A comparative study of bovine pericardium (periguard) and homologous sclera as lower eyelid spacer graft analogs in New Zealand white rabbits

PURPOSE

To compare bovine pericardium (Periguard; Bio-Vascular, Inc., St. Paul, MN, U.S.A.) and homologous sclera as spacer graft analogs in a rabbit model.

METHODS

A nonrandomized experimental animal study was conducted. Elliptical subconjunctival implants were placed in one lower eyelid each of 10 rabbits. Five rabbits received homologous sclera implants, and five received bovine pericardium implants. The rabbits were killed 7 weeks later, and the lower eyelids were examined clinically and histopathologically.

RESULTS

Rabbit eyelids implanted with Periguard had a more marked inflammatory reaction and more significant collagen lamellar disruption than eyelids implanted with homologous sclera, although clinically they appeared quite similar.

CONCLUSIONS

Although bovine pericardium elicited a more intense inflammatory response at the histopathologic level, both implants were similarly tolerated at the clinical level. These findings are consistent with animal and human investigations of bovine pericardium in other parts of the body, and warrant further studies into its potential use in the human eyelid.

Prevention of muscimol-induced long-term depression by brain-derived neurotrophic factor

1. The authors have recently reported a new protocol for inducing long-term depression through activation of GABAA receptors in the hippocampal slices. This long-term depression is reversed by bicuculline and potentiated by neurosteroids such as alphaxalone. It was also shown that glutamate receptor activity is not involved in the induction of this novel type of long-term depression. Brain derived neurotrophic factor is a member of the neurotrophins family widely expressed in the central nervous system. There is increasing evidence that indicate an important role for brain-derived neurotrophic factor in synaptic plasticity. It has been reported that brain-derived neurotrophic factor level is downregulated by GABA system. The present study investigated a possible relation between muscimol-induced long-term depression and brain-derived neurotrophic factor level. 2. Extracellular recordings were made in the CA1 pyramidal cell layer of rat hippocampal slices following orthodromic stimulation of Schaffer collateral fibers in stratum radiatum. 3. It was observed that brain-derived neurotrophic factor at concentration that did not have any effect itself on the population spike, prevents the induction of long-term depression by muscimol. In addition to this, K-252a an inhibitor of Trk type kinase blocked the prevention of muscimol-induced LTD by brain-derived neurotrophic factor. 4. The results suggest that there is an interaction between muscimol-induced long-term depression and brain-derived neurotrophic factor and may explain the post receptor mechanism of muscimol-induced long-term depression through a bilateral relation between GABAA activity and brain-derived neurotrophic factor.

Bovine pericardium versus homologous sclera as wrapping materials for hydroxyapatite ocular implants: an animal study

PURPOSE

We compared bovine pericardium and homologous sclera as wrapping materials for hydroxyapatite (HA) ocular implants in enucleated New Zealand white rabbits.

METHODS

Eighteen rabbits were unilaterally enucleated and the sockets implanted with 10-mm HA spherical implants. Six implants were wrapped with homologous sclera, 6 with bovine pericardium, and 6 were not wrapped. The rabbits were killed 7 weeks later and the sockets were examined clinically for inflammation and implant exposure. Exenterated specimens were assessed histopathologically for inflammation and vascularization.

RESULTS

No clinical evidence of implant exposure or extrusion was detected in rabbits receiving sclera or bovine pericardium wrapped implants. Histopathologically, the bovine pericardium displayed more inflammation in its outer portion, as well as more disruption of its lamellar arrangement than did the sclera. Fibrovascular in-growth was complete in all wrapped implants.

CONCLUSION

Bovine pericardium behaves similar clinically to homologous sclera as a wrapping material for spherical HA ocular implants in a rabbit model, and may represent a reasonable alternative to sclera in such procedures in humans.

Interindividual heterogeneity in the hypoxic regulation of VEGF: significance for the development of the coronary artery collateral circulation

BACKGROUND

The coronary artery collateral circulation may be beneficial in protecting against myocardial ischemia and necrosis. However, there is a tremendous interindividual variability in the degree of new collateral formation in patients with coronary artery disease. The basis for this interindividual heterogeneity is not understood. In this study we test the hypothesis that failure to generate collateral vessels is associated with a failure to appropriately induce with hypoxia or ischemia the angiogenic factor, vascular endothelial growth factor (VEGF).

METHODS AND RESULTS

We correlated the VEGF response to hypoxia in the monocytes harvested from patients with coronary artery disease with the presence of collaterals visualized during routine angiography. We found that there was a highly significant difference in the hypoxic induction of VEGF in patients with no collaterals compared with patients with some collaterals (mean fold induction 1.9+/-0.2 versus 3.2+/-0.3, P<0.0001). After subjecting the data to ANCOVA, using as covariates a number of factors that might influence the amount of collateral formation (ie, age, sex, diabetes, smoking, hypercholesterolemia), patients with no collaterals still have a significantly lower hypoxic induction of VEGF than patients with collaterals.

CONCLUSIONS

This study provides evidence in support of the hypothesis that the ability to respond to progressive coronary artery stenosis is strongly associated with the ability to induce VEGF in response to hypoxia. The observed interindividual heterogeneity in this response may be due to environmental, epigenetic, or genetic causes. This interindividual heterogeneity may also help to explain the variable angiogenic responses seen in other conditions such as diabetic retinopathy and solid tumors.

Impact of research on pediatric pain assessment and outcomes

PURPOSE

Pediatric nurses from varied practice and educational backgrounds learned about research by doing a ward-based study. The aim of the study was to determine if regular assessment of children's pain would improve their pain management and postoperative progress.

METHOD

Children, ages 5 to 17 years (n = 36), measured their pain every 4 hours postoperatively using the Wong-Baker Faces Pain Rating Scale. Outcomes regarding amount of analgesic given, subjective pain reports, time and progress of ambulation, and length of hospital stay were compared with data from a retrospective chart-review of a control group (n = 50).

FINDINGS

No statistically significant differences in these variables were found. An important clinical finding was that despite all children having prescribed PRN analgesic orders, one quarter of the children received no pain relief intervention. Also, one quarter of the children stated that their pain control was only partially effective.

CONCLUSIONS

Study results reinforce findings reported in the literature regarding ineffective pain management in children, and highlight a need for improved nursing practice. Clinical significance was achieved in terms of staff learning of the research process, increased awareness of pediatric pain management practices, improved ward morale, and inter-agency sharing of resources.

Ro 15-4513 alteration of pentobarbital dependence

This study investigated the ability of the benzodiazepine inverse agonist, Ro 15-4513, to alter the expression of physical dependence on pentobarbital. Male Sprague-Dawley rats were made physically dependent on pentobarbital by continuous. IP, infusion of escalating doses of pentobarbital for 12 days. In Experiment 1, pentobarbital dependent rats received either vehicle or Ro 15-4513, in doses of 5, 10, or 15 mg/kg, IP, periodically during the pentobarbital abstinence period. As expected, Ro 15-4513 produced a significant, dose-dependent, exacerbation of withdrawal signs in the pentobarbital dependent rats. In Experiment 2, either vehicle or Ro 15-4513, at a dose of 15 mg/ kg, was administered, IP, once daily during the 12 days of continuous pentobarbital infusion. During the subsequent pentobarbital abstinence period it was noted that the withdrawal signs were significantly reduced in the rats receiving the daily administration of Ro 15-4513. It is hypothesized that the benzodiazepine inverse agonist, Ro 15-4513, may inhibit the development of physical dependence on pentobarbital through an opposing action on the GABA-A receptor.

Hybridization of horseradish peroxidase-labeled probes and detection by enhanced chemiluminescence

This article describes the use of probes directly labeled with horseradish peroxidase in conjunction with enhanced chemiluminescence, which allows a flexible approach to hybridizations and detections. This system may be used with the following applications: Southern blots, Northern blots, colony and plaque screening for positive clones, YAC clone screening, and PCR products detection. The major steps required for the use of directly labeled HRP probes are hybridization, stringent washes, and detection.

Preparation of horseradish peroxidase-labeled probes

The direct labeling of nucleic acid probes with horseradish peroxidase (HRP) may be used in many membrane hybridization applications, including Southern blots, Northern blots, colony and plaque screening, PCR products detection/identification. This article describes the preparation method, which involves the labeling of a single-stranded nucleic acid probe with a positively charged HRP-parabenzoquinone-polyethyleneimine complex (labeling reagent). The associated hybridization and posthybridization protocols are relatively simple, which makes probes labeled directly with HRP particularly suitable for large scale screening, where tens or hundreds of blots are processed weekly.

Deceiving others/deceiving oneself: four cases of factitious rape

Although patients with factitious disorders typically seek the "patient" role through illness portrayals, some instead portray themselves falsely as "victims." We discuss the cases of four women who claimed to have been victims of rape; the allegations ultimately were disproved. Factitious rape may be prompted by a search for nurturance; by dissociation, leading individuals to believe that trauma earlier in life is ongoing; by a need to be rescued from real, current abuse; and by projection of anger onto specific male targets. Although dramatic, factitious rape is rare, we advocate thorough investigation of rape claims even when patients have known histories of deceptive behavior.

Enhanced chemiluminescence for the detection of membrane-bound nucleic acid sequences: advantages of the Amersham system

A range of nonradioactive nucleic acid labeling and detection systems have been developed that enable the user to label probes directly with enzyme molecules or indirectly with hapten-derivatized nucleotides. Horseradish peroxidase is used for the direct labeling procedures due to the ease of chemical modification and the relative thermal and chemical stability of this enzyme. Horseradish peroxidase has also been conjugated to a high-specificity antifluorescein antibody for detection of hapten (fluorescein)-labeled hybrids. Enhanced chemiluminescence is a light-emitting process optimized for the detection of low levels of horseradish peroxidase on membrane supports. Results are obtained as hard copy images on x-ray film.

Hybrid diffractive-refractive lenses and achromats

Hybrid elements containing optical power with both diffractive (holographic) and refractive components are shown to be useful for obtaining arbitrary or, in special cases, achromatic dispersive characteristics. In one configuration a volume holographic element is coated on the surface of a crown glass lens, and by varying the power distributions among the refractive and holographic components while maintaining constant overall optical power the effective Abbe V numbers of the resultant hybrid element are shown to span all real numbers excepting a narrow interval around zero. In the achromat case (V number = infinity), both refractive and diffractive components are of the same sign resulting in much smaller glass curvatures than in all-refractive achromat doublets or apochromat triplets. The large separation between holographic partial dispersions and available glass partial dispersions is shown to lead to hybrid three-color achromats with greatly reduced glass curvatures. Applications are expected to include broadband achromatic objectives and chromatic aberration corrector plates in high performance optical systems. Such corrector plates may have any net power (including zero) while exhibiting effective V numbers that are positive or negative and that span a wide range, e.g., +/-1 or +/-1000. Further advantages include reducing the need for choosing high dispersion glasses, which may be costly and difficult to grind or polish. High diffraction efficiency and broad spectral bandwidths (in excess of 3000 A) are obtained in the holographic optical elements using single-element central-stop and cascaded element designs.

Standardized endosonographic evaluation of prostate cancer: receiver-operator-characteristic analysis

A standardized endosonographic numeric method has been developed for the detection of prostate cancer. Eighty-six men were examined with a 5-MHz, 96-element linear-array probe. Mean gray-scale amplitudes were produced by a semiautomatic method for periprostatic fat and regions of interest within the external portion of the prostate gland that were visually suspicious for prostate cancer. Mean gray-scale amplitude ratios of visually abnormal areas of prostate to periprostatic fat (Ap/Af) were calculated. Pathologic confirmation of disease was obtained in all patients. Three different numeric Ap/Af ratios were compared with digital palpation and subjective visual interpretation of sonograms. The numeric method resulted in a consistently higher specificity, accuracy, and positive predictive value when compared with palpation and subjective interpretation. The initial results suggest that this technique may also detect atypical hyperplasia.

Simulation Of A Large Steam-CO Co-Injection Experiment

Abstract

A high-pressure steam-CO2 co-injection experiment, carried out in a 1.5 m diameter physical simulator packed with Athabasca oil sand, is described. The experimental run lasted/or 113 hours and consisted of two injection-drawdown cycles. During the run, 1454 kg of steam and 75.3 kg of carbon dioxide were injected (equivalent to 2.1 mole % CO2 in the mixture). This resulted in the recovery of 12.5% o/the initial bitumen in the oil sand.

The experimental data obtained was compared to the results of a numerical modelling study. Good agreement was obtained. Differences between the numerical simulation and experiment are discussed.

Results from steam-only predictions are used to discuss the merits of the steam-CO2 injection process relative to steam injection alone.

Introduction

Many experiments have been carried out at Alberta Research Council (ARC) in the last five years to test the effectiveness of additives on recovery of Athabasca bitumen. An adequate numerical simulation capability is useful in analyzing these runs. This capability also serves as a design aid for further experiments as well as serving a need for idealized studies.

The experiment that was simulated for this report (hereafter denoted "Run 15006") was the first run in the 150 cm pressure vessel in which stearn and CO2 were simultaneously injected into an oil sand pack of this physical size. The primary objective was to study recovery benefits from addition of CO2 to the injection stream. Other objectives were to study the rate of advance of temperature profiles in the bed during the run and to provide data to test a numerical simulation of the steam-C02 process. A three component model developed at ARC was used to simulate the above process. The model is a fully implicit thermal numerical simulator with the capability of handling a single additive. Objectives of the numerical simulation were principally to test the numerical model, and hence all its property data for a CO2/water/bitumen system.

Description of Experiment

The 150cm diameter simulator system (Fig. 1) consists of a large pressure vessel (150 cm ID by 270 cm high) designed to allow steam and gas to be injected simultaneously into the test bed under controlled flow rates. Oil sand is packed into this vessel and maintained at field overburden conditions by introducing a nitrogen blanket at the top of the cell. Feed streams were injected to the centre of the test bed via an injection well.

The three main systems are schematically illustrated in Figure 1. These are the injection system, test cell and production system. The steam portion of the injection system consists of a high pressure steam generator followed by a superheater. Flow turbines measure flow rate after the superheater and are marked "F" in Figure 1. Thermocouples and pressure, gauges are also in place, marked "T" and "P" in Figure 1. The steam generator operates at a constant flow rate. Pressure to the system is regulated by a control valve upstream of the superheater.

Retroperitoneal fibrosis with normal intravenous urogram

A 58 year old male presented with a two week history of low back pain and malaise. The intravenous urogram (IVU) at presentation was normal but within three months he had developed renal failure with bilateral ureteric obstruction on repeat IVU. Primary retroperitoneal fibrosis was confirmed at operation. This case demonstrates that retroperitoneal fibrosis may progress rapidly to renal failure within a few months of the first symptoms. In addition, the IVU may be normal in the early stages of the illness.

Endemic goitre, nutrition, and landholding in Bangladesh

Endemic goitre in adult females, cretinism, and anthropometry in children were examined in a goitrous area of Bangladesh. An area survey showed total goitre varying from 62.0 to 93.0%, visible goitre from 9.0 to 54.8% between areas. A village study examining thyroid size in 538 adult females and anthropometry in 116 children showed goitre prevalences varying significantly (p less than 0.001) but unpredictably with household landholding size; underweight and wasting varied inversely and significantly (p less than 0.01 and 0.05 respectively) with the same socioeconomic indicator. By household, there was no relationship between anthropometry in children and thyroid enlargement in the mother. Hormone analyses showed depressed serum T4, but no raised TSH. Only one deaf-mute cretin was found in the area. It is speculated that variation in goitre prevalence in this moderately severe endemic primarily reflects qualitative and quantitative changes in diet, as a function of the socioeconomic status of the household.