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PubMed2003

Molecular tweezers and clips as synthetic receptors. Molecular recognition and dynamics in receptor-substrate complexes.

The molecular tweezers (1, 2) and clips (3-7) containing naphthalene and benzene spacer units can be synthesized via repetitive Diels-Alder reactions by the use of a molecular "Lego" set consisting of bisdienophiles (8, 9, 14) and dienes (10, 13). The new receptors selectively bind electron-deficient neutral and cationic substrates in solution. Only the benzene-spaced tweezers form complexes with aliphatic substrates, whereas the other receptors bind aromatic substrates preferentially. HPLC studies with 1 and 2 chemically bonded to stationary phases give similar results for the heterogeneous systems. The formation of stable complexes between the water-soluble clip 5g and N-alkylpyridinium cations, such as N-methylnicotinamide and NAD(+), in aqueous solution illustrates the importance of the hydrophobic effect for arene-arene interactions. The dynamics of the complex formation and substrate mobility were investigated by the use of temperature-dependent liquid- and solid-state NMR spectroscopy. The electrostatic potential surface (EPS) of 1-7 is calculated to be surprisingly negative on the concave side of each molecule and, hence, complementary to the EPS of the electron-deficient substrates, suggesting that the attractive receptor-substrate interaction is here of predominantly electrostatic nature.

Benzene↗
PubMed2000

"Paper-clip" type triple helix formation by 5'-d-(TC)3Ta(CT)3Cb(AG)3 (a and b = 0-4) as a function of loop size with and without the pseudoisocytosine base in the Hoogsteen strand.

The formation of a DNA "paper-clip" type triple helix (triplex) with a common sequence 5'-d-(TC)(3)T(a)()(CT)(3)C(b)()(AG)(3) (a and b = 0-4) was studied by UV thermal melting experiments and CD spectra. These DNA oligomers form triplexes and duplexes under slightly acidic and neutral conditions, respectively. The stability of the formed triplexes (at pH 4.5) or duplexes (at pH 7.0 or 8.0) does not vary significantly with the size of the loops (a and b = 1-4). At pH 6.0, the triplex stability is, however, a function of a and b. It is also interesting to note that the oligomer 5'-d-(TC)(3)(CT)(3)(AG)(3) (a and b = 0) forms a stable triplex at pH 4.5 with a slightly lower T(m) value, due to dissociation of a base triad at one end and a distorted base triad at the other, observed by (1)H NMR. Thus, we have here a model system, 5'-d-(TC)(3)T(a)(CT)(3)C(b)(AG)(3), that could form a triplex effectively with (a and b = 1-4) and without (a and b = 0) loops under acidic conditions. In addition, the triplex formation of oligomers with replacement of one, two, or three 2'-deoxycytidine in the Hoogsteen strand by either 2'-deoxypseudoisocytidine (D) or 2'-O-methylpseudoisocytidine (M) was also studied in the sequence 5'-d-(TX)(3)T(2)(CT)(3)C(2)(AG)(3) (where X is C, D, or M). Both CD spectra and UV melting results showed that only D3 [(TX)(3) = (TD)(3)] and M3 [(TX)(3) = (TM)(3)] were able to form the paper-clip structure under both neutral and acidic conditions. This is because the N(3)H of a pseudoisocytosine base can serve as a proton donor without protonation. We hereby proved that the 2'-deoxypseudoisocytidine, similar to 2'-O-methylpseudoisocytidine, could replace 2'-deoxycytidine in the Hoogsteen strand to provide triplex formation at neutral pH.

Adenine↗
PubMed1997

Templating and Clipping Coordination Reactions Leading to Heteronuclear Trimetallic Complexes Containing Interlocking Rings.

We report the preparation of heterotrimetallic complexes with a Cu-complexed [2]-catenate structure, containing two other metals within the rings. Starting from a multidentate ligand 1 containing two terpy units (terpy 2,2':6',2"-terpyridine) and one dpp fragment (dpp 2,9-diphenyl-1,10-phenanthroline), a 29-membered macrocycle 2 was prepared in 59% yield by clipping of both terpy moieties of 1 with Ru(DMSO)(4)Cl(2) under high-dilution conditions. Threading of an additional equivalent of ligand 1 through macrocycle 2 was achieved by reaction with Cu(I), which acts as a template, forming a Cu(dpp)(2)(+)-type complex bearing two free terpy ligands. Reaction of this complex with different salts of Cu(II), Co(II), Fe(II), and Zn(II) gave the corresponding heteronuclear trimetallic catenates, as mixtures of diastereomers, again by clipping of both terpy units with the metal. The kinetic stability of the Ru complex prevents ligand scrambling. A somewhat different strategy, i.e., simultaneous formation of two rings from Cu(1)(2)(+) by reaction with Ru(DMSO)(4)Cl(2), afforded a catenate containing two Ru(terpy)(2)(+) complexes within the rings. The high stability of these Ru species allows the selective demetalation of Cu(I) to give a catenane containing a free tetrahedral coordination site.

Journal Article↗
PubMed1995

The structure of an intermediate in class II MHC maturation: CLIP bound to HLA-DR3.

A complex between HLA-DR3 and a fragment of invariant chain called CLIP was isolated from a human cell line defective in antigen presentation and its X-ray crystal structure determined. Previous data indicate that this complex is an intermediate in class II histocompatibility maturation, occurring between invariant chain-DR3 and antigenic peptide-DR3 complexes. The structure shows that the CLIP fragment binds to DR3 in a way almost identical to that in which antigenic peptides bind class II histocompatibility glycoproteins. The structure is the substrate for the loading of antigenic peptides by an exchange process catalysed by DM.

Amino Acid Sequence↗
PubMed1985

Effect of potassium depletion on two-kidney, one-clip renovascular hypertension in the rat.

There is considerable controversy about the hemodynamic effect of potassium in hypertension. To determine if K depletion could alter the control of blood pressure, studies were performed in rats with 2-kidney, 1-clip renovascular hypertension (RVH) after 3 to 6 wks of severe and moderate K depletion. After application of a 0.23 mm clip to the left renal artery, rats were placed on a K-replete (KR) (240 mEq/kg), a moderately K-depleted (KDM) (59 mEq/kg), or a severely K-depleted (KDS) (5 mEq/kg) diet. After 3 wks, mean arterial pressure (MAP) reached 154 +/- 3 in KR but only 121 +/- 2 in KDM (P less than 0.01) and 106 +/- 4 mm Hg in KDS (P less than 0.001). After 6 wks, MAP was 160 +/- 8 in KR, but only 132 +/- 5 in KDM (P less than 0.01) and 129 +/- mm Hg in KDS (P less than 0.01). Plasma K at 3 wks was 4.1 +/- .1 in KR, but only 3.5 +/- .1 in KDM (P less than 0.05) and 2.3 +/- .1 mEq/liter in KDS (P less than 0.001). This was associated with an 8% decrease in muscle K in KDM and a 16% decrease in muscle K in KDS. Although KDS animals did not grow during the 6 wks of study, KDM rats gained 60% as much weight at 3 wks, and, by 6 wks, weight gain was comparable in KDM (101 +/- 9) and KR (110 +/- 9 g) animals (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Calcium blockade versus ACE inhibition in clipped and unclipped kidneys of 2K-1C rats.

ACE inhibitors have been shown to worsen the kidney damage occurring distal to a renal artery stenosis. To determine if this effect was due to the decrease of arterial pressure or to an inhibition of the formation of angiotensin, we compared the effects of equihypotensive doses of an angiotensin converting enzyme inhibitor (enalapril) and a long-acting calcium antagonist (Ro 40-5967) in 2K-1C rats. The rats were treated for five weeks with either enalapril, Ro 40-5967, or were left untreated. A group of sham operated rats was used as control. At the end of the five-week treatment period, proteinuria, plasma urea and creatinine were measured and quantitative morphometry of the clipped and unclipped kidneys was performed. Ro 40-5967, despite an absence of inhibition of the renin-angiotensin system, worsened the lesions of the clipped kidney to the same extent as enalapril. In contrast, the effects of both drugs on the unclipped kidney were different. Ro 40-5967, and not enalapril, increased the weight and the glomerular surface area of the unclipped kidney. Ro 40-5967 did not change the glomerulosclerosis index, which was improved by enalapril. In contrast with enalapril, Ro 40-5967 decreased plasma urea and creatinine concentrations. Only enalapril decreased proteinuria which originated from the unclipped kidney as shown by nephrectomy experiments. We conclude that during ACE inhibition the fall in renal perfusion pressure seems to be the main determinant of the renal damage distal to a renal artery stenosis, independently of a blockade of the renin-angiotensin system.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1975

Renal prostaglandin synthesis in experimental renal-clip hypertension in the rat.

1. The hypothesis that suppression of prostaglandin E synthesis by indomethacin exacerbates renal-clip hypertension in the rat was investigated in four groups of rats. 2. Indomethacin was shown to exacerbate hypertension in renal-clip animals. 3. Synthesis of prostaglandin E, determined by gas--liquid chromatography, was suppressed in medullary tissue from the hypertensive animals irrespective of indomethacin treatment. 4. The findings support the concept that prostaglandins participate in the blood pressure regulatory function of the kidney but pose a number of unsolved questions.

Animals↗
PubMed1980

Effects of variations in sodium intake on the acute vasodepressor response to kininase II inhibition in rats with mild two-kidney, one-clip hypertension.

1. Unilateral renal artery constriction in rats maintained on a sodium-deplete, but not sodium-replete, diet induced an augmented acute vasodepressor response to kininase II inhibition produced by an intravenous injection of the dipeptidyl carboxypeptidase inhibitor captopril (250 microgram) during continuous saralasin-induced angiotensin II blockade (10 microgram/min). Dietary sodium restriction alone in sham-operated rats had no effect. 2. Acute bilateral adrenalectomy (18-24 h) did not preclude the demonstration of an augmented response to kininase II inhibition in sodium-depleted rats with benign two-kidney, one-clip hypertension. Neither did chronic administration of deoxycorticosterone acetate in intact rats elicit an augmented response. 3. The augmented acute vasodepressor response to kininase II inhibition in sodium-depleted rats with benign two-kidney, one-clip hypertension is probably due to bradykinin potentiation and secondary to an increased activity of the kallikrein-kinin system. The mechanism responsible for this apparent increase is not known, but neither hyperangiotensinemia nor hyperaldosteronism seems to play a role.

Adrenalectomy↗
PubMed1981

Haemodynamic changes after surgical reversal of chronic two-kidney, one-clip hypertension in the rat.

1. Within 24 h of surgical reversal of chronic Goldblatt two-kidney, one-clip hypertension in the rat, of greater than 4 months duration, blood pressure had fallen to normal levels. At this time there was no difference between the effects of removal of the clip or the ischaemic kidney but, at 60 days after reversal, the blood pressure of rats which had been nephrectomized was significantly higher than that of normal controls. 2. The fall in blood pressure was associated with a fall in total peripheral resistance to normal by 24 h despite the previous established fact that structural vascular changes take much longer to reverse. There was a corresponding rise in cardiac output, mainly due to an increase in stroke volume. Nephrectomized rats had a significantly higher stroke volume compared with those unclipped 24 h after operation. 3. As blood pressure can become normal in the presence of structural cardiovascular change by a fall in total peripheral resistance it would seem unlikely that resistance vessel hypertrophy is responsible for the maintenance of blood pressure in this model. Another peripherally acting mechanism therefore has to be postulated.

Animals↗
PubMed1982

Inhibition of adrenaline-forming enzyme in the brain prevents one-kidney, one-clip hypertension and deoxycorticosterone acetate-salt hypertension in the rabbit.

1. Phenylethanolamine N-methyltransferase (PNMT) converts noradrenaline into adrenaline and brain PNMT is elevated in spontaneously hypertensive and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. In view of the evidence for the involvement of central adrenergic neurons in renal hypertension, we measured the blood pressure response in one-clip, one-kidney Goldblatt hypertensive and DOCA-salt hypertensive rabbits to the PNMT inhibitor SK&F 64139, injected into the lateral cerebral ventricles. 2. Intracerebroventricular injection of SK&F 64139 (10 micrograms/kg) significantly attenuated the mean arterial blood pressure rise in one-clip, one-kidney and DOCA-salt rabbits, at 4 and 8 weeks. 3. These findings support the idea the hypertension in this animal model required an intact adrenaline biosynthetic process, and that central catecholaminergic neurons may be involved in the pathogenesis of low-renin dependent forms of hypertension.

Animals↗
PubMed1988

Increased levels of platelet-activating factor (1-O-alkyl-2-acetylglycerophosphocholine) in blood after reversal of renal clip hypertension in the rat.

1. This study analyses whole blood in acutely unclipped one-kidney, one-clip (1K, 1C) hypertensive rats for the presence of platelet-activating factor (PAF), a potent vasodilator and a putative mediator of the rapid blood pressure (BP) fall seen after unclipping. 2. Hypertensive 1K, 1C rats were anaesthetized and a carotid and jugular cannula were inserted for BP measurement and anaesthetic infusion respectively. After a stable level of anaesthesia was attained, the constrictive clip was removed and BP was recorded for 30 min. 3. Blood was drawn from the aorta directly into ice-cold acetone. The extract was analysed for PAF by a bioassay using 5-hydroxy-[14C]tryptamine-labelled platelets. 4. Rats which showed a BP fall had elevated levels of PAF [55 +/- 6 (SEM) pg/ml] (P less than 0.01). 5. This supports the hypothesis that activation of PAF biosynthesis may be a mechanism contributing to the fall in BP seen after unclipping the 1K, 1C hypertensive rat.

Animals↗
PubMed2002

Neurohormonal influences on maintenance and reversal of two-kidney one-clip renal hypertension.

The factors involved in maintenance and reversal of mean arterial blood pressure (MAP) in the chronic two-kidney one-clip hypertensive rat (2K1C-RHR) are still debated. The reduction in MAP after reversal of 2K1C hypertension has been ascribed either to release of a renal medullary depressor hormone (RMDH) or suppression of the renin-angiotensin and/or sympathetic nervous system. We studied in conscious rats: (i) The effects of angiotensin II receptor blockade (ARB; candesartan), sympathetic blockade (propranolol and phentolamine) or a combination on MAP in 6-week long 2K1C-RHR; (ii) The effects of reversal of 2K1C hypertension by removal of the constricting clip (unclipping, UC) or nephrectomy (Nx) on MAP, plasma renin activity (PRA) and noradrenaline (NA) spillover rates. The results show that: (i) MAP in the 2K1C-RHR was almost normalized by ARB but not significantly affected by the sympathetic blockade. The combination was not more effective than ARB alone; (ii) UC and Nx reduced MAP in 2K1C to similar levels as ARB. No significant changes in PRA or catecholamines could be detected in UC and Nx groups. We conclude that hypertension in 2K1C-RHR is maintained by the renin-angiotensin system without much contribution from the sympathetic nervous system. Furthermore, we found no evidence that UC of our model of 2K1C was associated with a generalized decrease in sympathetic tone or substantial release of RMDH from the unclipped kidney. Thus, we conclude that in the present model of 2K1C, both maintenance and reversal of hypertension are controlled by the renin-angiotensin system.

Angiotensin II↗
PubMed2003

Histopathological diagnosis of onychomycosis by periodic acid-Schiff-stained nail clippings.

BACKGROUND: The current laboratory methods for diagnosing fungal infections of the nails are the potassium hydroxide (KOH) scraping technique and fungal culture. However, due to the long incubation period required for fungal culture and the reported rate of approximately 30% false negative results observed when using these methods, a quick and highly specific screening test for diagnosing onychomycosis is urgently needed. OBJECTIVES: In a prospective study, to compare the traditional mycological diagnostics using culture medium and KOH preparation with the histopathological diagnosis of onychomycosis by periodic acid-Schiff (PAS)-stained nail clippings. METHODS: Material from 387 nails of 350 patients suspected of having onychomycosis was obtained and a KOH stain as well as two fungal cultures (Kimmig agar with and without cycloheximide) were prepared. In addition, the same specimen was histopathologically examined (PAS stain). RESULTS: Culture medium and KOH preparation respectively revealed 100 and 156 cases of onychomycosis, as compared with 182 cases by histological examination. Histological examination gave a significantly higher rate of positive results (P < 0.05). Considering the total number of positive results given by at least one of the three methods (total = 438), histological evaluation was found to give the highest rate of successful recognition of mycotic infection (41.6%). CONCLUSIONS: The histopathological evaluation of PAS-stained nail clippings is very quick and easy to perform, and will increase the frequency of diagnosing onychomycotic disease above that achieved by culture and KOH preparation alone. However, because information concerning the vitality of the fungi and accurate identification of the specific pathogen is not available through this investigation alone, mycological culture continues to remain the indisputable 'gold standard' of mycological diagnostics.

Adolescent↗
PubMed2001

Surveillance for carbon monoxide poisoning using a national media clipping service.

Using a novel method to review carbon monoxide (CO) exposures in the US, the role of CO detectors in prevention of CO-related deaths was studied. Using a national media clipping service, CO poisonings reported in the US were analyzed. The impact of CO detectors was investigated through nonfatal outcomes attributable to the presence of CO detectors and case fatality rate comparison among cities with and without CO detector ordinances. There were 4,564 CO exposures resulting in 406 (8.9%) fatalities. Of the exposures 2,617 (57.3%) occurred in the home, accounting for 374 (92.1%) deaths. Faulty heating systems constituted 2,540 (55.6%) exposures and 186 (45.8%) deaths, with alternate heating sources responsible for 389 (8.5%) exposures and 104 (25.6%) deaths. Cities with CO detector ordinances showed lower case fatality rates as reported in the media than those cities without ordinances (P <.001). There were 1,008 (24.2%) survivors who attributed their survival to the presence of a CO detector. A media clipping service provided insight into CO poisoning demographics. Despite its limitations, this tool may calibrate the positive impact of CO detectors on the prevention of CO-related deaths.

Carbon Monoxide Poisoning↗
PubMed2003

Endoscopic clip application as an adjunct to closure of mature esophageal perforation with fistulae.

BACKGROUND AND AIMS: Esophageal perforation is associated with high morbidity and mortality. Surgery and drainage are considered primary management. Conservative management is an option in a select group. Conservative treatment requires drainage, control of infection, nutritional support, and considerable patience. METHODS: We describe 3 cases in which endoscopic metallic clips were placed to close mature perforations with associated fistulae. All 3 patients underwent mucosal approximation of the defects under direct endoscopic visualization. RESULTS: A review of the literature revealed only 4 other reports of the use of endoclipping for esophageal perforation, one diagnosed immediately, a second within 24 hours, a third diagnosed after 2 days and endoclipped after prolonged mediastinal drainage, and a fourth believed to be chronic. The cases presented here represent well-established, mature defects. CONCLUSIONS: Endoscopic treatment of mature esophageal perforation with metallic clips can be performed to promote closure. In combination with other conservative medical efforts, this method can be used safely and effectively for selected patients.

Aged↗
PubMed2001

Varicocele: Laparoscopic clipping and color Doppler follow-up.

PURPOSE: The aim of this study was to evaluate the results of laparoscopic treatment of varicocele and findings of testicular volume and blood supply using color Doppler ultrasound scan on follow-up. METHODS: Fourteen patients aged 7 to 15 years old (median, 12.3 years) with left varicocele (grade II, n = 4; grade III, n = 10) underwent laparoscopic clipping of internal testicular vein and artery. At follow-up, both testes were scanned by ultrasonography in axial and longitudinal planes, and at least 3 measurements-length, width, and thickness-were taken to calculate testicular volumes. Arterial perfusion of the testes also was assessed. RESULTS: Operating time ranged from 25 to 80 minutes (mean, 60 minutes). There was no perioperative complication. At a mean follow-up of 14 months (range, 2 to 39 months) all children were asymptomatic with disappearance of varicocele. The volumes of bilateral testes were equal (difference in volumes less than 10%) in 9 children. Ipsilateral testicular hypertrophy was found in 3 children. There was no difference in arterial perfusion between the testes in each patient. Small transient ipsilateral hydrocele was observed in 2 patients. CONCLUSION: Laparoscopic clipping of testicular vein and artery was simple and effective for varicocele treatment and did not compromise testicular blood supply.

Adolescent↗
PubMed1976

[Clinical significance of encycling clips in neurosurgery].

It is reported how, in 5 cases of arterial haemorrhage, the ligature of an artery was avoided by the use of Heifetz encircling clips with teflon liner. Two of the five patients had aneurysms. The remaining 3 were suffering from brain tumours. Postoperative computer tomography together with neurological follow up examinations indicated, that in two cases there was no disturbance of cerebral circulation. With a carotid angiography it was possible to show that in the other three cases normal flow through the arteries was maintained, 2, 11 and 45 days after emplacement of the clip.

Adult↗