Sonography, CT, and MR imaging: a prospective comparison of neonates with suspected intracranial ischemia and hemorrhage.

BACKGROUND AND PURPOSE: Sonography, CT, and MR imaging are commonly used to screen for neonatal intracranial ischemia and hemorrhage, yet few studies have attempted to determine which imaging technique is best suited for this purpose. The goals of this study were to compare sonography with CT and MR imaging prospectively for the detection of intracranial ischemia or hemorrhage and to determine the prognostic value(s) of neuroimaging in neonates suspected of having hypoxic-ischemic injury (HII). METHODS: Forty-seven neonates underwent CT (n = 26) or MR imaging (n = 24) or both (n = 3) within the first month of life for suspected HII. Sonography was performed according to research protocol within an average of 14.4 +/- 9.6 hours of CT or MR imaging. A kappa analysis of interobserver agreement was conducted using three independent observers. Infants underwent neurodevelopmental assessment at ages 2 months (n = 47) and 2 years (n = 26). RESULTS: CT and MR imaging had significantly higher interobserver agreement (P < .001) for cortical HII and germinal matrix hemorrhage (GMH) (Grades I and II) compared with sonography. MR imaging and CT revealed 25 instances of HII compared with 13 identified by sonography. MR imaging and CT also revealed 10 instances of intraparenchymal hemorrhage (>1 cm, including Grade IV GMH) compared with sonography, which depicted five. The negative predictive values of neuroimaging, irrespective of technique used, were 53.3% and 58.8% at the 2-month and 2-year follow-up examinations, respectively. CONCLUSION: CT and MR imaging have significantly better interobserver agreement for cortical HII and GMH/intraventricular hemorrhage and can reveal more instances of intraparenchymal hemorrhage compared with sonography. The absence of neuroimaging findings on sonograms, CT scans, or MR images does not rule out later neurologic dysfunction.

Impaired cerebrovascular autoregulation after hypoxic-ischemic injury in extremely low-birth-weight neonates: detection with power and pulsed wave Doppler US.

PURPOSE: To evaluate regional cerebral blood flow with power and pulsed wave Doppler ultrasound (US) in extremely low-birth-weight neonates with periventricular leukomalacia (PVL), germinal matrix hemorrhage (GMH), or both. MATERIALS AND METHODS: The lenticulostriate arteries of 17 preterm neonates (birth weight < or = 1,100 g) were assessed daily with Doppler US during the first 5-6 days of life. The mean arterial pressure and bilateral peak velocity, resistive index, coronal vascular cross-sectional area, and product of the peak velocity and vascular cross-sectional area were measured. RESULTS: Five neonates developed PVL, GMH, or both; results of follow-up examinations in 11 patients were normal. One neonate with severe intrauterine growth retardation and renal tubular acidosis was excluded. Neonates with PVL, GMH, or both showed significantly greater mean values and more variable values of vascular cross-sectional area and product of peak velocity and cross-sectional area than neonates without PVL or GMH (P < .025). Mean resistive index was significantly lower in neonates with PVL, GMH, or both than in neonates without (P < .01). There were no significant differences between mean arterial pressure in neonates with and those without PVL, GMH, or both. CONCLUSION: By enabling the detection of autoregulatory fluctuations in cerebral blood flow associated with hypoxic-ischemic injury, power and pulsed wave Doppler US may enable identification of preterm neonates who are at risk of developing PVL, GMH, or both during the 1st week of life.

Deep fascial hyperintensity in soft-tissue abnormalities as revealed by T2-weighted MR imaging.

OBJECTIVE: The purpose of this study was to determine whether recently described criteria, including hyperintense T2-weighted signal or other abnormalities revealed by MR imaging within deep fascial planes, are specific for necrotizing soft-tissue infections. MATERIALS AND METHODS: We reviewed 22 MR imaging examinations that revealed abnormally high signal intensity within deep fascial planes on T2-weighted images. Twenty-one of the patients had clinical diagnoses other than necrotizing soft-tissue infection, including nonnecrotizing cellulitis (n = 4), abscess without evidence of necrotizing fasciitis (n = 5), and cellulitis with accompanying vascular thrombosis (n = 2). MR imaging was performed using T1-weighted spin-echo (range of TRs/range of TEs, 300-800/9-30) and fat-saturated T2-weighted fast spin-echo (3000-5000/76-108) sequences. Gadolinium-enhanced T1-weighted spin-echo MR images with fat saturation were obtained for 14 patients. Two reviewers, unaware of clinical diagnoses, evaluated each study for abnormalities in superficial and deep soft tissues and submitted a consensus diagnosis. RESULTS: Using only the described MR imaging criteria, we interpreted all cases as necrotizing cellulitis, including the cases of 21 patients who had nonnecrotizing conditions. CONCLUSION: Hyperintense T2-weighted signal within deep fascial planes and muscle, with or without contrast enhancement, is not specific for necrotizing soft-tissue infection. A variety of conditions exhibited similar findings and were indistinguishable from necrotizing soft-tissue infection.

Magnetization transfer contrast MRI of musculoskeletal neoplasms.

Magnetic resonance imaging (MRI) examinations were performed in 15 patients with musculoskeletal neoplasms to assess the value of magnetization transfer contrast in tumor characterization. Multiplanar gradient-recalled echo sequences (TR 500-600/TE 15-20/flip angle 20-30 degrees) were performed first without and then with magnetization transfer contrast generated by a zero degree binomial pulse (MPGR and MTMPGR). Standard T1-weighted spin echo images (SE; TR 300-400/TE 12-20) and either T2-weighted SE (TR 2000-2900/TE 70-80) or T2-weighted fast spin echo (FSE; TR 4000-5000/TE 100-119 effective) images were also obtained. Signal intensities on MTMPGR scans were compared to those on MPGR scans for both tumors and normal tissues. Signal intensity ratios (SIR) and contrast-to-noise ratios (CNR) were also compared for all sequences. MTMPGR images provided better contrast between pathologic tissues and muscle than did standard MPGR images, increasing both conspicuity of lesions and definition of tumor/muscle interfaces. Benign and malignant tumors, with the exception of lipoma, underwent similar degrees of magnetization transfer and could not be distinguished by this technique.

Differential expression of asialo GM1 on alloreactive cytotoxic T lymphocytes and lymphokine-activated killer cells.

The present study was undertaken to examine the differential expression of asialo GM1 (AsGM1) on the responding cells and effectors of alloreactive cytotoxic T lymphocytes (CTL) and lymphokine-induced activated killers (LAK). It was found that AsGM1 was expressed on the 3-day-cultured LAK effectors. Its expression gradually disappeared to the extent that AsGM1 became undetectable after 5 to 6 days of culturing. In contrast, AsGM1 was detected on 3-day CTL generated in mixed-lymphocyte cultures (bulk cultures); however, the levels of AsGM1 expression remained the same for at least 7 days. When examining the expression of AsGM1 on the responding cells, the reciprocal results were obtained. AsGM1 was expressed the LAK responders, but we were unable to demonstrate AsGM1 on CTL responders. Depletion of AsGM1+ cells from the responding population reduced subsequent CTL responses; however, CTL responses could be restored by adding conditioned media containing both interleukin 2 (IL-2) and other helper-T-cell factors and could not be restored by purified IL-2 alone adding at comparable doses. Reconstituting the AsGM1-depleted responders with Lyt-2-depleted splenocytes also restored the CTL response. Furthermore, depletion of AsGM1 cells from the responding population did not reduce the precursor frequency of allo-CTL, whereas the precursor frequency of LAK cells was reduced 42-fold. These findings show that the reduction of CTL responses after depletion of AsGM1+ cells was not due to the removal of precursors; instead, the defect appeared to be in the helper population. We further found that the helper defect was not due to impaired IL-2 production, because the endogenous production of IL-2 AsGM1-depleted responders was not reduced. Therefore, AsGM1+ cells may play a role in the helper pathway other than IL-2 production.

Expression and function of asialo GM1 in alloreactive cytotoxic T lymphocytes.

In the present study we examined asialo GM1 (AsGM1) expression and its function in alloreactive cytotoxic T lymphocytes (CTL). We consistently found that the cytotoxic activity of bulk culture-derived allo-CTL was susceptible to the treatment of anti-AsGM1 (alpha AsGM1) plus complement. To further determine whether the expression of AsGM1 was maintained in CTL, we examined cloned T cells. The expression of AsGM1 in the T cell clones was assessed by their susceptibility to lysis by alpha AsGM1 plus complement and the reduction or abrogation of their cytotoxic activity by this treatment. It was found that, with one exception, all Lyt-2+, Thy-1+ CTL clones were AsGM1+ (seven out of eight), independent of their class specificity (class I or class II). In contrast, all Thy-1+, L3T4+ CTL (2) or helper T cell (4) clones AsGM1-. These findings suggested that there was a close association between the expression of AsGM1 and the expression of Lyt-2. The cytotoxic reaction of the anti-class I MHC CTL clones that expressed AsGM1 was blocked by alpha AsGM1 or alpha Lyt-2 antibody. The Lyt-2+, AsGM1+ anti-class II MHC CTL clone-mediated lysis was inhibited by alpha AsGM1. Addition of AsGM1 in micelle form (AsGM1-M) alone also blocked the cytotoxic reactions. Addition of other structurally similar but antigenically different glycolipids or other non-AsGM1-containing liposome preparations did not affect CTL-mediated cytotoxicity. Furthermore, adding both alpha AsGM1 and AsGM1-M together at proper doses inhibited the blocking effect (deblocking) of either alone, and other structurally similar glycolipids did not inhibit the blocking. The deblocking was specific, since AsGM1-M did not affect the blocking by alpha Lyt-2. These findings indicate that not only is AsGM1 expressed in a majority of Lyt-2+ CTL clones, but it may also be involved in the CTL- target interaction to mediate lytic reaction.

Regulation of the cytotoxic activity of alloreactive cytotoxic T lymphocytes by helper cells and lymphokines.

The cytotoxic activity of alloreactive cytotoxic T lymphocytes (CTL) was maintained and augmented by transferring cells from a 5-day mixed lymphocyte culture MLC into a host culture (HC) containing indomethacin, freshly explanted normal spleen cells, and peritoneal cells which were syngeneic to the MLC cells. The MLC cells used in the transfer experiments were generated by culturing untreated H-2b splenic responders with irradiated H-2d stimulators, or were generated by culturing Lyt-2-depleted H-2b splenic responders with irradiated H-2d stimulators. The allo-CTL were found to be derived from the donor MLC (first culture) when unfractionated MLC cells were transferred into a host (second) culture and incubated for 5 days. In contrast, the allo-CTL were derived from host culture cells when Lyt-2-depleted MLC cells were transferred and the combined cultures incubated for 5 days. In the former case, the augmentation of MLC-derived cytotoxicity did not result from nonspecific expansion of all donor T cells; instead it was mediated by lymphokine(s), distinct from IL-2, produced by helper T cells generated in host culture, which appeared to selectively expand the antigen-specific CTL or to increase the cytotoxic activity of these CTL. The helper T cells were Thy-1+, L3T4+, and Lyt-2-. These findings indicate that antigen-nonspecific help was provided by helper cells or helper factors (lymphokines) generated in the host culture, which maintained and augmented the cytotoxic activity of the fully generated allo-CTL. This helper effect was also seen in the induction of primary allo-CTL responses which could be generated with fewer stimulating cells and with a stronger cytotoxic response at different R/S ratios tested. The generation of allo-CTL in second culture following transfer of Lyt-2-depleted MLC cells to host cultures appears to have involved antigen carryover from the MLC; however, antigen carryover alone was not sufficient. It appears that in the absence of Lyt-2+ suppressor T cells, antigen-specific help might be generated in donor cultures (Lyt-2-depleted MLC) which promoted or recruited the generation of antigen-specific CTL in host culture.

Production of T cell differentiation factor in syngeneic lymphocyte macrophage culture for cytotoxic T lymphocyte generation.

This study demonstrated that T cell differentiation factor (TCDF) was produced in syngeneic lymphocyte-macrophage cultures. Conditioned medium containing TCDF and interleukin 2 (IL 2) induced the differentiation of leukoagglutinin (LA)-activated cytotoxic T lymphocyte precursors (CTLp) into cytotoxic T lymphocyte (CTL) effectors. The production of TCDF and IL 2 peaked at day 4 to 5 in cultures containing normal spleen cells, syngeneic peritoneal macrophages, and indomethacin. Macrophages and T cells with Thy-1+, L3T4+, and Lyt-2- phenotype were needed for TCDF production. There was no requirement for xenogeneic serum in the culture medium; thus, TCDF could be produced in a syngeneic system. Recognition of self Ia molecules appeared to be essential for TCDF production, which was completely abolished by the addition of monoclonal anti-Ia antibody. In our experiments, removal of IL 2 from conditioned medium containing TCDF abolished its ability to generate LA-activated CTL. However, the cytotoxic response could be restored by the addition of a small amount (5 U/ml) of purified human recombinant IL 2 (HRIL 2), which alone was unable to generate LA-activated CTL at this dose. The generation of LA-activated CTL by high dose HRIL 2 (greater than 50 U/ml) was likely due to the endogenous production of TCDF. The bulk of TCDF could be separated from IL 2 by gel filtration in a Sephadex G-100 column. The peak of TCDF activity was concentrated at a m.w. of 16K dalton, and there was very little IL 2 activity in these fractions. When added alone to the LA-activated lymphocyte cultures, these active fractions were unable to induce CTL; supplementation of exogenous IL 2 was needed to restore the cytotoxic responses. Our findings indicate that both IL 2 and TCDF, which are needed in CTL generation. are produced in syngeneic cultures in the absence of antigenic or mitogenic stimulation.