A prostate-specific membrane antigen-targeted monoclonal antibody-chemotherapeutic conjugate designed for the treatment of prostate cancer

MLN2704 is an antibody-chemotherapeutic conjugate designed to target prostate-specific membrane antigen (PSMA). PSMA is a transmembrane receptor whose expression is largely restricted to prostatic epithelium and prostate cancer cells with its expression level increasing during the progression of malignancy. MLN2704 consists of a de-immunized, monoclonal antibody that is specific for PSMA conjugated to drug maytansinoid 1 (DM1), a microtubule-depolymerizing compound. After antibody binding to PSMA and the subsequent cellular internalization of this complex, DM1 is released leading to cell death. MLN2704 has an approximate half-life of 39 hours in scid mice bearing CWR22 tumor tissue, and the antibody effectively penetrates xenograft tumor tissue. Optimization of dosage and schedule of MLN2704 administration defined interdependency between these conditions that maximized efficacy with no apparent toxicity. Tumor growth delays of approximately 100 days could be achieved on the optimized schedule of one dose of 60 mg/kg MLN2704 every 14 days for five doses (q14dx5). The unconjugated antibody (MLN591) demonstrated essentially no antitumor activity and DM1 alone or a non-PSMA targeted antibody-DM1 conjugate was only weakly active. Furthermore, we show that MLN2704 is active in a novel model of osteoblastic prostate cancer metastasis.

Quantitative Analysis of Micro-CT Imaging and Histopathological Signatures of Experimental Arthritis in Rats

Micro-computed tomographic (micro-CT) imaging provides a unique opportunity to capture 3-D architectural information in bone samples. In this study of pathological joint changes in a rat model of adjuvant-induced arthritis (AA), quantitative analysis of bone volume and roughness were performed by micro-CT imaging and compared with histopathology methods and paw swelling measurement. Micro-CT imaging of excised rat hind paws (n = 10) stored in formalin consisted of approximately 600 30-mum slices acquired on a 512 x 512 image matrix with isotropic resolution. Following imaging, the joints were scored from H&E stained sections for cartilage/bone erosion, pannus development, inflammation, and synovial hyperplasia. From micro-CT images, quantitative analysis of absolute bone volumes and bone roughness was performed. Bone erosion in the rat AA model is substantial, leading to a significant decline in tarsal volume (27%). The result of the custom bone roughness measurement indicated a 55% increase in surface roughness. Histological and paw volume analyses also demonstrated severe arthritic disease as compared to controls. Statistical analyses indicate correlations among bone volume, roughness, histology, and paw volume. These data demonstrate that the destructive progression of disease in a rat AA model can be quantified using 3-D micro-CT image analysis, which allows assessment of arthritic disease status and efficacy of experimental therapeutic agents.

Investigation of techniques to quantify in vivo lesion volume based on comparison of water apparent diffusion coefficient (adc) maps with histology in focal cerebral ischemia of rats

Stroke lesion-volume estimates derived from calculated water apparent diffusion coefficient (ADC) maps provide a quantitative surrogate end-point for investigating the efficacy of drug treatment or studying the temporal evolution of cerebral ischemia. Methodology is described for estimating ischemic lesion volumes in a rat model of permanent middle cerebral artery occlusion (MCAO) based on absolute and percent-reduction threshold values of the water ADC at 3 h post-MCAO. Volume estimates derived from average ADC (ADC(av)) maps were compared with those derived from post-mortem histological sections. Optimum ADC thresholds were established as those that provided the best correlation and one-to-one correspondence between ADC- and histologically derived lesion-volume estimates. At 3 h post-MCAO, an absolute-ADC(av) threshold of 47 x 10(-5) mm(2)/s (corresponding to a 33% reduction in ADC(av) based on a contralateral hemisphere comparison) provided the most accurate estimate of percent hemispheric lesion volume (%HLV). Experimental and data analysis issues for improving and validating the usefulness of DWI as a surrogate endpoint for the quantification of ischemic lesion volume are discussed.

The macrosphere model: evaluation of a new stroke model for permanent middle cerebral artery occlusion in rats

BACKGROUND AND PURPOSE

The suture middle cerebral artery occlusion (MCAO) model is widely used for the simulation of focal cerebral ischemia in rats. This technique causes hypothalamic injury resulting in hyperthermia, which can worsen outcome and obscure neuroprotective effects. Herein, we introduce a new MCAO model that avoids these disadvantages.

METHODS

Permanent MCAO was performed by intraarterial embolization using six TiO(2) macrospheres (0.3-0.4 mm in diameter) or by the suture occlusion technique. Body temperature was monitored, functional and histologic outcome was assessed after 24 h. Additional 16 rats were subjected to macrosphere or suture MCAO. Lesion progression was evaluated using magnetic resonance imaging (MRI).

RESULTS

The animals subjected to suture MCAO developed hyperthermia (>39 degrees C), while the temperature remained normal in the macrosphere MCAO group. Infarct size, functional outcome and model failure rate were not significantly different between the groups. Lesion size on MRI increased within the first 90 min and remained unchanged thereafter in both groups.

CONCLUSIONS

The macrosphere MCAO model provides reproducible focal cerebral ischemia, similar to the established suture technique, but avoids hypothalamic damage and hyperthermia. This model, therefore, may be more appropriate for the preclinical evaluation of neuroprotective therapies and can also be used for stroke studies under difficult conditions, e.g., in awake animals or inside the MRI scanner.

Separating changes in the intra- and extracellular water apparent diffusion coefficient following focal cerebral ischemia in the rat brain

Selective intracellular (IC) and extracellular (EC) brain water apparent diffusion coefficient (ADC) values were measured in normal and ischemic rat brain. Selective T(1)-relaxation enhancement of the EC water, using intracerebroventricular (ICV) infusion of an NMR contrast reagent (CR), was used to separate the IC and EC signal contributions. In the CR-infused, normal brain (n = 4), T(1) = 235 +/- 10 ms and T(2) = 46 +/- 2 ms for IC water (85%) and T(1) = 48 +/- 8 ms and T(2) = 6 +/- 2 ms for EC water (15%). Volume-localized ADC(z) (z-gradient axis) values were 0.90 +/- 0.02 (EC+IC), 0.81 +/- 0.05 (IC), 0.51 +/- 0.02 (EC+IC), and 0.53 +/- 0.07 (IC), for normal, CR-infused, ischemic, and ischemic/CR-infused groups, respectively (ADC values are x10(-3) mm(2)/s; n = 5 for each group). Imaging ADC(z) values were 0.81 +/- 0.03 (EC+IC), 0.75 +/- 0.05 (IC), 0.51 +/- 0.04 (EC+IC), and 0.52 +/- 0.05 (IC), respectively, for the same groups. Imaging ADC(av) (average diffusivity) values for the same groups were 0.70 +/- 0.05 (EC+IC), 0.69 +/- 0.06 (IC), 0.45 +/- 0.06 (EC+IC), and 0.44 +/- 0.06 (IC), respectively. These results suggest that the IC water ADC determines the overall water ADC value in normal and ischemic rat brain.

Deconvolution of compartmental water diffusion coefficients in yeast-cell suspensions using combined T(1) and diffusion measurements

An NMR method is presented for measuring compartment-specific water diffusion coefficient (D) values. It uses relaxography, employing an extracellular contrast reagent (CR) to distinguish intracellular (IC) and extracellular (EC) (1)H(2)O signals by differences in their respective longitudinal (T(1)) relaxation times. A diffusion-weighted inversion-recovery spin-echo (DW-IRSE) pulse sequence was used to acquire IR data sets with systematically and independently varying inversion time (TI) and diffusion-attenuation gradient amplitude (g) values. Implementation of the DW-IRSE technique was demonstrated and validated using yeast cells suspended in 3 mM Gd-DTPA(2-) with a wet/dry mass ratio of 3.25:1.0. Two-dimensional (2D) NMR data were acquired at 2.0 T and analyzed using numerical inverse Laplace transformation (2D- and sequential 1D-ILT) and sequential exponential fitting to yield T(1) and water D values. All three methods gave substantial agreement. Exponential fitting, deemed the most accurate and time efficient, yielded T(1):D (relative contribution) values of 304 ms:0.023x10(-5) cm(2)/s (47%) and 65 ms:1.24x10(-5) cm(2)/s (53%) for the IC and EC components, respectively. The compartment-specific D values derived from direct biexponential fitting of diffusion-attenuation data were also in good agreement. Extension of the DW-IRSE method to in vivo models should provide valuable insights into compartment-specific water D changes in response to injury or disease. (c) 2002 Elsevier Science (USA).

Apoptosis-regulating proteins and prognosis in diffuse large B cell non-Hodgkin's lymphomas

We evaluated the expression of apoptosis-regulating proteins (p53, Bcl-2, Bax, Bak and Mcl-1) in paraffin-embedded tissues of 33 patients with diffuse large B cell non-Hodgkin's lymphoma, and assessed the relationship of these proteins to clinical outcome and response to chemotherapy. Our results showed that p53 expression was an independent immunohistochemical parameter related to a poor prognosis in these lymphomas. Bcl-2, Bax, Bak and Mcl-1 proteins, though highly expressed in almost all cases were not associated with prognosis or response to treatment.

Acute postischemic renormalization of the apparent diffusion coefficient of water is not associated with reversal of astrocytic swelling and neuronal shrinkage in rats

BACKGROUND AND PURPOSE

Initially decreased apparent diffusion coefficient (ADC) values are reversible if reperfusion is rapidly performed after focal brain ischemia. We sought to determine if reperfusion-induced renormalization of initially abnormal values indicates reversal of cellular, morphologic changes that occur during acute ischemia.

METHODS

Eighteen rats underwent 30 minutes of middle cerebral artery occlusion (MCAO) without reperfusion (group A, n = 6), with 1.5 hours of reperfusion (group B, n = 6), or with 12 hours of reperfusion (group C, n = 6). Diffusion- and perfusion-weighted MR images were obtained at the end of MCAO and 1.5 and 12 hours after reperfusion. Immediately after the final MR study, the brains were fixed by cardiac perfusion with 4% paraformaldehyde. Neuronal injury was evaluated on hematoxylin-eosin-stained slices, and astrocytic size was determined by the area of glial fibrillary acidic protein (GFAP) plus S-100 expression.

RESULTS

In group A in which ADC values decreased significantly, 47 +/-12% of the neurons were slightly shrunken; astrocytes were moderately swollen, and the area expressing GFAP plus S-100 was larger than that in the contralateral hemisphere (117 microm(2) +/- 6 vs 89 microm(2) +/- 2; P <.001). In group B in which ADC had renormalized, most neurons were moderately shrunken, and the frequency of such neurons was greater in group B (92% +/- 2) than in group A (P <.001); astrocytes were markedly swollen, and the area was larger than that in the contralateral hemisphere (123 microm(2) +/- 8 vs 85 microm(2) +/- 4, P <.001). In group C in which a secondary ADC decrease occurred, most neurons (94% +/- 3) were severely shrunken, and some had eosinophilic cytoplasm; astrocytes were disintegrated, and the area of GFAP plus S-100 expression was reduced (78 microm(2) +/- 4 vs 90 microm(2) +/- 5, P <.001).

CONCLUSION

Reperfusion-induced acute renormalization of ADC values is not associated with the reversal of neuronal shrinkage and astrocytic swelling that occur during ischemia. Conversely, the morphologic changes of astrocytes and neurons progressively worsen over time, although ADC values show a biphasic change.

Apocrine ductal carcinoma in situ of the breast: histologic classification and expression of biologic markers

Apocrine ductal carcinoma in situ (ADCIS) has been called a special type of ductal carcinoma in situ (DCIS) because the histologic grading is considered difficult using the classification schemes that have been proposed for common DCIS. However, ADCIS encompasses a spectrum of lesions with different morphologic aspects ranging from minimally atypical to overtly malignant. To define a classification scheme for ADCIS, 35 cases (22 pure and 13 associated with invasive carcinoma) were selected on the basis of conventional morphology on hematoxylin and eosin (H&E)-stained sections. Each case was assigned to 1 of 3 histologic grades (low, intermediate, and high) based on nuclear morphology and the presence of necrosis. In addition, the expression of hormone receptors p53, bcl-2, c-erbB-2, and Ki-67 was evaluated by immunohistochemistry, and the DNA ploidy was determined by image cytometry. Fifteen cases were classified as high histologic grade, 10 as low histologic grade, and the other 10 as intermediate grade. All but 4 cases, irrespective of grade, had the same hormonal immunophenotype: androgen receptor positivity (97.1%) and estrogen receptor and progesterone receptor negativity (94.3% and 97.1% respectively). Twenty-one cases (61.8%) showed p53 expression, and 47.1% of the cases were positive for c-erbB-2. The median positivity for Ki-67 was 5.2%. ADCIS has a unique morphologic and hormonal profile, distinct from common DCIS, deserving a specific classification. The proposed classification scheme allows for categorization of ADCIS according to the most important morphologic features already seen in common DCIS, ie, nuclear grade and necrosis. The expression of biologic markers other than hormonal receptors and bcl2 in ADCIS seems in general to be similar to that in common DCIS. Ki-67 and c-erbB-2 are expressed more frequently in intermediate and high histologic grade ADCIS.

Temporal evolution of Diffusion / Perfusion Mismatch in a Rat Stroke Model

P69

Background and Purpose: Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) can rapidly detect lesions in acute ischemic stroke. Studies show that lesions by PWI are sometimes larger than those of DWI in patients with acute ischemic stroke, suggests that the mismatch between DWI and PWI is potentially predictive of tissue at high risk for evolving into infarction. The aims of this study were to detect the evolution of the DWI/PWI mismatch in permanent focal experimental ischemia and transient focal experimental ischemia. Methods: Rats were subjected to permanent (n=8) and 60 minutes of temporary ischemia (n=8) using the intraluminal middle cerebral artery occlusion method and then underwent DWI and PWI after occlusion. Rats in the transient ischemic experiments were reperfused 60 minutes after occlusion. An apparent diffusion coefficient map and a cerebral blood flow index map were used to calculate the percent hemispheric lesion volume (%HLV) for each MRI parameter. Results: In permanent ischemia, %HLVs by DWI were 21%, 45%, 60%, 87%, and 101% of %HLV by PWI at 15, 30, 60, 90 and 120 minutes after ischemia, respectively. The ratio did not change after 120 minutes. With 60 minutes of temporary ischemia, the changes were almost the same as those in permanent ischemia before reperfusion. After reperfusion the lesions on PWI were smaller than those on DWI. The DWI lesion did not increase after reperfusion, and was the almost the same size as just before reperfusion. Conclusions: The DWI/PWI mismatch disappears at 2 hours after permanent ischemia, and the region of DWI/PWI mismatch can be saved from ischemic damage if reperfused early, but ischemic lesions seen on DWI can not be reduced by reperfusion after 60 minutes of temporary ischemia in this rat stroke model.

Prediction of secondary ischemic lesions with diffusion-weighted imaging after transient middle cerebral artery occlusion in rats

P75

Background and Purpose: Previous studies demonstrated that secondary ischemic lesions documented by diffusion-weighted imaging might be smaller than, larger than or similar to initial lesions that occur during ischemia. The purpose of this study was to investigate if the size of secondary lesions can be predicted. Methods: Twelve rats underwent 30 minutes of transient middle cerebral artery occlusion with the intraluminal suture method. Diffusion- and perfusion-weighted images were performed just before reperfusion, 90 minutes and 24 hours after reperfusion. The ischemic lesion size was calculated by tracing visual abnormalities on the apparent diffusion coefficient (ADC) maps. Cerebral blood flow index (CBF i ) ratio was calculated by dividing the ipsilateral CBF i by the contralateral CBF i . Based on difference between initial and secondary lesion volume, rats were assigned to reperfusion-benefit group (n=6) where secondary lesions were smaller than initial lesions (less than 85% of initial lesions) and reperfusion-nonbenefit group (n=6) where secondary lesions were similar to or larger than initial lesions (more than 85% of initial lesions). Results: At 90 minutes after reperfusion, the initial ischemic lesions almost disappeared in both groups. At 24 hours, secondary lesions were 54±11% (mean±SD) of the initial lesions in the reperfusion-benefit group and 100±14% of the initial lesions in the reperfusion-nonbenefit group (p<0.001). There was no difference in ADC values (47±2×10 -5 mm 2 /s vs 46±5×10 -5 mm 2 /s, p=0.7) and CBF i ratio (0.62±0.06 vs 0.67±0.04, p=0.2) between the two groups before reperfusion. However, the initial lesion volume was significantly smaller in the reperfusion-benefit group than in the reperfusion-nonbenefit group (125±54 mm 3 vs 195±36 mm 3 , p=0.037). Conclusions: Changes of ADC values and CBF before reperfusion are unable to predict if initial ischemic lesions will eventually shrink or not after reperfusion. Smaller size of initial lesions may suggest that secondary lesions will be smaller than initial lesions.

Growth pattern of ischemic lesions with different initial volume in a permanent middle cerebral artery occlusion model

P94

Background and Purpose: Diffusion-weighted imaging (DWI) allows measurement of ischemic lesions in a real-time manner and is used increasingly for evaluation of stroke therapy. This study was to determine if lesion growth is different when the initial lesion volumes on DWI are different after permanent middle cerebral artery occlusion (MCAO) in rats. Methods: Twelve Sprague-Dawley male rats were subjected to permanent MCAO with the intraluminal suture method. DWI was performed at 30, 60, 90, 150, 210, and 270 minutes after occlusion. The ischemic lesion areas were determined by visually tracing the hyperintense border on DWI, and the lesion volumes were calculated by multiplying the areas by the slice thickness. Based on the initial lesion volume at 30 minutes, the rats were evenly assigned to two groups: group A with smaller initial volume (<130 mm 3 , n=6) and group B with larger initial volume (≥130 mm 3 , n=6). Results: The initial lesion volumes at 30 minutes were significantly different between two groups (106±14 mm 3 vs 189±38 mm 3 , p<0.001), and the lesion volumes were also different thereafter (189±35 mm 3 vs 270±76 mm 3 at 270 minutes, p=0.04). The absolute increased volumes at 270 minutes, however, had no difference between two groups (84±32 mm 3 in group A and 82±44 mm 3 in group B, p=0.93). The percent increase of the lesion volume in group A was bigger than that in group B (80±30% vs 42±17% at 270 minutes, p=0.02). Conclusions: The growth rate of the ischemic lesion is larger if the initial lesion volume is smaller, but the absolute increase of the lesion volume is similar regardless of the difference of the initial lesion volume. These findings are of importance in evaluating the efficacy of stroke therapy when the initial lesion volumes are different.

Inside-out versus standard artery graft to repair a sensory nerve in rats

It is known that a vein graft provides a good microenvironment for axon regeneration in motor peripheral nerves, but the use of artery graft for regeneration of sensory nerves is controversial. We sectioned the saphenous nerve and repaired it by using heterologous inside-out and standard artery graft techniques in rats. After 4, 12, and 20 weeks, the graft and the distal stump were observed under electron microscopy. In each period studied, the pattern, diameters, and thickness of the myelin sheaths of the regenerated axons were measured in the graft and distal stump. There was capillary invasion in both the graft and distal stump, especially in the inside-out artery graft group. Regenerated nerve fibers were prominent in both heterologous artery grafts 4 weeks after the surgical procedures. Conversely, in the distal stump, regenerated nerve fibers were observed only after 12 weeks. In both the inside-out artery graft and standard artery graft, no statistical difference in the diameters and thickness of the myelinated fibers after 20 weeks was observed.

Multispectral analysis of the temporal evolution of cerebral ischemia in the rat brain

A major difficulty in staging and predicting ischemic brain injury by magnetic resonance (MR) imaging is the time-varying nature of the MR parameters within the ischemic lesion. A new multispectral (MS) approach is described to characterize cerebral ischemia in a time-independent fashion. MS analysis of five MR parameters (mean diffusivity, diffusion anisotropy, T2, proton density, and perfusion) was employed to characterize the progression of ischemic lesion in the rat brain following 60 minutes of transient focal ischemia. k-Means (KM) and fuzzy c-means (FCM) classification methods were employed to define the acute and subacute ischemic lesion. KM produced an estimate of lesion volume that was highly correlated with postmortem infarct volume, independent of the age of the lesion. Overall classification rates for KM exceeded FCM at acute and subacute time points as follows: KM, 90.5%, 94.4%, and 95. 9%; FCM, 82.4%, 90.6%, and 82.6% (for 45 minutes, 180 minutes, and 24-120 hours post MCAO groups). MS analysis also offers a formal method of combining diffusion and perfusion parameters to provide an estimate of the ischemic penumbra (KM classification rate = 70.3%). J. Magn. Reson. Imaging 2000;12:842-858.

Secondary decline in apparent diffusion coefficient and neurological outcomes after a short period of focal brain ischemia in rats

This study was designed to characterize the initial and secondary changes of the apparent diffusion coefficient (ADC) of water with high temporal resolution measurements of ADC values and to correlate ADC changes with functional outcomes. Fourteen rats underwent 30 minutes of temporary middle cerebral artery occlusion (MCAO). Diffusion-, perfusion-, and T2-weighted imaging was performed during MCAO and every 30 minutes for a total of 12 hours after reperfusion (n = 6). Neurological outcomes were evaluated during MCAO, every 30 minutes for a total of 6 hours and at 24 hours after reperfusion (n = 8). The decreased cerebral blood flow during MCAO returned to normal after reperfusion and remained unchanged thereafter. The decreased ADC values during occlusion completely recovered at 1 hour after reperfusion. The renormalized ADC values started to decrease secondarily at 2.5 hours, accompanied by a delayed increase in T2 values. The ADC-defined secondary lesion grew over time and was 52% of the ADC-defined initial lesion at 12 hours. Histological evaluation demonstrated neuronal damage in the regions of secondary ADC decline. Complete resolution of neurological deficits was seen in 1 rat at 1 hour and in 6 rats between 2.5 and 6 hours after reperfusion; no secondary neurological deficits were observed at 24 hours. These data suggest that (1) a secondary ADC reduction occurs as early as 2.5 hours after reperfusion, evolves in a slow fashion, and is associated with neuronal injury; and (2) renormalization and secondary decline in ADC are not associated with neurological recovery and worsening, respectively.

Multimodal evoked potentials and the ovarian cycle in young ovulating women

There is controversy over how hormonal conditions influence cerebral physiology. We studied pattern-shift visual evoked potentials (PS-VEP), brain stem auditory evoked potentials (BAEP) and short-latency somatosensory evoked potentials (SSEV) in 20 female volunteers at different phases of the menstrual cycle (estrogen phase, ovulatory day and progesterone phase). Statistical analysis showed decreased latencies for P100 (PS-VEP), N19 and P22 (SSEV) waves in the progesterone phase compared with the estrogen phase. There was no significant difference between the estrogen and the ovulation day values. Comparing the three above stages, there were no significant differences in the brainstem auditory evoked potentials. The reduction of the latencies of the potentials generated in multisynaptic circuits provides the first consistent neurophysiological basis for a tentative comprehension of human pre-menstrual syndrome.

Transient and permanent resolution of ischemic lesions on diffusion-weighted imaging after brief periods of focal ischemia in rats : correlation with histopathology

BACKGROUND AND PURPOSE

The early ischemic lesions demonstrated by diffusion-weighted imaging (DWI) are potentially reversible. The purposes of this study were to determine whether resolution of initial DWI lesions is transient or permanent after different brief periods of focal brain ischemia and to evaluate histological outcomes.

METHODS

Sixteen rats were subjected to 10 minutes (n=7) or 30 minutes (n=7) of temporary middle cerebral artery occlusion or sham operation (n=2). DWI, perfusion-weighted imaging (PWI), and T(2)-weighted imaging (T(2)WI) were performed during occlusion; immediately after reperfusion; and at 0.5, 1.0, 1.5, 12, 24, 48, and 72 hours after reperfusion. After the last MRI study, the brains were fixed, sectioned, stained with hematoxylin and eosin, and evaluated for neuronal necrosis.

RESULTS

No MRI or histological abnormalities were observed in the sham-operated rats. In both the 10-minute and 30-minute groups, the perfusion deficits and DWI hyperintensities that occurred during occlusion disappeared shortly after reperfusion. The DWI, PWI, and T(2)WI results remained normal thereafter in the 10-minute group, whereas secondary DWI hyperintensity and T(2)WI abnormalities developed at the 12-hour observation point in the 30-minute group. Histological examinations demonstrated neuronal necrosis in both groups, but the number of necrotic neurons was significantly higher in the 30-minute group (95+/-4%) than in the 10-minute group (17+/-10%, P<0.0001).

CONCLUSIONS

Transient or permanent resolution of initial DWI lesions depends on the duration of ischemia. Transient resolution of DWI lesions is associated with widespread neuronal necrosis; moreover, permanent resolution of DWI lesions does not necessarily indicate complete salvage of brain tissue from ischemic injury.

Temporal evolution of ischemic injury evaluated with diffusion-, perfusion-, and T2-weighted MRI

OBJECTIVE

Ischemic lesions seen on diffusion-weighted imaging (DWI) are reversible if reperfusion is performed within minutes after the onset of ischemia. This study was designed to determine whether acute reversibility of DWI abnormalities is transient following brief temporary focal brain ischemia and to characterize the temporal evolution of in vivo ischemic lesions.

METHODS

Eight rats were subjected to 30 minutes of temporary middle cerebral artery occlusion and underwent diffusion-, perfusion-, and T2-weighted MRI during occlusion; immediately after reperfusion; 30, 60, and 90 minutes after reperfusion; and 12, 24, 48, and 72 hours after reperfusion. Average apparent diffusion coefficient (ADCav) values and the cerebral blood flow index (CBFi) ratio were calculated in both the lateral caudoputamen and overlying cortex at each time point. The size of the in vivo ischemic abnormalities was calculated from the ADCav and the T2 maps. Postmortem triphenyltetrazolium chloride (TTC) staining was used to verify ischemic injury.

RESULTS

Both the CBFi ratio and ADCav values declined significantly in the two regions during occlusion. The CBFi ratio recovered immediately after reperfusion and remained unchanged over 72 hours. However, ADCav values returned to normal at 60 to 90 minutes and secondarily decreased at 12 hours after reperfusion as compared with those in the contralateral hemisphere. The extent of the in vivo ischemic lesions maximized at 48 hours and was highly correlated with TTC-derived lesion size.

CONCLUSIONS

Acute recovery of initial ADCav-defined lesions after reperfusion is transient, and secondary ADCav-defined lesions develop in a slow and delayed fashion.

Neuroprotective effects of a novel broad-spectrum cation channel blocker, LOE 908 MS, on experimental focal ischemia: a multispectral study

Thirty-four rats undergoing 90 minutes of temporary middle cerebral artery occlusion were randomly and blindly assigned to vehicle or (RS)-(3,4-dihydro-6, 7-dimethoxyisoquinoline-1-gamma1)-2-phenyl-N,N-di-2-(2, 3, 4-trimethoxyphenyl)ethyl acetamide (LOE 908 MS; 0.5 mg/kg) i.v. bolus at 30 minutes after arterial occlusion followed by a 5 mg/kg/hr i.v. infusion for 3.8 hours (n =17/group). Perfusion-, diffusion- and T(2)-weighted magnetic resonance imaging was performed before treatment and repeatedly after treatment. Multispectral analysis was used to define ischemic abnormalities. The size of the ischemic abnormalities, including the ischemic core and penumbra, was not different between the two groups before treatment. However, a significant difference in ischemic lesion size was detected beginning 1.5 hours after treatment. The size of the ischemic core was significantly smaller in the treatment group, while the size of the ischemic penumbra was similar in the two groups at 85 minutes after arterial occlusion. Postmortem infarct size at 24 hours was significantly smaller in the drug-treated group than in the placebo group. These results demonstrate that LOE 908 MS can reduce ischemic lesion size, which is probably attributable to inhibition of expansion of the ischemic core. J. Magn. Reson. Imaging 1999;10:138-145.

Lymphoid hyperplasia, CD45RBhigh to CD45RBlow T-cell imbalance, and suppression of Type I diabetes mellitus result from TNF blockade in NOD-->NOD-scid adoptive T cell transfer

Sustained antibody-mediated inhibition of tumor necrosis factor (TNF) activity offers protection against Type I (insulin-dependent) diabetes mellitus in non-obese diabetic (NOD) mice. The mechanism of this effect, however, has remained obscure: TNFalpha might be required for the development of specific immune responses to islet antigens or it could directly participate in destruction of beta cells. In this study, autoimmune destruction of beta cells was initiated in NOD-severe combined immunodeficient (scid) mice by transfer of NOD splenic T-cells to induce diabetes. The blockade of TNFalpha activity was achieved during a narrow window of time after transfer. Transient inhibition of TNFalpha greatly reduced the number of islet lymphocytes and the incidence of diabetes in recipients of prediabetic NOD spleen cells. Protection extended beyond the interval of effective TNF blockade. Furthermore, the protective effect was only observed if cells were obtained from 6-week-old donors. The suppression of autoimmunity was reversible in the context of adoptive transfer as indicated by the transfer of splenocytes from the primary recipient to a second NOD-scid host led to a diabetic outcome. The blockade of TNFalpha was accompanied by a considerable increase in spleen size and doubling of the total splenocyte count, suggesting that TNFalpha might normally eliminate a transplanted T-cell subset within the recipients. Further analysis showed an increase in the absolute count of CD4 + T cells and pronounced distortion of the CD45RBhigh to CD45RBlow ratio, with a relative augmentation in the CD45RBlow count in the spleen. TNFalpha appears to regulate the number and subtype distribution of a transplanted T cell population.

Reconsiderations about the clinical importance of the sympathetic skin response

Over the last few years, neurologists have been showing increasing interest in the study of the sympathetic skin response (SSR). In the present report we describe a simple method that permitted us to determine a wide variation of SSR in response to different stimuli such as respiration, deglutition, blinking, skeletal movements, biting, auditory or light stimuli, vocalization, and sphincter contraction. These results raise doubts about the role of SSR as a complementary diagnostic method.

Compression of the peripheral branches of the sciatic nerve by lipoma

The authors report two female patients with chronic sensitive and motor findings in lower limbs caused by compression of distal branches of sciatic nerve by lipoma. Similar cases were not described on literature. Nerve conduction studies allowed to localize the exact site of compression. At surgery, lipomas compressing the deep peroneal nerve (case 1) and the posterior tibial nerve (case 2) were observed. Histologic studies of tumors confirmed the diagnoses.