Patrick T. Cahill

Oligosaccharides Interfere with the Establishment and Progression of Experimental Pneumococcal Pneumonia

Oligosaccharides that block the adherence of bacteria to epithelial cells in vitro--lacto-N-neotetraose (LNnT) and its alpha2-3- and alpha2-6-sialylated derivatives--were tested for their abilities to attenuate the course of pneumococcal pneumonia and to prevent colonization of the nasopharynx in animal models. Intratracheal administration of these agents concurrently with bacteria dramatically decreased pneumococcal load in the lungs of rabbits and conferred protection from bacteremia. The oligosaccharides ameliorated pneumonia and bacteremia when given therapeutically 24 h after infection was established. When administered intranasally, neoglycoconjugates of the active oligosaccharides prevented colonization of the nasopharynx of infant rats. In addition to in vitro anti-adherence properties, LNnT acted directly on cultured lung epithelial cell lines to induce changes such that pneumococcal adherence was prevented for prolonged periods. These activities encourage continued development of oligosaccharides as a class of potentially preventive and therapeutic agents for infectious diseases.

MR imaging of pleural effusions.

To investigate the in vivo magnetic resonance (MR) characteristics of pleural effusions, MR imaging was performed on 22 patients who also underwent thoracentesis. Correlation of the MR scans with results of thoracentesis revealed significant differences among three types of effusions: transudates (T) (n = 4), simple exudates (SE) (n = 9), which did not have malignant cells or infection, and complex exudates (CE) (n = 9), which did have malignant cells or infection. Using normalized MR intensities, CE were more intense than SE, which were brighter than T. The second and third echoes (TE 66 and 99 ms) provided the best differentiation for these three classes of effusions, with p less than 0.06 and p less than 0.006, respectively. Qualitative visual assessment of the increase in signal intensity was also useful in differentiating among the three types of effusions (p less than 0.02). Effective T2 values (normalized to fat) were significantly shorter for exudates than for T (p less than 0.02). Heterogeneity, loculation, and size of effusions were well evaluated on MR. Magnetic resonance is not specific for the etiology of effusions. Nevertheless, with analysis of both quantitative and qualitative parameters, MR may provide an effective noninvasive means for the initial characterization and serial follow-up of pleural effusions.

DIRECT IN VIVO OBSERVATION OF TRANSVENTRICULAR ABSORPTION IN THE HYDROCEPHALIC DOG USING MAGNETIC RESONANCE IMAGING

RATIONALE AND OBJECTIVES.A model of chronic noncommunicating hydrocephalus in canines was developed, and gadolinium- DTPA (Gd-DTPA)-enhanccd magnetic resonance imaging, physiologic and morphologic studies were performed to investigate transventricular absorption of cerebrospinal fluid. METHODS.Chronic hydrocephalus was induced in 12 mongrel dogs by injection of a silastic mixture into the prepontine cisterns. Ventricular pressure was measured during the development of hydrocephalus, and lateral ventriculo-ventricular perfusions with Gd-DTPA were performed under controlled conditions during serial magnetic resonance imaging studies. RESULTS.Hydrocephalus developed over an average of 129 ± 24 days after induction, and the intraventricular pressure increased from an initial level of 14 ± 4 cm H2O to a stabilized plateau of 25 ± 5 cm H2O. Increased signal intensity in the brain matter, as seen on magnetic resonance images of chronic hydrocephalic dogs perfused with Gd-DTPA in the lateral ventricles, was consistent with the presence of the contrast agent in the periventricular extracellular space. This increased signal intensity was not observed in control animals. CONCLUSIONS.These results provide direct evidence of transventricular absorption in chronic hydrocephalus.

MR appearance of radiation hepatitis

The histopathologic changes of radiation hepatitis have been well described. The magnetic resonance (MR) appearance, however, has been described only in two case reports. We obtained serial MR scans of patients undergoing therapeutic irradiation for Hodgkins lymphoma to determine the time course of changes in signal intensity of the liver. We found an increased signal intensity of the irradiated portion of the liver on T2-weighted images. Changes first detected at 4 weeks following 3600 cGy to the abdomen returned to normal signal intensity within 60 days following completion of radiation therapy. One patient demonstrated a subtle increase in signal intensity of the irradiated region as early as 7 days after receiving 2000 cGy. Our results suggest that MR imaging is a useful noninvasive means of tracing the course of radiation hepatitis.

Role of delayed intraaortic balloon pumping in treatment of experimental myocardial infarction

Intraaortic balloon pumping improves coronary blood flow characteristics while simultaneously reducing myocardial oxygen demands by reducing aortic systolic pressure. Clinical application of intraaortic balloon pumping has largely been in the high risk patient (cardiogenic shock, postinfarction angina, left main coronary artery disease and unstable angina) for support during diagnostic studies or cardiac surgery, or both. In addition, there is some evidence that balloon pumping immediately after coronary occlusion reduces the size of experimentally induced myocardial infarcts. In this study, myocardial infarcts were produced by ligation of the left anterior descending coronary artery in 12 dogs, 6 of which were treated with balloon counterpulsation beginning 3 hours after coronary occlusion. All dogs were killed 8 hours after coronary ligation. Intraaortic balloon pumping resulted in the expected hemodynamic changes (decreased aortic systolic pressure, left ventricular end-diastolic pressure and heart rate and increased aortic peak diastolic pressure). In addition, there was a significant reduction in infarct size in the group with balloon pumping as determined with epicardial S-T segment mapping, myocardial imaging with technetium-99m-glucoheptonate and histochemical staining with nitroblue tetrazolium. These results suggest that even when instituted as long as 3 hours after coronary occlusion, intraaortic balloon pumping results in significant reduction in infarct size and, it might be speculated, the mortality and morbidity associated with acute myocardial infarction may also be decreased.

Quantitation of normal canine hippocampus formation volume: Correlation of MRI with gross histology

The hippocampal formation possesses an important role in the development and maintenance of short-term memory. In this study, magnetic resonance imaging (MRI) and gross histology were used to quantify the volume of the hippocampal formation in canines. High resolution MRI, using 1 mm thick slices and an intraplanar resolution of 0.35 mm was performed at 2.0 T both in vivo and in vitro following in situ fixation. The volumes of the hippocampal formations were determined from MR images and compared to those obtained from one mm thick gross histologic sections. The average volume of the canine hippocampal formation, measured from in vivo and in vitro MR images was 476.0 +/- 79.5 and 467.3 +/- 53.7 mm3, respectively. Determined from gross histology, the volume of the hippocampal formation was 463.6 +/- 24.1 mm3. Quantitation of the canine hippocampal formation using in vivo MRI showed good correlation with in vitro MRI and histology, verifying the reliability and reproducibility of in vivo MRI measurements. High resolution MRI using 1 mm thick slices through the whole canine hippocampal formation is necessary for accurate volume determination of a structure of this size.

Transmission line analysis of noncylindrical birdcage resonators

Transmission line theory, validated for the standard cylindrical birdcage coil, has been employed for the analysis of a rectangular birdcage resonator which is useful for MR imaging of the hand. Due to lack of cylindrical symmetry in the rectangular coil, RF field uniformity was evaluated and found to be critically dependent upon the choice of column from which the coil was linearly driven. Effective L1 and L2 inductance elements were determined using known formulas for self and mutual inductance contributions, and compensation of the different inductance elements of the hand coil was performed to produce cylindrically symmetric birdcage current patterns. RF field mapping using the Biot-Savart law demonstrated a rectangular coil sensitivity 22% greater than a comparable cylindrical version. MR hand and wrist images were acquired using the rectangular birdcage coil. In addition, transmission line analysis was extended to other noncylindrical birdcage geometries.

Two Years Experience With A Broadband Cable Network In An 1100-Bed Hospital

Early in 1983, a three-cable broadband network was installed in The New York Hospital-Cornell Medical Center using well-established cable-TV technology. This network was configured in a vertical tree topology. Currently, it extends over thirteen floors vertically and over two city blocks horizontally. It has now survived several major renovations on the various floors of the hospital. This survivability is a result of the siting of the main tree and of the isolation gained for the branches through the strategic placement of amplifiers. This communications system was designed in a modular fashion for later expansion and so that seven types of functions could be supported on the network without the addition of a new functional level disrupting the functions already existing on the system. Thus far, two functions (real-time image consultation and computer sharing) have been implemented, and two other functions (analog image storage and data base management) are in the prototype stage. Perhaps the most significant feature of our experience thus far has been the ease and utility of analog transmission and storage of images. This experience has lead us to postpone and even de-emphasize digital transmission and storage in our future plans.