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Biomedical subjects

K M Wilson

Publications and source records attributed to K M Wilson.

At least 73 records · Page 4Linked to original sources
PubMed1990

Different pathways of [3H]inositol phosphate formation mediated by alpha 1a- and alpha 1b-adrenergic receptors.

The types of inositol phosphates (InsPs) formed in response to activation of alpha 1-adrenergic receptor subtypes were determined in collagenase-dispersed renal cells and hepatocytes by high pressure liquid chromatography separation. In hepatocytes, which contain only the alpha 1b subtype, norepinephrine stimulated rapid (10-s) formation of [3H]Ins(1,4,5)P3 and [3H]Ins(1,3,4)P3 and slower (5-min) formation of Ins(1,4)P2 and Ins(1)P. Selective inactivation of alpha 1b receptors by chloroethylclonidine almost completely blocked the effects of norepinephrine in hepatocytes. In renal cells, which contain both alpha 1a and alpha 1b receptors in a 60:40 ratio, norepinephrine did not significantly increase the size of any peaks until 5 min after agonist activation. At this time, only a peak eluting with Ins(1)P and one eluting shortly after Ins(1,4)P2 were significantly elevated. Incubation with norepinephrine for 2 h caused small but significant increases in peaks co-eluting with Ins(1)P and Ins(1,4,5)P3 in renal cells; however, only the increase in Ins(1)P was inhibited by chloroethylclonidine pretreatment. Extraction under neutral conditions suggested that cyclic InsPs may be the primary compounds formed in response to norepinephrine in renal cells. Removal of extracellular Ca2+ caused a 60% reduction in the InsP response to norepinephrine in renal cells but had no effect in hepatocytes. These results suggest that activation of alpha 1a and alpha 1b receptor subtypes results in formation of different InsPs and that the response to alpha 1a activation may require influx of extracellular Ca2+.

Animals↗
PubMed1990

Effect of aspirin infusions on platelet function in humans.

1. The inhibitory effects of aspirin on platelet function in vitro have been shown to be both time (over 3 h) and concentration (1-10 mumol/l) dependent. 2. To determine if these effects occurred in vivo, four volunteers received intravenous infusions on four occasions, to give constant plasma aspirin concentrations of 0, 1, 2 and 4 mumol/l over 3 h. Infusions were performed at intervals of at least 2 weeks. 3. Before and during the infusions, blood was taken for assay of aspirin concentrations, and measurements of platelet aggregation in response to collagen, adenosine 5'-pyrophosphate and arachidonate. Thromboxane generation after stimulated platelet aggregation and whole-blood coagulation was also measured. 4. At each aspirin concentration, both platelet aggregation and thromboxane generation in response to collagen and arachidonate were inhibited progressively over the 3 h infusion period. Greatest inhibition was seen during the 4 mumol/l infusion, which produced maximal or near-maximal inhibition by the third hour. 5. Thromboxane generated during whole-blood coagulation was similarly inhibited in both a time- and concentration-dependent manner throughout all aspirin infusions. 6. The progressive nature of the inhibition of platelet function with these low aspirin concentrations may be due to either slow aspirin transport across the platelet membrane or delayed interaction with cyclo-oxygenase.

Adenosine Diphosphate↗
PubMed1990

Comparison of alpha 1-adrenergic receptor-stimulated inositol phosphate formation in primary neuronal and glial cultures.

alpha 1-Adrenergic receptor binding sites and norepinephrine-stimulated 3H-inositol phosphate (3H-InsP) accumulation were measured in primary cultures of neurons and glia from 1-day-old rat brains. The density of alpha 1-adrenergic receptor binding sites was approximately three times higher in membranes from neurons compared to glia. Although norepinephrine was slightly more potent in stimulating 3H-InsP formation in neurons than in glia, the maximal response was greater in glial cells. Norepinephrine-stimulated 3H-InsP formation remained constant for [3H]inositol prelabelling periods of 1-14 days in neurons, whereas the response increased with time in glia and was maximal after 7-10 days of prelabelling. Both the incorporation of [3H]inositol into lipid and basal levels of 3H-InsPs were lower in glial cells than in neurons, which accounted for the greater percent stimulation in glia. Pretreatment with phenoxybenzamine decreased norepinephrine-stimulated 3H-InsP formation in a dose-dependent manner in both neurons and glia by decreasing the maximal response without altering potency. HPLC separation showed that similar types of 3H-InsPs were accumulated in neurons and glial cells. These results demonstrate that alpha 1-adrenergic receptors exist on both neurons and glial cells and activate 3H-InsP accumulation in both cell types. Although receptor density is higher in neurons than in glia, the 3H-InsP response is higher in glia. This difference does not appear to be due to different receptor reserves, but may be due to differential coupling mechanisms in the two cell types.

Adrenergic alpha-Antagonists↗
PubMed1990

Alpha 1-adrenergic receptor subtypes and formation of inositol phosphates in dispersed hepatocytes and renal cells.

The ability of alpha 1a- and alpha 1b-adrenergic receptor subtypes to stimulate [3H]inositol phosphate [( 3H]InsP) formation was examined in collagenase-dispersed hepatocytes and renal cells. alpha 1-Adrenergic receptor binding sites were labeled with 125I-BE 2254, and the proportion of alpha 1a and alpha 1b subtypes was determined with chloroethylclonidine (CEC) and WB 4101. Hepatocytes contained only alpha 1b-adrenergic receptors, whereas renal cells had approximately equal proportions of both subtypes. Pretreatment of renal cells with CEC selectively inactivated the alpha 1b subtype, leaving a homogeneous population of alpha 1a receptors. Norepinephrine stimulated [3H]InsP accumulation to a similar extent in both hepatocytes and renal cells. Pretreatment with CEC inactivated this response completely in hepatocytes but only partially in renal cells. WB 4101 was 1000-fold more potent in inhibiting the [3H]InsP response in renal cells than hepatocytes; however, some of this difference was due to rapid metabolism of WB 4101 by hepatocytes. After correction for metabolism, WB 4101 was still 11-fold more potent in inhibiting norepinephrine-stimulated [3H]InsP formation in hepatocytes (alpha 1b) than in CEC-pretreated renal cells (alpha 1a). These results demonstrate that both alpha 1a- and alpha 1b-adrenergic receptor subtypes activate formation of [3H]InsP, although the molecular mechanisms by which these responses occur remain to be determined.

Animals↗
PubMed1990

Pertussis toxin inhibits norepinephrine-stimulated inositol phosphate formation in primary brain cell cultures.

Norepinephrine (NE) increased formation of [3H]inositol phosphates ( [3H]InsPs) in primary cultures of neuronal and glial cells from 1-day-old rat brain. This response appeared to be mediated by alpha 1-adrenergic receptors, because prazosin was 40-fold more potent than yohimbine in blocking it. Pretreatment with pertussis toxin (PTX) dose-dependently decreased this response by 70-80%. The IC50 for PTX (7 ng/ml) was similar to that for blocking of alpha 2-adrenergic receptor-mediated decreases in cyclic AMP accumulation in the same cells. PTX pretreatment caused only a small, not statistically significant, inhibition of the [3H]InsP response to the muscarinic cholinergic receptor agonist carbachol in these cells. Radioligand binding studies showed that both neuronal and glial cultures contained mixed populations of alpha 1a- and alpha 1b-adrenergic receptor subtypes. Selective inactivation of the alpha 1b population by chloroethylclonidine reduced NE-stimulated [3H]InsP formation by 25 +/- 6%. Pretreatment with both PTX and chloroethylclonidine caused additive decreases (90 +/- 3%) in the NE response. NE-stimulated [3H]InsP formation was partially dependent on extracellular calcium, because it was decreased 64 +/- 6% by removal of calcium and 56 +/- 13% by addition of 1 mM CdCl2, although it was not affected by 1 microM nifedipine. These results suggest that NE stimulates [3H]InsP formation in neuronal and glial cultures through a pertussis toxin-sensitive guanine nucleotide-binding protein. This response appears to be mediated primarily by the alpha 1a subtype and may be subsequent to calcium influx.

Animals↗
PubMed1989

Tumor necrosis factor-mediated cytotoxicity by tumor-associated macrophages.

We have directly demonstrated that macrophages present within solid EMT6 mammary tumors (of BALB/c origin) produce TNF-alpha (TNF). These tumor-associated macrophages lysed WEHI-164, a TNF-sensitive cell line, very efficiently. This cytotoxicity was abrogated in the presence of anti-TNF antisera. In contrast, EMT6 cells, the tumor from which the macrophages were obtained, were not effectively lysed by the macrophages and were 100-fold less sensitive to lysis by recombinant mouse TNF. Thus, marked heterogeneity exists among tumors regarding sensitivity to TNF-mediated cytotoxicity. Similarly, macrophages which infiltrate into EMT6 multicellular spheroids implanted into the peritoneal cavity as well as free cells within the cavity exhibited TNF-mediated cytotoxicity of WEHI-164 cells, but failed to lyse EMT6 cells. The kinetics of lysis by these cells was similar to that of recombinant mouse TNF.

Animals↗
PubMed1989

Sweat gland carcinoma of the hand (malignant acrospiroma).

A case of malignant acrospiroma of the hand is reported. This rare sweat gland carcinoma recurs locally in 50% of patients, with distant metastases occurring in 60% of patients. The prognosis for 5-year disease-free survival is less than 30%. Although the histopathologic findings of tumor-free margins and negative regional lymph node dissection indicate a good prognosis in most carcinomas, they do not guarantee a good prognosis in malignant acrospiroma because of the aggressive characteristics of this tumor.

Adenocarcinoma↗
PubMed1989

Radiation-induced DNA damage and repair in quiescent and proliferating human tumor cells in vitro.

The purpose of this study was to examine radiation-induced DNA strand breakage and repair in quiescent and proliferating human tumor cells in vitro and determine their relationship to radiation sensitivity and potentially lethal damage repair (PLDR). Using centrifugal elutriation we have isolated from fed plateau-phase cultures of HEp-3 human squamous carcinoma cells, relatively pure populations of quiescent and proliferating cells. This was confirmed by both [3H]-thymidine labelling and acridine orange (AO) staining with flow cytometry. Quiescent cells were more sensitive to ionizing radiation (Do = 0.97 Gy) than were proliferating cells (Do = 1.28 Gy). However, quiescent cells showed higher repair of potentially lethal damage (PLDR) than did proliferating cells. Repair of single-strand breaks (ssb) and double-strand breaks (dsb) as measured by filter elution did not differ significantly between quiescent and proliferating cells. For both populations, ssb and dsb repair kinetics and final damage remaining were the same, suggesting that repair of DNA strand breaks is not entirely responsible for the difference in radiation sensitivity between quiescent and proliferating cells.

Carcinoma, Squamous Cell↗
PubMed1989

Regional variations in alpha 1-adrenergic receptor subtypes in rat brain.

alpha 1-Adrenergic receptor subtypes were differentiated by their affinities for the competitive antagonist WB 4101 and their sensitivities to inactivation by chlorethylclonidine (CEC) in eight rat brain regions. WB 4101 showed low Hill coefficients for inhibition of specific 125I-[2-beta-(4-hydroxyphenyl)ethylaminomethyl]tetralone (125IBE) binding in all regions. Nonlinear regression analysis showed that there were two binding sites with different affinities for WB 4101 in each region. The proportions of these sites varied among regions, although the affinity of WB 4101 for each site remained constant. Thalamus and cerebral cortex had the highest proportion of low-affinity sites, whereas hippocampus and pons-medulla had the highest proportion of high-affinity sites. Pretreatment with CEC in hypotonic buffer significantly reduced the density of 125IBE binding sites in all brain regions. Cerebral cortex and cerebellum had the highest proportion of CEC-sensitive sites, whereas hippocampus and spinal cord had the highest proportion of CEC-insensitive sites. There was a significant correlation between the proportion of binding sites with a low affinity for WB 4101 and those sensitive to inactivation by CEC.

Animals↗
PubMed1989

Vasopressin in neuronal cultures from neonatal rat brain.

This study was performed to characterize and quantify vasopressin in neuron-enriched primary cultures of whole brains from 1-day-old rats and to compare such cultures between spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. Vasopressin was extracted from cells and evaluated by radioimmunoassay and high-pressure liquid chromatography. Radioimmunoassay of high-pressure liquid chromatography fractions from cell extracts showed that the major peak of immunoreactivity comigrated with synthetic vasopressin. Cell vasopressin content increased in a graded manner when one to six dishes (plated 8 x 10(6) cells/dish) were pooled (8.7 +/- 0.5 to 67.7 +/- 8.2 pg/dish). When the number of plated cells per dish was increased (2 to 16 x 10(6) cells), there was also a graded rise in dish vasopressin content (3.4 +/- 0.4 to 15.3 +/- 3.9 pg). Treatment of cultures with 100 aM to 1 nM of angiotensin II for 5 minutes caused a dose-dependent decrease in cell vasopressin content. Furthermore, the decrease in cell vasopressin content of cultures treated with 1 nM angiotensin II (12.6 +/- 0.8 to 7.0 +/- 1.0 pg/10(6) cells, p less than 0.05) corresponded with the increase in medium vasopressin concentration (3.8 +/- 0.5 to 7.5 +/- 2.3 pg/ml) and this vasopressin-releasing effect of angiotensin II was blocked by [Sar1, Thr8]angiotensin II. Treatment of cultures with potassium chloride (56 mM) and acetylcholine chloride (5.5 microM) also resulted in significant decreases in cell vasopressin content.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1988

Effects of increased circulating angiotensin II (AII) on fluid exchange and binding of AII in the brain.

Previous studies have shown that elevated levels of circulating angiotensin II (AII) can influence the binding capacity of this peptide for its receptors in peripheral tissues, but the effect of increased circulating levels of AII on its receptors in the brain has not been well-defined. In the present study, the effect of chronic subcutaneous infusions of AII on: (1) the binding of AII to neuronal membranes from the diencephalon (hypothalamus, thalamus and septum) (HTS) of the brain; (b) water intake and urine output, (c) blood pressure, and (d) their interrelationships was evaluated in rats. Significant increases in daily water intake and urine output accompanied chronic infusions of AII at a rate of 125 ng/kg/min. Both blood pressure and the concentration of aldosterone in plasma were also elevated in these rats. The acute dipsogenic response to either central (10 ng) or peripheral (100 micrograms/kg, SC) administration of AII was also tested both in controls and in rats receiving chronic infusions of AII at a rate of either 40 or 125 ng/kg/min, and no differences were observed. Analysis of the HTS region of the brain revealed a significant increase in the specific binding of AII in AII-infused rats compared to controls. Scatchard analysis of the specific binding of AII to its receptors in the HTS of rats treated with 40 ng AII/kg/min for 6 days revealed a significant increase in the number of binding sites for AII compared to controls (Bmax 12.13 vs. 8.79 fmol/mg protein), but no change in binding affinity (Kd).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1988

Inhibition of platelet aggregation and thromboxane production by low concentrations of aspirin in vitro.

1. The aspirin concentrations previously reported to inhibit platelet aggregation in vitro (40-500 mumol/l) are much greater than those required in vivo in man (5 mumol/l). 2. Human platelet-rich plasma was incubated with buffer or various aspirin concentrations at 37 degrees C for up to 4.5 h. Platelet aggregation and thromboxane generation were measured in response to collagen (0.4-6.3 micrograms/ml) and adenosine 5'-pyrophosphate (0.5-4 mumol/l). 3. The concentration of aspirin needed to inhibit platelet aggregation in response to a critical concentration of aggregating agent (lowest concentration to cause greater than 50% aggregation) was lower than that required for higher concentrations of aggregating agent. 4. With more prolonged incubation times with aspirin, lower concentrations of aspirin inhibited platelet aggregation. 5. Inhibition of platelet aggregation and thromboxane formation by 10 mumol/l aspirin was maximal by 90 min. There was progressive inhibition by 3 mumol/l aspirin during incubation for 270 min. By the end of this time there was also significant inhibition by 1 mumol/l aspirin. 6. The apparent discrepancy between inhibitory aspirin concentrations in vivo and those observed in vitro in previous studies appears to have been resolved by extending the incubation time of platelets with low aspirin concentrations, thus mimicking the conditions in vivo.

Aspirin↗
PubMed1988

Double-blind study of an alpha 2 agonist in the treatment of irritable bowel syndrome.

A double-blind crossover trial of the alpha 2 agonist lidamidine hydrochloride in 72 patients with irritable bowel syndrome is reported. Lidamidine was found to have no significant effect on frequency and severity of abdominal pain or abdominal bloating. It did cause a statistically significant reduction in frequency of defaecation (P = 0.005), but this was of a degree unlikely to be of clinical importance. Although alpha 2 agonists inhibit gastrointestinal motility in animals this study suggests that lidamidine hydrochloride does not have a useful therapeutic role in irritable bowel syndrome.

Adolescent↗
PubMed1988

Captopril and the response to stress in the spontaneously hypertensive rat.

The purpose of this study was to determine the effect of chronic blockade of the brain renin-angiotensin system on the hormonal response to stress in spontaneously hypertensive rats (SHR). To this end, we measured changes in plasma corticosterone, vasopressin, plasma renin activity, aldosterone, norepinephrine, and epinephrine in SHR treated with a 4-week intracerebroventricular infusion of captopril (osmotic minipump, 1.25 micrograms/hr) or vehicle in response to cold stress (4 degrees C x 4 hours) or ether stress (5 minutes). Within the fourth week of treatment, the average systolic blood pressure of captopril-treated SHR was significantly lower than that of vehicle-treated rats. Basal plasma levels of corticosterone, but not vasopressin, were significantly lower in SHR treated with captopril. In response to cold stress, captopril-treated SHR showed significantly lesser increases in both corticosterone and vasopressin than did vehicle-treated SHR. There were no differences in basal plasma levels of norepinephrine, epinephrine, plasma renin activity, or aldosterone between captopril-treated and vehicle-treated SHR, and both groups showed elevations of a similar magnitude after exposure to cold. In response to ether stress, captopril-treated SHR also showed significantly smaller increases in corticosterone and vasopressin than did vehicle-treated SHR. These results suggest that chronic intracerebroventricular administration of captopril, through blockade of the brain renin-angiotensin system, alters the hormonal response of SHR to stress.

Adrenocorticotropic Hormone↗
PubMed1988

Long-term captopril treatment. Angiotensin II receptors and responses.

The purpose of this study was to elucidate the mechanism of the antihypertensive effect of the angiotensin I (Ang I) converting enzyme inhibitor captopril in spontaneously hypertensive rats (SHR). Drinking responses, peripheral vascular reactivity, and angiotensin II (Ang II) receptor binding in both the brain and vascular smooth muscle were examined in control and captopril-treated SHR. Pregnant and nursing dams were treated with oral captopril (100 mg/kg). After weaning, offspring were maintained on captopril (50 mg/kg). The average systolic pressures after 21 weeks of captopril treatment were 122 +/- 3 mm Hg (male) and 118 +/- 4 mm Hg (female) as compared with 169 +/- 4 mm Hg (male) and 162 +/- 2 mm Hg (female) in age-matched controls. Drinking responses to intracerebroventricular (10 ng) and subcutaneous (100 micrograms/kg) administration of Ang I and II were attenuated in captopril-treated SHR in comparison to control SHR. Ang II receptor binding in the hypothalamus, thalamus, and septum of captopril-treated SHR was also significantly reduced. In contrast to a depressed angiotensinergic system in the brain, peripheral vascular reactivity to Ang II, as determined in isolated, artificially perfused kidneys, was elevated. Threshold and ED50 values for Ang II were significantly lower in captopril-treated SHR than in controls. Ang II receptor binding in aortic smooth muscle cells prepared from captopril-treated SHR was also significantly greater than in cells from controls. Thus, lifetime treatment with captopril induced alterations in the renin angiotensin systems in the periphery and brain that were manifested by changes in receptor binding and responsiveness to Ang II.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1987

Comparison of fluorescence intensity of Hoechst 33342-stained EMT6 tumour cells and tumour-infiltrating host cells.

Hoechst 33342 is a fluorescent dye used for cell selection from tumours based upon intratumour location. When the dye is administered i.v. to tumour-bearing animals, cellular fluorescence is directly related to the proximity of cells to blood vessels. The present study compared inherent Hoechst fluorescence between in vitro-stained EMT6/Ro (mouse mammary sarcoma) cells and host cells, to determine if these populations have different staining characteristics that may influence cell selection procedures. Tumour cell fluorescence exceeded host cell staining by 8-fold when pure cell populations (EMT6/Ro monolayer cells, mouse spleen and peritoneal cells) were compared, and 3-fold for tumour cell-enriched and host cell-enriched populations from solid tumours. Inherent uptake of HO 33342 appeared to be correlated with cell volume. These differences in inherent dye uptake between host and tumour cells were found to be minor in comparison to the fluorescence gradient between the 10% brightest and 10% dimmest (78-fold) cell populations from in vivo-stained tumours.

Animals↗
PubMed1987

Specific (EMT6) and non-specific (WEHI-164) cytolytic activity by host cells infiltrating tumour spheroids.

The development of a serum-free, low-protein culture medium has allowed the detection of tumour-specific cytolytic cells in EMT6 immunized mice bearing EMT6 multicellular tumour spheroids. Spheroid associated (SAC) and peritoneal (PC) effector cells were specific to EMT6 as the target cell, not killing line 1, P815 or RIF-1. The natural killer (NK) cell sensitive target YAC-1 was also not lysed by SAC or PC, indicating undetectable levels of NK cells present within infiltrated spheroids. In contrast, high levels of cytolytic activity were present in SAC, PC and spleen cells against WEHI-164, a line sensitive to natural cytotoxic (NC) and macrophage mediated killing. The EMT6 specific activity was mediated by Thyl+, Lyt2+ cells. The anti-WEHI-164 effector cell population was Thyl-, Lyt2-. The WEHI-164 killer cells were present in SAC and PC from unimmunized mice while the EMT6 specific effector cells were not. After separation of SAC and PC by size using centrifugal elutriation, anti-EMT6 activity was present only in the lymphocyte fraction while anti-WEHI-164 activity was enriched in the macrophage fraction.

Animals↗