Restriction Spectrum Imaging Improves Risk Stratification in Patients with Glioblastoma

BACKGROUND AND PURPOSE

ADC as a marker of tumor cellularity has been promising for evaluating the response to therapy in patients with glioblastoma but does not successfully stratify patients according to outcomes, especially in the upfront setting. Here we investigate whether restriction spectrum imaging, an advanced diffusion imaging model, performed after an operation but before radiation therapy, could improve risk stratification in patients with newly diagnosed glioblastoma relative to ADC.

MATERIALS AND METHODS

Pre-radiation therapy diffusion-weighted and structural imaging of 40 patients with glioblastoma were examined retrospectively. Restriction spectrum imaging and ADC-based hypercellularity volume fraction (restriction spectrum imaging-FLAIR volume fraction, restriction spectrum imaging-contrast-enhanced volume fraction, ADC-FLAIR volume fraction, ADC-contrast-enhanced volume fraction) and intensities (restriction spectrum imaging-FLAIR 90th percentile, restriction spectrum imaging-contrast-enhanced 90th percentile, ADC-FLAIR 10th percentile, ADC-contrast-enhanced 10th percentile) within the contrast-enhanced and FLAIR hyperintensity VOIs were calculated. The association of diffusion imaging metrics, contrast-enhanced volume, and FLAIR hyperintensity volume with progression-free survival and overall survival was evaluated by using Cox proportional hazards models.

RESULTS

Among the diffusion metrics, restriction spectrum imaging-FLAIR volume fraction was the strongest prognostic metric of progression-free survival (P = .036) and overall survival (P = .007) in a multivariate Cox proportional hazards analysis, with higher values indicating earlier progression and shorter survival. Restriction spectrum imaging-FLAIR 90th percentile was also associated with overall survival (P = .043), with higher intensities, indicating shorter survival. None of the ADC metrics were associated with progression-free survival/overall survival. Contrast-enhanced volume exhibited a trend toward significance for overall survival (P = .063).

CONCLUSIONS

Restriction spectrum imaging-derived cellularity in FLAIR hyperintensity regions may be a more robust prognostic marker than ADC and conventional imaging for early progression and poorer survival in patients with glioblastoma. However, future studies with larger samples are needed to explore its predictive ability.

Iterative probabilistic voxel labeling: automated segmentation for analysis of The Cancer Imaging Archive glioblastoma images

BACKGROUND AND PURPOSE

Robust, automated segmentation algorithms are required for quantitative analysis of large imaging datasets. We developed an automated method that identifies and labels brain tumor-associated pathology by using an iterative probabilistic voxel labeling using k-nearest neighbor and Gaussian mixture model classification. Our purpose was to develop a segmentation method which could be applied to a variety of imaging from The Cancer Imaging Archive.

MATERIALS AND METHODS

Images from 2 sets of 15 randomly selected subjects with glioblastoma from The Cancer Imaging Archive were processed by using the automated algorithm. The algorithm-defined tumor volumes were compared with those segmented by trained operators by using the Dice similarity coefficient.

RESULTS

Compared with operator volumes, algorithm-generated segmentations yielded mean Dice similarities of 0.92 ± 0.03 for contrast-enhancing volumes and 0.84 ± 0.09 for FLAIR hyperintensity volumes. These values compared favorably with the means of Dice similarity coefficients between the operator-defined segmentations: 0.92 ± 0.03 for contrast-enhancing volumes and 0.92 ± 0.05 for FLAIR hyperintensity volumes. Robust segmentations can be achieved when only postcontrast T1WI and FLAIR images are available.

CONCLUSIONS

Iterative probabilistic voxel labeling defined tumor volumes that were highly consistent with operator-defined volumes. Application of this algorithm could facilitate quantitative assessment of neuroimaging from patients with glioblastoma for both research and clinical indications.

Recovery of white matter tracts in regions of peritumoral FLAIR hyperintensity with use of restriction spectrum imaging

BACKGROUND AND PURPOSE

DTI is being increasingly used to visualize critical white matter tracts adjacent to brain tumors before neurosurgical resection. However, brain tumors, particularly high-grade gliomas, are typically surrounded by regions of FLAIR hyperintensity that include edema, which increase isotropic diffusion, degrading the ability of standard DTI to uncover orientation estimates within these regions. We introduce a new technique, RSI, which overcomes this limitation by removing the spherical, fast diffusion component introduced by edema, providing better analysis of white matter architecture.

MATERIALS AND METHODS

A total of 10 patients with high-grade gliomas surrounded by FLAIR-HI that at least partially resolved on follow-up imaging were included. All patients underwent RSI and DTI at baseline (FLAIR-HI present) and at follow-up (FLAIR-HI partially resolved). FA values obtained with RSI and DTI were compared within regions of FLAIR-HI and NAWM at both time points.

RESULTS

RSI showed higher FA in regions of FLAIR-HI and NAWM relative to DTI, reflecting the ability of RSI to specifically measure the slow, restricted volume fraction in regions of edema and NAWM. Furthermore, a method by time interaction revealed that FA estimates increased when the FLAIR-HI resolved by use of standard DTI but remained stable with RSI. Tractography performed within the region of FLAIR-HI revealed the superior ability of RSI to track fibers through severe edema relative to standard DTI.

CONCLUSIONS

RSI improves the quantification and visualization of white matter tracts in regions of peritumoral FLAIR-HI associated with edema relative to standard DTI and may provide a valuable tool for neurosurgical planning.

Improved conspicuity and delineation of high-grade primary and metastatic brain tumors using "restriction spectrum imaging": quantitative comparison with high B-value DWI and ADC

BACKGROUND AND PURPOSE

Restriction spectrum imaging is a sensitive DWI technique for probing separable water diffusion compartments in tissues. Here, we evaluate RSI-CMs derived from the spherically-restricted water compartment for improved tumor conspicuity and delineation from nontumor tissue and reduced sensitivity to edema compared with high-b-value DWI and ADC.

MATERIALS AND METHODS

RSI was performed in 10 presurgical patients: 4 with glioblastoma, 3 with primary CNS lymphoma, and 3 with metastatic brain tumors. Multidirectional DWI data were collected at b = 500, 1500, and 4000 s/mm(2). Quantification of tumor conspicuity, edema conspicuity, and relative sensitivity to edema for RSI-CMs; DWI at b = 4000 (DWI-4000); and ADC were compared in manually drawn VOIs. Receiver operating characteristic curves were used to evaluate the sensitivity and specificity of each method for delineating tumor from normal-appearing WM.

RESULTS

Significant TC was seen with both RSI-CMs and DWI-4000, but not ADC. Significant EC was seen with ADC, but not RSI-CMs or DWI-4000. Significantly greater TC was seen with RSI-CMs compared with DWI-4000. Significantly reduced RSE was seen with RSI-CMs compared with both DWI-4000 and ADC. Greater sensitivity and specificity for delineating tumor from normal-appearing WM were seen with RSI-CMs (AUC = 0.91) compared with both DWI-4000 (AUC = 0.77) and ADC (AUC = 0.66).

CONCLUSIONS

RSI-CMs offer improved conspicuity and delineation of high-grade primary and metastatic brain tumors and reduced sensitivity to edema compared with high-b-value DWI and ADC.

Identification of second harmonic optical effects from vaccine coated gold microparticles

This study investigates the optical effects observed from uncoated and protein vaccine coated gold microparticles while imaging with two-photon excitation in the Mie scattering regime. When observed with time correlated single photon counting fluorescence lifetime microscopy, the emission from the gold microparticles appeared as an intense instrument-limited temporal response. The intensity of the emission showed a second-order dependence on the laser power and frequency doubling of the emitted light was observed for fundamental light between 890 and 970 nm. The optical effect was attributed to two-photon induced second harmonic generation. The vaccine coated gold microparticles had a much weaker second harmonic signal than the uncoated gold microparticles. Chemical analysis of the surface of the gold microparticles revealed that the vaccine coating decreases the surface charge thereby diminishing the observed second harmonic signal. These optical properties can be exploited to identify both the location of the protein vaccine coating as well as the gold microparticles in vitro and potentially to investigate the vaccine delivery kinetics in vivo.

Temporal cortex hypermetabolism in Down syndrome prior to the onset of dementia

BACKGROUND

Adults with Down syndrome (DS) are at increased risk for dementia and provide an opportunity to identify patterns of brain activity that may precede dementia. Studies of early Alzheimer's disease (AD) and risk of AD show decreased function in posterior cingulate and temporal cortex as initial indicators of the disease process, but whether the origin and sequence of predementia brain changes are the same in DS is unknown.

METHODS

The regional cerebral glucose metabolic rates (GMR) among middle-aged nondemented people with DS (n = 17), people with moderate AD (n = 10), and age-matched control subjects (n = 24) were compared using PET during a cognitive task.

RESULTS

Statistical parametric mapping conjunction analyses showed that 1) both DS and AD groups had lower GMR than their respective controls primarily in posterior cingulate and 2) compared with respective controls, the subjects with DS had higher GMR in the same areas of inferior temporal/entorhinal cortex where the AD subjects had lower GMR. The same results were replicated after 1 year of follow-up.

CONCLUSIONS

As the DS subjects were not clinically demented, inferior temporal/entorhinal cortex hypermetabolism may reflect a compensatory response early in disease progression. Compensatory responses may subsequently fail, leading to neurodegenerative processes that the authors anticipate will be detectable in vivo as future GMR decreases in inferior temporal/entorhinal cortex are accompanied by clinical signs of dementia.

Lesions of the basolateral amygdala complex block propofol-induced amnesia for inhibitory avoidance learning in rats

BACKGROUND

As the unitary theory of anesthesia gives way to the "multiple sites, multiple mechanisms" concept, the sites involved in mediating the components of anesthesia must be identified. In the current study, we test the hypothesis that the basolateral amygdala complex (BLAC) is a brain site involved with mediating propofol-induced amnesia.

METHODS

Male Sprague-Dawley rats were divided into two groups, sham-operated control animals and rats given bilateral excitotoxic N-methyl-D-aspartate lesions of the BLAC. For each group, animals were given intraperitoneal saline or propofol (25 mg/kg) 5 min before inhibitory avoidance learning. Rats were given a foot shock (0.4 mA) upon entering the dark side of a two-sided apparatus. Rats could escape additional shock by returning to and staying in the light side. Training ended after shock avoidance for greater than 60 s. Memory was tested at 24 h. Longer latencies to enter the dark side 24 h after training imply better memory.

RESULTS

Sham-saline-treated animals had a robust memory latency (median latency [interquartile range] = 300 [163-567] s). Sham-propofo-treated animals exhibited a significant anterograde amnesia (latency = 63 [14-111] s) (P < 0.05 vs. sham-saline-treated animal). Both the saline-injected and propofol-injected animals with BLAC lesions showed robust memory (latency = 300 [264-485] and 323 [143480] s, respectively). These latencies did not differ from performance in the sham-saline-treated group and were significantly higher than the latency of the sham-propofol-treated group (both P < 0.05).

CONCLUSIONS

Discrete BLAC lesions blocked the amnestic effect of propofol. BLAC activity appears to be a requirement for propofol-induced amnesia. This finding suggests that the BLAC is a key brain site mediating anesthetic-induced amnesia.

Sex-related difference in amygdala activity during emotionally influenced memory storage

We tested the possibility suggested by previous imaging studies that amygdala participation in the storage of emotionally influenced memory is differentially lateralized in men and women. Male and female subjects received two PET scans for regional cerebral glucose-one while viewing a series of emotionally provocative (negative) films, and a second while viewing a series of matched, but emotionally more neutral, films. Consistent with suggestions from several previously published studies, enhanced activity of the right, but not the left, amygdala in men was related to enhanced memory for the emotional films. Conversely, enhanced activity of the left, but not the right, amygdala in women was related to enhanced memory for the emotional films. These results demonstrate a clear gender-related lateralization of amygdala involvement in emotionally influenced memory, and indicate that theories of the neurobiology of emotionally influenced memory must begin to account for the influence of gender.

Measurement of glutathione levels in intact roots of Arabidopsis

Levels of glutathione were measured for different cell types in roots of intact Arabidopsis seedlings after labelling with monochlorobimane to give fluorescent glutathione S-bimane (GSB) and imaging using confocal laser scanning microscopy with excitation at 442 nm. Labelling increased to a plateau in most cell types after about 15-20 min and the GSB accumulated rapidly in the vacuole. Formation of GSB in the cytoplasm was not affected by treatment with sodium azide; however, vacuolar transport of GSB was substantially inhibited under these conditions. We infer that vacuolar sequestration was mediated by a tonoplast glutathione S-conjugate pump. Quantitative estimates of the cytoplasmic glutathione concentration involved correction for the loss in fluorescence signal with depth into the specimen using an empirically determined model derived in situ from a permeabilized root. Correction for the dilution experienced on transport into the vacuole also required an estimate of the amount of cytoplasm present in each cell type. This was achieved in two stages: first, the levels of protein were mapped after fixation, permeabilization and labelling with fluroescein isothiocyanate. Second, the corresponding cytoplasmic volume was determined as 40% for epidermal cells in the elongation zone by manual segmentation of the cytoplasm in serial optical sections. Values of relative cytoplasmic volume for other cells were extrapolated in proportion to their protein content. Using this approach, cytoplasmic glutathione concentrations were found to be 2-3 mM in most cell types. There was a marked difference between the central cells and the neighbouring, rapidly dividing initials, and between the columella cells and the outermost cells of the root cap. In the latter case, the difference was equalized in the presence of azide. This might indicate that additional cell-cell movement and preferential sequestration of GSB can occur during the detoxification process in an intact system.

pH gradients are not associated with tip growth in pollen tubes of Lilium longiflorum

The cytoplasmic pH of growing pollen tubes of Lilium longiflorum Thunb. was measured using the pH-sensitive fluorescent dye 2′,7′-bis-(carboxyethyl)-5(6′)-carboxyfl uorescein and confocal fluorescence ratio imaging. The average cytoplasmic pH in the clear zone of the pollen tube tip was pH 7.11, and no consistent pH gradients were detected in the clear zone, averaging around -1.00 milli pH unit microm(−1), or along the first 50 microm of the tube (3.62 milli pH units microm[-1]). In addition, no correlation was observed between the absolute tip cytoplasmic pH or the pH gradient and the pollen tube growth rates. Shifts of external pH to more acidic pH values (pH 4.5) caused a relatively small acidification by 0.18 pH units, whereas a more alkaline external pH &gt;7.0 caused a dramatic increase in cytoplasmic pH and growth stopped immediately. Stimulation of the plasma membrane H+-ATPase by fusicoccin, resulted in an increase of tube growth but no change in cytoplasmic pH. On the other hand, vanadate (250–500 microM), a putative inhibitor of the pump, stopped tube growth and a slight cytoplasmic alkalinisation of 0.1 pH units was observed. Vanadate also arrested fusicoccin-stimulated growth and stimulated an increased alkalinisation of around 0.2 pH units. External application of CaCl2 (10 mM) caused a small acidification of less than 0.1 pH units in the clear zone, whilst LaCl3 (250 microM) caused slight and rather variable perturbations in cytoplasmic pH of no more than 0.1 pH units. Both treatments stopped growth. It was inferred from these data that tip-acid cytoplasmic pH gradients do not play a central role in the organisation or maintenance of pollen tube tip growth.

Cell proliferation and hair tip growth in the Arabidopsis root are under mechanistically different forms of redox control

We provide evidence that the tripeptide thiol glutathione (GSH) participates in the regulation of cell division in the apical meristem of Arabidopsis roots. Exogenous application of micromolar concentrations of GSH raised the number of meristematic cells undergoing mitosis, while depletion of GSH had the opposite effect. A role for endogenous GSH in the control of cell proliferation is also provided by mapping of GSH levels in the root meristem using the GSH-specific dye monochlorobimane and confocal laser scanning microscopy. High levels of GSH were associated with the epidermal and cortical initials and markedly lower levels in the quiescent center. The mechanisms controlling cell division could also be triggered by other reducing agents: ascorbic acid and dithiothreitol. Our data also reveal significant plasticity in the relationship between the trichoblast cell length and the hair it subtends in response to alterations in intracellular redox homeostasis. While mechanisms that control trichoblast elongation are influenced by nonspecific redox couples, root hair tip growth has a more specific requirement for sulfhydryl groups. The responses we describe here may represent the extremes of redox control of root plasticity and would allow the root to maintain exploration of the soil under adverse conditions with minimal cell divisions and root hair production or capitalize on a favorable environment by production of numerous long hairs. Redox sensing of the environment and subsequent redox-dependent modulation of growth and development may be crucial components in the strategies plants have evolved for survival in a fluctuating environment.

Four-dimensional imaging of living chondrocytes in cartilage using confocal microscopy: a pragmatic approach

Regulation of cell volume is a fundamental cellular homeostatic mechanism in the face of osmotic stress. In normal articular cartilage, chondrocytes are exposed to a changing osmotic environment. We present a comprehensive protocol for studying the volume regulatory behavior of chondrocytes within intact cartilage tissue using confocal laser-scanning microscopy. Our data acquisition regime optimizes both signal-to-noise and cell viability during time-lapsed three-dimensional (3-D) (x, y, z, t) imaging. The porcine cartilage is treated as an integrated component of the imaging system, and we demonstrate methods for the direct assessment of tissue-induced axial attenuation and image distortion. Parameterized functions describing these two components of image degradation are used to correct experimental data. The current study also highlights the problems associated with the analysis and visualization of four-dimensional (4-D) images. We have devised two new types of data reconstruction. The first compresses each 3-D time point into a single quantitative view, termed a coordinate view. From these reconstructions we are able to simultaneously view and extract cell measurements. A second type, a 4-D reconstruction, uses color to represent relative changes in cell volume, again while maintaining the morphological and spatial information. Both these approaches of image analysis and visualization have been implemented to study the morphology, spatial distribution, and dynamic volume behavior of chondrocytes after osmotic perturbation. We have mapped chondrocyte shape, arrangement, and absolute volume in situ, which vary significantly from the tissue surface through to the underlying bone. Despite the rigid nature of the extracellular matrix, cartilage cells are osmotically sensitive and respond to stimulation of volume regulatory mechanisms. The combined techniques of confocal laser-scanning microscopy and vital cell labeling have enabled us to study, for the first time, the response of chondrocytes in situ to changes in interstitial osmotic pressure.

Replication and transcription sites are colocalized in human cells

HeLa cells synchronized at different stages of the cell cycle were permeabilized and incubated with analogues of nucleotide triphosphates; then sites of incorporation were immunolabeled with the appropriate fluorescent probes. Confocal microscopy showed that sites of replication and transcription were not diffusely spread throughout nuclei, reflecting the distribution of euchromatin; rather, they were concentrated in ‘foci’ where many polymerases act together. Transcription foci aggregated as cells progressed towards the G1/S boundary; later they dispersed and became more diffuse. Replication was initiated only at transcription sites; later, when heterochromatin was replicated in enlarged foci, these remained sites of transcription. This illustrates the dynamic nature of nuclear architecture and suggests that transcription may be required for the initiation of DNA synthesis.

Symmetry, flexibility and permeability in the structure of yeast retrotransposon virus-like particles

The virus-like particles (VLPs) of the yeast retrotransposon Ty are genetically, structurally and functionally analogous to retroviral nucleocapsids or cores. Like retroviral cores Ty-VLPs package and possibly promote the enzyme activities for reverse transcription and integration, as well as encapsulating the RNA that is the intermediate in retrotransposition. Here we show that Ty-VLPs assemble into symmetrical structures across a broad distribution of particle sizes. This spread of sizes violates the principle of quasi-equivalent packing. In addition, RNase accessibility experiments suggest that these particles form an open structure that does not protect the encapsulated RNA. These features distinguish Ty-VLPs from typical spherical viral capsids in both structure and function.

Combination chemotherapy with cisplatin and nifedipine: synergistic antitumor effects against a cisplatin-resistant subline of the B16 amelanotic melanoma

Cisplatin has become one of the most commonly prescribed cytotoxic chemotherapeutic agents. Unfortunately, the cure rate is low due to the development or outgrowth of cisplatin-resistant cells which repopulate tumors, resulting in patient death. We reported previously that the calcium channel blocker nifedipine enhances the antitumour actions of cisplatin (cis-diamminedichloroplatinum (II] against murine tumors which are inherently cisplatin-sensitive (B16a) or inherently cisplatin-resistant (3LL). We have developed an induced cisplatin-resistant tumor variant (B16a-Pt) that is 30 times more resistant to cisplatin than its cisplatin-sensitive parent line. In short-term studies, we report that nifedipine significantly enhanced the cytotoxicity of cisplatin against primary B16a-Pt tumors and their spontaneous pulmonary metastases. In long term studies, we report that combination therapy with nifedipine and cisplatin results in significantly enhanced survival.

Imaging of immunogold labelled antigens on capping thymocytes by confocal reflection contrast scanning optical microscopy

Confocal laser scanning optical microscopy (CLSM) in the reflection contrast mode has been used to image single 40 nm gold particles, and to study changes in the distribution of gold label associated with capping of the leukocyte sialoglycoprotein (LSGP) antigen on the surface of fixed rat thymocytes, labelled with the mouse monoclonal antibody W3/13 and a goat anti-mouse IgG immunogold conjugate. This imaging method has also been applied to live thymocytes labelled with gold-conjugated antibodies, to study the dynamics of the capping process.

In vitro polymorphism and phase transitions of the neurofilamentous network isolated from the giant axon of the squid (Loligo pealei L.)

Using electron microscopy (EM), optical diffraction and image reconstruction techniques, we have demonstrated polymorphism of neurofilamentous network (NFN) in vitro based on phase transitions of the protein assemblies. The specific polymorphic appearances depended upon a number of factors, such as K+, Mg2+, Ca2+ ions, as well as the charge and hydration state of the molecules. Furthermore, modifications initiated by the state of phosphorylation of the sidearm proteins played an important role, especially in determining the sidearm disposition of the NFN. The Ca2+-activated protease removed the sidearms. Other enzymes activated by Ca2+ may initiate new association patterns of the peptide remnants and the intercoiling of two smooth neurofilaments (NFs) into paired helical filament-like (PHF-like) strands. Prolonged storage of the isolated NFs in Rubinson-Baker solution resulted in autocrosslinking and intercoiling of modified NFN components. The in vitro polymorphism and phase transitions of squid NFN induced under controlled conditions have been compared to modifications of cytoskeleton observed by EM in frontal lobe biopsies of Alzheimer patients. We conclude that similar processes, as induced in vitro, do occur in neurons of Alzheimer patients.

X-ray diffraction patterns from microtubules and neurofilaments in axoplasm

Freshly extracted axoplasm from giant axons of the marine fan worm Myxicola infundibulum and the squid Loligo can be pulled into fibres that contain highly oriented cytoskeletal elements suitable for X-ray diffraction. A major advantage of studying axoplasmic components by this technique is that it allows essentially native structures and their interactions to be examined. We describe here the analyses of the X-ray diffraction patterns. We show that in Myxicola the pattern can be explained by diffraction from both neurofilaments and microtubules, whilst in Loligo the pattern arises solely from microtubules. At low resolution, X-ray patterns obtained from dehydrated axoplasmic microtubules resemble strongly the Fourier transforms generated from electron micrographs of negatively stained specimens. Hydration of axoplasmic fibres produced reversible changes in the X-ray pattern intensities, although the layer-line positions were unaltered. On the 4 nm layer-line, the intensity of the J3 reflection was dramatically reduced on hydration, though its position was unchanged. Hydration also affected the J10/J16 reflections, which increased in intensity, though here again the positions of the peaks were little altered. The X-ray patterns from our hydrated fibres resemble those produced by others from fibres of purified microtubules, though in our patterns contrast is generated towards the centre of the wall. We interpret our findings in the light of current ideas about microtubule structure as determined by X-ray diffraction and electron microscope techniques.

Effect of irrigation on soil oxygen status and root and shoot growth of wheat in a clay soil

Two watering treatments (flood and control) were applied to undisturbed (bulk density �? 1.6 mg mm-3 ) and repacked �? 1.2 mg mm-3 ) cylinders of Marah clay loam. The cylinders (0.75 m o.d. by 1.4 m deep) were housed in a lysimeter facility. Wheat (cv. Egret) was grown in the cylinders and the soil was either kept well watered with frequent small amounts of water (control treatment) or subjected to three separate periods, ranging from 4 to 72 h, of surface inundation (flood treatment). The greater pore space and better drainage of the repacked soil ensured that its average level of soil oxygen (O2) was about three times that of the undisturbed soil. Nevertheless, inundation of the soil surface for either 48 or 72 h rapidly decreased soil O2 levels in both soils. Root growth in these soils appeared to be slowed when soil O2 levels became less than 15% of the maximum that would occur in dry, aerated soil. Root growth ceased in both repacked and undisturbed soil cores after a 48-h flooding, when the soil O2 status was probably < 10% of the maximum. Root growth was greatest in the repacked soil with controlled water additions. The ranking of treatments, by either root intercept counts or O2 status, were the same. Leaf and stem growth were not very sensitive to the root zone conditions, but this may have been due to the advanced stage of plant growth when the treatments were applied and to the generally low nitrogen status of all treatment plants. There was a 44% reduction in yield from the best to the worst aerated soil treatment. The data show that if soil O2 levels become low as the result of flooding, root growth of wheat will stop and grain yield will be substantially decreased. Greatly improved aeration of these fine-textured soils is only possible if both the internal drainage properties of the soil are improved and prolonged periods of surface inundation are avoided.

Application of a lateral compression clamp in the management of mandibular fractures

A lateral compression clamp system has been used in the treatment of fractures of the mandible. It provides rigid fixation and promotes earlier osteogenesis at the fracture site. Intermaxillary fixation can often be eliminated in edentulous persons and greatly reduced in duration when necessary as an adjunct to fixation in patients with teeth. These significant qualities make the compression clamp quite beneficial in the treatment plan and postoperative management of many otherwise difficult cases. Having evaluated our experiences with compression clamps, we believe that this approach deserves further attention and may contribute to a solution of the controversy that often exists regarding the management of mandibular fractures in both edentulous patients and those with a compromised complement of teeth.