Phylogeny of the genus Rhagoletis (Diptera: Tephritidae) inferred from DNA sequences of mitochondrial cytochrome oxidase II

Despite a considerable literature describing the biology of flies in the tephritid genus Rhagoletis, the phylogenetic relationships of the more than 60 species classified within the genus are not well resolved. Knowledge of these relationships is important, not only in terms of obtaining information that will be useful for the control of Rhagoletis where it is an agricultural pest, but also in determining what role host plant shifts have played in the generation of Rhagoletis species diversity, a focal point in debate over the role of sympatric speciation in the evolutionary process. In this paper, the phylogenetic history of 28 Rhagoletis species and 6 species in related tephritid genera is inferred from nucleotide sequences of subunit II of the mitochondrial cytochrome oxidase (COII) gene and the adjacent tRNALeu/COII intergenic region. Analyses of the data using distance and character-state approaches suggest the following: (i) the genus Rhagoletis as currently defined is not monophyletic; (ii) the 5 predominantly North American Rhagoletis species groups do constitute a monophyletic assemblage; (iii) the North American species groups form 2 clades, 1 consisting of taxa in the R. pomonella and R. tabellaria species groups (plus R. fausta), and the other consisting of taxa in the R. ribicola, R. cingulata, and R. suavis species groups; and (iv) the origin(s) of the North American species groups is obscure, as evidenced by the recovery of clades containing both Palearctic and Neotropical taxa. Areas of congruence and conflict with published phylogenies of Rhagoletis are examined and, while many areas of conflict may be due to an insufficient number of characters or incomplete taxon sampling, we cannot discount the possibility that real differences exist between the Rhagoletis mitochondrial DNA gene tree and the Rhagoletis species tree.

Extensin from suspension-cultured potato cells: a hydroxyproline-rich glycoprotein, devoid of agglutinin activity

Enhanced deposition and cross-linking of hydroxyproline-rich glycoproteins (HRGPs) in the plant cell wall is acknowledged to contribute to the formation of a resistant barrier against pathogen infection. We have isolated, from suspension-cultured potato (Solanum tuberosum L. cv. Desiree) cells, two forms of soluble HRGP, a cross-linked and a monomeric form; the latter can be converted to the cross-linked form by incubation with tomato extensin peroxidase and H2O2. The monomeric form was purified by Sephacryl S-200 gel-filtration, reverse-phase high-performance liquid chromatography and Mono-S cation-exchange chromatography into two isoforms (A, a minor form; B, a major form). The properties of the B isoform were further investigated. A quantitative enzyme-linked immunosorbent assay of the B isoform, using tomato extensin antiserum, showed a titration curve at a high antibody-dilution range comparable to that of purified tomato extension monomer (M.D. Brownleader and P.M. Dey, 1993, Planta 191: 457-469). The amino acid and carbohydrate compositions were similar to those of tomato extensin, but did not match well with the other two HRGPs from potato, potato lectin and potato bacterial agglutinin. These observations demonstrate the similarities of the B isoform to extensin. The homogeneity of the B isoform was demonstrated by its ability to be fully cross-linked in vitro, leaving no residual protein, into a high-molecular-weight form by the action of extensin peroxidase. The trifluoroacetic acid-deglycosylated sample migrated as a single protein band on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Moreover, SDS-PAGE and matrix-assisted laser desorption/ionisation-time of flight mass spectrometry indicated a molecular weight of approximately 67 kDa. Circular-dichroism spectroscopy demonstrated that the molecule possess an extended polyproline II helix conformation with no evidence of alpha-helix or beta- sheet secondary structure. In conclusion, we refer to this HRGP as potato extensin. As proposed for other extensins, potato extensin is likely to play a role in cell wall architecture and plant disease resistance.

Calcium channel blockers in heart failure: help or hindrance?

Since their development, calcium channel blocking agents have stimulated interest in their potential benefit for a variety of cardiovascular disorders, including heart failure. The rationale for the potential benefit of calcium channel blockers in heart failure is multi-factorial, including vasodilation, correction of perturbed diastolic relaxation, anti-ischemic action, and potential for inhibiting myocyte hypertrophy and injury. Despite these potential benefits, the degree of salutary influence has remained controversial, and a number of studies have suggested potential adverse action in patients with heart failure, perhaps linked to either negative inotropic action or to reflex neurohormonal activation. Diversity among different agents, particularly with regard to tissue selectivity and pharmacokinetics may imply substantial differences in the relative benefits and risks in various subgroups of patients with heart failure. One trial with the newer dihydropyridine agent, amlodipine, indicates benefit to survival in patients with moderate to severe heart failure and reduced ejection fraction. The reproducibility of this finding and the mechanism for this benefit deserves further investigation.

The Yarrowia lipolytica gene PAY5 encodes a peroxisomal integral membrane protein homologous to the mammalian peroxisome assembly factor PAF-1

Pay mutants of the yeast Yarrowia lipolytica fail to assemble functional peroxisomes. One mutant strain, pay5-1, lacks normal peroxisomes and instead contains irregular vesicular structures surrounded by multiple unit membranes. The pay5-1 mutant is not totally deficient in peroxisomal matrix protein targeting, as a subset of matrix proteins continues to localize to a subcellular fraction enriched for peroxisomes. The functionally complementing gene PAY5 encodes a protein, Pay5p, of 380 amino acids (41,720 Da). Pay5p is a peroxisomal integral membrane protein homologous to mammalian PAF-1 proteins, which are essential for peroxisome assembly and whose mutation in humans results in Zellweger syndrome. Pay5p is targeted to mammalian peroxisomes, demonstrating the evolutionary conservation of the targeting mechanism for peroxisomal membrane proteins. Our results suggest that in pay5 mutants, normal peroxisome assembly is blocked, which leads to the accumulation of the membranous vesicular structures observed.

A phospholipase A2-like pseudogene retaining the highly conserved introns of Mojave toxin and other snake venom group II PLA2s, but having different exons

Mojave toxin is a neurotoxic, heterodimeric phospholipase A2 (PLA2) from the venom of the Mojave rattlesnake (Crotalus scutulatus scutulatus) and is characteristic of all rattlesnake presynaptic neurotoxins. Here, we describe a phospholipase A2 pseudogene (psi-Mtx) located 2,000 nucleotides upstream, and on the opposite DNA strand, from a gene for Mojave toxin acidic subunit (Mtx-a). The pseudogene lacks the first exon and a few segments of noncoding DNA found in functional snake venom PLA2 genes, but does have the coding information for a complete PLA2 protein. psi-Mtx retains the unusual gene sequence similarity pattern found in functional viperid PLA2 genes. When compared to genes from C. s. scutulatus and the Hahn snake (Trimeresurus flavoviridus), psi-Mtx shows strong conservation of nocoding regions and variable protein-coding regions. Although the nocoding regions of psi-Mtx are conserved with respect to other viperid PLA2 genes, the three exons code for a unique PLA2-like protein similar in sequence to ammodytoxin b found in the venom of the western sand viper (Vipera ammodytes ammodytes). The structure of these genes suggests a common ancestor for all viperid PLA2 genes. Phylogenetic analysis of psi-Mtx, Mtx-a, Mtx-b, pgPLA 1a, and pgPLA 1b suggest that psi-Mtx diverged from an ancestral sequence before the presumed gene duplication event leading to Mtx-a and Mtx-b. However, analysis of the basis of coding regions alone gives a conflicting result.

Cystic fibrosis airway epithelia fail to kill bacteria because of abnormal airway surface fluid

Despite an increased understanding of the cellular and molecular biology of the CFTR Cl- channel, it is not known how defective Cl- transport across airway epithelia causes chronic bacterial infections in cystic fibrosis (CF) airways. Here, we show that common CF pathogens were killed when added to the apical surface of normal airway epithelia. In contrast, these bacteria multiplied on CF epithelia. We found that bactericidal activity was present in airway surface fluid of both normal and CF epithelia. However, because bacterial killing required a low NaCl concentration and because CF surface fluid has a high NaCl concentration, CF epithelia failed to kill bacteria. This defect was corrected by reducing the NaCl concentration on CF epithelia. These data explain how the loss of CFTR Cl- channels may lead to lung disease and suggest new approaches to therapy.

Intraoperative force-setting did not improve the mechanical properties of an augmented bone-tendon-bone anterior cruciate ligament graft in a goat model

It has been hypothesized that load affects the mechanical properties of an anterior cruciate ligament graft while it remodels. The goal of this study was to use an existing goat model to evaluate the effect of intraoperative set force on the postoperative mechanical properties of an autograft that had been augmented with a synthetic segment. The following questions were addressed. Do augmented autografts set with a high force intraoperatively have improved structural and material graft properties and lower anterior-posterior knee laxity at 3 months after surgery, compared with autografts set with a low intraoperative force? How do the structural and material properties of these implanted autografts compare with the mechanical properties of an intact anterior cruciate ligament or an unimplanted control autograft? The anterior cruciate ligament was reconstructed in seven goats with use of a composite graft consisting of a bone-patellar tendon-bone autograft and a synthetic augmentation device. A force-setting technique was used intraoperatively to establish the load-sharing between the autograft and augmentation segments such that the autograft carried either a high (16.5 N in four animals) or low (1.5 N in three animals) level of force, while the total force in the composite graft remained constant. Tensile testing was performed at 3 months after surgery to determine the material and structural properties of the autograft, the intact anterior cruciate ligament from the normal contralateral knee, and a control bone-patellar tendon-bone graft of similar size that was harvested from the contralateral knee at the time of necropsy and had never been implanted in the joint. The structural and material properties of the autografts initially set to high or low loads at surgery were not significantly different after 3 months of implantation. The strength and stiffness of the implanted tendons were an average of 24 and 20% of the strength and stiffness of the normal anterior cruciate ligament and 31 and 62% of the control tendons, respectively. Intraoperative set force in an augmented anterior cruciate ligament graft at the levels chosen in this study did not significantly affect weakening of the autograft at 3 months.

Effects of substrates and phosphate on INT (2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl tetrazolium chloride) and CTC (5-cyano-2,3-ditolyl tetrazolium chloride) reduction in Escherichia coli

The effects of substrates of primary aerobic dehydrogenases, and inorganic phosphate on aerobic INT and CTC reduction in Escherichia coli were examined. In general, INT produced less formazan than CTC, but INT (+) cell counts remained near values of CTC (+) cells. INT and CTC (+) cell numbers were higher than plate counts on R2A medium using succinate, formate, lactate, casamino acids, glucose, glycerol (INT only) and no substrate. Formate resulted in the greatest amount of INT and CTC formazan. Reduction of both INT and CTC was inhibited above 10 mmol l-1 phosphate, and this appeared to be related to decreased rates of O2 consumption. Formation of fluorescent CTC (+), but not INT (+) cells was also inhibited in a concentration dependent manner by phosphate above 10 mmol l-1. From light microscopic observations it appeared CTC formed increasing amounts of poorly or non-fluorescent formazan with increasing phosphate. Therefore, use of phosphate buffer in excess of 10 mmol l-1 may not be appropriate in CTC and INT reduction assays.

Intravaginal stimulation randomized trial

PURPOSE

The effectiveness of intravaginal electrical stimulation was compared to standard therapy in the treatment of genuine stress urinary incontinence and detrusor instability.

MATERIALS AND METHODS

A total of 57 women with urinary incontinence was evaluated with video urodynamics and voiding diaries before and after treatment. Of the women 18 with stress urinary incontinence were randomized to electrical stimulation or Kegel exercise and 38 with detrusor instability were randomized to anticholinergic therapy or electrical stimulation.

RESULTS

Of patients using electrical stimulation in the stress urinary incontinence group 66% improved and 72% of the patients with detrusor instability treated with electrical stimulation improved. These rates were not statistically significant when compared to traditional therapy.

CONCLUSIONS

Electrical stimulation is safe and at least as effective as properly performed Kegel and anticholinergic therapy in the treatment of stress urinary incontinence and detrusor instability.

Comparison of the performance characteristics of three generations of membrane oxygenators: Univoxregistered, Univoxreqistered Goldtrademark and SpiralGoldtrademark

With continuous enhancement in oxygenator design, the question is raised as to how these changes actually impact the performance of the oxygenator. The recent addition of two new oxygenators by the Bentley Division of Baxter Healthcare Corporation provided us with a unique opportunity to compare the performance of each device and isolate the impact of each design change on performance. While the basic design and flow patterns have remained the same, application of the Duraflo II treatment has produced the Univox Gold and a change in the fibre-winding technique has produced the SpiralGold. This study compared the effects of heparin coating (Univox to Univox Gold) and fibre-winding (Univox Gold to SpiralGold) on gas and heat transfer and resistance to blood flow (pressure drop). Six oxygenators of each model were evaluated utilizing an in vitro single pass circuit, which first conditioned bovine blood to the Association for the Advancement of Medical Instrumentation (AAMI) venous standards. Blood flows of 4.0, 5.0, 6.0 and 7.0 l/min, FiO2 values of 1.0, 0.8 and 0.6, and gas-to-blood flow ratios of 0.5, 1.0 and 1.5 were chosen as test variables. Data generated included oxygen transfer, carbon dioxide transfer, arterial pO2, resistance to blood flow, and coefficient of heat exchange. The results indicate that the Duraflo II treatment does not have a significant effect on gas and heat transfer or resistance to blood flow. The fibre-winding technique employed with the new SpiralGold, however, has improved significantly gas exchange and arterial pO2 when compared with the previous Univox models. Resistance to blood flow and coefficient of heat exchange were not affected significantly by the winding technique.

Genetic diversity of Burkholderia solanacearum (synonym Pseudomonas solanacearum) race 3 in Kenya

Genetic diversity among isolates of the bacterial plant pathogen Burkholderia solanacearum (synonym Pseudomonas solanacearum) race 3 biovar II of Kenya was determined by PCR with repetitive sequences (ERIC and BOX repetitive primer sets) and pulsed-field gel electrophoresis of genomic DNA digested by rare-cutting restriction endonucleases (RC-PFGE). The study comprised 46 isolates collected during 1992 from the major potato-growing regions of Kenya (45 were identified as race 3 biovar II, and 1 belonged to race 3 biovar N2) and 39 reference isolates from 19 other countries. RC-PFGE identified 10 distinct profile types among the Kenyan race 3 biovar II isolates (29 of the isolates exhibited identical profiles) and a further 27 distinct profile types among the reference isolates. ERIC and BOX primer sets were unable to differentiate race 3 biovar II isolates within the Kenyan population but differentiated a further two distinct profile types among the reference isolates. The race 3 biovar N2 isolate had a highly distinct RC-PFGE and repetitive sequence PCR profile. Statistical analysis of the data identified biogeographic trends consistent with conclusions drawn from previous studies on the origin and worldwide dissemination of race 3 biovar II isolates; however, genomic fingerprinting by RC-PFGE revealed a level of genetic diversity previously unrealized.

Influence of prepubertal dietary regimen on mammary growth of Holstein heifers

One hundred-sixteen Holstein heifers (mean BW, 175 kg) were randomly assigned to diets of alfalfa silage or corn silage and were fed to gain approximately 725 or 950 g/d in order to study the influence of prepubertal diet and rate of gain on mammary growth and milk production. Blood was collected before puberty for hormone determination, and 8 heifers per group were killed at puberty for evaluation of tissue variables. Serum growth hormone was reduced, and IGF-I was increased, in the group of heifers reared at a high rate of gain on the corn silage diet. Accompanying the decline in growth hormone, total mammary parenchymal DNA and RNA was reduced in heifers reared at a high rate of gain on the corn silage diet. Mammary parenchyma in heifers of the latter group contained a greater volume of adipocytes and a lower volume of epithelial cells than did mammary parenchyma in heifers of other groups. Data are consistent with previous investigations that showed a deleterious effect of prepubertal rapid weight gain on mammogenesis when accompanied by excess body fat deposition. However, this effect did not cause a decline in subsequent milk production.

Estrogen inhibits the response-to-injury in a mouse carotid artery model

The atheroprotective effects of estrogen are well documented, but the mechanisms responsible for these effects are not well understood. To study the role of physiologic (nanomolar) estrogen levels on the arterial response-to-injury, we applied a mouse carotid artery injury model to ovariectomized C57BL/6J mice. Mice were treated with vehicle (-E2, n = 10) or 17 beta-estradiol (+E2, n = 10) for 7 d, subjected to unilateral carotid injury, and 14 d later contralateral (normal = NL) and injured carotids from -E2 and +E2 animals were pressure fixed, harvested, and analyzed by quantitative morphometry. E2 levels in +E2 mice were consistently in the nanomolar range (2.1-2.5 nM) at days 0, 7, and 14. At 14 d, measures of both intimal and medial area were markedly increased in the -E2 group: (-E2 vs NL, P < 0.05 for both), but were unchanged from normal levels in the +E2 group (+E2 vs NL, P = NS and +E2 vs -E2, P < 0.05 for both). Cellular proliferation, as assessed by bromodeoxyuridine (BrdU) labeling, was significantly increased over NL in the -E2 mice, but this increase was markedly attenuated in the estrogen replacement group (total BrdU positive cells/section: NL = 6.4 +/- 4.5; -E2 = 113 +/- 26, +E2 = 40 +/- 3.7; -E2 vs NL, P < 0.05; +E2 vs NL, P = NS; -E2 vs +E2, P < 0.05). These data (a) demonstrate significant suppression of the mouse carotid response-to-injury by physiologic levels of estrogen replacement; (b) support the utility of this model in the study of the biologic effects of estrogen on the vascular-injury response; and (c) suggest a direct effect of estrogen on vascular smooth muscle cell proliferation in injured vessels.

Detection of partial anomalous right pulmonary venous return with an intact atrial septum by transesophageal echocardiography

Partial anomalous pulmonary venous drainage with intact atrial septum is a rare congenital anomaly. We report a case of a 63-year-old woman who recently had dyspnea on minimal exertion and was found to have pulmonary hypertension, right atrial enlargement, and right ventricular enlargement by two-dimensional transthoracic echocardiography. Transesophageal echocardiography demonstrated anomalous venous drainage of the right lung into the superior vena cava with an intact interatrial septum. This diagnosis was confirmed by angiography and the patient underwent successful repair. This case illustrates the importance of locating all four pulmonary veins in patients with pulmonary hypertension or suspected intracardiac shunt in addition to scanning the atrial septum.

A mouse model for the delta F508 allele of cystic fibrosis

The most common cause of cystic fibrosis is a mutation that deletes phenylalanine 508 in cystic fibrosis transmembrane conductance regulator (CFTR). The delta F508 protein is misprocessed and degraded rather than traveling to the apical membrane. We used a novel strategy to introduce the delta F508 mutation into the mouse CFTR gene. Affected epithelia from homozygous delta F508 mice lacked CFTR in the apical membrane and were Cl-impermeable. These abnormalities are the same as those observed in patients with delta F508 and suggest that these mice have the same cellular defect. 40% of homozygous delta F508 animals survived into adulthood and displayed several abnormalities found in human disease and in CFTR null mice. These animals should provide an excellent model to investigate pathogenesis and to examine therapies directed at correcting the delta F508 defect.

Magnesium-dependent stimulation of protein synthesis by the insulin mimic, pervanadate

The insulin mimic, peroxide of vanadate (pervanadate), stimulated 35S-methionine incorporation into Xenopus oocyte protein in a Mg(2+)-dependent manner. Reducing the extracellular Mg2+ concentration from 1.0 to 0.1 mM decreased the pervanadate-stimulated component of incorporation by 35%; with 0.01 mM Mg2+ or lower, the pervanadate-stimulated component was abolished. In addition, reducing extracellular Mg2+ to 0.01 mM inhibited about 50% of the insulin-stimulated component of methionine incorporation. Mg2+ depletion had no effects on incorporation in controls or when protein synthesis was stimulated by Zn2+ or bovine growth hormone. Thus, not all substances that stimulated protein synthesis showed a dependence on extracellular Mg2+. Reducing extracellular Ca2+ had no effects on methionine incorporation in control cells or in cells stimulated by pervanadate or insulin. When oocytes maintained in a paraffin oil medium were brought into contact with a 0.5 microliter droplet of buffer containing the Mg2+ indicator dye, mag-fura-2, and pervanadate, apparent droplet Mg2+ decreased rapidly, indicating net uptake by the cells. Insulin also caused a net uptake of Mg2+. In contrast, apparent extracellular Mg2+ was constant when cells were in contact with droplets containing no effectors. Together, these data indicate that extracellular Mg2+, but not Ca2+, is involved in the stimulation of protein synthesis by pervanadate, and to a lesser extent by insulin. Pervanadate appears to induce a net uptake of Mg2+, and this change in membrane transport may be an early event in signalling the increase in translation.

The PAH2 gene is required for peroxisome assembly in the methylotrophic yeast Hansenula polymorpha and encodes a member of the tetratricopeptide repeat family of proteins

Peroxisome assembly mutants in the methylotrophic yeast, Hansenula polymorpha, were selected by a novel procedure involving the inability of mutants to use both oleic acid and methanol as carbon sources. These compounds are both metabolized within peroxisomes through two different enzymatic pathways. 15 mutant strains called mut (methanol non-utilizing) were isolated. These strains were assigned to ten genetic complementation groups. Subcellular fractionation analysis showed that peroxisomal matrix enzymes were mislocalized to the cytoplasm in mut strains. Electron microscopy confirmed that the inability of mut strains to grow on oleic acid and methanol was due to defects in peroxisome assembly. Functional complementation of a mutant strain, mut2, with a plasmid library of H. polymorpha genomic DNA sequences has identified a gene, PAH2, that restores growth on methanol and the correct localization of matrix enzymes to the peroxisome. PAH2 encodes Pah2p, a polypeptide of 569 amino acids that is a member of the tetratricopeptide repeat (TPR) family of proteins. Pah2p shows identity with Pas8p and Pas10p, two proteins required for peroxisome assembly in the yeasts Pichia pastoris and Saccharomyces cerevisiae, respectively, and which have been suggested to be receptors that recognize peroxisomal targeting signal-1 (PTS1) motifs.

Modification of cerebral laser-Doppler flow oscillations by halothane, PCO2, and nitric oxide synthase blockade

We investigated whether nitric oxide (NO) played a role in the generation of cerebrocortical flow oscillations and their modification by hypocapnia, hypercapnia, and halothane administration. Parietal cortical laser-Doppler flow (LDF) was monitored transcranially in anesthetized (barbiturate + 0-1.0% halothane), artificially ventilated, adult male Sprague-Dawley rats. Thirty minutes after infusion of N omega-nitro-L-arginine methyl ester (L-NAME, 20 mg/kg i.v.) mean arterial pressure (MAP) increased from 105 +/- 10 to 132 +/- 15 mmHg (P < 0.02), while mean LDF decreased from 159 +/- 36 to 135 +/- 30 perfusion units (PU, P < 0.05). Oscillations in LDF at a frequency of 6.3-7.8 cycles/min and amplitude of 10% were induced or augmented by L-NAME but not by D-NAME or indomethacin (2 mg/kg i.p.). L-arginine (200 mg/kg) abolished the oscillations post-L-NAME at constant MAP. Sodium nitroprusside infusion (10(-5) M, 5-50 microliters/min) reversed the L-NAME-induced increase in MAP and decrease in mean LDF but did not attenuate the flow oscillations. Hypocapnia post-L-NAME decreased LDF to 110 +/- 20 PU (P < 0.001) and augmented the flow oscillations (amplitude: 11-31%). Hypercapnia (5% CO2) or halothane (0.4-1.0%) suspended the oscillations in the presence of L-NAME. The results suggest that NO synthase activity inhibits cerebrocortical flow oscillations, and NO is not an obligatory mediator of the effects of halothane, hypocapnia, and hypercapnia on oscillatory activity.

The role of nitric oxide in cerebrocortical laser Doppler flow response to halothane in the rat

Laser Doppler flowmetry was utilized to investigate whether nitric oxide (NO) plays a role in the cerebrocortical hyperemic effect of halothane in rats. A particular objective was to elucidate whether the increased vascular tone or the removal of basal NO secondary to NO synthase inhibition influenced the response to halothane. The animals were anesthetized with i.p. pentobarbital for surgery and 90 min later were ventilated with 1.0 minimum alveolar concentration (MAC) halothane for 1 h to achieve a steady-state baseline. The control group was infused with either 1 ml of saline or 20 mg/kg of D-NAME, and the treatment group received 20 mg/kg of L-NAME intravenously. In a subset of the treatment group, we restored baseline flow and vascular tone using i.v. sodium nitroprusside (SNP). Mean arterial pressure (MAP) was maintained constant with an infusion of phenylephrine (0.5-5 micrograms/kg/min). Then, 30 to 45 min later, inspired halothane was raised to 1.7 MAC in each group, and the increase in laser Doppler flow (LDF) was measured. On increasing halothane MAC in the control group, LDF increased by 28 +/- 4%. L-NAME increased MAP by 21 +/- 4% and reduced baseline LDF by 26 +/- 2%. In the L-NAME-only treated group, 1.7 MAC halothane increased LDF by 12 +/- 3%, significantly less than control. The decrease in cerebrovascular resistance induced by increasing inspired halothane MAC was similar in the control group and in the L-NAME treated group at 23 +/- 6% and 22% +/- 7, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

A new platinum balloon-expandable stent (Angiostent) mounted on a high pressure balloon: acute and late results in an atherogenic swine model

BACKGROUND

Randomized studies have proven the efficacy and safety of stent placement to treat de novo coronary stenosis. However, the poor radio-opacity and the use of an additional high-pressure balloon to fully expand the stent are the major limitations of the currently clinically-approved stents.

OBJECTIVE

We evaluated the safety, efficacy, angiographic and histologic effect of a new platinum balloon expandable stent mounted on a high-pressure balloon in Yucatan miniature swine fed high cholesterol diet.

METHODS

Fifteen Angiostents (NuMED, Inc., Hopkinton, NY and Angiodynamics, Glens Falls, NY) (coronary stent was 3, 3.5, or 4 mm in diameter and 12 mm long; renal and carotid stents were 5 mm in diameter and 13 mm long) mounted on a high-pressure balloon were placed percutaneously in blood vessels of 10 pigs [5 in circumflex (CX), 2 in left anterior descending (LAD), 5 in renal and 3 in carotid arteries]. The stent was 10-20% larger than the native vessel diameter. All animals received 5000 I.U. of heparin during the procedure and were maintained on 325 mg aspirin daily. Follow-up angiography and histology in the animals was performed at 2, 4, 12, 20, 26 and 52 weeks.

RESULTS

The stents were easily visualized with fluoroscopy and placed in all animals without episodes of balloon rupture or embolization. There was no episode of acute thrombosis. Follow-up angiography in the animals revealed patency of all renal and carotid stents, however, 2/7 coronary stents in the animals revealed angiographic lumen narrowing (> 20%) at 20 and 52 weeks. Histologic examination revealed neointimal formation at the stent site with an average neointimal thickness ranging from 325-650 microns.

CONCLUSION

This stent was safe in this animal model, easily deployed, had excellent radio-opacity and with good short-term patency without anticoagulation. Clinical trials and experience is underway.

Laser-Doppler measurement of the effects of halothane and isoflurane on the cerebrovascular CO2 response in the rat

We used laser-Doppler flowmetry to compare the effects of the volatile anesthetics, isoflurane and halothane, on the cerebrovascular response to CO2 inhalation in male Sprague-Dawley rats. The effects of 0.5 and 1.5 minimum alveolar anesthetic concentrations (MAC) of halothane and isoflurane on the microcirculatory response to CO2 were compared at 22, 36, and 66 mm Hg end-tidal partial pressure of carbon dioxide (ETCO2). An additional group of animals was anesthetized by continuous barbiturate infusion (10-20 mg.kg-1.h-1). Arterial blood pressure was maintained at control levels throughout the experiment using an infusion of phenylephrine (0.5-5 micrograms.kg-1.min-1). Laser-Doppler flow (LDF) was greater at 1.5 MAC than at 0.5 MAC at each ETCO2 for both anesthetics. The CO2 reactivity (percent LDF change/mm Hg change ETCO2) from hypocapnia to normocapnia was similar to that from normocapnia to hypercapnia. CO2 reactivity with barbiturate infusion and 0.5 MAC isoflurane were 1.78 +/- 0.19 and 2.28 +/- 0.22 (no difference), respectively, both being greater than that with 0.5 MAC halothane at 1.19 +/- 0.14 (P < 0.05). A similar difference was suggested at 1.5 MAC halothane and 1.5 MAC isoflurane (1.99 +/- 0.25 and 2.67 +/- 0.35, respectively). The CO2 reactivity was greater at 1.5 MAC halothane compared to 0.5 MAC halothane. The results of this study suggest that an increase in arterial CO2 may increase cerebrocortical red cell flow more with isoflurane than with halothane, at least at moderate anesthetic concentrations.

Suture guide for retropubic vesicourethral suspension

Retropubic suspension of the urethrovesical neck can be facilitated with the use of a metal suture guide. This guide permits efficient, accurate placement of paravaginal sutures and eliminates the risk of finger needle puncture, thus reducing operative time and providing a safer technique.

An electrical model for Periplaneta americana pronotal integument: an epidermal location for hydration-dependent resistance

Measurements of electrical resistance appear to be useful indicators of porosity and related water permeability in insect cuticle. To develop an adequate understanding of how such measurements relate to the physical and structural properties of the integument, we made detailed determinations of resistance and impedance values for pronotal cuticle in adult male Periplaneta americana. The most consistent estimates were obtained by averaging measurements across the integument on both sides of the midline at several intervals starting 15 min after electrode application. Pronotal resistance varied inversely with water content, from about 10 k omega cm2 in hydrated cockroaches to about 40 k omega cm2 in dehydrated insects. Though the dermal gland canals appear to act as the main conductive pathway across the cuticle, the variable 'barrier' is located in the epidermal layer, since removal of the epidermis from isolated pronota also removes most of the variable component of the integumental resistance. Comparison of measurements between two external electrodes with single-electrode measurements revealed a 'shunt' pathway parallel to the cuticle surface; modelling this shunt suggested that it was variable and located mostly internal to the cuticle, supporting an epidermal location for a variable barrier. Impedance measurements over a range of frequencies showed the integument to be electrically complex, and a model is proposed to account for its properties.