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Biomedical subjects

C S Wilcox

Publications and source records attributed to C S Wilcox.

At least 91 records · Page 5Linked to original sources
PubMed1994

Differential expression and induction of mRNAs encoding two inducible nitric oxide synthases in rat kidney.

We used quantitative PCR methods and renal microdissection to characterize the expression of inducible nitric oxide synthase (iNOS) mRNAs in rat kidney and cultured glomerular mesangial cells. A partial cDNA homologous to murine macrophage iNOS (macNOS), but distinct from rat vascular smooth muscle iNOS (vsmNOS), was cloned from normal rat kidney. macNOS was the principal iNOS isoform tonically expressed in microdissected glomeruli, proximal tubules, medullary thick ascending limbs (mTAL), cortical and inner medullary collecting ducts (IMCD), and cultured mesangial cells, whereas vsmNOS was the major isoform expressed in arcuate and interlobular arteries. Basal macNOS expression was greatest in mTALs and IMCDs. Restriction mapping of RT-PCR products indicated that basal expression of macNOS mRNA was comparable to that of vsmNOS in cortex, but greater than vsmNOS in outer and inner medulla. However, compared to controls, lipopolysaccharide (LPS)-treated rats exhibited a much greater proportion of vsmNOS mRNA and higher levels of total iNOS mRNA in each zone. Similarly, TNF alpha and IF-gamma preferentially induced expression of vsmNOS mRNA in cultured mesangial cells. We conclude that two iNOS isoforms are constitutively and heterogeneously expressed in the normal rat kidney, and that endotoxemia and cytokines differentially induce their expression.

Amino Acid Oxidoreductases↗
PubMed1994

A double-blind, placebo-controlled study comparing mianserin and amitriptyline in moderately depressed outpatients.

We report on the results of a study comparing mianserin with amitriptyline and placebo, in outpatients with major depression (DSM-III 296.2 or 296.3). One hundred and forty-nine patients were randomized to mianserin (n = 50), amitriptyline (n = 50) or placebo (n = 49). Medication was taken in a nightly (qhs) dose. During Week 1, the maximum dose was 60 mg mianserin, 120 mg amitriptyline or two placebo capsules. Beginning at Day 7 (through Day 42) maximum dosages were 150 mg mianserin, 300 mg amitriptyline or five placebo capsules. At multiple weeks and endpoint, statistically significant reductions in the Hamilton Depression Scale (HAM-D) 17- and 21-item scores were recorded for both active drugs compared with placebo. Positive results with the HAM-D were corroborated by other measures of efficacy. There were no statistically significant differences between mianserin and amitriptyline in terms of efficacy; however, the results do suggest a more rapid therapeutic response for mianserin compared with amitriptyline, in terms of percentage of patients showing > or = 50% improvement at Weeks 2 (30% vs 23%) and 4 (61% vs 44%). The most common adverse experiences were somnolence (amitriptyline and mianserin 60%, placebo 31%) and dry mouth (amitriptyline 76%, mianserin 30% and placebo 20%). Our results indicate that mianserin is clearly superior to placebo, compares favorably with amitriptyline, and is a safe, well-tolerated, effective medication in the treatment of depressed outpatients.

Adult↗
PubMed1994

Immunocytochemical localization of distinct isoforms of nitric oxide synthase in the juxtaglomerular apparatus of normal rat kidney.

Nitric oxide (NO) is a messenger molecule that functions as a vasodilator and accounts for the biologic activity of endothelium-derived relaxing factor (EDRF). The enzyme responsible for NO production, NO synthase (NOS), exists in different isoforms. Some are expressed constitutively in various tissues, whereas others require induction by endotoxin and cytokines. There is evidence that NO plays an important role in the regulation of basal renal vascular resistance and in the tubuloglomerular feedback response. Specific antibodies to a constitutive NOS isolated from rat brain (B-NOS) and an inducible NOS isolated from rat aortic smooth muscle (VSM-NOS) were used to establish the cellular and subcellular distribution of NOS in the kidney. Kidneys from normal rats were preserved and processed for light and electron microscopic immunohistochemical studies using both a preembedding and a postembedding horseradish peroxidase technique. By light microscopy, strong immunostaining for B-NOS was observed in the juxtaglomerular apparatus, where it was located in cells of the macula densa. In contrast, immunostaining for VSM-NOS was specifically located in the terminal afferent arteriole and occasionally also in the initial efferent arteriole in the juxtaglomerular apparatus. In addition, faint immunostaining was present in the entire distal tubule. There was no labeling of arcuate or interlobular arteries. The injection of lipopolysaccharide was associated with increased immunostaining for VSM-NOS in the afferent arteriole but had no effect on B-NOS staining. By electron microscopy, B-NOS immunostaining was present throughout the cytoplasm of the macula densa cells, where it appeared to be associated mainly with small vesicles. Immunostaining for VSM-NOS in the afferent arteriole exhibited a patchy distribution in some cells, whereas other cells were stained throughout the cytoplasm. These results indicate that two distinct isoforms of NOS are present in the juxtaglomerular apparatus and support the hypothesis that NOS is involved in the regulation of tubuloglomerular feedback and glomerular capillary pressure.

Amino Acid Oxidoreductases↗
PubMed1994

Renal vasoconstriction with U-46,619; role of arachidonate metabolites.

Thromboxane A2 (TxA2) or its stable mimetic U-46,619 can increase the generation of arachidonate metabolites. Therefore, these studies were designed to investigate the role of prostaglandins, TxA2, and leukotrienes in the renal vascular response to U-46,619. Anesthetized rats were studied during a basal period and during an intra-aortic infusion of vehicle or U-46,619 (1 micrograms/kg per minute). U-46,619 reduced the GFR and the RBF without changing the mean arterial pressure or the femoral vascular resistance. All of the effects of U-46,619 were blocked by pretreatment with the TxA2/prostaglandin H2 receptor antagonist SQ-29,548. Pretreatment with the cyclo-oxygenase inhibitor indomethacin did not modify the renal vascular response to U-46,619. However, pretreatment with the TxA2 synthesis inhibitor UK-38,485 or with the leukotriene D4/E4 antagonist LY-163,443 markedly blunted the U-46,619-induced increase in renal vascular resistance and the decrease in GFR. These results indicate that the renal vascular response to U-46,619 is receptor mediated and is promoted by TxA2 and leukotriene D4/E4.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1994

Are selective serotonin reuptake inhibitors well tolerated in somatizing depressives?

This retrospective evaluation included 89 patients who participated in two independent clinical investigations of the antidepressant medications paroxetine and fluoxetine. Baseline gastrointestinal (GI) somatic symptoms, as indicated by the baseline scores on the Hamilton Rating Scale for Depression (HAM-D) items 11, 12, and 16, the Symptom Checklist (SCL) items 19 and 40, and the Covi Anxiety Scale somatic anxiety item were analyzed for their discriminative ability in predicting which patients would subsequently develop adverse GI side effects on medication. Subjects with baseline complaints of nausea or upset stomach (SCL #40), GI somatic symptoms (HAM-D #11 and #12, Covi somatic anxiety), or weight loss (HAM-D #16) were not statistically more likely to develop GI side effects on paroxetine or fluoxetine. Only a baseline complaint of appetite loss (SCL #19) was associated with subsequent GI side effects on paroxetine to a statistically significant degree (p < .05).

Adult↗
PubMed1993

Nitric oxide mediates renal vasodilation during erythropoietin-induced polycythemia.

The renal blood flow (RBF) of patients with polycythemia rubra vera is increased despite the high hematocrit (Hct) which elevates the whole blood viscosity. Since blood viscosity determines the shear force on the endothelium which is a major stimulus to nitric oxide (NO) release, we investigated the hypothesis that renal vasodilation during erythropoietin-induced erythrocytosis is mediated by the L-arginine-NO pathway. Groups of Sprague-Dawley rats received thrice weekly injections of erythropoietin (E) for two to five weeks; responses were contrasted with normal rats (N) which received sham injections. The first group was studied after five weeks of erythropoietin injections which led to sharp increases in Hct (E: 72 +/- 3 vs. N: 44 +/- 1%) and mean arterial pressure (MAP: 126 +/- 3 vs. 107 +/- 3 mm Hg). These rats had an elevated basal RBF whether measured by the clearance and renal extraction of PAH or by a transit-time renal blood flow meter. Subsequent groups were studied after two to three weeks of erythropoietin which raised the Hct more modestly to 59 +/- 2%. In this group, the basal MAP was similar in E and N rats. Graded doses of the NO synthase inhibitor, N omega-monomethyl-L-arginine (L-NMA) led to a steeper rise in MAP in E than N; at the highest doses, the MAP had increased by 36 +/- 2 in E and 23 +/- 3 mm Hg in N (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A volume-independent component to postdiuretic sodium retention in humans.

Net sodium (Na) loss during diuretic administration is limited by postdiuretic renal salt retention. This could be a homeostatic response to extracellular fluid volume (ECV) depletion. However, rats infused with loop diuretics develop structural and functional adaptations in the distal nephron that enhance NaCl reabsorption. Therefore, the hypothesis that postdiuretic Na retention in humans contains a volume-independent component was tested. Normal volunteers were equilibrated to a 120 mmol/24 h Na intake. For the first protocol, subjects received, in random order, a placebo, bumetanide (B), or bumetanide accompanied by an infusion of an electrolyte solution at a rate adjusted to match urine flow and thereby to obviate Na losses (bumetanide plus volume replacement; B + VR). After the completion of B diuresis, there was a positive Na balance that restored 70% of the Na loss within 42 h. However, this positive Na balance was prevented by volume replacement (B + VR). For the second protocol, subjects received, in random order, a placebo injection and a 100-mmol NaCl load (P + NaCl) or a bumetanide injection plus volume replacement in addition to a 100-mmol NaCl load (B + VR + NaCl). Over the ensuing 42 h, 94% of the load was eliminated when it was infused alone (P + NaCl). In contrast, only 9% was eliminated when it was given with bumetanide and volume replacement (B + VR + NaCl). It was concluded that postdiuretic Na retention in normal human subjects is due both to ECV depletion and to volume-independent Na retention manifest as an inability to excrete a modest NaCl load.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Angiotensin II receptor subtypes on adrenal adenoma in primary hyperaldosteronism.

Patients with an aldosterone-producing adenoma (APA) characteristically fail to show an increase in plasma aldosterone (PA) concentration with maneuvers that increase angiotensin II (Ang II), yet they retain a brisk response of PA to adrenocorticotrophic hormone. Therefore, adrenal Ang II receptor binding was characterized in a patient with APA who had a blocked PA response to Ang II infusion before adrenalectomy. The binding of [125I]Sar1,IIe5-Ang II in adrenal gland and tumor was fully displaced by excess Ang II. In the tumor, 98% of [125I]Sar1,IIe5-Ang II binding was displaced by the AT, receptor antagonist losartan, yet only 5% was displaced by the AT2 receptor antagonist PD-123,319. Autoradiography of the adrenal gland itself showed a predominance of AT1 receptors in the cortex and AT2 receptors in the medulla. The tumor showed a predominance of AT1 receptors, but there was some evidence of a limited population of AT2 receptors. The tumor and adjacent adrenal contained high concentrations of Ang II. In conclusion, a defect in Ang II-stimulated aldosterone secretion in APA occurs despite high concentrations of Ang II in the adrenal and the presence of specific, high-affinity Ang II receptor binding sites.

Adenoma↗
PubMed1992

Newer tests for the diagnosis of renovascular disease.

OBJECTIVE: To evaluate published reports of diagnostic methods for renovascular hypertension, including Doppler ultrasonography, magnetic resonance imaging, the captopril test, and captopril scanning. DATA SOURCES: MEDLINE and selected references from appropriate published articles. STUDY SELECTION: Studies included those that calculated sensitivities and specificities; studies that derived diagnostic criteria without application to another population of patients were excluded. Consensus of both authors was necessary for inclusion. DATA EXTRACTION: Articles were critically assessed independently by the authors and a consensus critique was developed. DATA SYNTHESIS: Major sources of variability exist in the investigations of recently developed tests for renovascular hypertension. These include variability in patient populations, performance of tests, and determination of outcome measures. CONCLUSIONS: Among the newer diagnostic tests, both magnetic resonance imaging and Doppler ultrasonography hold promise for the anatomic detection of renal artery stenosis, but clear diagnostic criteria have not been universally accepted. There is more information concerning the captopril test, which has a sufficiently high sensitivity to be useful in the screening of high-risk patients for renovascular hypertension. Scans after captopril administration, which appear to be more specific, may enable the prediction of a blood pressure response to angioplasty or surgery.

Captopril↗
PubMed1992

Nitric oxide synthase in macula densa regulates glomerular capillary pressure.

Tubular-fluid reabsorption by specialized cells of the nephron at the junction of the ascending limb of the loop of Henle and the distal convoluted tubule, termed the macula densa, releases compounds causing vasoconstriction of the adjacent afferent arteriole. Activation of this tubuloglomerular feedback response reduces glomerular capillary pressure of the nephron and, hence, the glomerular filtration rate. The tubuloglomerular feedback response functions in a negative-feedback mode to relate glomerular capillary pressure to tubular-fluid delivery and reabsorption. This system has been implicated in renal autoregulation, renin release, and longterm body fluid and blood-pressure homeostasis. Here we report that arginine-derived nitric oxide, generated in the macula densa, is an additional intercellular signaling molecule that is released during tubular-fluid reabsorption and counters the vasoconstriction of the afferent arteriole. Antibody to rat cerebellar constitutive nitric oxide synthase stained rat macula densa cells specifically. Microperfusion of the macula densa segment of single nephrons with N omega-methyl-L-arginine (an inhibitor of nitric oxide synthase) or with pyocyanin (a lipid-soluble inhibitor of endothelium-derived relaxation factor) showed that generation of nitric oxide can vasodilate the afferent arteriole and increase glomerular capillary pressure; this effect was blocked by drugs that prevent tubular-fluid reabsorption. We conclude that nitric oxide synthase in macula densa cells is activated by tubular-fluid reabsorption and mediates a vasodilating component to the tubuloglomerular feedback response. These findings imply a role for arginine-derived nitric oxide in body fluid-volume and blood-pressure homeostasis, in addition to its established roles in modulation of vascular tone by the endothelium and in neurotransmission.

Amino Acid Oxidoreductases↗
PubMed1992

Characterization of rat glomerular thromboxane A2 receptors: comparison to rat platelets.

This study was designed to characterize rat glomerular thromboxane A2 (TxA2) receptors and compare them to rat platelet TxA2 receptors. The radioligand binding characteristics of the receptors were characterized using [125I][1S-(1 alpha,2 beta(5Z),3 alpha-(1E,3R*),4 alpha]-7-[3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)-7-oxabicyclo- [2.2.1]heptan-2yl]-5-heptenoic acid ([125I]BOP), a TxA2 agonist. Equilibrium binding with [125I]BOP, as well as competitive binding assays between [125I]BOP and 13-azapinane TxA2 receptors antagonists, were performed in rat glomerular membranes (RGM) and washed rat platelets (WRP). [125I]BOP identified a single class of TxA2 receptor sites in glomerular membranes with a Kd of 318 +/- 55 pM and a Bmax of 260 +/- 62 fmol/mg protein (n = 14). [125I]BOP was displaced by the TxA2 agonist 15S-hydroxy-11 alpha,9 alpha(epoxymethano)-prosta-5Z,13E-dienoic acid (U-46,619) (IC50 = 22 +/- 6 nM, n = 3), the antagonist SQ-29,548 (IC50 = 41 +/- 7 nM, n = 4), and stereoselectively by the antagonists (-)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid (L-657,925) (IC50 = 0.27 +/- 0.04 nM, n = 3) and (+)-9-chlorobenzyl-6-fluoro-1,2,3,4-tetrahydrocarbazol-1-yl acetic acid (L-657,926) (IC50 = 124 +/- 0 nM, n = 2). The ability of six 13-azapinane TxA2 antagonists to compete with [125I]BOP was evaluated. The rank orders for the 13-azapinanes showed no significant correlation between RGM and WRP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

ACE inhibitors in the diagnosis of renovascular hypertension.

Effective therapy is available but the diagnosis of renovascular hypertension is often elusive. Those affected constitute a minority of the hypertensive population, and traditional screening tests have poor sensitivity and specificity. The merits and limitations of the captopril challenge test and the captopril renogram, alone or in combination, are discussed.

Captopril↗
PubMed1992

Use of buspirone in patients with generalized anxiety disorder and coexisting depressive symptoms. A meta-analysis of eight randomized, controlled studies.

This report presents the results of a retrospective analysis of pooled efficacy data from eight studies in which buspirone was compared to placebo in 520 patients with generalized anxiety disorder (GAD). In addition to evaluating overall efficacy in the composite patient data base, four criteria were used to identify subsets of patients with GAD who had coexisting depressive symptoms of at least moderate intensity: (1) a score of > or = 2 on the Hamilton Anxiety (HAM-A) Rating Scale item 6 (depressed mood), (2) a score of > or = 2 on the Hamilton Depression (HAM-D) Rating Scale item 1 (depressed mood), (3) a HAM-D total score of > or = 18, or (4) a HAM-D Retardation Factor value (items 1, 7, 8, and 14) greater than the median for the group. Overall, patients treated with buspirone demonstrated significant (p < or = 0.001) improvement over baseline in total HAM-A scores compared to patients who received placebo. Buspirone also produced significant (p < or = 0.001) global improvement compared to placebo as assessed by the attending physician. Of the GAD patients stratified according to the four criteria for coexisting depressive symptoms, a substantial percentage (44-64%) of the total patient sample exhibited significant depressive symptoms as part of their anxiety disorder. Patients with GAD and coexisting depressive symptoms of at least moderate intensity exhibited significantly greater improvement with buspirone compared to placebo treatment regardless of the stratification criterion used. They also responded at least as well or better to buspirone therapy as did those with GAD who had less intense depressive symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Potentiation of tubuloglomerular feedback in the rat by thromboxane mimetic. Role of macula densa.

UNLABELLED: Because endogenous thromboxane A2 (TXA2) potentiates the tubuloglomerular feedback response (TGF), we studied the mechanism of action of TXA2 by using a stable TXA2/prostaglandin (PG) H2 mimetic, U-46,619. Intravenous infusion of U-46,619 at 100 ng.kg-1.min-1 reduced the GFR and the single-nephron (SN)GFR measured from the distal tubule (macula densa function intact), whereas the SNGFR measured from the proximal tubule (macula densa function interrupted) was not changed consistently. 10-100-fold higher rates of infusion of U-46,619 were required to raise blood pressure or femoral vascular resistance. The regulation of glomerular capillary pressure (PGC) by TGF was assessed in anesthetized rats from changes in proximal stop flow pressure (PSF) and/or SNGFR during perfusion of the loop of Henle (LH) with artificial tubular fluid (ATF). Orthograde loop perfusion and retrograde perfusion of U-46,619 into the macula densa segment reduced PSF. Responses to luminal U-46,619 were blunted by a TXA2-PGH2 receptor antagonist. Orthograde loop perfusions with luminal U-46,619 increased net Cl absorption, whereas coperfusion with furosemide (10(-4) M) blunted the response to U-46,619 by 68%. These data indicated that the luminal U-46,619 might increase the signal for TGF activation by increasing Cl reabsorption in macula densa cells. However, since 80 +/- 4% of [3H]U-46,619 perfused via the LH was reabsorbed peritubular capillaries (PTC) were perfused with U-46,619 to test additional extra-luminal actions. PTC perfusion with U-46,619 again increased TGF by reducing PSF selectively only while macula densa function was intact during perfusion of the LH with ATF. CONCLUSIONS: (a) TGF is potentiated by U-46,619 given systematically, via the lumen of the LH by orthograde or retrograde perfusions or via the PTC; (b) at the lower doses tested, reduction of PGC and SNGFR by U-46,619 depends on tubular fluid delivery and reabsorption by the macula densa; (c) potentiation of TGF by U-46,619 entails preglomerular vasoconstriction which may be elicited in part by an increased signal due to increased net chloride reabsorption in the LH and presumably macula densa cells and by an increased sensitivity of the arteriole to macula densa-derived signals; (d) activation of TGF may contribute to the selective vasoconstriction of the renal vascular bed by low doses of U-46,619.

Animals↗
PubMed1992

Effect of captopril on the release of the components of the renin-angiotensin system into plasma and lymph.

UNLABELLED: The effects of captopril on the intrarenal renin-angiotensin system were assessed from measurements in arterial plasma, renal venous plasma, and renal lymph from salt-depleted dogs. In the basal state, immunoreactive angiotensin II (Ang II) in renal venous plasma averaged only 60 +/- 12% (P less than 0.01) of arterial plasma, although the concentration of Ang II in renal lymph was 2.0 +/- 0.4-fold (P less than 0.05) greater. The Ang II concentration of renal lymph incubated ex vivo at 37 degrees C doubled in 10 to 15 min, which was the time taken to collect renal lymph samples. Compared with arterial plasma, renal lymph contained lower concentrations (P less than 0.01) of renin substrate and angiotensin-converting enzyme but higher concentrations of active (5.3 +/- 2.1-fold) and inactive (8.9 +/- 3.2-fold) renin. Although captopril increased the secretion of active renin into renal venous plasma by six-fold, the secretion of total renin was unchanged because of a reciprocal fall in the secretion of inactive renin. The percent reduction in renal vascular resistance with captopril correlated with the percent fall in Ang II in renal lymph (r = 0.70). IN CONCLUSION: (1) all components of the renin-angiotensin system are represented in the renal interstitium, as reflected in lymph; (2) Ang II concentrations in renal lymph in vivo approximate arterial levels; (3) increased secretion of active renin into plasma during intrarenal infusion of captopril into denervated kidneys is due predominantly to renin activation; and (4) renal vascular resistance may depend on the concentration of Ang II in the renal interstitium.

Angiotensin I↗
PubMed1992

Predictors of placebo response: a retrospective analysis.

This retrospective evaluation involved 197 patients from independent clinical investigations of four antidepressant medications. Six variables were analyzed for their discriminative utility in predicting placebo response rates: gender; marital status; age; education; duration of illness; and severity of depressive symptomatology, as measured by Hamilton Rating Scale for Depression (HAM-D or HDRS) scores. Men were slightly more responsive to placebo than were women (29.8%, n = 94 vs. 24.3%, n = 103). Married patients demonstrated the highest probability of a positive placebo response (38.15%, n = 76), as compared with widowed/separated/divorced (21.9%, n = 73) or single (16.7%, n = 48) patients. A trend toward an increased probability of placebo response was detected for patients aged 60 and above (35.7%, n = 14). Educational level achieved and duration of illness were not predictive. Severity of illness proved most noteworthy, with the placebo response rate higher in the more mild patients (40.8%, n = 27 vs. 23.4%, n = 77).

Adolescent↗
PubMed1992

Paroxetine in major depression: a double-blind trial with imipramine and placebo.

Paroxetine is a selective serotonin reuptake inhibitor which is being developed as an antidepressant. Previous studies suggest it is effective in the treatment of depression and has a low incidence of side effects. The authors report on a 6-week, randomized, prospective trial of paroxetine, imipramine, and placebo in 120 outpatients with major depression. The results showed that paroxetine was significantly superior to placebo in relieving depression. There were no significant differences in antidepressant efficacy between paroxetine and imipramine. However, paroxetine was also significantly superior to placebo on several measures of anxiety. Imipramine either was not superior on these measures or took longer to show a significant difference. Paroxetine lacked the typical anticholinergic side effects that accompanied imipramine therapy. The results show that paroxetine is an effective antidepressant that may have value especially when depression is accompanied by significant anxiety.

Adult↗