The mobility of the brachycephalic canine nostril in relation to the degree of nostril stenosis

Previous studies have shown that the most reliable external conformational risk factor of whether a brachycephalic dog will develop Brachycephalic Obstructive Airway Syndrome (BOAS) is the status of nostril stenosis, assessed as a static observation using the brachycephalic nostril grading scheme. The nostrils however are a dynamic structure, opening further when the dog is exercising, sniffing or panting. The hypothesis of this study was that brachycephalic dogs with open or mildly stenotic nostrils are more likely to have nostril mobility whilst dogs with moderately or severely stenotic nostrils are more likely to have immobile nostrils. A retrospective study of dogs presented for BOAS assessment at two UK referral centres between 2012 and 2020 was performed. Data extracted included nares stenosis status and nares mobility. A mesocephalic pilot control group was recruited from a third referral centre. Statistical analysis was performed with χ2, Cochran-Armitage, spearman's rho and linear-by-linear tests as appropriate. Of the 974 brachycephalic dogs included in the study: 124 had open nostrils (68.5% mobile); 212 mildly stenotic nostrils (58.5% mobile); 379 moderately stenotic nostrils (35% mobile) and 259 severely stenotic nostrils (19.3% mobile). The nostril stenotic status was significantly associated with nostril wing mobility (χ2 =135.55; P<0.0001). When considering open and mildly stenotic (considered acceptable) nostrils versus moderate and severely stenotic nostrils, mobility was 62% versus 25.5% (χ2= 135.88; P = <0.0001). All 27 mesocephalic dogs had nostril mobility. Brachycephalic dogs with moderate and severely stenotic nares have reduced nasal mobility compared to brachycephalic dogs with mildly stenotic and open nares. Data is further evidence that dogs with moderately and severely stenotic nares should not be bred.

The surgical care of diabetic feet: a survey about clinics, acute care, and the surgical specialists involved

INTRODUCTION

Diabetic foot problems are becoming increasingly common. Diabetic foot care services are fundamental in managing them, and there is the further issue of acute surgery for foot sepsis. The involvement of different surgical specialists has been variable; this survey aimed to provide information about current service provision.

METHODS

Questionnaires were emailed to Vascular Society members, and targeted approaches were then undertaken.

RESULTS

We aimed to obtain information from 61 localities identified as providing shared services, and received informative responses from 46 (75%). These described diabetic foot clinics each day (11%), or once (50%), twice (13%) or three times (17%) weekly - attended regularly by vascular surgeons, and less frequently by orthopaedic surgeons. The frequency of clinics was considered inadequate by 30% of respondents, and only 75% reported written policies for diabetic foot care pathways. Operations for acute foot sepsis are done by vascular surgeons in 98% of localities and by orthopaedic surgeons in 22% (in some localities by both): the latter are orthopaedic foot specialists in all localities but two. Both specialties perform a range of foot procedures, including toe/foot-preserving operations. Major amputations are done by vascular surgeons in 98% of localities and by orthopaedic surgeons in only 9%. All deformity correction procedures are performed by orthopaedic surgeons.

CONCLUSION

This survey shows that diabetic foot clinics are now held frequently in most localities. There is variation in the involvement of vascular and orthopaedic surgeons. Some localities need to consider increased provision of clinics and better defined pathways of care.

Bioavailable phytoprostanes and phytofurans from Gracilaria longissima have anti-inflammatory effects in endothelial cells

BACKGROUND

An array of bioactive compounds with health-promoting effects has been described in several species of macroalgae. Among them, phytoprostanes (PhytoPs) and phytofurans (PhytoFs), both autoxidation products of α-linolenic acid, have been seen to exert immunomodulatory and antiinflammatory activities in vitro. The purpose of this study was to explore the bioaccesibility, bioavailability, and bioactivity of PhytoPs and PhytoFs obtained from the edible red algae Gracilaria longissima, and to gain insight into the anti-inflammatory activity of their bioavailable fraction in human endothelial cells.

METHODS

The PhytoPs and PhytoFs profile and concentration of G. longissima were determined by UHPLC-QqQ-MS/MS. Algal samples were processed following a standardised digestion method including gastric, intestinal, and gastrointestinal digestion. The bioavailability of the PhytoPs and PhytoFs in the characterized fractions was assessed in a Caco-2 cell monolayer model of the intestinal barrier. The inflammation response of these prostaglandin-like compounds in human endothelial cells, after intestinal absorption, was investigated in vitro.

RESULTS

Simulated digestions significantly reduced the concentration of PhytoPs and PhytoFs up to 1.17 and 0.42 μg per 100 g, respectively, on average, although permeability through the Caco-2 cell monolayer was high (up to 88.2 and 97.7%, on average, respectively). PhytoP and PhytoF-enriched extracts of raw algae impaired the expression of ICAM-1 and IL-6 inflammation markers. The inflammation markers progressed in contrast to the relative concentrations of bioactive oxylipins, suggesting pro- or anti-inflammatory activity on their part. In this aspect, the cross-reactivity of these compounds with diverse receptors, and their relative concentration could explain the diversity of the effects found in the current study.

CONCLUSIONS

The results indicate that PhytoPs and PhytoFs display complex pharmacological profiles probably mediated through their different actions and affinities in the endothelium.

"Anterior interosseous nerve syndrome (Kiloh Nevin Syndrome) revealing Gantzer muscle and simultaneous myasthenia gravis"

There hasn't been a previous case report of the anterior interosseous nerve injury secondary to the presence of the muscle of Gantzer in a patient with myasthenia gravis in literature before. The anterior interosseous nerve compressive syndrome, also known as Kiloh-Nevin syndrome, is a rare disorder comprising less than 1% of all upper limb neuropathies. Establishing the etiology of anterior interosseous nerve compressive syndrome is challenging because of the lack of specific clinical findings or testing. Herein is the case of a 46 years-old male presented with left eye ptosis, ophthalmoparesis, diplopia, and right-hand weakness. On physical examination, the Pinch Grip test was positive. Electromyography studies showed neurogenic atrophy in the muscles innervated by the anterior interosseous nerve, as well as a pathological decrement of the muscle action potential of more than 10% on repetitive nerve stimulation. Concluding that the presence of the Gantzer muscle caused anterior interosseous nerve compressive syndrome was mainly a diagnosis of exclusion, after careful consideration of other possible etiologies including carpal tunnel syndrome, cervical radiculopathy, and Parsonage-Turner Syndrome. Even though anterior interosseous nerve compressive syndrome is very rare, clinical suspicion ought to arise in the presence of weak radial flexor digitorum profundus and flexor pollicis longus muscles. This case highlights the importance of a thorough medical history, a meticulous physical examination, and particularly the significance of electromyography studies in diagnosing different neuropathological entities. When appropriate, these steps offer information crucial to the differential diagnosis and eventual surgical management, assisting physicians in making informed and accurate treatment decisions.

Optimization of Free Phytoprostane and Phytofuran Production by Enzymatic Hydrolysis of Pea Extracts Using Esterases

Given the growing interest in phytoprostanes (PhytoPs) and phytofurans (PhytoFs) in the fields of plant physiology, biotechnology, and biological function, the present study aims to optimize a method of enzymatic hydrolysis that utilizes bacterial and yeast esterases that allow the appropriate quantification of PhytoPs and PhytoFs. To obtain the highest concentration of PhytoPs and PhytoFs, a response surface methodology/Box-Behnken design was used to optimize the hydrolysis conditions. Based on the information available in the literature on the most critical parameters that influence the activity of esterases, the three variables selected for the study were temperature (°C), time (min), and enzyme concentration (%). The optimal hydrolysis conditions retrieved differed between PhytoPs (21.5 °C, 5.7 min, and 0.61 μg of enzyme per reaction) and PhytoFs (20.0 °C, 5.0 min, and 2.17 μg of enzyme per reaction) and provided up to 25.1- and 1.7-fold higher contents relative to nonhydrolyzed extracts. The models were validated by comparing theoretical and experimental values for PhytoP and PhytoF yields (1.01 and 1.06 theoretical/experimental rates, respectively). The optimal conditions were evaluated for their relative influence on the yield of individual nonesterified PhytoPs and PhytoFs to define the limitations of the models for obtaining the highest concentration of most considered compounds. In conclusion, the models developed provided valuable alternatives to the currently applied methods using unspecific alkaline hydrolysis to obtain free nonesterified PhytoPs and PhytoFs, which give rise to more specific hydrolysis of PhytoP and PhytoF esters, reducing the degradation of free compounds by classical chemical procedures.

Comparative Study of the Phytoprostane and Phytofuran Content of indica and japonica Rice (Oryza sativa L.) Flours

Phytoprostanes and phytofurans (PhytoPs and PhytoFs, respectively) are nonenzymatic lipid peroxidation products derived from α-linolenic acid (C18:3 n-3), considered biomarkers of oxidative degradation in plant foods. The present work profiled these compounds in white and brown grain flours and rice bran from 14 rice cultivars of the subspecies indica and japonica by ultrahigh performance liquid chromatography coupled to electrospray ionization and triple quadrupole mass spectrometry. For PhytoPs, the average concentrations were higher in rice bran (0.01-9.35 ng g^-1) than in white and brown grain flours (0.01-1.17 ng g^-1). In addition, the evaluation of rice flours for the occurrence PhytoFs evidenced average values 1.77, 4.22, and 10.30 ng g^-1 dw in rice bran, brown grain flour, and white grain flour, respectively. A significant correlation was observed between total and individual compounds. The concentrations retrieved suggest rice bran as a valuable source of PhytoPs and PhytoFs that should be considered in further studies on bioavailability and bioactivity of such compounds.

Aortic aneurysm association with SLE - a case-control study

OBJECTIVES

Aortic aneurysm is a life threatening cardiovascular complication in patients with systemic lupus erythematosus (SLE).The purpose of this study was to investigate the association between SLE and occurrence of aortic aneurysms.

METHODS

Patients with SLE were compared with age- and sex-matched controls regarding the proportion of aortic aneurysm in a case-control study. Chi-square and t-tests were used for univariate analysis and a logistic regression model was used for multivariate analysis. The study was performed utilizing the medical database of Clalit Health Services.

RESULTS

The study included 5018 patients with SLE and 25,090 age- and sex-matched controls. The proportion of aortic aneurysm in patients with SLE was increased compared with the proportion in controls (0.6% and 0.1%, respectively, p < 0.001). In a multivariate analysis SLE was associated with the coexistence of aortic aneurysms (odds ratio 2.06, 95% confidence interval 1.21-3.51).

CONCLUSIONS

Patients with SLE have a higher proportion of aortic aneurysms as compared with matched controls. Therefore, physicians treating patients with SLE should be aware of this life threatening association.

Correction: Phytoprostanes in almonds: identification, quantification, and impact of cultivar and type of cultivation

Correction for ‘Phytoprostanes in almonds: identification, quantification, and impact of cultivar and type of cultivation’ by A. M. Carrasco-Del Amor et al., RSC Adv., 2015, 5, 51233–51241.

Hand-assisted Laparoscopic Donor Nephrectomy and Cytokine Changes

BACKGROUND

Laparoscopic living-donor nephrectomy (LDN) exerts systemic effects causing transaminitis and increased urinary neutrophil gelatinase-associated lipocalm (NGAL) excretion. Hand-assisted laparoscopic donor nephrectomy, which tends to be shorter with less pneumoperitoneum, may be hypothesized to produce less systemic stimulation than total laparoscopic LDN.

METHODS

Serial urine and serum samples were collected from 15 patients undergoing HALDN. Samples were analyzed for NGAL and kidney injury molecule 1 (KIM-1) levels preoperatively and 24 hours post-surgery. Data relating to alanine aminotransferase, creatinine, and estimated glomerular filtration rate was also analyzed in 48 live donors preoperatively and at 24 hours and 48 hours post-surgery and compared to published data on LDN.

RESULTS

Expected changes to creatinine and estimated glomerular filtration rates were observed in the donors. Compared to the preoperative levels, alanine aminotransferase levels showed a significant decrease at 24 hours (P = .004) and were not significantly different from baseline levels at 48 hours (P = .08). Serum KIM-1 and NGAL levels remained unchanged (P = .89 and P = .14, respectively) at 24 hours after donation. Similarly, urinary levels of KIM-1 and NGAL were not statistically significantly different after donation. Mean operating time for this cohort was 1 hour, 36 minutes.

CONCLUSIONS

In contrast to other published data, our cohort did not exhibit changes to liver function tests or biomarker changes after donor nephrectomy. This could be because of the lower operative time (96 minutes vs. 216 minutes) or because of the intermittent release of the pneumoperitoneum in the hand-assisted method which may exert less of a systemic inflammatory response.

Phytoprostanes in almonds: identification, quantification, and impact of cultivar and type of cultivation

The phytoprostane profile in 11 almonds cvs varied greatly according to the genotype and several factors (agricultural system conventional or ecological and irrigation).

Pyrolysis Mass Spectrometry of Protected Phosphotriester Oligodeoxyribonucleotides

Pyrolysis mass spectrometry is shown to be a useful tool in the analysis of the protected intermediate deoxy oligonucleotides synthesized by the phosphotriester approach. Characteristic ions of the protected nucleic acid bases and terminal substituents appear in the mass fragmentation pattern which allows a rapid control of the attachment of the polynucleotide block in the chemical synthesis.

Ion Selective Resins: Development and Applications for Nuclear Waste Management

Organic based ion selective resins have some similar attributes: case of synthesis, high metal ion complexation ability, and flexibility for different nuclear waste management applications. For most chelating polymers, the ligand is deemed to be of primary importance for the interaction with the targeted metal ion. The role of the polymer matrix is usually ignored. For ion specific resins, the polymer structure is formed to a specific metal ion. Using the molecular imprinting technique, resins can be formed with functional groups and cavities for a target metal ion. Ion selective resins have been developed for the separation of Cs. The methods and concepts used for the development of the Cs specific resins have been applied to the development of selective resins for Eu (a trivalent actinide model). The resulting resins are characterized by FTIR spectroscopy, moisture regain, and ion exchange capacity. The incorporation of 8-hydroxyquinoline into the resin increases selectivity for Eu over La. The results for the Eu study indicate ion specific resins can be developed for the separation of trivalent actinides from nuclear waste.

Isoprostanes and phytoprostanes: Bioactive lipids

Polyunsaturated fatty acids (PUFA) are important constituents in all eukaryotic organisms, contributing to the structural integrity of biological membranes and serving as precursors for enzymatically-generated local hormones. In addition to these functions, PUFA can generate by a free radical-initiated mechanism, key products which participate in a variety of pathophysiological processes. In particular, free radical-catalyzed peroxidation of PUFA leads to in vivo formation of isoprostanes (IsoP), neuroprostanes (NeuroP), and phytoprostanes (PhytoP) which display a wide range of biological actions. IsoP are now the most reliable indicators of oxidative stress in humans. In this review, we will discuss some advances in our knowledge regarding two cyclic PUFA derivatives, IsoP and PhytoP, and how their biological roles may be clarified through new approaches based on analytical and synthetic organic chemistry.

Is there a Minimum Caseload that Achieves Acceptable Operative Mortality in Abdominal Aortic Aneurysm Operations?

BACKGROUND

Studies have shown correlation between operative workload and mortality for major operations. Is there a threshold for case volume that predicts an acceptable mortality for abdominal aortic aneurysm surgery?

METHODS

Hospital Episode Statistics (HES) Data for England between 1997-2002 was analysed using ICD-10 codes I71.x and OPCS-4 codes L16.x-L26.x. Mortality was identified by the method of discharge.

RESULTS

31,078 operations on abdominal aortic aneurysms were studied in 223 NHS Trusts. 6,007 in-hospital deaths were identified in both elective and emergency cases (overall mortality rates 7.7% and 40%, respectively). Trusts with large elective workloads had reduced mortality for both elective and emergency operations. Using parabolic regression and logarithmic transformation, 14 elective operations per Trust per year was identified as a cut-off point above which the decrease in mortality rate with increasing case volume was relatively small. A similar effect was not seen with increasing emergency workload alone.

CONCLUSION

HES data analysis suggests increasing elective workload correlates with lower in-hospital mortality for elective and emergency operations on abdominal aortic aneurysm. Data suggests a range of hospital caseload that correlate with an acceptable elective and emergency mortality rate.

Serum lactate and base deficit as predictors of mortality after ruptured abdominal aortic aneurysm repair

OBJECTIVE

Whole body hypoperfusion and lower torso ischaemia-reperfusion contribute to post-operative organ dysfunction in patients undergoing repair of ruptured abdominal aortic aneurysm (AAA). Serum lactate and base deficit are markers of tissue ischaemia and are used to assess the adequacy of resuscitation. This study examines the prognostic value of immediate post-operative levels of serum lactate and base deficit in ruptured AAA.

METHODS

Thirty patients (24 men and 6 women of median age 74, range 51-85, years) who survived to at least 12h after ruptured AAA repair were studied retrospectively. The relationship between immediate post-operative lactate, base deficit and mortality was determined.

RESULTS

Fifteen patients (50%) died, all from organ failure. An elevated lactate (>2.1 mmol/l) and base deficit (<-2 mmol/l) were present in 20 (67%) and 27 (90%) patients, respectively. Lactate (p<0.001) and base deficit (p=0.003) were significantly higher in non-survivors compared with survivors. Lactate (p=0.021) and base deficit levels (p=0.028) were independently significant for predicting mortality and a significant interaction existed between lactate and base deficit levels for predicting mortality (p=0.027). The sensitivity and specificity of lactate > or =4.0 mmol/l was 13 of 15 (87%) and 12 of 15 (80%), respectively, and base deficit < or =-7 mmol/l was 12 of 15 (80%) and 12 of 15 (80%), respectively. The likelihood ratios for a positive result with the defined cut-off values for lactate and base deficit were 4.3 and 4.0, respectively. Lactate > or =4.0 mmol/l and base deficit <or =-7 mmol/l were associated with a 94.5% probability of death while lactate < or =4.0 mmol/l and base deficit > or =-7 mmol/l were associated with a 4% probability of death.

CONCLUSION

These data demonstrate that an immediate post-operative serum lactate > or =4.0 mmol/l and base deficit < or =-7 mmol/l are good predictors of outcome after ruptured AAA repair. The prognostic value of these simple and inexpensive tests require corroboration in a larger prospective study.

A Q-methodological study of hearing voices: a preliminary exploration of voice hearers' understanding of their experiences

Using Q-methodology and structured interviews, this preliminary study set out to explore how a diverse range of voice hearers construed their experience of hearing voices. Following factor analysis of 20 completed Q-sorts, six factors emerged. Pejorative media stereotypes about voice hearers were rejected, and despite the dominance of the biomedical model in our culture, on no factor did participants adhere to all of the biomedical concepts. All six factors endorsed some elements of psychological discourse on voice-hearing experiences. It is argued that attempting to understand voice hearers within a single theoretical framework may limit or adversely affect engagement and understanding of an individual. Consistent with previous research, users of mental-health services were more likely to find voices frightening and perceive them as negative experiences than non-users. However, some non-users found managing some of their voices difficult despite having seemingly positive beliefs about the experience of hearing voices. Comment is made on the potential therapeutic implications of this study along with some acknowledgement of its limitations.

Syntheses and preliminary pharmacological evaluation of the two epimers of the 5-F2t-isoprostane

The total synthesis of the 5-F2t-isoprostane 1 and its 5-epimer 2 from diacetone-D-glucose is described. We report preliminary data on the vascular properties of these compounds.

Tandem mass spectrometric quantification of 8-iso-prostaglandin F2alpha and its metabolite 2,3-dinor-5,6-dihydro-8-iso-prostaglandin F2alpha in human urine

Whole body synthesis of F2-isoprostanes, a family of cyclooxygenase-independent eicosanoids formed by free-radical catalysed peroxidation, should be best assessed by quantifying their urinary metabolites. Two methods for the quantitative determination of F2-isoprostane metabolites in human urine performing either thin-layer chromatography (TLC) (method A) or high-performance liquid chromatography (HPLC) (method B) prior to GC-tandem MS are described. Method A allows for simultaneous quantification of 8-iso-PGF2alpha, one prominent member of the F2-isoprostane family, and its major urinary metabolite, 2,3-dinor-5,6-dihydro-8-iso-PGF2alpha. Mean excretion was found to be 223 and 506 pg/mg creatinine of 8-iso-PGF2alpha and 2,3-dinor-5,6-dihydro-8-iso-PGF2alpha, respectively (n=14). A tight correlation existed between the urinary excretion of these two isoprostanes (r=0.86). Method B enables quantification of dinor-dihydro metabolites of various F2-isoprostanes including 8-iso-PGF2alpha. 2,3-Dinor-5,6-dihydro-8-iso-PGF2alpha was found to be an abundant dinor-dihydro F2-isoprostane metabolite. Validity of method A was proven by a combination of HPLC with TLC prior to GC-tandem MS analysis. A correlation was observed between the urinary concentrations of 2,3-dinor-5,6-dihydro-8-iso-PGF2alpha measured by GC-MS and GC-tandem MS (r=0.84).

Structure of an oligonucleotide containing a N-(2-deoxy-beta-D-erythro-pentofuranosyl)formamide residue facing a guanine

Formamide residue is a major oxidative DNA damage product from ionizing radiation on thymine residues in DNA. We report NMR and molecular modeling studies on a DNA duplex structure which contains guanine opposite formamide residue. Formamide residue exists as either the cis and trans isomer. For the trans and the cis isomers, we find that guanine and formamide are stacked inside the helix and are hydrogen bonded. The oligonucleotide adopts globally a B form structure for the two isomers. Conformational changes are observed between the two isomers.

Substituent effects in the selective reductive opening of epoxides with borohydrides in the presence of beta-cyclodextrin

The opening of ortho-substituted phenyl oxiranes by borohydrides is described both in aqueous and solid phases. Some remarkable differences in the regioselectivity and inversion of enantioselectivity of oxirane ring-opening are reported. The results obtained are compared with previous studies and have allowed some factors governing the reactivity, the regio- and stereoselectivity of this reaction to be evaluated. Preferential orientations of the substrate included inside the cyclodextrin are proposed from these results. Copyright 1999 Wiley-Liss, Inc.

Identification and measurement of endogenous beta-oxidation metabolites of 8-epi-Prostaglandin F2alpha

F2-isoprostanes are prostaglandin-like compounds derived from nonenzymatic free radical-catalyzed peroxidation of arachidonic acid. 8-epi-Prostaglandin (PG) F2alpha, a major component of the F2-isoprostane family, can be conveniently measured in urine to assess noninvasively lipid peroxidation in vivo. Measurement of major metabolites of endogenous 8-epi-PGF2alpha, in addition to the parent compound, may be useful to better define its formation in vivo. 2,3-Dinor-5,6-dihydro-8-epi-PGF2alpha is the only identified metabolite of 8-epi-PGF2alpha in man, but its endogenous levels are unknown. In addition to this metabolite, we have identified another major endogenous metabolite, 2,3-dinor-8-epi-PGF2alpha, in human and rat urine. The identity of these compounds, present at the pg/ml level in urine, was proven by a number of complementary approaches, based on: (a) immunoaffinity chromatography for selective extraction; (b) gas chromatography-mass spectrometry for structural analysis; (c) in vitro metabolism in isolated rat hepatocytes; and (d) chemical synthesis of the enantiomer of 2,3-dinor-5, 6-dihydro-8-epi-PGF2alpha as a reference standard. In humans, the urinary excretion rate of both dinor metabolites is comparable with that of 8-epi-PGF2alpha. Both metabolites increase in parallel with the parent compound in cigarette smokers, and they are not reduced during cyclooxygenase inhibition. Another beta-oxidation product, 2, 3,4,5-tetranor-8-epi-PGF2alpha, was identified as a major product of rat hepatocyte metabolism. In conclusion, at least two major beta-oxidation products of 8-epi-PGF2alpha are present in urine, which may be considered as additional analytical targets to evaluate 8-epi-PGF2alpha formation and degradation in vivo.

Yes. No. Maybe. That's about as firm as the guidance gets over launching a provider-sponsored health plan. Strategy roundtable

Few participants in our roundtable on provider-sponsored health plans see them the same way. Some are gearing up new products, others are scaling back or getting out. Yet they agreed on one thing: The financial risks are tremendous.

Repair and mutagenic potency of 8-oxoG:A and 8-oxoG:C base pairs in mammalian cells

Replication of the oxidative lesion 8-oxo-7,8-dihydroguanine (GO) leads to the formation of both 8-oxo-7,8-dihydroguanine:adenine (GO:A) and 8-oxo-7,8-di-hydroguanine:cytosine (GO:C) pairs. The repair and mutagenic potency of these two kinds of base pairs were studied in simian COS7 and human MRC5V1 cells using the shuttle vector technology. Shuttle vectors carrying a unique GO residue opposite either a C or an A were constructed, then transfected into recipient mammalian cells. DNA repair resulting in G:C pairs and mutation frequency, were determined using resistance to digestion by the Ngo MI restriction enzyme for screening and DNA sequencing of suspect mutants. Results showed that the GO:C mismatch was well repaired since almost no mutations were detected in the plasmid progeny obtained 72 h after cell transfection. The GO:A pair was poorly repaired since only 32-34% of the plasmid progeny contained G:C whereas two thirds contained A:T at the original site. Repair kinetics measured with a non-replicating vector deleted by 13 bp at the SV40 replication origin, showed that GO:A was slowly repaired. Only 30% of the mispairs were corrected in 12 h. During this time 100% of the plasmids containing GO:A pairs were replicated as seen by the replication kinetics in a vector with an intact SV40 replication origin. These results show that, under our experimental conditions, replication is occurring before completion of DNA repair which explains the high mutagenic potency of the GO:A mispair.

Solution structure of N-(2-deoxy-D-erythro-pentofuranosyl)urea frameshifts, one intrahelical and the other extrahelical, by nuclear magnetic resonance and molecular dynamics

The presence of a N-(2-deoxy-D-erythro pentofuranosyl)urea (henceforth referred to as deoxyribosylurea) residue, ring fragmentation product of a thymine, in a frameshift situation in the sequence 5'd(AGGACCACG).d(CGTGGurTCCT) has been studied by 1H and 31P nuclear magnetic resonance and molecular dynamics. At equilibrium, two species are found in slow exchange. We observe that the deoxyribosylurea residue can be either intra- or extrahelical within structures which otherwise do not deviate strongly from that of a B-DNA as observed by NMR. Our study suggests that this is determined by the nature and number of hydrogen bonds which this residue can form as a function of two possible isomers. There are two possible structures for the urea side chain, either cis or trans for the urido bond which significantly changes the hydrogen bonding geometry of the residue. In the intrahelical species, the cis isomer can form two good hydrogen bonds with the bases on the opposite strand in the intrahelical species, A4 and C5, which is not the case for the trans isomer. This results in a kink in the helical axis. For the major extrahelical species, the situation is reversed. The trans isomer is able to form two good hydrogen bonds, with G13 on the same strand and A7 on the opposite strand. For the extrahelical species, the cis isomer can form only one hydrogen bond. In this major structure the NMR data show that the bases which are on either side of the deoxyribosylurea residue in the sequence, G14 and T16, are stacked over each other in a way similar to a normal B-DNA structure. This requires the formation of a loop for the backbone between these two residues. This loop can belong to one of two families, right- or left-handed. In a previous study of an abasic frameshift [Cuniasse et al. (1989) Biochemistry 28, 2018-2026], a left-handed loop was observed, whereas in this study a right-handed loop is found for the first time in solution. The deoxyribosylurea residue lies in the minor groove and can form both an intra- and an interstrand hydrogen bond.

Sodium-independent carrier-mediated inositol transport in cultured renal epithelial (LLC-PK1) cells

In addition to the concentrative, Na(+)-dependent inositol transport system demonstrated in many cell types, carrier-mediated, Na(+)-independent inositol transport is also shown to exist in LLC-PK1 renal epithelia. Inhibition of inositol uptake in Na(+)-free saline by 0.1 mM phloretin, and self-inhibition by net concentrations of inositol exceeding 10 mM, demonstrate the carrier-mediation of the Na(+)-independent uptake and distinguish it from flux through anion channels. The Na(+)-dependent uptake exhibits higher affinity for inositol, as seen by the stronger self-inhibition at lower inositol concentrations in Na+ saline. Kinetic analyses indicate a Km of 178 microM and a Vmax of 2447 pmol/min per microgram DNA for the Na(+)-dependent system, whereas the lower affinity, lower capacity Na(+)-independent system manifests a Km of 5.2 mM and a Vmax of 249 pmol/min per microgram DNA. the Na(+)-independent uptake further differs from the Na(+)-dependent transport by the lack of inhibitory effect of 10 microM glucose, and the greater relative inhibition of phloretin compared to that of phlorizin. Both types of uptake appear to localize predominantly to the basal-lateral cell surface. The Na(+)-independent transport is bidirectional, functioning in efflux as well as influx of inositol.