Myelography, CT and MRI in leukaemic infiltration of the lumbar theca

A 25-year-old woman with acute lymphoblastic leukaemia, while in remission, developed paraparesis, with faecal and urinary incontinence. CT demonstrated increased density of the lumbar theca and enlargement of the nerve roots. Myelography showed complete obstruction below the L3 level. MRI showed increased signal intensity in the lumbar sac on T1 weighting, and the cauda equina enhanced with gadolinium-DTPA. Lymphoblasts were seen in the lumbar spinal fluid. After chemotherapy, these abnormalities resolved, as did the paraparesis and incontinence.

Detection of renal allograft dysfunction with color Doppler flow ultrasound

Thirty-six color Doppler flow (CDF) ultrasound studies were performed on 28 allograft kidneys to assess the capability of this technique in diagnosing transplant dysfunction through morphology and Doppler spectra. The composite score obtained from ultrasound images showed no statistical significance. Quantitative studies with Pulsatility Index (PI) and Resistive Index (RI) after localization of the arcuate, interlobar, segmental and main renal arteries by CDF revealed significant differences between normal functioning graft kidneys and the group of acute rejection, as well as the group of acute tubular necrosis (ATN) (P < 0.05). No apparent change was demonstrated in patients with chronic rejection. When PI was greater than 1.60 or RI was greater than 0.80, the transplant kidney was more likely to be rejected, though possibility of ATN should be considered. RI was easier to calculate, and correlated better than PI with the serum creatinine level. CDF expedited the Doppler spectrum study.

Ependymoma of the cauda equina presenting with subarachnoid hemorrhage

A 16-year-old girl had an ependymoma at the L2 and L3 level that bled into the dural sac, presenting clinically as intracranial subarachnoid hemorrhage. MR depicted the tumor and hemorrhage on both T1- and T2*-weighted images. The blood in the dural sac appeared hyperintense on the T1-weighted images.

Cationized Bowman-Birk protease inhibitor as a targeted cancer chemopreventive agent

The conjugate of the Bowman-Birk inhibitor (BBI) with poly(D-lysine) (PDL-ss-BBI) has been suggested as a lung-targeted anti-carcinogenic agent. The authors demonstrate that PDL-ss-BBI, given i.p., reduces the tumor number in the lungs of 3-methylcholanthrene treated mice (61-71% compared to control group) in a dose-dependent manner, but is toxic to the treated animals at a high dosage. In order to develop a better lung-targeted anti-carcinogenic agent, spermine-conjugated BBI (spermine-BBI) was synthesized by coupling BBI to spermine through amide bonds using a carbodiimide-mediated reaction. Results from in vitro transformation assays demonstrated that spermine-BBI was at least as effective as BBI in reducing the transformation yield in C3H10T1/2 cells. When injected intravenously into mice [125I]spermine-BBI accumulated to a greater extent in the lungs and the liver compared to BBI. The in vitro cytotoxicity of spermine-BBI in C3H10T1/2 cells was 30-fold less than that of PDL-ss-BBI. These results suggest that spermine-BBI is likely to be an improved cancer chemopreventive agent compared to BBI or PDL-ss-BBI.

Neurilemmoma of the oculomotor nerve presenting as an orbital mass: MR findings

Neurilemmoma of the oculomotor nerve is rare and infrequently presents as an orbital mass. We report a neurilemmoma arising from the cavernous sinus with its major part extending into the orbit. The Antoni A part of the neurilemmoma showed intermediate signal intensity in both T1- and T2-weighted MR images and exhibited postcontrast enhancement. The Antoni B part revealed hypointensity on T1-weighted images, hyperintensity in T2-weighted images, and showed no contrast enhancement.

Disseminated tuberculomas in spinal cord and brain demonstrated by MRI with gadolinium-DTPA

Intramedullary tuberculoma is rare, and there has been no report of concurrent intramedullary and intracerebral tuberculomas. We report a 30-year-old man with miliary tuberculosis of the lung. He suffered sudden paraplegia due to tuberculomas in the thoracic spinal cord and MRI showed more tuberculomas in the cervical spinal cord, brain stem, and cerebral and cerebellar hemispheres. The tuberculomas were isointense on the T1-weighted images, and hyperintense on the T2-weighted images; there was marked enhancement with intravenous gadolinium-DTPA. All the tuberculomas were very small 1 year after antituberculous chemotherapy.

[Detection of the myelination process of Chinese infants by 1.0T MRI]

To establish the myelination process of brain of Chinese infants, our study consisted of seventy-five infants ranging in age from 5 days to 2 years old. They were studied with a 1.0 T superconductive MRI. In the new born, myelination could be seen in the brainstem, middle cerebellar peduncle, and posterior limb of the internal capsule in both T1WI and T2WI. Then the myelination process rapidly progressed month by month. Myelination of the centrum semiovale and optic radiation could be seen in T1WI in the newborn up to 3 months old, and in T2WI at 3-5 months old. The myelination of the splenium and the genu of corpus callosum were seen at 3-6 months in T1WI and 5-6 months in T2WI. Myelination of the occipital lobe and frontal lobe were seen at 3-6 months and 5-10 months in T1WI, and 8-14 months, 10-16 months in T2WI respectively. In 7-10 months, the brain appeared as an "early adult pattern" in T1WI; while, in T2WI, the brain appeared as an "early adult pattern" at 14-18 months old. The understanding of the myelination process in infants is important and essential for the judgement of the infantile brain and for the diagnosis of many CNS diseases of infants.

Brefeldin A enhances receptor-mediated transcytosis of transferrin in filter-grown Madin-Darby canine kidney cells

The effects of brefeldin A (BFA) on transferrin (Tf) transcellular transport, Tf receptor (TfR) distribution, and TfR-mediated endocytosis in filter-grown Madin-Darby canine kidney (MDCK) cells were studied. BFA (1.6 micrograms/ml) markedly enhanced the transcytosis of 125I-labeled Tf (125I-Tf) in both apical-to-basal and basal-to-apical directions; yet, BFA did not enhance the transcytosis of either native horseradish peroxidase (HRP) or membrane-bound HRP-poly(L-lysine) conjugates. Furthermore, this enhanced transcytosis of 125I-Tf was abolished either by competition with excess unlabeled Tf or by incubation at temperatures less than or equal to 25 degrees C. In addition, BFA treatment to MDCK cells: (a) increased 125I-Tf specific binding to the apical membrane and decreased 125I-Tf specific binding to the basal membrane; (b) decreased TfR recycling at the basolateral membrane; (c) altered the apical/basolateral distribution of TfRs in favor of the apical side; and (d) markedly increased 59Fe extraction, but not transcytosis, from apically endocytosed 59Fe-loaded Tf. These effects are consistent with a model in which BFA alters the traffic pattern of internalized Tf by decreasing basolateral TfR recycling, while diverting the nonrecycled fraction to the apical side of the cell. Our results indicate that, unlike the reported inhibition of polymeric IgA transcytosis (Hunziker, W., Whitney, J. A., and Mellman, I. (1991) Cell 67, 617-627), BFA can enhance the transcytosis of Tf in MDCK cells. Thus, by altering the intracellular traffic of ligand-receptor complexes, BFA can elicit either a decrease or an increase in transcytosis depending on the nature of the intracellular receptor processing.

[CT and MRI of parasellar cavernous hemangioma in two cases]

Extracerebral cavernous hemangioma is a rare entity, only 51 cases have been reported up to 1991. Most of the extracerebral cavernous angiomas occur in the parasellar region and easily extend to the sella; with CT and MRI views entirely different from those of intracerebral cavernous hemangiomas. The CT scan shows a good, homogeneous enhanced tumor, similar to a meningioma, yet lacking calcification or bony hyperostosis. In MRI, the characteristic findings of extracerebral cavernous hemangioma are the very high signal intensity in the T2 weighted image, and strong homogeneous enhancement by Gadolinium-DTPA. Here we report two cases of parasellar cavernous hemangioma. A 68-year-old male patient shown to have a dumbbell tumor in the parasellar and sellar regions by CT scan, showed a high density before contrast, and good enhancement by an iodine contained contrast medium. The tumor had a very high signal intensity in the T2 weighted image of MRI and a good, homogeneous enhancement by Gadolinium-DTPA, yet a carotid angiogram showed it was avascular. Surgical removal was abandoned in view of the probability of massive bleeding. The second case was a 34-year-old man, who had had a skin hemangioma on the right side of the face since his childhood. For the past 3 months, he had suffered from ptosis, and limitation of eye movement which was found to be due to 3rd and 4th cranial nerve palsy. CT showed a good enhanced tumor mass in the left side of the parasellar region with sellar extension. MRI also showed a high intensity in T2WI and good, homogeneous enhancement by Gadolinium-DTPA. A carotid angiogram revealed some tumor stain. Surgical removal. in this case, was also impossible due to its intracavernous sinus location and the probability of massive bleeding.

[Intracranial germ cell tumors]

We report on 19 cases of intracranial germ cell tumors, including 12 male and 7 female patients; the average age was 16.5 +/- 4.9 years. These tumors included germinoma in 15 cases, yolk sac tumor in 3 cases, embryonal cell carcinoma in 1 case, and mixed tumor in 3 cases. Each of 5 cases had 2 to 3 different kinds of tumor cells, either in one tumor or in different tumors. The locations of tumors were pineal region in 13 cases, suprasellar region in 3 cases, basal ganglion-thalamus in 3 cases, and cerebral hemispheres in 4 cases. Six of them had 2 or more locations. One case had spinal seeding and extraneural metastasis to the liver, retroperitoneum and neck lymph nodes. Eighteen cases received CT scan and 6 cases received MRI examinations, all the tumors had good enhancement by iodium content contrast medium in CT and Gadolinium-DTPA in MRI. Alfa-fetoprotein was elevated in yolk sac tumor, AFT and HCG were elevated only slightly or remained normal in germinoma. Germinomas had good response to radiation therapy and chemotherapy, while nongerminoma had poor response and worse prognosis.

Differential expression of Hz-1 baculovirus genes during productive and persistent viral infections

Hz-1 viral RNA transcription was studied during productive and persistent infections. The RNAs were localized to 10- to 30-kb regions within the viral genome, and the timing of their expression was determined. During productive infections, we detected 101 virus-specific transcripts that could be grouped into three categories by time of appearance. At 2 h postinoculation (p.i.), a total of 34 virus-specific transcripts were detected. An additional 51 and 16 virus-specific transcripts appeared between 4 and 6 h p.i. and at 8 h p.i., respectively. After 8 h, no new transcripts were found. Under conditions of persistent infection, we detected only one viral persistency-associated transcript (PAT1). The region of the viral DNA which encodes PAT1 was cloned. During productive infections, three transcripts were derived from this region. Each had the same polarity as PAT1. One of them was of the same size as PAT1 and had similar, if not identical, 3' and 5' ends. This report provides detailed and very useful information concerning sequentially expressed transcripts of the Hz-1 baculovirus.

Polarity in the transcytotic processing of apical and basal membrane-bound peroxidase-polylysine conjugates in MDCK cells

A conjugate of horseradish peroxidase (HRP) to poly(L-lysine) (PLL) was used to characterize a non-lysosomal proteolytic compartment in the MDCK Strain I epithelial cell line. This compartment is expressed in a polar fashion, and is capable of degradation of the PLL moiety in the conjugate followed by release of HRP via a basal-to-apical, but not apical-to-basal, transcytotic pathway. This uptake, cleavage, and transport process appears to require approximately 2 hr, as there is a 2 hr lag-time between conjugate administration to the basal surface and HRP release to the apical medium. Monensin (10 microM) failed to inhibit this process, indicating that participation of the trans-Golgi network (TGN) in the trafficking of internalized conjugate is not the rate-determining step. Inhibition of HRP transport was found to be elicited by 50 micrograms/ml leupeptin, but only when applied to the basal surface. Brief trypsinization of either the basal or apical surfaces of cells preloaded with HRP conjugate showed no appreciable inhibitory effect on the apical release of HRP, indicating that an intracellular compartment rather than surface-bound enzymes is responsible for the degradation of the PLL moiety in the conjugate. Our results demonstrate the presence of an intracellular proteolytic compartment which is accessible in the basal-to-apical, but not apical-to-basal, transport pathway; and this compartment can be exploited for the transcytosis of membrane-bound molecules.

Dural arteriovenous malformation of the transverse sinus with sinus occlusion: report of a case

We report a case of dural arteriovenous malformation (AVM) of the transverse sinus with sinus occlusion. This 49-year-old man developed right parietal lobe dysfunction with acute onset. Computed tomography and magnetic resonance imaging (MRI) showed a non-hemorrhagic venous infarct in the subcortical white matter of the right parietal lobe, and diffusely dilated subcortical veins. Thrombosis of the right internal jugular bulb was also revealed on MRI. Cerebral angiography showed a dural AVM in the posterior fossa with occlusion of the right transverse sinus and retrograde venous drainage into the superior sagittal sinus, causing diffuse engorgement of the superficial cortical and the deep intramedullary veins. The focal neurologic deficits in this case were due to a non-hemorrhagic venous infarct in the subcortical white matter of the right parietal lobe secondary to retrograde cortical venous drainage.

Cystic spinal neurilemmoma on magnetic resonance imaging

We report a complete cystic change of intradural neurilemmoma at the T12-L1 level. T1-weighted MRI images with gadolinium-DTPA clearly enhanced the thin capsule of the cystic tumour.

Locations of cerebral infarctions in tuberculous meningitis

The locations of cerebral infarctions were studied in 14 patients with tuberculous meningitis (TBM) and 173 patients with noninflammatory ischemic stroke (IS). In patients with TBM, 75% of infarctions occurred in the "TB zone" supplied by medial striate and thalamoperforating arteries; only 11% occurred in the "IS zone" supplied by lateral striate, anterior choroidal and thalamogeniculate arteries. In patients with IS, 29% of infarctions occurred in the IS zone, 29% in the subcortical white matter, and 24% in (or involving) the cerebral cortex. Only 11% occurred in the TB zone. Bilaterally symmetrical infarctions of the TB zone were common with TBM (71%) but rare with IS (5%).

MR imaging in radiation myelopathy

PURPOSE

Using MR imaging, we assessed the signal, size, and enhancing characteristics of the cervical cord in patients in whom radiation myelopathy developed after radiotherapy for nasopharyngeal carcinoma.

PATIENTS AND METHODS

Ten patients, 3 men and 7 women, aged from 32 to 77 years, were included. MR imaging was performed 1 to 53 months after clinical manifestations of myelopathy.

RESULTS

Two cases showed atrophy of the cervical cord without abnormal signal intensity; in the others, a long segment of the cervical cord demonstrated low signal intensity on T1-weighted images and high signal intensity on T2- or T2*-weighted images. Some of these cases also showed swelling of the cord. Focal enhancement at C1-C2 area after intravenous administration of Gd-DTPA was seen in four cases.

CONCLUSIONS

There is a correlation between the time of MR imaging after onset of symptoms and MR findings. When MR scans were obtained more than 3 years after onset of symptoms, atrophy of the cervical cord was noted without abnormal signal intensity. When MR was performed less than 8 months after onset of symptoms, a long segment of the cervical cord demonstrated abnormal signal intensity with or without associated swelling of the cord and focal enhancement.

Tissue localization of methotrexate-monoclonal-IgM immunoconjugates: anti-SSEA-1 and MOPC 104E in mouse teratocarcinomas and normal tissues

Methotrexate (MTX) was coupled to the tumor-targeting monoclonal IgM, anti-SSEA-1 and the non-targeting myeloma IgM, MOPC 104E. At 24-h intervals following injection, drug deposition in MH-15 teratocarcinomas and in several normal tissues was followed by immunoperoxidase microscopy using the M16 monoclonal antibody to MTX. MTX-anti-SSEA-1 was deposited on the surface and in the interior of living tumor cells 24 h after injection; at 48 h and after, only low-level binding to necrotic tissue was found. There was no significant gradation in staining from the outside to the interior of the tumors. In tumors, the control MOPC 104E immunoconjugate was detectable only in necrotic tissue. Binding to SSEA-1-expressing normal tissues was undetectable, except for pericryptal fibroblasts in the small intestine. No significant pathology was found in normal tissues that are SSEA-1 positive. High levels of the immunoconjugate were detected in the liver, where MTX was found predominantly in Kupffer cells and possibly in hepatocytes; again, no significant morphological changes were associated with this retention. Thus tumor-associated antigens can be suitable targets for antibody-drug conjugates even when present in normal tissues and in large quantities, provided that the antigens in normal tissues are inaccessible. Moreover, deposition in viable tumor tissue can be assessed using monoclonal antibodies to methotrexate.

MRI of sequela of transverse myelitis

A 4-year-old boy developed acute paraplegia, associated with sensory impairement and bowel and urinary dysfunction after an URI. MRI showed diffuse hyperintensity in T2WI in the spinal cord below the T6 level. Acute transverse myelitis was diagnosed based on the clinical presentations and MRI findings. The patient had poor recovery and two months later, a follow-up MRI disclosed a severe diffuse atrophic change of the spinal cord in the affected segment.

Internal carotid artery occlusion in painful ophthalmoplegia

Two patients with left painful ophthalmoplegia, caused by infiltrating lesion in left superior orbital fissure and/or cavernous sinus, subsequently developed left cerebral infarction associated with occlusion of the proximal portion of left internal carotid artery demonstrated by CT and angiogram. It thus is worthy to remind that painful ophthalmoplegia may have the possibility of resulting in cerebral infarction associated with carotid occlusion.

[Detection of physiological deposition of iron in the brain using 1.0-T high field MR]

It has been well documented that high field magnetic resonance imaging can detect the location of physiological deposition of iron in the brain; such as in the globus pallidus, red nucleus, substantia nigra and dentate nucleus. The areas depict very low signal intensity in the long TR and the long TE imaging (T2 weighted image), because the iron enhances the T2 relaxation time. The purpose of this study was to determine the detectability of iron deposition in the brain by our 1.0-T high field MR, compared with 1.5-T MR which was used by most authors. We collected 160 MRI cases of the brain, and observed also signal void areas in the basal ganglion, brainstem or cerebellum. Our T2WI was TR 2000-3000 msec, TE 80-120 msec. We found that the 1.0-T MR clearly detected the iron deposition in the globus pallidus, red nucleus, substantia nigra and dentate nucleus of adults, with additional areas in the putamen and caudate nucleus of aged people. Shortcomings of the 1.0-T MRI for detecting iron deposition include: the margin of iron deposition was not very sharp in some cases, and for children under detectability was markedly inferior to the 1.5-T MR.

Isolation of variants of Chinese hamster ovary cells with abnormally low levels of GSH: decreased ability to cleave endocytosed disulfide bonds

Mutants of Chinese hamster ovary cells were selected for resistance to a 3 hour exposure to 4 microgram/ml N-methyl-N'-nitro-N-nitrosoguanidine and tested for glutathione (GSH) levels. Six of eight clones that survived the initial treatment had reduced GSH levels ranging from 26 to 61% of wild-type values. These eight cell lines were tested for their susceptibility to a drug conjugate in which methotrexate (MTX) is disulfide-linked to poly(D-lysine) (MTX-SS-PDL) to test their capacity to cleave the endocytosed disulfide bond and release free MTX from this otherwise undegradable drug conjugate. We had shown that wild-type cells were killed by approximately 1 x 10(-7) M MTX given as free drug, as MTX-poly(L-lysine) or as MTX-SS-PDL, but were not affected by MTX-poly(D-lysine). All six lines with abnormally low levels of GSH were resistant to MTX-SS-PDL. The variants with the lowest levels of GSH (MNR-5 and MNR-10) were tested further and showed near-normal sensitivity to MTX and MTX poly(L-lysine). As expected, both lines were hypersensitive to melphalan. They were, however, normally sensitive to diphtheria toxin and ricin, indicating that some cleavage of the interchain disulfides in these protein toxins occurs even when cellular GSH is abnormally low. The lesser GSH requirement for toxin activation may be due to their extraordinary potency.

Chronic osteomyelitis with epidural abscess: CT and MR findings

A case of chronic osteomyelitis in the occipital bone associated with underlying chronic epidural abscess was diagnosed by skull radiography, CT, and MR. Skull radiography showed diffuse sclerosis of the occipital bone and dural calcifications. Computed tomography demonstrated thickened sclerotic changes of the osteomyelitic area, dural calcifications, and epidural fluid collection. The area of chronic osteomyelitis displayed, essentially, no signal intensity in the T1-weighted and T2-weighted MR images. The chronic epidural abscess had heterogeneous signal intensity on T1-weighted images and good enhancement after Gd-diethylenetriamine pentaacetic acid administration. On T2-weighted images the abscess had relatively homogeneous high signal intensity.

Magnetic resonance imaging in two patients with radiation myelopathy

Findings of magnetic resonance imaging (MRI) in 2 patients with radiation myelopathy are reported. One patient developed Brown-Séquard syndrome 7 months after radiotherapy for carcinoma of the nasopharynx. MRI done 8 months after clinical manifestations revealed long segmental enlargement of the cervical cord, low signal intensity on T1-weighted images and high signal intensity on T2-weighted images of the cervical cord. The other patient presented with bulbar palsy and Brown-Séquard syndrome 4 years after radiotherapy for carcinoma of the nasopharynx. MRI done 1 month after clinical manifestations showed a high signal intensity area on T2-weighted images of the medulla oblongata and the higher cervical cord. These findings corresponded well with the neurological level. In a proper clinical setting, findings of MRI may be helpful in the diagnosis of radiation myelopathy.

Polylysine conjugates of Bowman-Birk protease inhibitor as targeted anti-carcinogenic agents

Bowman-Birk protease inhibitor (BBI), an 8000 mol. wt polypeptide with anti-carcinogenic activity, was coupled to poly(D-lysine) (BBI-SS-PDL) and poly(L-glutamate) (BBI-SS-PLG) with a disulfide-cross-linking agent, N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP). In vitro transformation assays showed that BBI-SS-PDL, but not BBI-SS-PLG, retained the full anticarcinogenic activity of BBI. When administered i.v. to Balb/c mice, a selective localization in the lungs was found with BBI-SS-PDL but not with BBI or BBI-SS-PLG. At 30 min, 3 h and 24 h after the injection of BBI-SS-PDL, the amounts of BBI in the lungs were 118%, 74% and 19% of the injected dose/g of tissue respectively. At the same time points, the amount of radioactivity in the lungs of mice injected with BBI was 5%, 3% and 1% of the injected dose/g of tissue respectively. Therefore, higher amounts of BBI could be targeted to the lungs by injecting BBI as a PDL conjugate. BBI-SS-PDL was also retained in the lungs for a longer period of time than free BBI. In previous studies, BBI has been shown to suppress lung carcinogenesis. The results presented here suggest that BBI-SS-PDL could be more effective than BBI as an anti-carcinogenic agent for the lung.

Effects of deoxycholate on the transepithelial transport of sucrose and horseradish peroxidase in filter-grown Madin-Darby canine kidney (MDCK) cells

Madin-Darby canine kidney (MDCK) epithelial cells grown on microporous polycarbonate filters were used as a model system to investigate the mechanisms of enhancement by deoxycholate in the transepithelial transport of horseradish peroxidase (HRP) and 14C-sucrose. Deoxycholate at 0.025% had no effect on the transepithelial electrical resistance (TEER); a fivefold enhancement on the transepithelial transport of HRP, but not on that of 14C-sucrose, was observed. Deoxycholate at 0.05% induced a reversible decrease of TEER; a 2- and 50-fold enhancement on the transepithelial transport of 14C-sucrose and HRP, respectively, was observed. At 0.1%, deoxycholate induced an irreversible decrease in TEER and the epithelial barrier in the cell monolayer was completely eliminated. A 3.3-fold increase in cellular uptake in HRP, but not in 14C-sucrose, was also observed in the presence of 0.025% deoxycholate. The increase in cellular uptake was abolished when HRP was conjugated to polylysine. These results suggest that deoxycholate can increase the transepithelial transport by at least two different mechanisms, i.e., a transcellular pathway, possibly due to the enhancement of cellular uptake of selective molecules, and a nonselective paracellular pathway, due to the loosening of tight junctions by deoxycholate at higher concentrations.

[MRI of white matter pathways]

CT scan shows some relatively large white matter pathways such as corpus callosum or internal capsule, while MRI provides more sophisticated display of cerebral white matter pathways, based partly on difference in the water content, which improves contrast resolution of structures that cannot be appreciated on CT scanning. The white matter shows slightly high signal intensity in T1WI as compared with the peripheral gray matter. In contrast, it is relatively low signal intensity in long TR sequence. The signal intensity is correlated with myelination, density of myelin fibers and possibly iron deposition. In this study, we collected data on 30 patient, aged from 3 to 60 years average 38 years of normal MRI study of the brain. We routinely obtained T1 Weighted image (T1WI, TR/TE 500-600/20 msec), dual echoes image of proton density image (PDI, TR/TE 2000-3000/20 msec), T2 weighted image (T2WI, TR/TE 2000-3000/80-120 msec), in axial and coronal sections. In some cases sagittal section was also imaged. We identified the white matter pathways based on the data from the axial and coronal sections of 2 autopsy specimens. We also consulted several textbooks and literature reviews of gross and MRI anatomy. The following white matter pathways could be clearly observed on MRI: 1. Projection fibers: corona radiata and internal capsule; 2. Commissural fibers: corpus callosum and anterior commissure; 3. Associated fibers: superior occipito-frontal fasciculus, superior longitudinal fasciculus, ucinate fasciculus, cingulum bundle, optic radiation fornix and mammillothalamic tract.

Cleavage of disulfide bonds in endocytosed macromolecules. A processing not associated with lysosomes or endosomes

Whereas there is biological evidence that the reductive cleavage of disulfide bonds is critical for the activation of endocytosed macromolecules such as toxins, immunotoxins, and other drug carriers, virtually nothing is known about the specifics of this cleavage. To study this process, a model compound was synthesized in which a radioiodinated tyramine was linked through a disulfide bond to an undegradable carrier, poly(D-lysine), known to be efficiently endocytosed. Cultured Chinese hamster ovary cells were pulse-labeled with this probe, and the disulfide cleavage was measured as released acid-soluble radioactivity at different times of chase. Pulse-labeled cells were also subjected to subcellular fractionation to identify intracellular structures associated with disulfide cleavage. Cleavage began without lag, amounted to about approximately 7% of the initial cell-bound radioactivity in the first hour and continued for more than 6 h. It was abolished in the presence of N-ethylmaleimide. When sulfhydryl groups present at the cell surface were blocked with cell-impermeant sulfhydryl reagent, the initial phase of disulfide cleavage was inhibited, indicating that cleavage began at the cell surface. A long-lasting intracellular phase of disulfide cleavage began after about approximately 30 min of chase. Subcellular fractionation and kinetic analysis indicated that neither lysosomes nor endosomes were participating in that phase, leaving the Golgi apparatus as the most probable site of endocytic disulfide cleavage.

Transcellular processing of disulfide- and thioether-linked peroxidase--polylysine conjugates in cultured MDCK epithelial cells

Horseradish peroxidase (HRP) was conjugated to nondegradable polycationic poly(D-lysine) (PDL) through either a thioether (HRP-S-PDL) or a disulfide (HRP-SS-PDL) linkage. The binding and transcytosis of these conjugates was studied in Madin-Darby canine kidney (MDCK) cell monolayers grown on 3-microns microporous polycarbonate filters. Conjugation of HRP to PDL with both linkages markedly increased the binding of this protein onto the cell monolayers. However, an enhancement of the transcellular transport of HRP in both apical-to-basal and basal-to-apical directions was observed only in HRP-SS-PDL, but not in HRP-S-PDL. HRP-SS-PDL transport was inhibited by colchicine and by 4 degrees C incubation. The transport of 14C-sucrose was not affected by the presence of conjugates. These results indicate that the transport of the conjugate across the cell monolayers was due to a transcellular process rather than to any leakage of the cell junction caused by polycations. The disulfide linkage between HRP and PDL was cleaved rapidly at the basal and, to a lesser extent, at the apical surface of the cell. Neuraminidase treatment decreased the binding of the conjugates onto the cell surface, but did not decrease the transcellular transport, suggesting that not all surface-bound conjugates were available for transcytosis. These results demonstrate that disulfide linkages can be cleaved during transcytosis in MDCK cells. The cleavage, however, occurs mostly at the binding site on the cell surface, which may prevent the cellular uptake of the intact conjugate.

Acid-sensitive dissociation between poly(lysine) and histamine-modified poly(glutamate) as a model for drug-releasing from carriers in endosomes

Histamine was coupled to poly(L-glutamate) (PLG) to give a copolymer, poly(glutamylhistamineglutamate) (PHG), with approx. 40% of carboxyl groups in PLG being modified. Unlike either poly(L-histidine) (PLH) or PLG, PHG precipitated only in buffers with pH between 4 and 5. A complex was formed between PHG and poly(L-lysine) (PLL) at pH 7, but it was rapidly dissociated at pH 5 or lower. When PHG-linked transferrin (Tf-PHG) was used to deliver a PLL-conjugated [3H]methotrexate ([3H]MTX-PLL) in K562 leukemia cell cultures, an intracellular accumulation of the radioactivity was observed. These results suggest that a copolymer with both imidazole and carboxyl groups can be useful in the design of acid-sensitive, carrier-mediated drug delivery systems.

Proteolytic processing in a non-lysosomal compartment is required for transcytosis of protein-polylysine conjugates in cultured Madin-Darby canine kidney cells

The transcytosis of horseradish peroxidase, as well as its poly(L-lys) and poly(D-lys) thioether conjugates, was investigated in Strain I Madin-Darby canine kidney (MDCK) cell monolayers grown on 0.4 microns pore size polycarbonate membranes in Costar Transwells. The 3 types of HRP had almost identical rates of transport during the first 2 hr of incubation. However, a significant increase of basal-to-apical transport was detected beginning at 3 hr only in Transwells containing the poly(L-lys) conjugate. This increase was inhibited by colchicine (2 microM) and by the Bowman-Birk protease inhibitor (0.1 mg/ml), but not by NH4Cl (10 mM) or chloroquine (0.1 mM). The increase was abolished either by prior trypsinization of the conjugate or by incubation at 4 degrees C. Ultrafiltration studies indicated that the transcytosed poly(L-lys) conjugate was smaller in size than the original conjugate. These results indicate that the conjugate was processed during transcytosis in a non-lysosomal proteolytic compartment, where its poly(L-lys) moiety was selectively degraded, allowing active peroxidase to be released into the apical medium.

A cytostatic protein isolated from the conditioned medium of mouse monocytic leukemia WEHI-3 cell cultures

A cytostatic factor (CF) with a molecular mass of 50 kDa was purified to more than 16,000-fold from the conditioned medium of LPS-treated mouse myelomonocytic leukemia (WEHI-3) cell cultures. The activity of CF was completely destroyed by heating at 70 degrees C for 10 min, 50 degrees C for 30 min, or by the treatment in pH 3 buffer for 2 h. CF showed a strong growth inhibitory effect on CHO cells, as well as several other unrelated cell lines, e.g., K562 and L1210, but not on L929 cells. It also inhibited Con A-induced mitogenesis in mouse and rat spleen cells. The growth inhibitory effect of CF, however, was highly reversible; CHO cells were able to regain the normal growth after removal of the factor from the culture medium. Our results suggest that CF is a protein secreted by WEHI-3 cells, which is distinct from other known macrophage- or tumor-derived cytotoxic proteins.

In vivo antitumor effect of methotrexate conjugated to a monoclonal IgM antibody specific for stage-specific embryonic antigen-1, on MH-15 mouse teratocarcinoma

Methotrexate (MTX) was coupled to an IgM monoclonal antibody specific for stage-specific embryonic antigen-1 (SSEA-1), and the resulting immunoconjugate (MTX-anti-SSEA-1) was used for in vivo drug targeting in mice bearing MH-15 teratocarcinoma. Immunoconjugates having an average of 65 mol MTX/mol antibody retained full antigen-binding capacity. Mice bearing well-established tumors (approx. 1 g) were treated i.v. using the immunoconjugate. MTX-anti-SSEA-1 at 15 mg/kg of drug had significant antitumor activity with no significant systemic toxicity. Neither an irrelevant isotype-matched conjugate, MTX-MOPC-104E, prepared from the MOPC 104E myeloma protein, nor free MTX injected alone or with either antibody had any significant antitumor effect. These results indicate that IgMs can be effective drug carriers for tumor targeting in spite of their high molecular mass, and that antigens that are selectively accessible in tumors, even though present in normal tissues, can be suitable targets for in vivo chemoimmunotherapy.

Increase of poly(L-lysine) uptake but not fluid phase endocytosis in neuraminidase pretreated Madin-Darby canine kidney (MDCK) cells

The uptake of Poly(L-lysine) conjugates in cultured cells has been used as a model for non-specific adsorptive endocytosis of cationic macromolecules. To study the effect of glycocalyx desialylation on the uptake of cationic macromolecules in epithelial cells, Madin-Darby canine kidney (MDCK) cell monolayers were treated with neuraminidase and incubated with Poly(L-lysine) conjugates. Neuraminidase pretreatment of MDCK cells resulted in a 40% increase in the uptake of Poly(L-lysine) whereas trypsin pretreatment did not. Neuraminidase pretreatment did not increase the endocytosis of fluid phase markers in MDCK cells, nor the uptake of Poly(L-lysine) in L929 fibroblasts. These results suggest that the negative charges, rather than the glycoprotein matrices of glycocalyx, play an important role in the control of the uptake of cationic macromolecules in epithelial cells.

Stable variant of LM fibroblast defective in fluid-phase but competent in receptor-mediated endocytosis

The F-40 cell line, a stable variant of LM fibroblasts selected for its resistance to polyethylene glycol (PEG)-induced fusion (Roos and Davidson: Somatic Cell and Molecular Genetics 6:381-391, 1980), has a decreased capacity to internalize fluid-phase markers and nonspecifically surface-bound macromolecules. It is not defective in exocytosis since, after a short sucrose pulse, it releases the same fraction of ingested sucrose into the medium as does the parental line. F40 cells have a normal capacity to carry out receptor-mediated endocytosis, as tested with 125I-alpha-2 macroglobulin (alpha-2 MG) and 125I-transferrin (Tf), and to recycle Tf receptor to the cell surface. These data demonstrate that receptor-mediated and non-receptor mediated endocytosis are distinct processes that can be altered independently. Of the many membrane fusions occurring in the course of endocytosis, the only one that appears associated with the defect in cell fusion characteristic of F40 cells is the formation of primary endocytotic vesicles engaged in non-receptor-mediated internalizations.

Methotrexate-poly(lysine) as a selective agent for mutants of Chinese hamster ovary cells defective in endocytosis

Methotrexate (MTX) covalently linked to poly(L-lysine) [poly(Lys)] enters cells by endocytosis, is degraded in lysosomes and, upon liberation of small molecular methotrexate, is cytocidal to Chinese hamster cells in culture. This drug conjugate was used to select mutants resistant to MTX-poly(Lys), which were examined for defects in endocytosis. Two mutants resistant to MYX-poly(Lys) and sensitive to free MTX, MPL 3-4 and MPL 2-5, internalized the conjugate in normal fashion, but had a decreased ability to degrade it to small molecular drug. The magnitude of this defect in the two mutants correlated with their level of resistance. In addition, both mutants were cross resistant to diphtheria toxin and modeccin and hypersensitive to ricin. While MPL 3-4 internalized MTX-poly(Lys) and inulin normally, it showed decreased endocytosis via the mannose-6-phosphate receptor and decreased uptake of 125I-alpha-2 macroglobulin. Acidification of subcellular fractions was measured using the partitioning of acridine orange. In MPL 3-4, the ATP-driven acidification of the endosome-containing cell fractions was slightly decreased (80% of controls), while acidification of the heavy lysosome-containing fraction was normal. Complementation analysis using hybrids of MPL 3-4 x MPL 2-5 indicated that the mutations occurred at the same gene, but were expressed with different severity. This genotype is identical to that of the End 2 mutants described by Roff et al. (1986). Thus, surprisingly, mutants with identical genotypes were isolated independently by totally different selection procedures.

Targeting, internalization, and cytotoxicity of methotrexate-monoclonal anti-stage-specific embryonic antigen-1 antibody conjugates in cultured F-9 teratocarcinoma cells

Methotrexate (MTX) conjugates of a monoclonal antibody, anti-SSEA-1, containing an average of 45 mol MTX/mol of immunoglobulin M, were prepared by a carbodiimide coupling reaction. Binding experiments indicate that conjugation does not decrease the affinity of the antibody for its antigen. The conjugate strongly inhibits the growth of SSEA-1-bearing F-9 teratocarcinoma cells, with 50% inhibitory dose of 4.5 nM MTX, which makes it more active than free MTX (50% inhibitory dose of 15 nM). The drug-free antibody is not cytotoxic to F-9 cells at the concentrations used. The high efficacy of the conjugated drug may be due in part to the fact that anti-SSEA-1 antibody is an immunoglobulin M. MTX conjugated to nonspecific immunoglobulin M has little inhibitory effect (50% inhibitory dose of 150 nM). When acting on SSEA-1 negative cells, the two conjugates have only a small but identical effect. Thiamine pyrophosphate, an inhibitor of MTX transport, can prevent the cytotoxicity of the free MTX but not that of the anti-SSEA-1 conjugate. Leupeptin, an inhibitor of lysosomal protease, can partially protect F-9 cells against the antibody conjugate but not against free MTX. These results indicate that the MTX antibody conjugate binds specifically to F-9 cells, and is internalized and intracellularly degraded to release a small molecular active drug. Pretreatments of F-9 cells for 1 h with unlabeled antibody inhibits the subsequent uptake of identical concentration of labeled conjugate. The rate of internalization, however, regains almost normal values within 4 h, indicating a rapid reappearance of free antigenic sites at the cell surface.

Altered endocytosis in a mutant of LM fibroblasts defective in cell-cell fusion

Mutants of LM fibroblasts selected for their decreased ability to undergo polyethylene glycol-induced cell-to-cell fusion (F40 subline) were examined for possible alterations of their ability to carry out endocytosis. Both fluid-phase endocytosis of inulin and horseradish peroxidase and nonreceptor mediated adsorptive endocytosis of poly(L-lysine) were reduced to 60% of control values. Comparable results were obtained when the uptake of poly(L-lysine) was measured as internalization of surface-bound label in label-free medium or following continuous exposure. Accelerated breakdown of internalized label was ruled out as a cause for decreased label accumulation. Accelerated exocytosis is an unlikely cause, and it is suggested that the decreased uptake is due to a decrease in the constitutive membrane vesiculation process that leads to the formation of endocytotic vesicles. The capacity of F40 cells to degrade internalized horseradish peroxidase and poly(L-lysine) was not impaired, nor was their susceptibility to the cytotoxic action of methotrexate-poly(L-lysine). This drug conjugate must be degraded inside cells and release small molecular methotrexate in order to be cytocidal. These data suggest that only the first step of nonspecific endocytosis is impaired, while the subsequent steps that require fusion of endosomes to lysosomes proceed normally. Since the formation of primary endosomes requires membrane fusion through the external aspect of the plasma membrane and in that respect resembles cell-cell fusion, we propose the hypothesis that the observed decrease in endocytosis is related to the decreased ability of F40 cells to fuse with each other, and reflects a decreased efficiency of fusion processes at the external face of the plasma membrane.

Tumor location and drug targeting using a monoclonal antibody (anti-SSEA-1) and antigen-binding fragments

Both murine and heterotransplanted human nonseminomatous germ-cell tumors have been successfully located by external scintigraphy using radioiodinated anti-SSEA-1, a monoclonal IgM, and its pepsin-derived antigen-binding fragment, F(ab')2 mu. Antibody localization in the tumor is mainly due to antigenic specificity, rather than to nonspecific trapping, and depends strongly on the amount of time after injection. The antibody has been used for drug targeting in vitro and in vivo.

Disulfide spacer between methotrexate and poly(D-lysine). A probe for exploring the reductive process in endocytosis

Poly(D-lysine) is taken up avidly by cultured cells through adsorptive endocytosis and can serve as a carrier to increase cellular uptake of other molecules. While direct conjugation of methotrexate to poly(D-lysine) yields a conjugate devoid of cytotoxic effects because poly(D-lysine) is not digested in lysosomes, the indirect conjugation using a triglycine spacer or a disulfide spacer strongly inhibits the growth of both the wild type and the methotrexate transport-defective Chinese hamster ovary cells. Cell treatment with 3 mM NH4Cl or 50 micrograms/ml leupeptin prevents the effect of conjugate with the triglycine spacer, but not of conjugate with the disulfide spacer. On the other hand, preincubation with 2-mercaptoethanol abolishes the effect of the drug-disulfide conjugate in the methotrexate transport-defective mutant, but not the effect of the drug-triglycine conjugate. The disulfide conjugate shows an identical cytotoxic effect in alpha-minimal essential medium and RPMI 1640 media, even though cells grown in the latter have only half the glutathione content as cells grown in the former medium. We conclude that the reductive process through which methotrexate is released from the disulfide spacer (a) occurs inside cells and not at the cell surface, (b) requires neither acid pH nor lysosomal enzymes, and (c) is not mediated by a glutathione-disulfide exchange reaction requiring high glutathione concentrations. Although the cellular compartment in which this reductive process occurs is not yet identified, there are reasons to assume that it is prelysosomal.

Colorimetric determination of microgram quantities of polylysine by trypan blue precipitation

A simple and sensitive method for the determination of polylysine in solution is described. Polylysine is quantitatively precipitated with trypan blue. The absorbance of unbound dye in the supernatant is inversely proportional to the concentration of this polyamino acid. The precipitation is identical for all sizes of polylysine of molecular weight 13,000 or higher, and is prevented by the addition of either polyanions or serum. The measurable range of polylysine hydrobromide is between 1 and 10 micrograms/ml, which is about 10-fold lower than that by the published methyl orange precipitation method.

Binding sites and endocytosis of heparin and polylysine are changed when the two molecules are given as a complex to Chinese hamster ovary cells

This paper characterizes the complex formed in vitro between polylysine and heparin in the presence of heparin excess, and investigates the interaction of this complex with the surface of Chinese hamster ovary cells. It examines the kinetics of surface binding and cellular uptake of the complex and shows that both processes can be distinguished from those of free heparin and free polylysine. The view that these three ligands bind to different surface sites is further supported by the fact that their interaction with cells is influenced differently by cell detachment with trypsin, detachment with EGTA or exposure to acid pH. Membrane transport of the complex is a saturable process suggestive of receptor-mediated endocytosis. It is, however, less effective than would be expected on the basis of the binding kinetics. Only 40% of the complex bound at 0 degrees C is internalized during a 2 h reincubation period at 37 degrees C, suggesting some degree of uncoupling between binding and endocytosis. These data confirm prior results obtained with methotrexate-polylysine conjugates. We had shown that the addition of heparin to a medium containing a methotrexate-polylysine conjugate leads unexpectedly to a marked cellular uptake of drug conjugate, which is capable of killing cells that are otherwise resistant to free methotrexate (Shen, W.-C. and Ryser, H.J.-P. (1981) Proc. Natl. Acad. Sci. USA 78, 7589-7593). The polylysine X heparin complex is therefore of interest as a potential carrier for intracellular drug delivery through endocytosis.

Selective killing of Fc-receptor-bearing tumor cells through endocytosis of a drug-carrying immune complex

A soluble immune complex was used as a drug carrier targeted to Fc-receptor-positive cells. Two receptor-positive tumor cell lines, WEHI-3 and M5076, were exposed to methotrexate-human serum albumin conjugate (MTX-HSA) in the presence and absence of anti-HSA antiserum. Both cell types were killed by 30 nM MTX when the drug conjugate was given in the presence of antiserum but were totally unaffected in the absence of antiserum. Drug-free HSA given with antiserum had no effect. Both cell lines responded similarly despite their marked difference in phagocytotic activity. One of the two lines, M5076, is defective in MTX transport and hence resistant to free MTX. Since this line would not be affected by MTX released extracellularly from MTX-HSA, its susceptibility implies that MTX is released inside cells, after endocytosis of the complex, and that endocytosis circumvents the transport defect. Two cell lines lacking Fc receptors (CHO and L929) were not influenced by the drug complex. The pharmacologic effect is mediated by a specific ligand-receptor interaction, since Fc receptor-positive cells are protected by an excess of unconjugated HSA and by the addition of a small amount of staphylococcal protein A, which binds to the Fc portion of IgG. These data demonstrate that Fc receptors can be exploited for cellular drug delivery using a common antigen-antibody complex as a drug carrier.

Heparin interaction with cultured cells: possible role of fibronectin in uncoupling surface binding and endocytosis

Cellular uptake of 3H-heparin by cultured Chinese hamster ovary cells does not follow the pattern that would be expected on the basis of binding kinetics. It is essentially non-saturable and its low pinocytotic index is consistent with fluid-phase endocytosis, while surface binding is saturable and suggests the presence of specific receptors. Most of the surface-bound heparin is released into the medium and only minimal amounts are internalized when temperature is shifted from 0 degree to 37 degrees C. This uncoupling of surface binding and endocytosis may be due to the binding of heparin to an external surface macromolecule that is only loosely attached to the plasma membrane, and may therefore escape endocytosis. Fibronectin is a likely candidate to provide that type of binding site. Heparin has been found to bind specifically to a number of mammalian cells (Kjellen et al., 1977; Glimelius et al., 1978; Shanberge et al., 1976; Fabian et al., 1978), but no attempt was made in those studies to distinguish between surface binding and cellular uptake. Heparin is transported into cells when complexed to other macromolecules (Fabian et al., 1978; Shen and Ryser, 1981; Morad et al., 1982) and does then exert some cellular effects (Shen and Ryser, 1981). Despite the wide clinical use of heparin, little is known about its membrane transport and intracellular effects, although endocytosis of other polyanions has been shown to inhibit phago-lysosomal fusion in macrophages (Geisow et al., 1980).(ABSTRACT TRUNCATED AT 250 WORDS)