne, P. Poulety, and M. Johannes (1988) J. Biochem. Biophys. Methods 15, 255-266). Direct sulfonation can be used when samples are relatively free of contaminating nucleic acids and is a useful alternative to end-labeling. These highly sensitive techniques may be suitable when the DNA source is of limited quantity or in instances where radiolabeling is not permitted.

Animals↗
PubMed1989

Bradykinin stimulates phosphoinositide metabolism and prolactin secretion in rat anterior pituitary cells.

Bradykinin stimulated prolactin secretion from monolayer cultures of rat anterior pituitary cells, the stimulation being greater from the cells of male rats. This stimulated secretion was accompanied by a rise in total inositol phosphate accumulation, suggesting that the action of bradykinin is mediated by phosphoinositide hydrolysis. The increase in inositol phosphate accumulation was biphasic; a further sharp rise occurred when the concentration of bradykinin exceeded 1 mumol/l. This may indicate that bradykinin acts on other cell types in the pituitary gland. Bradykinin had no effect on growth hormone secretion from cells of normal pituitary glands, or on prolactin secretion and phosphoinositide metabolism in GH3 rat pituitary tumour cells. Bradykinin receptor antagonists (both B1 and B2) had no effect on either bradykinin-stimulated inositol phosphate accumulation or prolactin secretion. Kallikreins, the enzymes responsible for the generation of kinins, are known to be present in the adenohypophysis. Therefore, the results presented here would suggest that kinins may have a role as paracrine agents in the pituitary gland.

Animals↗