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Biomedical subjects

J Morrissey

Publications and source records attributed to J Morrissey.

At least 19 recordsLinked to original sources
PubMed1992

Protein increases glomerular eicosanoid production and activity of related enzymes.

We examined the in vitro production of PGE2, 6-keto PGF1 alpha and TxB2 by isolated glomeruli from rats fed a low (6% casein) or a high (40% casein) protein diet for approximately eight weeks. Glomeruli from high protein-fed rats produced significantly greater amounts of PGE2, 6-keto PGF1 alpha and TxB2 under basal conditions and in response to the addition of 100 nM angiotensin II (Ang II) than glomeruli from low protein-fed rats. To elucidate the mechanisms by which greater protein intake enhanced the glomerular production of eicosanoids, we explored phospholipase (A2 and C) and cyclooxygenase activity in glomeruli isolated from low- or high-protein fed rats. PE-specific PLA2 activities were significantly increased in glomeruli from rats fed a high protein diet when compared to a low protein diet. On the other hand, PC-specific PLA2 activities were significantly decreased in glomeruli from rats fed a high protein diet. No significant difference in PIP2-PLC activities was detected between glomeruli of the two dietary groups. The cyclooxygenase content and activity was significantly greater in glomeruli from rats fed a high protein diet than in glomeruli from rats fed a low protein diet. Glomeruli of rats fed a 50/50 mixture of the diets (23% casein) had amounts and activity of cyclooxygenase and activities of PE-specific PLA2 intermediate between those of high and low protein-fed animals. In conclusion, increased synthesis of eicosanoids by glomeruli from rats fed a high protein diet may be mediated by increases in the amount and activity of cyclooxygenase coupled with enhanced activity of PE-specific PLA2.

Angiotensin II↗
PubMed1992

Effects of dietary protein on eicosanoid production and on the activity of related enzymes in glomeruli and tubules.

Glomeruli obtained from rats fed a high-protein diet for 8 weeks produce increased amounts of eicosanoids due to greater activity of both PE-specific phospholipase A2 and cyclooxygenase. Eicosanoid synthesis in response to angiotensin II is also greater in glomeruli from rats fed a high-protein diet when compared to rats fed a low-protein diet. There was also increased synthesis of eicosanoids in medullary/papillary tubules but not in proximal cortical tubules of rats fed a high-protein diet. This appears to be due to increased activity of PC-specific phospholipase A2 and cyclooxygenase in medullary/papillary tubules.

Animals↗
PubMed1991

Changes in lipid environment decrease Na, K-ATPase activity in obstructive nephropathy.

Unilateral ureteral obstruction markedly alters sodium and water reabsorption by the affected kidney. These abnormalities may be due, at least in part, to decreased Na,K-ATPase activity in various segments of the nephron during obstruction. The reason for this decreased activity has, however, remained speculative. The present study examines the potential mechanisms underlying the decreased Na,K-ATPase activity in obstruction. The Na,K-ATPase activity was markedly reduced in basolateral membrane vesicles prepared from the cortex of the obstructed kidney of rats with unilateral ureteric obstruction of 24 hours duration when compared to basolateral membrane vesicles from contralateral kidneys of the same rats or to basolateral membrane vesicles from kidneys of sham operated animals. However, no such difference was present three days post-release of unilateral ureteric obstruction. When basolateral membrane vesicles were incubated with sodium dodecyl sulphate to permeabilize the vesicles, no difference in the proportion of enzyme latency was detected between the basolateral membrane vesicles from obstructed kidneys and those from sham operated rats. Immunoblotting with antibodies to the alpha subunit of Na,K-ATPase revealed equal amounts of enzyme in the basolateral membrane vesicles from contralateral kidneys, obstructed kidneys and sham operated rats. When incubated with liposomes under conditions conducive to fusion and lipid exchange the activity of Na,K-ATPase in basolateral membrane vesicles from obstructed kidneys was reconstituted almost to normal levels. This increase in enzyme activity did not occur in basolateral membranes from contralateral kidneys or in membranes from kidneys of sham operated rats incubated in the same manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1991

Localization and polar distribution of several G-protein subunits along nephron segments.

Guanine nucleotide binding proteins (G-proteins) are heterotrimeric proteins involved in signal transduction in epithelia. In addition to possessing a polarized epithelium the nephron is composed of well defined segments, each with distinct receptors, transporters and other functions. Since different G-proteins interact with different receptors, a differential distribution of the various G-protein subunits would be expected. To investigate this possibility, polyclonal antipeptide antibodies to several G-protein subunits were used to examine the distribution of these proteins in nephron segments and their localization to apical or basal membrane domains. Immunoblotting of cortical membrane vesicles demonstrated the presence of G-proteins in both the brush border and basolateral membrane. Staining with G alpha common and G alpha s antibodies demonstrated more of these G-protein subunits in the brush border than basolateral membrane. G-protein beta subunits were also present in greater quantity in brush border membranes. Immunocytochemical analysis demonstrated good antigenic preservation and basically confirmed the results of immunoblotting of renal cortex. G-proteins were also found to be differentially distributed in the medulla, the amounts increasing with proximity to inner medulla. Only G alpha s and G beta subunits were demonstrated in glomeruli, but all subunits examined were detected in brush borders of proximal and apical membrane of distal tubules in cortex. In outer medulla G alpha s was detected in both basolateral and brush borders of some tubules and only brush borders of others, G alpha i2 and G beta were found in brush border and G alpha i3 was not detected in this area.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Mechanism of enhanced eicosanoid production by isolated glomeruli from rats with bilateral ureteral obstruction.

Isolated glomeruli from rats with bilateral ureteral obstruction (BUO) of 24-h duration produced significantly greater amounts of prostaglandin (PG) E2 and 6-keto-PGF1 alpha in vitro than glomeruli from sham-operated control (SOC) rats. This increase was abolished by the angiotensin-converting enzyme (ACE) inhibitor, enalaprilat, given in vivo. To elucidate the mechanisms responsible for enhanced eicosanoid production by glomeruli from rats with BUO, we measured the activities of phospholipase (PL) A2 and C and cyclooxygenase in glomeruli isolated from SOC and BUO rats. L-alpha-Phosphatidylcholine (PC)-specific and L-alpha-phosphatidylethanolamine (PE)-specific PLA2 activities were significantly greater in glomerular membranes from rats with BUO than from SOC rats. Likewise, both the activity and amount of cyclooxygenase were significantly greater in glomerular membranes of rats with BUO. Cyclooxygenase and the PE-specific PLA2 in glomerular membranes of rats with BUO remained at the levels seen in SOC rats when animals were treated in vivo before BUO with the ACE inhibitor, enalaprilat, and the thromboxane synthase inhibitor, OKY-046. Thus inhibition of vasoconstrictor formation leads to subsequent inhibition of vasodilator formation. In contrast to PE-specific PLA2, PC-specific PLA2 activities were further increased in glomerular membranes from both SOC and BUO rats pretreated with the two drugs.s The activity of phosphatidylinositol 4,5-bisphosphate-specific phospholipase C (PIP2 PLC) was significantly decreased in glomeruli from rats with BUO compared with SOC rats. We conclude that the increased synthesis of vasodilatory eicosanoids by glomeruli from rats with BUO may be mediated by enhanced activities of PE-specific PLA2 and cyclooxygenase, which are apparently stimulated by the vasoconstrictors angiotensin and thromboxane.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

The noncalcemic analogue of vitamin D, 22-oxacalcitriol, suppresses parathyroid hormone synthesis and secretion.

OCT, a non-calcemic analogue of 1,25(OH)2D3 has been found to have a more potent activity than that of 1,25(OH)2D3 regarding cell differentiation and immunopotentiation activity, and to prolong the average life span of MRL/l mice. Recently, we found that OCT effectively suppressed the secretion and synthesis of PTH without inducing hypercalcemia. In primary cultures of bovine parathyroid cells, OCT was capable of suppressing PTH release in a dose-dependent manner. OCT was also active in vivo, and, like 1,25(OH)2D3, decreased the pre-pro(PTH) mRNA levels. In a group of rats with CRF, daily administration of OCT, 8 ng i.p. for 2 weeks returned PTH levels to normal without changes in serum calcium. Preliminary results in dogs with CRF indicated that after the administration of OCT 5 micrograms i.v., N-terminal PTH decreased by 76% without changes in Ca. In conclusion, OCT may provide a unique contribution to the treatment of secondary hyperparathyroidism.

Animals↗
PubMed1990

Effects of high concentrations of glucose on PTH secretion in parathyroid cells.

We examined the effects of high concentrations of glucose on PTH secretion from cultured bovine parathyroid cells. Increasing medium concentration of glucose caused suppression of PTH secretion. A significant suppression of PTH secretion was found within 48 hours of incubation with as little as 15 mM glucose. The addition of choline chloride to the medium did not suppress PTH secretion, although the osmolality was the same as that of the medium containing 50 mM glucose. When cells previously exposed to 50 mM glucose were reincubated in the medium containing 5 mM glucose for another 48 hours, a complete recovery of PTH secretion was observed. In the cells exposed to 50 mM glucose, the magnitude of the response of PTH secretion to 10(-6) M isoproterenol was blunted. Acid-urea gel electrophoresis revealed that the pattern of intact PTH and fragments secreted from cells exposed to high concentration of glucose was similar to that from control cells. Removal of insulin from the medium resulted in a suppression of PTH secretion similar to changes observed with high concentrations of glucose. The suppressive effects of high concentrations of glucose and lack of insulin were additive. However, we cannot exclude from the present studies whether the suppressive effects of the lack of insulin on PTH secretion was secondary to the fact that insulin may be required for the maintenance of parathyroid cells. The present studies demonstrate that glucose directly modulates PTH secretion in primary parathyroid cell culture.

Animals↗
PubMed1990

Eicosanoid production by isolated glomeruli of rats with unilateral ureteral obstruction.

The production of PGE2 6-keto PGF1 alpha and TxB2 under basal conditions and after exposure to angiotensin II was examined in vitro in isolated glomeruli from sham-operated control rats and rats with unilateral ureteral obstruction of 24 hour duration, that were or were not pretreated with an inhibitor of the angiotensin I converting enzyme (ACE). Basal prostanoid production was greater in glomeruli from the obstructed kidney (OK) than in glomeruli from the contralateral kidney (CLK) of rats with obstruction or glomeruli from the kidneys of sham-operated rats. Glomeruli obtained from the CLK of rats with unilateral obstruction also produced more PGE2 and 6-keto PGF1 alpha than glomeruli obtained from kidneys of sham-operated rats. Administration of an ACE inhibitor to rats with unilateral obstruction in vivo returned basal prostanoid production in vitro to levels seen in glomeruli of sham-operated rats. The increase in prostanoid production in response to angiotensin II added in vitro was less in glomeruli from rats with unilateral obstruction than in glomeruli from sham-operated rats. However, the response was restored to that seen in glomeruli of sham-operated rats after blockade of angiotensin II synthesis in vivo in rats with unilateral obstruction. Blockade of angiotensin II synthesis in sham-operated rats did not affect prostanoid synthesis by their glomeruli.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1990

Effects of probucol on renal function in rats with bilateral ureteral obstruction.

To ascertain the potential role of reactive oxygen metabolites in the pathophysiology of obstructive uropathy, we examined the effect of probucol, an antioxidant agent, on renal function in normal rats and rats with unilateral release of bilateral ureteral obstruction (BUO) of 24 hours duration. Rats were fed either a standard diet or a standard diet containing one percent probucol for two weeks prior to study. Probucol lowered serum cholesterol in both normal and BUO rats. Probucol did not significantly affect renal function in normal rats. BUO rats given probucol had greater inulin and PAH clearances at three to five hours and three days following release of BUO than rats with BUO not given probucol. Kidneys from obstructed rats had higher levels of malondialdehyde, an index of lipid peroxidation, a greater number of leukocytes in the cortex, decreased levels of reduced glutathione and increased levels of oxidized glutathione. Renal cortex from obstructed rats treated with probucol had significantly higher levels of reduced glutathione than kidneys of obstructed rats not given probucol. A decrease in cholesterol, using another lipid-lowering agent, lovastatin, did not modify renal function in rats with BUO. The data can be interpreted to indicate a role for reactive oxygen species in the pathophysiology of obstructive nephropathy. The improved renal function seen in probucol-treated rats with BUO may be due to an effect of this agent in affecting accumulation of reactive oxygen metabolites and/or decreasing the number of leukocytes infiltrating the renal cortex.

Animals↗
PubMed1990

Role of ANG II in eicosanoid production by isolated glomeruli from rats with bilateral ureteral obstruction.

The production of prostaglandin (PG) E2, 6-keto-PGF1 alpha, and thromboxane B2 (TxB2) under basal conditions and after exposure to angiotensin II (ANG II) or arginine vasopressin (AVP) was examined in vitro in isolated glomeruli. The glomeruli were obtained from control rats and rats with bilateral ureteral obstruction (BUO) of 24-h duration that were pretreated or not with an inhibitor of the angiotensin I converting enzyme (ACE). Basal prostanoid production was greater in isolated glomeruli from BUO rats than in controls. Administration of an ACE inhibitor, enalaprilat, given in vivo returned basal prostanoid production by isolated glomeruli of BUO rats to levels seen in glomeruli of control rats. The prostanoid production in response to addition of ANG II or AVP in vitro was blunted in glomeruli from BUO rats, but the response was restored to "normal" after blockade of ANG II synthesis in vivo in BUO rats. Blockade of ANG II synthesis in vivo did not affect prostanoid synthesis by isolated glomeruli of control rats. The prostanoid generation in response to addition of both ANG II and arachidonic acid in vitro compared with ANG II addition alone was not significantly stimulated in glomeruli from BUO rats. In contrast, it was significantly stimulated in glomeruli of control rats. The results indicate that endogenous ANG II has an important role in the increased synthesis of prostanoids found in isolated glomeruli of rats with BUO and that the in vitro prostanoid production in response to ANG II and AVP can be restored to normal when the synthesis of ANG II is inhibited in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1990

Role of guanine nucleotide binding protein, cytosolic calcium and cAMP in fluoride-induced suppression of PTH secretion.

In the present studies, we used fluoride and pertussis toxin, potent modulators of guanine nucleotide binding proteins (G proteins), to examine the role of G proteins, cytosolic calcium ([Ca]i) and cAMP in the regulation of PTH secretion from dispersed bovine parathyroid cells. NaF suppressed PTH secretion and cAMP content and increased [Ca]i levels in a dose-dependent manner. Prior removal of extracellular calcium with EGTA completely blocked the NaF-induced increase in [Ca]i, but did not prevent the NaF-induced inhibition of PTH secretion and cAMP content. Pretreatment with 10(-5) M verapamil or 10(-4) M diltiazem blocked neither the NaF-induced suppression of PTH secretion and cAMP content nor the increase in [Ca]i. Manganese chloride (10(-4) M) significantly inhibited the NaF-induced increase in [Ca]i, but did not block the NaF-induced suppression of PTH secretion and cAMP content. Pertussis toxin blocked neither the NaF-induced increase in [Ca]i nor suppression of PTH secretion and cAMP content. Our data suggest that (1) NaF might stimulate a calcium channel resulting in the increase in [Ca]i by acting on a G protein in a manner resistant to the inhibition by pertussis toxin; (2) the NaF-induced increase in [Ca]i is not directly linked to the suppression of PTH secretion, and (3) the NaF-induced suppression of PTH secretion might be explained at least in part by the decrease in cell cAMP content.

Animals↗
PubMed1989

Evaluating organizational design to assure technology transfer: the case of the Community Clinical Oncology Program.

Current theories of organizational performance are used to guide researchers at the Health Services Research Center of the University of North Carolina at Chapel Hill and the University of Illinois Survey Research Laboratory in the evaluation of the National Cancer Institute's Community Clinical Oncology Program (CCOP) and to derive policy options to enhance program operations. CCOP represents an innovative mechanism designed to improve the accrual of patients to phase III clinical trials, involve community-based oncologists in clinical research, and potentially to disseminate new information on the state-of-the-art cancer treatment to areas distant from cancer centers and research-oriented medical centers. Examined in this evaluation of the second phase of the CCOP are the ability of the 52 currently funded CCOPs and 17 research bases to accrue patients to cancer treatment and cancer control research protocols, their influence on the patterns of practice for cancer treatment in CCOP communities, and their influence on cancer control awareness and activity among primary care physicians. The evaluation applies selected organizational perspectives to describe the intraorganizational and interorganizational characteristics of the CCOPs, research bases, and the Institute that may affect the performance of the CCOP. This organizational approach relates the accrual and influence of the CCOP to controllable aspects of the program's design and management strategies that can be changed through policies directed by the National Cancer Institute. These policies include the criteria used to select CCOPs, the role of research bases in the development and implementation of treatment and cancer control research protocols, and the use of accrual credits.

Academies and Institutes↗
PubMed1989

The noncalcemic analogue of vitamin D, 22-oxacalcitriol, suppresses parathyroid hormone synthesis and secretion.

1,25-Dihydroxyvitamin D (1,25-(OH)2D3) directly suppresses the secretion and synthesis of PTH in vivo and in cell culture. This compound has been used to treat secondary hyperparathyroidism associated with renal failure, but in some patients prolonged treatment with 1,25-(OH)2D3 results in hypercalcemia. An analogue of 1,25-(OH)2D3 with little or no calcemic activity, 22-oxacalcitriol (OCT), was recently developed. We confirmed this lack of calcemic activity by acute and chronic administration to normal rats. A single intraperitoneal injection of vehicle (propylene glycol), OCT, or 1,25-(OH)2D3 (1.0 micrograms/rat) increased calcium by 0.32, 0.30, and 1.40 mg/dl, respectively. When rats were given daily injections of vehicle or 0.5 micrograms of either 1,25-(OH)2D3 or OCT for 4 d, calcium did not change in the rats receiving vehicle or OCT, but increased from 8.4 to 11.4 mg/dl in the rats treated with 1,25-(OH)2D3. In primary cultures of bovine parathyroid cells, 10 nM OCT was as active as 10 nM 1,25-(OH)2D3, suppressing PTH release by 33%. This suppression is due, at least in part, to blocking of transcription of the PTH gene. Using a probe prepared by random prime labeling of an Msp I fragment of plasmid PTHm122, we found that a single 40-ng dose of OCT or 1,25-(OH)2D3 depressed PTH mRNA levels by 70-80% by 48 h when compared with vehicle. Thus, OCT is a very effective suppressor of PTH secretion with virtually no calcemic activity. This analogue may be a valuable tool for the treatment of secondary hyperparathyroidism.

Animals↗
PubMed1989

Regulation of cytosolic pH in bovine parathyroid cells: effect of fluoride.

In the present investigation, sodium fluoride (NaF) was employed to explore the role of guanine nucleotide-binding proteins (G-proteins), protein kinase-C, or cytosolic calcium [( Ca]i) in the regulation of cytosolic pH [( pH]i) in dispersed bovine parathyroid cells, using the pH-sensitive fluorescent dye BCECF. When cells acidified by nigericin in Na-free medium were resuspended in Na-containing buffer, [pH]i returned to basal levels. This recovery was blocked by continued removal of Na+ or the addition of amiloride. NaF (10 mM) increased [32P]phosphate incorporation into phosphatidylinositol bisphosphate, suggesting an increase in phosphatidylinositol bisphosphate turnover. NaF caused an initial acidification, followed by an alkaline recovery in a dose-dependent manner (1-10 mM). Amiloride blocked the NaF-induced alkaline recovery. The protein kinase-C activator phorbol 12-myristate 13-acetate (10(-7) M) caused cytosolic alkalinization, while the protein kinase-C inhibitor H7 (6 x 10(-5) M) significantly inhibited the NaF-induced alkaline recovery. Pertussis toxin (1 microgram/ml) did not affect the NaF-induced changes in [pH]i. Removal of extracellular Ca2+ with EGTA blocked the NaF-induced increase in [Ca]i and alkaline recovery. Ionomycin (5 x 10(-7) M) caused cytosolic alkalinization, but pretreatment with EGTA inhibited the ionomycin-induced cytosolic alkalinization. The present studies clearly demonstrated the presence of an amiloride-sensitive Na+/H+ exchanger in parathyroid cells. Our findings suggest that the NaF-induced cytosolic alkaline recovery was via two complementing pathways: 1) activation of protein kinase-C, followed by stimulation of a Na+/H+ exchanger, and 2) existence of extracellular calcium and/or an increase in [Ca]i.

Amiloride↗
PubMed1989

Combined effects of dexamethasone and 1,25-dihydroxyvitamin D3 on parathyroid hormone secretion in cultured bovine parathyroid cells.

The present studies investigate the effects of glucocorticoids on the function of the parathyroid glands using primary cultures of bovine parathyroid cells. Treatment of parathyroid cell cultures with dexamethasone for 48 h caused a dose-dependent stimulation of PTH secretion. The minimal concentration of dexamethasone required for a significant stimulation of PTH secretion was 0.1 nM. The stimulatory effect of dexamethasone on the secretion of PTH was found within 12 h of treatment with 100 nM dexamethasone. The steroids deoxycorticosterone and cortexolone, which do not have glucocorticoid activity were without effect of PTH secretion. Since glucocorticoids may modulate the effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] in other tissues, additional studies were performed to evaluate the interactions of glucocorticoids and 1,25-(OH)2D3. Addition of 1,25-(OH)2D3 to parathyroid cell cultures for 48 h significantly suppressed PTH secretion. In the presence of dexamethasone, however, 1,25-(OH)2D3 also significantly decreased PTH secretion, although it did not reduce PTH secretion to control levels. The treatment of parathyroid cell cultures with 100 nM dexamethasone did not affect the parathyroid cell content of 1,25-(OH)2D3 receptors. In summary, these studies indicate that glucocorticoids significantly increase the secretion of PTH in vitro. This stimulatory effect can be inhibited by 1,25-(OH)2D3. The parathyroid gland is an additional site of physiological antagonism of glucocorticoids and 1,25-(OH)2D3.

Animals↗
PubMed1988

Bradykinin-activated membrane-associated phospholipase C in Madin-Darby canine kidney cells.

Previous studies have demonstrated that bradykinin stimulates the rapid release of inositol 1,4,5 trisphosphate (IP3) from membrane phosphatidylinositol 4,5 bisphosphate (PIP2) in Madin-Darby canine kidney (MDCK) cells. Since current evidence would suggest that the activation of phospholipase C (PLC) is mediated through a guanine nucleotide-binding protein in receptor-mediated activation of PLC, we evaluated the role of guanine nucleotide proteins in receptor-mediated (bradykinin-stimulated) activation of PLC in MDCK cells. Bradykinin at 10(-7) M produced a marked increase in IP3 formation within 10 s increasing from a basal level of 46.2 to 686.6 pmol/mg cell protein a 15-fold increase. Pretreatment of MDCK cells in culture with 200 ng/ml of pertussis toxin for 4 h reduced the bradykinin-stimulated response to 205.8 pmol/mg protein. A 41-kD protein substrate in MDCK membranes was ADP ribosylated in vitro in the presence of pertussis toxin. The ADP ribosylation in vitro was inhibited by pretreatment of the cells in culture with pertussis toxin. Membranes from MDCK cells incubated in the presence of [3H]PIP2/phosphatidyl ethanolamine liposomes demonstrated hydrolysis of [3H]PIP2 with release of [3H]IP3 when GTP 100 microM or GTP gamma S 10 microM was added. Bradykinin 10(-7) M added with GTP 100 microM markedly increased the rate of hydrolysis within 10 s, thus demonstrating a similar time course of PLC activation as intact cells. These results demonstrate that bradykinin binds to its receptor and activates a membrane-associated PLC through a pertussis toxin-sensitive, guanine nucleotide protein.

Adenosine Diphosphate↗