Common-path off-axis incoherent Fourier holography with a maximum overlapping interference area

In this Letter, we present a new method for recording spatially incoherent common-path off-axis Fourier holograms. This method records the three-dimensional (3D) information of an object into a Fourier hologram without the need of any mechanical scanning with incoherent illumination. The proposed setup consists of two gratings to form a common-path configuration, and two customized cells to create a rotational and radial shearing interferometer. While the first grating is placed on the first image plane, the second grating shifts axially from the second image plane to build off-axis geometry. A lens is used to combine two beams to generate the maximum overlapping area at the hologram plane. Proof-of-concept experiments confirm the ability of such a system to achieve the maximum overlapping interference area, stability of the system against the vibration of surrounding environment, numerical reconstruction using only one fast Fourier transform, and 3D capability to capture a 3D object illuminated by an LED light.

Spatially incoherent common-path off-axis color digital holography

We describe a new method for recording spatially incoherent common-path off-axis color digital holograms. We present the theoretical and experimental evidence to demonstrate an incoherent common-path off-axis color digital holographic (ICOCH) system capable of capturing information from three-dimensional color objects under incoherent illumination, both in transmission and reflection modes. Fresnel incoherent correlation holography (FINCH), a common-path system, is a frequently used incoherent holography technique. Our proposed system is conceptually similar to an advanced form of FINCH; moreover, it has three advantages over this advanced form of FINCH. First, removal of the spatial light modulator makes our system simpler and more cost-effective. Second, removal of the polarizer or analyzer allows for greater light throughput. Third, the off-axis optical configuration enables separation of zero-order and twin images with only a single exposure per color rather than requiring three exposures per color for in-line holography FINCH. Therefore, we believe that this simple and cost-effective system with high light throughput can acquire incoherent holograms for different colors involving single exposure for each color, which makes the ICOCH system suitable for many applications.

Spatially incoherent off-axis Fourier holography without using spatial light modulator (SLM)

We present a spatially incoherent dual path Fourier holographic system. Conceptually it is similar to Fourier incoherent single channel holography (FISCH). Although our incoherent off-axis Fourier holographic (IOFH) system does not have the robustness of a single channel system, it has three advantages over FISCH, with two being quite obvious from setup. First, no SLM is required, thus making the system simple and cost-effective. Second, it is capable of high light throughput because in FISCH, the use of SLM reduces light intensity in half by splitting one beam into two; furthermore, an analyzer is required to create interference which also reduces light intensity. The third advantage, which makes this IOFH system applicable even for on-axis samples (as opposed to samples in a half plane as is necessary for FISCH), is achieved by tilting one mirror. Here we demonstrate our system with a sample in half plane as in FISCH for different axial positions, and then by placing the object on an optical axis and tilting one mirror. The reconstructed images demonstrate holographic capabilities of our IOFH system for both on-axis and half plane sample locations.

Periodontal associations in cardiovascular diseases: The latest evidence and understanding

Periodontal and cardiovascular diseases (CVD) are inflammatory diseases. Recent epidemiological studies have associated the effect of periodontitis on CVD progression. Findings of oral pathogens in carotid atheromas provided a plausible relationship between these two diseases. One possible mechanism is the infiltration of oral/periodontal pathogens through inflamed and ulcerated gingival epithelium. This results in translocation of oral pathogens throughout the systemic circulation affecting vascular tissues, and initiating a cascade of inflammatory reactions detrimental to the cardiovascular system. In addition, leakage of pro-inflammatory cytokines/chemokines from the ulcerated periodontium into the bloodstream may cause the production of hepatic acute-phase proteins. Moreover, as chronic bacteremia occurs, the adaptive immune system is activated. Antibodies produced in response to periodontal pathogens trigger a cross-reaction between endothelial cells and modified low-density lipoprotein to enhance the movement of lipids into cells within the vessel wall. Some antibodies and inflammatory cytokines promote the Th1 response, thereby further activating macrophages within the atheroma. These plausible mechanisms are contributing factors in initiating and propagating atherogenesis. This review discusses the current understanding of CVD pathology/periodontitis, potential underlying mechanisms regarding this association, and general guidelines for treating patients with CVD risks.

Sol-gel deposition of iridium oxide for biomedical micro-devices

Flexible iridium oxide (IrOx)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrOx electrodes with long lifetime, high stability and repeatability. Such sensors can be used for long-term measurements. Various dimensions of sol-gel iridium oxide electrodes including 1 mm × 1 mm, 500 µm × 500 µm, and 100 µm × 100 µm were fabricated. Sensor longevity and pH dependence were investigated by immersing the electrodes in hydrochloric acid, fetal bovine serum (FBS), and sodium hydroxide solutions for 30 days. Less pH dependent responses, compared to IrOx electrodes fabricated by electrochemical deposition processes, were measured at 58.8 ± 0.4 mV/pH, 53.8 ± 1.3 mV/pH and 48 ± 0.6 mV/pH, respectively. The on-probe IrOx pseudo-reference electrodes were utilized for dopamine sensing. The baseline responses of the sensors were higher than the one using an external Ag/AgCl reference electrode. Using IrOx reference electrodes integrated on the same probe with working electrodes eliminated the use of cytotoxic Ag/AgCl reference electrode without loss in sensitivity. This enables employing such sensors in long-term recording of concentrations of neurotransmitters in central nervous systems of animals and humans.

Circulating fibrocytes are increased in children and young adults with pulmonary hypertension

Chronic inflammation is an important component of the fibroproliferative changes that characterise pulmonary hypertensive vasculopathy. Fibrocytes contribute to tissue remodelling in settings of chronic inflammation, including animal models of pulmonary hypertension (PH). We sought to determine whether circulating fibrocytes were increased in children and young adults with PH. 26 individuals with PH and 10 with normal cardiac anatomy were studied. Fresh blood was analysed by flow cytometry for fibrocytes expressing CD45 and procollagen. Fibrocyte numbers were correlated to clinical and haemodynamic parameters, and circulating CC chemokine ligand (CCL)2 and CXC chemokine ligand (CXCL)12 levels. We found an enrichment of circulating fibrocytes among those with PH. No differences in fibrocytes were observed among those with idiopathic versus secondary PH. Higher fibrocytes correlated to increasing mean pulmonary artery pressure and age, but not to length or type of treatment. Immunofluorescence analysis confirmed flow sorting specificity. Differences in plasma levels of CCL2 or CXCL12, which could mobilise fibrocytes from the bone marrow, were not found. We conclude that circulating fibrocytes are significantly increased in individuals with PH compared with controls. We speculate that these cells might play important roles in vascular remodelling in children and young adults with pulmonary hypertension.

Antituberculosis cycloartane triterpenoids from Radermachera boniana

Three new triterpenoids, bonianic acids A (1) and B (2) and 3-O-acetyluncaric acid (3), were isolated from the leaves and twigs of Radermachera boniana, together with six known compounds, ursolic acid (4), oleanolic acid (5), 3-epi-oleanolic acid (6), 3α-O-acetyl-α-boswellic acid (7), ergosterol peroxide (8), and β-sitostenone (9). Ergosterol peroxide (8) and bonianic acids A (1) and B (2) exhibited significant activity against Mycobacterium tuberculosis H37Rv strain.

Macroscopic thrombus formation on angioplasty equipment following antithrombin therapy with enoxaparin

Increasing evidence suggests that treatment with the low molecular weight heparin enoxaparin during percutaneous coronary intervention (PCI) is safe and effective. We evaluated the incidence and consequences of periprocedural macroscopic thrombus formation on PCI equipment following antithrombin therapy with enoxaparin. Between April 2003 and December 2004, all patients undergoing cardiac catheterization following antithrombin therapy with enoxaparin were evaluated. All patients had blood sampled at the onset of procedure for subsequent measurement of anti-factor-Xa levels. Of the 4,504 patients who underwent PCI during this period, in 122 (3%) the procedure was performed within 8 hr of treatment with subcutaneous enoxaparin and no additional unfractionated heparin (UFH) was used periprocedurally. Of these, macroscopic thrombus was observed on PCI equipment in 6 patients (5%) necessitating withdrawal of all catheters and wires. All patients had therapeutic anti-factor-Xa levels at the time of PCI, and had been treated with double antiplatelet therapy with aspirin and clopidogrel. No periprocedural thrombus was observed in 356 patients who were >12 hr of the last dose of enoxaparin and received UFH at the time of PCI. Following observation of thrombus, additional anticoagulation with UFH resulted in significant epistaxis in one patient. In another patient, the procedure was complicated by distal coronary embolization. Percutaneous coronary intervention following antithrombin therapy with enoxaparin is associated with a 5% incidence of macroscopic thrombus formation on PCI equipment. The necessity for subsequent exchange of all equipment and/or the need for additional anticoagulation may have disastrous consequences for the patient. Our findings suggest that the safety of antithrombin therapy with low molecular weight heparin during PCI requires further evaluation.

In vivo detection of postictal perturbations of cerebral metabolism by use of proton MR spectroscopy: preliminary results in a canine model of prolonged generalized seizures

BACKGROUND AND PURPOSE

Biochemical studies of seizures in patients and laboratory animals have monitored postictal perturbations in cerebral metabolism with either invasive techniques or with such noninvasive techniques as nuclear medicine, MR imaging, in vivo phosphorus MR spectroscopy (MRS), and in vivo proton MRS at field strengths of 1.5 T or above. We investigated postictal metabolic changes in a generalized seizure model with in vivo proton MRS at 0.5 T, in which the combination of glutamate and glutamine resonances (denoted glx) can be modeled as a singlet.

METHODS

Five adult mongrel dogs underwent control and postictal experiments in which single-voxel proton MR spectra were obtained from the right frontal lobe cortex with a point-resolved spectroscopy technique approximately every 20 minutes for 3 hours. N-acetylaspartate (NAA), glx, and creatine (Cr) were quantified in absolute millimolar units with a cerebral water-referenced algorithm. Inter- and intrasubject differences in mean metabolite concentrations collected throughout the 3-hour period were compared using an unpaired, two-tailed Student's t test at a.05 level of significance.

RESULTS

We found a significant increase (15.4%) in the postictal intersubject mean glx concentration, as well as a 23.7% postictal decrease in the intersubject mean Cr concentration. A trend toward a subtle decrease in postictal intersubject mean NAA concentration was not statistically significant. We also observed a substantial qualitative increase in the combination of postictal lactate and free fatty acid peaks.

CONCLUSIONS

The glx, NAA, lactate, and free fatty acid results are in general agreement with previous studies of postictal perturbations in cerebral metabolism measured with invasive biochemical or noninvasive high-field-strength in vivo MRS detection assays. Given a high sensitivity for glx at 0.5 T relative to 1.5 T, further studies of postictal mesial temporal lobe structures are warranted in chronic animal preparations that model temporal lobe epilepsy.

Farnesoid X-activated receptor induces apolipoprotein C-II transcription: a molecular mechanism linking plasma triglyceride levels to bile acids

The farnesoid X-activated receptor (FXR; NR1H4), a member of the nuclear hormone receptor superfamily, induces gene expression in response to several bile acids, including chenodeoxycholic acid. Here we used suppression subtractive hybridization to identify apolipoprotein C-II (apoC-II) as an FXR target gene. Retroviral expression of FXR in HepG2 cells results in induction of the mRNA encoding apoC-II in response to several FXR ligands. EMSAs demonstrate that recombinant FXR and RXR bind to two FXR response elements that are contained within two important distal enhancer elements (hepatic control regions) that lie 11 kb and 22 kb upstream of the transcription start site of the apoC-II gene. A luciferase reporter gene containing the hepatic control region or two copies of the wild-type FXR response element was activated when FXR-containing cells were treated with FXR ligands. In addition, we report that hepatic expression of both apoC-II and phospholipid transfer protein mRNAs increases when mice are fed diets supplemented with cholic acid, an FXR ligand, and this induction is attenuated in FXR null mice. Finally, we observed decreased plasma triglyceride levels in mice fed cholic acid- containing diets. These results identify a mechanism whereby FXR and its ligands lower plasma triglyceride levels. These findings may have important implications in the clinical management of hyperlipidemias.

CTP:phosphocholine cytidylyltransferase, a new sterol- and SREBP-responsive gene

The CTP:phosphocholine cytidylyltransferase (CT) gene encodes the rate-controlling enzyme in the phosphatidylcholine biosynthesis pathway. CTalpha mRNA levels, like farnesyl diphosphate synthase and the LDL receptor, are repressed when human or rodent cells are incubated with exogenous sterols and induced when cells are incubated in lipid-depleted medium. A putative sterol response element (SRE) was identified 156 bp upstream of the transcription start site of the CTalpha gene. Electrophoretic mobility shift assays demonstrate that recombinant SREBP-1a binds to the wild-type SRE identified in the CTalpha promoter but not to oligonucleotides containing two mutations in the SRE. In other studies, a luciferase reporter construct under the control of the murine CTalpha proximal promoter was transiently transfected into cells. The activity of the reporter was repressed after addition of sterols to the medium and induced when the cells were incubated in lipid-depleted medium. The activity of the CTalpha-luciferase reporter was also induced when cells were cotransfected with plasmids encoding either SREBP-1a or SREBP-2. In contrast, no induction was observed under the same conditions when the CTalpha promoter-reporter gene contained two mutations in the SRE. In addition, the induction of the wild-type CTalpha promoter-reporter gene that occurs in cells incubated in lipid-depleted medium is attenuated when dominant-negative SREBP is cotransfected into the cells. These studies demonstrate that transcription of the CTalpha gene is inhibited by sterols and activated by mature forms of SREBP. We conclude that SREBP-regulated genes are involved not only in the synthesis of cholesterol, fatty acids, triglycerides, and NADPH, but also, as shown here, in the synthesis of phospholipids.

Identification of the DNA binding specificity and potential target genes for the farnesoid X-activated receptor

The farnesoid X-activated receptor (FXR; NR1H4) is a member of the nuclear hormone receptor superfamily and functions as a heterodimer with the 9-cis-retinoic acid receptor (RXR). In order to determine the optimal DNA binding sequence for the FXR/RXR heterodimer, we have utilized the selected and amplified binding sequence imprinting technique. This technique identified a number of related sequences that interacted with FXR/RXR in vitro. The consensus sequence contained an inverted repeat of the sequence AGGTCA with a 1-base pair spacing (IR-1). This sequence was shown to be a high affinity binding site for FXR/RXR in vitro and to confer ligand-dependent transcriptional activation by FXR/RXR to a heterologous promoter. Electrophoretic mobility shift assays and transient transfection assays were used to investigate the importance of the core half-site sequences, spacing nucleotide, flanking sequences, and orientation and spacing of the core half-sites on DNA binding and ligand-dependent transcriptional activation by FXR/RXR. These studies demonstrated that the FXR/RXR heterodimer binds to the consensus IR-1 sequence with the highest affinity, although FXR/RXR can bind to and activate through a variety of elements including IR-1 elements with changes in the core half-site sequence, spacing nucleotide, and flanking nucleotides. In addition, FXR/RXR can bind to and transactivate through direct repeats. Three genes were identified that contain IR-1 sequences in their proximal promoters. These elements were shown to bind FXR/RXR in vitro and to confer FXR/RXR-dependent transcriptional activation to a heterologous promoter in response to a bile acid or synthetic retinoid. The endogenous mRNA levels of one of these genes, phospholipid transfer protein, were shown to be induced by FXR and FXR ligands. The identification of the IR-1 and related elements as high affinity binding sites and functional response elements for FXR/RXR and the identification of a target gene for FXR/RXR should assist in the identification of additional genes regulated by FXR/RXR.

Facial port wine stains in childhood: prediction of the rate of improvement as a function of the age of the patient, size and location of the port wine stain and the number of treatments with the pulsed dye (585 nm) laser

In this study we examined the rate of decrease in size of facial port wine stains (PWS) as a function of number of treatments, lesion size, lesion location and patients' age. This study was performed at the University of Colorado Hospital Outpatient Dermatology Center, Denver, U.S.A. A consecutive sample of 91 patients 18 years of age or younger with facial PWS in which the entire lesion was treated at each visit were studied. Included were all patients who had a minimum of five treatments or complete clearance of their lesion in fewer than five treatments. Patients were evaluated following one, five and 10 treatments with the pulsed (450 s) dye (585 nm) laser. Improvement was defined as the percentage decrease in the size of the PWS. For all patients, the first five treatments resulted in a mean decrease in size of 55% while the second five treatments (38 patients) only improved the mean decrease in size by 18%. Grouped by location, the mean decreases in size from the first five and the second five treatments were as follows: central forehead = 100%, 0%; peripheral face = 58%, 28%; central face = 48%, 14%; and mixed (combination of peripheral and central face) = 21%, 9%. All central forehead PWS completely cleared within five treatments while none of the mixed PWS did so even with an average of 14 treatments. Grouped by size, mean decrease in size was highest for small lesions; < 20 cm2 = 67%, 21%; 20 to < 40 cm2 = 45%, 8%; and > 40 cm2 = 23%, 29%. Grouped by age, mean decrease in size was highest for young children: < 1-year-old = 63%, 33%; 1 to < 6 years = 48%, 15%; and older than 6 years = 54%, 10%. For all patients studied, maximal improvement was obtained in the first five treatments. Major determinants of treatment response in order of decreasing importance are PWS location, size and patients' age. The most successful responses are seen in young patients (less than 1 year old) with small PWS (under 20 cm2) that are located over bony areas of the face such as the central forehead. These three determinants may be useful tools to guide patient expectations and to predict the rate of improvement of PWS to pulsed dye laser treatment.

Analytical methods for the characterization of cationic lipid-nucleic acid complexes

Five analytical assays are described that provide a platform for systematically evaluating the effect of formulation variables on the physical properties of cationic lipid-DNA complexes (lipoplexes). The assays are for (i) lipid recovery, (ii) total DNA, (iii) free DNA, (iv) nuclease sensitivity, and (v) physical stability by filtration. Lipid recovery was determined by measuring lipid primary amino groups labeled with the fluorescamine reagent in the presence of the detergent Zwittergent. Zwittergent was effective at disrupting lipoplexes, making the primary amine accessible to the fluorescamine reagent. Total DNA was determined with the PicoGreen reagent, also in the presence of Zwittergent. The PicoGreen assay in the absence of Zwittergent gave the percentage of the total DNA that was not complexed with cationic lipid. The results of this assay for free DNA agreed well with the amount of DNA that could be separated from complexes by centrifugation as well as with the amount of DNA that was accessible to DNase I digestion. Monitoring the lipid and DNA recoveries after filtration through polycarbonate membranes provided a quantitative method for assessing changes in lipoplex physical characteristics. Together, these assays provide a convenient high-throughput approach to assess physical properties of lipoplexes, allowing systematic evaluation of different formulations.

Postoperative pain relief following laparoscopic tubal sterilization with silastic bands

OBJECTIVE

To evaluate postoperative pain relief of intramuscular ketorolac, topical bupivacaine, and placebo in patients undergoing laparoscopic tubal sterilization with silastic bands.

METHODS

One hundred five women undergoing laparoscopic tubal sterilization with silastic bands were randomized to one of three groups: one received intramuscular ketorolac and topical placebo applied to the fallopian tubes, the second received intramuscular placebo and topical bupivacaine, and the third received intramuscular placebo and topical placebo. Surgical procedures, anesthesia, and recovery were conducted with standardized protocols. Postoperative pain perception was graded using the modified McGill pain intensity scale at 30 minutes postoperatively, at discharge from the recovery room, and the next morning by telephone interview. Other measured variables included postoperative vomiting, additional analgesia requirement, and length of time spent in the recovery room.

RESULTS

Only topical bupivacaine was found to decrease postoperative pain scores significantly over those with placebo, at 30 minutes postoperatively (median score 2 compared with 4, P = .002) and at discharge from the recovery room (median score 2 compared with 3, P = .03). There was no significant decrease in pain scores with intramuscular ketorolac compared with placebo. No differences in pain scores were found between the three groups at the next morning phone call. There were no significant differences between the three groups with respect to requirements for supplemental pain medications in the recovery room, incidence of postoperative vomiting, or length of time spent in the recovery room.

CONCLUSION

Topical bupivacaine decreases postoperative pain scores significantly compared with placebo in women undergoing laparoscopic tubal sterilization with silastic bands.

Ionic versus nonionic paramagnetic contrast media in differentiating between scar and herniated disk

PURPOSE

To compare the MR contrast enhancement produced by ionic and nonionic paramagnetic contrast media in herniated disk fragments with that in epidural scar tissue.

METHODS

A recurrent herniated disk was modeled in canines by using laminectomy to place a fragment of disk cartilage in the epidural space. The dogs were studied 88 and 90 days after laminectomy with MR imaging enhanced with an ionic or a nonionic paramagnetic contrast medium. Contrast enhancement of the epidural scar tissue and the epidural disk fragment was measured at 2, 22, and 45 minutes after the injection.

RESULTS

Contrast enhancement was consistently and significantly higher in scar tissue than in disk fragments, although the difference decreased between 2 and 45 minutes after administration of contrast medium. Enhancement of disk fragments was less with the ionic than with the nonionic contrast medium. Contrast between the disk fragments and scar was also greater with the ionic than with the nonionic medium.

CONCLUSIONS

The contrast between recurrent disk fragments and scar tissue is affected by the timing of the scan and the choice of contrast medium. Scans obtained immediately after the injection of contrast medium show more contrast between disk fragment and scar than do delayed scans. Recurrent herniated disk fragments are more effectively shown by ionic than by nonionic media.

The etiology of focal spinal arachnoiditis. An experimental study

Focal arachnoiditis and back pain have been attributed to potentially irritating substances leaking into the spinal canal from the lumbar intervertebral disc or facet joints. Through experimentation this hypothesis was tested: the nucleus pulposus (escaping from the intervertebral disc), lactic acid (from anaerobic glycolysis in the disc), chondroitin sulfate (a component of glycosaminoglycans in the disc), or synovial fluid (from degenerating facet joints) causes inflammation in the meninges if it contacts the dura mater. The test and control substances were injected into the epidural space of monkeys. Twelve weeks later the animals were killed; the dural sac was exposed by total lumbar laminectomy, grossly inspected, and then removed, fixed, sectioned, stained, and examined microscopically. Nucleus pulposus produced significant fibrosus in the arachnoid and epidural spaces; the other substances did not cause fibrosus or inflammation. The study suggests that leakage of nucleus pulposus into the epidural space causes an inflammatory response in the arachnoid and epidural spaces.

MR contrast enhancement: an experimental study in postlaminectomy epidural fibrosis

PURPOSE

To measure the effect of contrast medium dose, time elapsed since injection, and maturity of epidural scar tissue on the enhancement of scar tissue in MR imaging.

METHODS

We imaged 12 beagle dogs with MR at 10 to 60 days after lumbar laminectomy, and at necropsy we obtained exactly correlating histologic sections. Contrast enhancement of scar tissue at 2, 15, 40, and 60 minutes after 0.1 and 0.3 mmol of paramagnetic contrast medium per kilogram was measured. Contrast enhancement was analyzed with respect to the dose of contrast medium, the time of imaging, and the maturity of scar tissue.

RESULTS

Epidural scar tissue enhanced more intensely at 2 and at 15 minutes than at 40 or at 60 minutes. Consistently greater enhancement was observed with the dose of 0.3 mmol/kg than with the dose of 0.1 mmol/kg. Regions of loosely organized scar tissue enhanced less intensely and less quickly than did more organized scar tissue.

CONCLUSION

Contrast enhancement in scar tissue can be heightened by increasing the dose of contrast medium from 0.1 to 0.3 mmol/kg and by obtaining images within 15 minutes of injection.

Effect of repeated injections of chymopapain in the epidural space

Because arachnoiditis occurred in a previous experimental study, the authors performed additional experimental injections of chymopapain in the epidural space. Four monkeys received epidural injections of 100 units of chymopapain in 1.2 mL of saline on days 1, 8, and 16 of the experiment; four control animals received injections of 1.2 mL of 0.9% saline on the same days. Both groups were killed on the 84th day. The dural sac was removed, fixed, sectioned, stained, and examined microscopically. No significant changes were found in the arachnoid, dura, or epidural space of the treated animals. Chymopapain, even if injected repeatedly into the epidural space, does not cause significant scarring in the meninges.

Synergy of chymopapain and diatrizoate studied in an experimental model

The effect of diatrizoate on the chronic toxicity of chymopapain in the epidural space was studied. Chymopapain was injected epidurally into four monkeys; chymopapain plus diatrizoate meglumine, into four. In 3 months, neither group developed significantly more arachnoiditis than a control group of animals that had received epidural injections of physiologic saline. No synergistic effect of chymopapain and diatrizoate on the meninges was detected.

Effect of experimental root sheath compression on dura

The cause of dural scars and nerve root degeneration sometimes associated with herniated nucleus pulposus has not been explained. We studied experimentally the effect on the dura of its compression. Four animals had laminectomy and placement of a bone chip to elevate the left L4 nerve root sheath. As controls, four animals had laminectomy alone. Four weeks later, treated animals had no more arachnoid fibrosis than controls. The study does not support the hypothesis that chronic mechanical compression causes dural fibrosis.

Measurement of cerebrospinal fluid movement in the spine. An experimental technique

The authors devised a new technique for measuring cerebrospinal fluid movement in the spine. With gated list mode acquisition of radioactive emissions, bulk flow, oscillations, and dispersion of a bolus of isotope can be measured. The accuracy of the technique was measured in a simulation in which fluid oscillated at 71 cycles/minute and displaced at 6.5 cm/minute. With this method, the measured oscillation frequency and amplitude and the rate of translation were within 10% of actual values.

An experimental model to study contrast enhancement in MR imaging of the intervertebral disk

MR imaging after IV gadolinium-DTPA administration has demonstrated contrast enhancement in traumatized lumbar intervertebral disks. To characterize the morbid anatomy that correlates with the contrast enhancement, we developed a canine model of traumatized intervertebral disks. Diskectomy was performed with a nucleotome and the spines were imaged biweekly with MR and Gd-DTPA. The spines were studied at necropsy, and their anatomic abnormalities correlated with contrast enhancement detected by MR imaging. Our preliminary results indicate that contrast enhancement occurs where granulation tissue develops in traumatized intervertebral disks.

Effect of chymopapain on the meninges studied in an experimental model

The effect of chymopapain and contrast media in the epidural space on meninges has not been studied conclusively. The authors injected chymopapain into the epidural space of monkeys and measured the degree of arachnoid fibrosis that resulted. Animals were given injections of 1.2 mL of diatrizoate (280 mg iodine per milliliter), chymopapain (100 IU/mL), kaolin (100 mg/mL) (as a positive control), or saline (0.9%) (as a negative control). Three months later the animals were killed; the dural sac was removed intact and was fixed, sectioned, stained, and examined with light microscopy. Kaolin-treated animals developed mild to marked fibrosis of the dura. The saline- and diatrizoate-treated animals developed little or no evidence of fibrosis. One of four chymopapain-treated animals developed degenerative changes in dorsal nerve roots and fibrosis in the adjacent arachnoid. The other chymopapain-treated animals had little or no evidence of fibrosis. The studies suggest that neither diatrizoate nor chymopapain causes arachnoid fibrosis.