Isolation of pheromone precursor genes of Magnaporthe grisea

In heterothallic ascomycetes one mating partner serves as the source of female tissue and is fertilized with spermatia from a partner of the opposite mating type. The role of pheromone signaling in mating is thought to involve recognition of cells of the opposite mating type. We have isolated two putative pheromone precursor genes of Magnaporthe grisea. The genes are present in both mating types of the fungus but they are expressed in a mating type-specific manner. The MF1-1 gene, expressed in Mat1-1 strains, is predicted to encode a 26-amino-acid polypeptide that is processed to produce a lipopeptide pheromone. The MF2-1 gene, expressed in Mat1-2 strains, is predicted to encode a precursor polypeptide that is processed by a Kex2-like protease to yield a pheromone with striking similarity to the predicted pheromone sequence of a close relative, Cryphonectria parasitica. Expression of the M. grisea putative pheromone precursor genes was observed under defined nutritional conditions and in field isolates. This suggests that the requirement for complex media for mating and the poor fertility of field isolates may not be due to limitation of pheromone precursor gene expression. Detection of putative pheromone precursor gene mRNA in conidia suggests that pheromones may be important for the fertility of conidia acting as spermatia.

Dynamic helical biphasic CT emerges as a potential tool for the diagnosis of proximal arterioportal shunting

BACKGROUND/AIMS

This article reports our preliminary observation regarding the diagnostic ability of dynamic helical biphasic computed tomography (CT) for proximal arterioportal shunting in hepatoma patients as compared with that of conventional angiography.

METHODOLOGY

Three hundred and sixty patients with clinically-suspected liver lesions received both dynamic helical biphasic CT scan and conventional angiography of the liver. The criteria for diagnosis of proximal arterioportal (AP) shunting in dynamic helical biphasic CT included early and strong enhancement of main portal vein or its major branches approaching the density of the aorta, or enhancement of the portal vein earlier than opacification of the splenic vein and superior mesenteric vein in the arterial phase. The angiographic diagnosis of proximal AP shunting was made if there was early opacification of the main portal vein or its major branches in the arterial phase. Peripheral subsegmental small AP shunting was excluded from our study. The existence and extent of AP shunting were compared in these two imaging modalities.

RESULTS

Dynamic helical biphasic CT scan demonstrated proximal AP shunting in 23 patients. All of these patients harbored hepatoma. Conventional angiography showed proximal AP shunting in 20 patients, which were all positive on dynamic helical CT. Dynamic helical biphasic CT demonstrated the presence of proximal AP shunting in 3 more patients than conventional angiography did. The extent of AP shunting was well correlated between these two imaging modalities in 17 patients.

CONCLUSIONS

From our preliminary experience, the diagnostic accuracy of dynamic helical biphasic CT for proximal AP shunting in patients with hepatoma seemed to be comparable to, or even surpassed that of conventional angiography. It seems that faint AP shunting in patients with large hepatoma might be missed by conventional angiography.

Computerized tomographic angiography in the evaluation of cerebral infarction

BACKGROUND

To evaluate the feasibility of computerized tomographic angiography (CTA) for the diagnosis of cerebral infarction.

METHODS

Fourteen patients (nine men, five women; average age, 60 years) who presented with symptoms of acute cerebral infarction underwent computerized tomography (CT) and CTA, using a Picker PQ 2000 Spiral CT. The infarcted area was first evaluated by CT and then occlusive sites of arteries were evaluated by CTA.

RESULTS

In seven patients in the very early stage of acute cerebral infarction involving the middle cerebral artery (MCA) territory, the initial CT did not clearly demonstrate the infarcted area. CTA detected the occlusive site of the MCA and helped anticipate the area of infarction. Follow-up CT confirmed the infarction clearly. CTA was not useful for small infarctions in the basal ganglia, thalamus or brainstem.

CONCLUSIONS

CTA in association with CT is a feasible and good technique for the diagnosis of early-stage acute cerebral infarction. It can detect the occlusive sites in the main arteries, especially the middle cerebral artery, and as of benefit for anticipation of the ensuing edematous area. However, for small infarcts in the basal ganglia, CTA does not provide good diagnostic images.

Proximal arterioportal shunting associated with hepatocellular carcinoma: features revealed by dynamic helical CT

OBJECTIVE

This study investigated the findings revealed by dynamic helical CT of proximal arterioportal shunting associated with hepatocellular carcinoma. We also evaluated the diagnostic capability of this imaging technique to reveal the mass in patients with hepatocellular carcinoma.

CONCLUSION

On dynamic helical CT, proximal arterioportal shunting altered liver perfusion and tumor enhancement. Heterogeneous enhancement of liver parenchyma and decreased enhancement of hepatomas diminished diagnostic capability on the arterial dominant phase image. However, with the addition of imaging in the arterial portal phase, lesion conspicuity improved.

Dynamic helical CT as a novel technique for diagnosing hepatic perfusion disorders

BACKGROUND/AIMS

Perfusion disorders of the liver have seldom been studied by computed tomography (CT). Recent new-generation helical CT by speeding up the scanning time proves it is possible to evaluate these disorders. The purpose of this study is to demonstrate the various patterns of hemodynamic change of the liver in both normal and diseased status by dynamic helical CT technique.

METHODOLOGY

In a period of 1 year, about 1,000 patients received dynamic helical CT examination of the liver due to either clinical suspicion of liver lesions or liver lesions of unknown nature. The examination was performed with a Picker PQ 2000 CT scanner. In total, 100 cc of iodinated contrast agent was injected at a rate of 3.5 cc per second. Two sets of images were acquired at 22 seconds and 75 seconds after the initiation of the contrast injection. Different patterns of hemodynamic change were found and the etiologies and mechanisms were investigated.

RESULTS

Sixty-two cases were found to have perfusion disorder of the liver. Thirty cases were associated with tumors such as hepatoma (17), hemangioma (4) and hepatic metastasis (3). The other 32 cases were non-tumor associated. The perfusion disorders appeared due to liver cirrhosis, anatomic variant, iatrogenic injury, liver abscess, etc. The mechanisms for these perfusion disorders were classified as portal vein compression or thrombosis, arterioportal shunting, hepatic artery encasement, local hyperremic change, aberrant blood supply, steal effect, hepatic venous outflow obstruction, etc. These disorders presented as subcapsular, focal nodular, wedge-shaped, segmental, lobar, or even diffuse in shape and distribution.

CONCLUSIONS

Dynamic helical CT opens a new window for demonstrating and understanding various hepatic perfusion disorders which reflect the hemodynamic change of the liver in both normal and diseased conditions.

Analysis of selective gene activation in yeast by differential display

TATA box binding protein-associated factors (TAF(II)s) are dispensable for transcription of most genes in yeast. To further investigate the in vivo functions of TAF(II)s, differential display was used to identify a small subset of yeast genes whose transcription is dependent on yeast TAF(II)145, the core TAF(II) component that contacts TATA box-binding protein (TBP). Messenger RNA profiles derived from a wild-type TAF(II)145 strain and a temperature-sensitive taf(II)1145 strain were analyzed. Those genes whose messenger RNA level was greatly reduced in the temperature-sensitive taf(II)145 strain were cloned and further characterized. The procedure for performing differential display described here is modified from protocols provided by the manufacturer (Display Systems) and optimized for the yeast system.

Moyamoya disease causes acute subdural hematomas and sudden death: a case report

A 59-year-old woman suffered from sudden onset of severe headache and vomiting for five days, with normal consciousness. A computerized tomography (CT) scan showed acute subdural hematomas in the right frontal and left frontotemporoparietal regions. As there was no history of head injury, the patient underwent bilateral carotid angiography. The left carotid angiogram showed total occlusion of the left middle cerebral and anterior cerebral arteries with a moyamoya pattern of collateral circulation. Five days later, the patient suddenly lost consciousness associated with right hemiparesis. An emergency CT scan disclosed diffuse acute brain tissue edema in the left cerebral hemisphere with uncal/transtentorial herniation, caused by acute infarction in the territory of the left middle cerebral artery. The patient died 10 hours later. The acute infarction was considered to have been caused by subdural hematomas compressing the transdural anastomoses, thus eliminating all blood supply to the region of the left middle cerebral artery.

Molecular identification of a role for tyrosine 167 in the function of the human intestinal proton- coupled dipeptide transporter (hPepT1)

hPepT1 is a proton-coupled peptide transporter that mediates the absorption of di- and tripeptides. Here we show that tyrosine 167 (Y167) in transmembrane domain 5 (TMD5) of this 12-transmembrane spanning protein contributes to its transport function. We identified this particular amino acid by a computer model of the arrangement of the TMDs of hPepT1 and investigated its role by site-directed mutagenesis and dipeptide uptake studies. [3H]Gly-sar uptake in cells transiently transfected with Y167A-hPepT1 was abolished completely, even though the level of Y167A-hPepT1 expression by Western blot analysis and cell surface expression by immunofluorescence microscopy was similar to those of the wild type. Therefore, mutation affected transport function, but apparently not the steady-state protein level or trafficking of the transporter to the plasma membrane. Moreover, mutation of Y167 into phenylalanine, serine, or histidine all abolished gly-sar uptake in transfected HEK 293 cells. Taken together, these findings suggest that Y167 plays an essential role in hPepT1 function, perhaps due to the unique chemistry of its phenolic side chain.

Acute subdural hematoma with subarachnoid hemorrhage caused by an intracranial aneurysm: a case report

The occurrence of a subdural hematoma caused by the rupture of an intracranial aneurysm is rare. In our case, the patient is a 43-year-old woman who suffered from sudden onset of severe headache. Computed tomographic (CT) scan disclosed a subdural hematoma associated with subarachnoid hemorrhage. CT angiography and digital subtraction angiography revealed an elongated aneurysm adhering to the dura in the left Sylvian fissure. The subdural hematoma was evacuated and the aneurysm clipped. The patient made a full recovery.

Myelination arrest demonstrated using magnetic resonance imaging in a child with type I GM1 gangliosidosis

An 18-month-old girl was diagnosed as having GM1 gangliosidosis, on the basis of the clinical symptoms of muscle stiffness, developmental retardation, hepatosplenomegaly, and kyphoscoliosis and a laboratory study that revealed a deficiency in the lysosomal degradative enzyme beta-galactosidase. Magnetic resonance T1-weighted images showed persistent hyperintensity in the bilateral thalami, brainstem, and deep cerebellum at 14 and 18 months of age, indicating arrest of the myelination process in these areas, and that the arrest had occurred at the newborn stage. There was no myelination in the basal ganglia and diffuse leukomalacia developed in the cerebral hemispheres. Only supportive treatment was given; the patient died at 2 years of age. Myelination arrest at the newborn stage associated with progressive leukomalacia is a possible characteristic of GM1 gangliosidosis.

The Neurospora rca-1 gene complements an Aspergillus flbD sporulation mutant but has no identifiable role in Neurospora sporulation

The Aspergillus nidulans flbD gene encodes a protein with a Myb-like DNA-binding domain that is proposed to act in concert with other developmental regulators to control initiation of conidiophore development. We have identified a Neurospora crassa gene called rca-1 (regulator of conidiation in Aspergillus) based on its sequence similarity to flbD. We found that N. crassa rca-1 can complement the conidiation defect of an A. nidulans flbD mutant and that induced expression of rca-1 caused conidiation in submerged A. nidulans cultures just as was previously observed for overexpression of flbD. Thus, the N. crassa gene appears to be a functional homologue of A. nidulans flbD and this is the first demonstration of functional complementation of an A. nidulans sporulation defect using a gene from an evolutionarily distant fungus. However, deletion of the rca-1 gene in N. crassa had no major effect on growth rate, macroconidiation, microconidiation, or ascospore formation. The only phenotype displayed by the rca-1 mutant was straight or counterclockwise hyphal growth rather than the clockwise spiral growth observed for wild type. Thus, if rca-1 is involved in N. crassa development, its role is subtle or redundant.

Yeast TAF(II)145 functions as a core promoter selectivity factor, not a general coactivator

In yeast, TATA box binding protein associated factors (TAF(II)s) are dispensable for transcription of most genes. Here we use differential display to identify a small subset of yeast genes whose transcription in vivo requires yTAF(II)145. Promoter-mapping studies reveal, unexpectedly, that the region of a gene that renders it yTAF(II)145-dependent is not the upstream activating sequence, which contains the activator-binding sites, but rather the core promoter. In fact, a core promoter requiring yTAF(II)145 retained that requirement when its transcription was directed by several unrelated upstream activating sequences and even in the absence of an activator. Taken together, our results indicate that yTAF(II)145 functions in recognition and selection of core promoters by a mechanism not involving upstream activators.

Yeast TAF(II)145 required for transcription of G1/S cyclin genes and regulated by the cellular growth state

TFIID comprises the TATA box-binding protein and a set of highly conserved associated factors (TAF(II)s). yTAF(II)145, the core subunit of the yeast TAF(II) complex, is dispensable for transcription of most yeast genes but specifically required for progression through G1/S. Here we show that transcription of G1 and certain B-type cyclin genes is dependent upon yTAF(II)145. At high cell density or following nutrient deprivation, yeast cells cease division, enter a G0-like state, and terminate transcription of most genes. In this stationary phase, we find that the levels of yTAF(II)145, several other yTAF(II)s, and TBP are drastically reduced. Collectively, our results indicate that yTAF(II)145 and other TFIID components have a specialized role in transcriptional regulation of cell cycle progression and growth control.

Cross-pathway and pathway-specific control of amino acid biosynthesis in Magnaporthe grisea

The gene encoding the small subunit of the arginine-specific carbamoyl phosphate synthetase, ARG2, of Magnaporthe grisea was characterized to examine the basic regulation of biosynthetic genes in this plant pathogen. The transcript of the ARG2 gene contains an upstream open reading frame (uORF) that is similar to uORFs found in the homologous genes of Neurospora crassa (arg-2) and Saccharomyces cerevisiae (CPA1), suggesting that the M. grisea gene is translationally regulated by a mechanism that is conserved in these fungi. Amino acid imbalance leads to elevated levels of ARG2 mRNA, indicating that in addition to translational control, ARG2 is subject to cross-pathway transcriptional control. A DNA-binding activity that has properties similar to those of the global transcriptional regulator mediating cross-pathway control in N. crassa was detected in M. grisea cell extracts. Thus, it appears that both specific regulation of ARG2 by arginine and global regulation of amino acid biosynthesis are present in M. grisea and highly conserved among M. grisea, N. crassa, and S. cerevisiae.

Transcellular delivery of an insulin-transferrin conjugate in enterocyte-like Caco-2 cells

Insulin, acylated with dimethylmaleic anhydride, was conjugated to transferrin (Tf) via a disulfide linkage. The molar insulin: Tf ratio in the conjugate was 3:1. The insulin-Tf conjugate (insulin-Tf) was tested for the transport of insulin across enterocyte-like Caco-2 cell monolayers by the process of transferrin receptor (TfR)-mediated transcytosis. The uptake of insulin-Tf in Caco-2 cells was TfR-mediated but no insulin receptor-mediated. Transport studies showed that insulin-Tf transport was 5- to 15-fold higher than free insulin transport across Caco-2 cells in both apical-to-basal and basal-to-apical directions. Brefeldin A (BFA), an agent that we have previously shown to cause an increase in TfR transcytosis, further enhanced the transport of the conjugated insulin three-fold in both directions; thus, a combination of the conjugate and BFA can cause a net 45-fold increase in the apical-to-basolateral transport of insulin across Caco-2 cell monolayers. The transported conjugate was intact as indicated by elution on a Sephadex G-50 column. Insulin in the transcytosed conjugate, unlike the original dimethylmaleyl insulin, was capable of binding to anti-insulin antibodies, indicating that free amino groups of insulin were regenerated either during or after the transcytotic process. Because Caco-2 cell monolayers provide a good model for intestinal epithelium, the insulin-Tf conjugate in combination with BFA can be a rational approach to increase the oral absorption of insulin in vivo.

Paclitaxel and nocodazole differentially alter endocytosis in cultured cells

PURPOSE

Microtubule-based transport facilitates the endocytosis of exogenous macromolecules. We have determined how microtubule accumulation and disassembly alter endocytosis.

METHODS

The effects of paclitaxel, which promotes microtubule assembly, and nocodazole, which promotes microtubule disassembly, on fluid-phase and receptor-mediated endocytosis were measured using uptake of horseradish peroxidase and 125I-transferrin, respectively. Changes in membrane and microtubule organization were examined by fluorescence microscopy.

RESULTS

Neither paclitaxel (4 microM, 60 min pretreatment) nor nocodazole (1 microgram/ml, 60 min pretreatment) significantly inhibited fluid-phase endocytosis. However, paclitaxel caused a redistribution of fluorescent fluid-phase marker to the periphery. Both paclitaxel and nocodazole treatment significantly (p < or = 0.05) reduced the initial uptake of 125I-transferrin at 5 min to approximately 50% of control. Despite the similarity of the effects on initial endocytic uptake, the effects on steady state accumulation of 125I-transferrin were quite distinct. Exposure of CV-1 cells to paclitaxel for an additional 30, 60 or 90 min also showed reduced accumulation of 125I-transferrin up to a maximum significant (p < or = 0.05) inhibition of 48% +/- 10% of control at 90 min. In contrast, nocodazole caused an initial significant (p < or = 0.05) increase in 125I-transferrin accumulation after 30 min (159% +/- 13% of control), while by 90 min 125I-transferrin accumulation had returned to control levels. Microtubule content, particularly of stable microtubules, was increased in CV-1 cells by paclitaxel, but abolished by nocodazole treatment.

CONCLUSIONS

Our data show that changes in the microtubule array can alter the dynamics of receptor movement through the endosomal pathway. However, microtubule assembly versus disassembly have different effects.

Comparison of pharmacokinetic parameters of a polypeptide, the Bowman-Birk protease inhibitor (BBI), and its palmitic acid conjugate

PURPOSE

The alteration of the pharmacokinetic parameters of the polypeptide BBI through conjugation with palmitic acid was examined.

METHODS

125I-BBI or 125I-Pal-BBI was administered iv to 6 week old CF-1 mice at a dose of 3 mg/kg. The mice were sacrificed at 5, 10, 20, 60, 120, 240, 360, and 480 min and the total radioactivity was determined for blood and each organ. The blood was analyzed on a Sephadex G-50 size-exclusion column to determine the amount of intact polypeptide present in the blood. From the amount of intact polypeptide at each time point, the pharmacokinetic parameters were determined.

RESULTS

By conjugating three palmitic acids to each BBI molecule, the area under the curve (AUC) and mean residence time (MRT) increase by a factor of 10.8 and 2.8, respectively. There was also a difference in the organ distribution between the two treatments; while 125I-BBI was rapidly cleared from the kidneys, 125I-Pal-BBI was predominantly to the liver. Subsequent studies suggested that the binding of the conjugate to non-albumin serum proteins was most likely the cause of the altered pharmacokinetics.

CONCLUSIONS

The residence time in the blood and the lipophilicity of BBI were increased upon conjugation with palmitic acid through a reversible disulfide linkage. Pharmacokinetic studies showed an increase in the AUC and a decrease in kidney clearance in palmitic acid conjugates, indicating a potential increase of the therapeutic efficacy of the polypeptide drug.

Nucleus-associated pools of Rna1p, the Saccharomyces cerevisiae Ran/TC4 GTPse activating protein involved in nucleus/cytosol transit

Rna1p is the GTPase activating enzyme for Ran/TC4, a Ras-like GTPase necessary for nuclear/cytosolic exchange. Although most wild-type Rna1p is located in the cytosol, we found that the vast majority of the mutant Rna1-1p and, under appropriate physiological conditions, a small portion of the wild-type Rna1p cofractionate with yeast nuclei. Subnuclear fractionation studies show that most of the Rna1p is tightly associated with nuclear components, and that a portion of the active protein can be solubilized by treatments that fail to solubilize inactive Rna1-1p. To learn the precise nuclear locations of the Rna1 proteins, we studied their subcellular distributions in HeLa cells. By indirect immuno-fluorescence we show that wild-type Rna1p has three subcellular locations. The majority of the protein is distributed throughout the cytosol, but a portion of the protein is nucleus-associated, located at both the cytosolic surface and within the nucleoplasm. Mutant Rna1-1p is found at the outer nuclear surface and in the cytosol. We propose that a small pool of the wild-type Rna1p is located in the nuclear interior, supporting the model that the same components of the Ran/TC4 GTPase cycle exist on both sides of the nuclear membrane.

Malignant soft tissue sarcoma of the hypopharynx successfully treated by radiotherapy alone

Sarcoma of the hypopharynx has been reported very rarely in the literature, only six cases having been found among all head and neck malignancies reported to SEER (Surveillance, Epidemiology, and End Results) during 1973-1987. We report a 14-year-old boy with a huge malignant soft tissue sarcoma arising from the hypopharynx. Tracheostomy and feeding gastrostomy were performed as emergency life-saving procedures. Surgical resection had been attempted, but abandoned. Because of the rapidity of tumor growth, we gave the patient a course of accelerated radiotherapy (170 cGy/fraction, two fractions per day) with a total dose of 7140 cGy within one month. A series of endoscopy and imaging studies demonstrated complete regression of the tumor, and the patient is currently alive without evidence of disease 3.5 years after treatment. We conclude that for an unresectable tumor without distant metastasis, radiation therapy may be tried. The time, dose, and fractionation of radiotherapy should be carefully designed and individualized.

Los1p, involved in yeast pre-tRNA splicing, positively regulates members of the SOL gene family

To understand the role of Los1p in pre-tRNA splicing, we sought los1 multicopy suppressors. We found SOL1 that suppresses both point and null LOS1 mutations. Since, when fused to the Ga14p DNA-binding domain, Los1p activates transcription, we tested whether Los1p regulates SOL1. We found that las1 mutants have depleted levels of SOL1 mRNA and Sol1p. Thus, LOS1 appears to positively regulate SOL1. SOL1 belongs to a multigene family with at least two additional members, SOL2 and SOL3. Sol proteins have extensive similarity to an unusual group of glucose-6-phosphate dehydrogenases. As the similarities are restricted to areas separate from the catalytic domain, these G6PDs may have more than one function. The SOL family appears to be unessential since cells with a triple disruption of all three SOL genes are viable. SOL gene disruptions negatively affect tRNA-mediated nonsense suppression and the severity increases with the number of mutant SOL genes. However, tRNA levels do not vary with either multicopy SOL genes or with SOL disruptions. Therefore, the Sol proteins affect tRNA expression/ function at steps other than transcription or splicing. We propose that LOS1 regulates gene products involved in tRNA expression/function as well as pre-tRNA splicing.

Water-soluble fatty acid derivatives as acylating agents for reversible lipidization of polypeptides

A novel method allowing the conjugation of a fatty acid to a peptide or protein in aqueous buffer is described in this paper. L-Cysteinyl 2-pyridyl disulfide (CPD) (III), which was obtained by reacting L-cysteine (I) with 2,2-dithiopyridine (II), was reacted with the N-hydroxysuccinimide ester of palmitic acid (IV) to yield a water-soluble derivative of palmitic acid, termed Pal-CPD (V). Pal-CPD (V) could be reacted with a sulfhydryl-containing peptide or protein in aqueous buffer to yield the palmitic acid-derivatized conjugate (VI). The palmitic acid-derivatized Bowman-Birk protease inhibitor (BBI), synthesized using this conjugation method, was demonstrated to have 140-fold higher uptake into Caco-2 cell monolayers compared to native-BBI. The biological activity of the conjugate, as assessed using an in vitro transformation assay, was retained.

Somatosensory evoked potential study in cervical radiation myelopathy

BACKGROUND

To correlate the findings of median nerves somatosensory evoked potentials (SEPs) with clinical manifestations and magnetic resonance (MR) findings in cervical radiation myelopathy after therapeutic irradiation for nasopharyngeal carcinoma.

METHODS

Median nerve somatosensory evoked potentials (SEPs) were recorded in 10 patients with cervical radiation myelopathy. Seven patients were studied by SEP once, two patients received SEP twice, and one patient, three times.

RESULTS

On the basis of the median nerve SEP findings, three groups were identified: Group I, normal SEP responses (N9, N13 and N20); Group II, normal N13 with abnormal N20; Group III, Normal or abnormal N9 with both abnormal N13 and N20.

CONCLUSIONS

The size, eccentricity and extension to the dorsal columns of the lesions correlated well with SEP findings. When the lesions were confined mainly to the lateral column without much involvement of the dorsal columns, SEP findings were normal; with more extensive lesions involving the dorsal columns, SEPs became abnormal.

MRI in internal cerebral vein thrombosis: case note

A 40-year-old man developed general malaise, dizziness and progressive headache 1 week after acute haemorrhagic conjunctivitis. Bizarre behaviour, confusion and adversive seizures occurred later. MRI showed haemorrhagic infarct in the bilateral basal ganglia and thalamus and abnormal signal density in the internal cerebral veins. Bilateral carotid angiography showed no filling of superior sagittal sinus and internal cerebral veins. With MRI, cerebral venous thrombosis can be suspected and diagnosed earlier than before, obviating any invasive investigation.

Cerebral magnetic resonance imaging of preterm infants after corrected age of one year

A total of 17 very-low-birth-weight (range from 625-1500 grams) preterm infants received brain magnetic resonance imaging (MRI) study at a mean corrected age of 23 months (range from 15-33 months). They were classified into two groups. In Group 1 (12 cases) the cranial ultrasound study was normal during infancy. There were two cases with typical change of periventricular leukomalacia (PVL) detected by MRI study; both showed spastic diplegia. In Group 2 (five cases) ultrasound study was abnormal during infancy while the MRI confirmed the change of PVL in these cases whose ultrasound study showed typical change of PVL. In two cases of intraventricular hemorrhage (IVH) Grade I and III separately, the MRI also revealed the change of PVL, but only the case of IVH grade III had spastic diplegia. The myelination process of all cases were completed as normal term infants. In conclusion, brain MRI confirmed the PVL change discovered by cranial ultrasound and the results were strongly correlated with spastic type cerebral palsy. For those infants with an abnormal neurological examination, MRI may be useful for diagnosis of PVL in spite of normal ultrasound findings during the newborn period.

Serial MRI changes in radiation myelopathy

Using MRI we assessed the changes in signal, size, and contrast enhancement characteristics of the cervical spinal cord in radiation myelopathy developing after radiotherapy for nasopharyngeal carcinoma. We studied two men and five women, aged 40-77 years. The first MRI study was performed 1-4 months after the initial clinical manifestations of myelopathy, and follow-up MRI 2-22 months after the onset of symptoms. On the first study, all patients showed low signal intensity in a long segment of the cervical spinal cord on T1-weighted images, high signal on T2*-weighted images, and focal contrast enhancement at C1-2. In five patients there was also swelling of the spinal cord. The site of eccentric focal contrast enhancement correlated with the clinical manifestations. Follow-up imaging less than 10 months after the onset of symptoms showed no significant changes in signal intensity. Focal contrast enhancement at C1-2 remained the same in three patients, was more dense and larger in one, and less dense in another. Subsidence of swelling was seen in two patients. Atrophy of the spinal cord at C1-2, without abnormal signal and with faint contrast enhancement at C1-2 was revealed as early as 10 months after the onset of symptoms, but the contrast enhancement disappeared by 22 months. There was no correlation between clinical manifestations and spinal cord atrophy on MRI.

Angiographic findings in Tolosa-Hunt syndrome: a case report

A 71-year-old man suffered from left-side throbbing headache over the region of the fifth cranial nerve first division, followed by left ptosis and ophthalmoplegia. Under tentative diagnosis of Tolosa-Hunt syndrome (THS), oral prednisolone 60 mg was given daily. His headache and ophthalmoplegia dramatically improved within 24 hours. Magnetic resonance (MR) imaging and computed tomography (CT) of the head were negative. However, irregularity in the siphon of the left internal carotid artery was disclosed by angiography. This case illustrates that angiography may be useful in diagnosing THS, when CT and MR imaging are negative.

Disposition of positively charged Bowman-Birk protease inhibitor conjugates in mice: influence of protein conjugate charge density and size on lung targeting

The influence of conjugate charge density and size on the targeting of cationic Bowman-Birk inhibitor (BBI) conjugates to the lungs was studied in mice. The biodistribution of BBI, either as the native protein or in the conjugated form (conjugated to a dicationic, tetracationic, or polycationic carrier), indicated that by increasing the charge density of BBI conjugates, the lung accumulation of the conjugates administered intravenously (i.v.) can be increased. The order of lung accumulation in these studies was as follows: polycationic- > tetracationic- > dicationic-conjugated BBI > BBI. The influence of conjugate size on lung accumulation was studied in three experiments. First, the biodistribution of poly(D-lysine) carriers of equal charge density but different molecular weight demonstrated that lung accumulation of polycationic carriers increases with an increase in carrier size. Second, the biodistributions of BBI, tyramine-derivatized poly(D-lysine)3 kDa, and poly(D-lysine)3 kDa conjugated to BBI indicated that an increase in conjugate size alone is not sufficient to promote the lung accumulation of cationic BBI conjugates. Finally, the biodistribution poly(D-lysine) complexed with heparin showed that targeting of a conjugate to the lungs can be abolished by neutralizing the charge on the carrier. Collectively, data in this paper demonstrate that the carrier-mediated targeting of BBI to the lungs is dependent on (a) cationization of BBI, (b) the conjugate positive charge density, and (c) the size of the cationic conjugate if the charge density is maintained. Also, the data show the size of the conjugate alone does not make a significant impact on lung accumulation.

[Structure and biological properties of a conjugate of Bowman-Birk type soy proteinase inhibitor with a block copolymer of ethylene oxide and propylene oxide]

The structure of the conjugate of Bowman-Birk soybean proteinase inhibitor (BBI) with the block copolymer of ethylene oxide and propylene oxide (proxanol) containing five moles of proxanol per mole of protein, has been studied. Data from reverse phase hydrophobic HPLC suggest that the conjugate is less hydrophobic compared to native BBI. A shift of the second derivative UV absorption spectrum for the conjugate towards the shortwave region indicates a greater accessibility of the Tyr-59 residue localized in the interdomain region of the BBI molecule for the solvent. It has been assumed that the conjugate-induced increase in Ki for chymotrypsin may be due to both disturbances in the intact structure of the interdomain region of BBI and screening of the anti-chymotrypsin reactive center as a result of hydrophobic interactions of propylene oxide blocks of proxanol with exposed hydrophobic groups around the reactive center. Supporting evidence in favour of BBI molecule hydrophilization as a result of modification by proxanol can be derived from decreased conjugate penetration into intestinal epithelial cells as well as from the slow elimination of the conjugate from mouse blood stream.

Embolization of carotid cavernous fistula by means of direct puncture through the superior orbital fissure

PURPOSE

To embolize carotid cavernous fistulas (CCFs) by means of transorbital puncture of the cavernous sinus (CS) and the cavernous segment of the internal carotid artery (ICA) through the superior orbital fissure.

MATERIALS AND METHODS

Five patients with CCF were treated with embolization of the CS, and six were treated with embolization of both the CS and the cavernous portion of the ICA after transorbital puncture. All except one had previously undergone occlusion of the ipsilateral proximal ICA before direct transorbital puncture.

RESULTS

The fistulas in these cases were all obliterated completely. Only two patients had temporary ptosis. No other remarkable complications were noted. The patent ICA on the side of the fistula in one patient remained patent after embolization.

CONCLUSION

Direct transorbital puncture through the superior orbital fissure is an alternate treatment for CCF, especially when the ipsilateral ICA has been occluded.

Carbamylation decreases the cytotoxicity but not the drug-carrier properties of polylysines

The charge density of Poly(D-lysine) was reduced by the carbamylation of the lysyl residues with potassium cyanate. A decrease in the charge density of poly(D-lysine) by 25% and 50% reduced the cytotoxicity of the ligand to cultured L929 cells by a 5-, and a 20 to 25-fold level, respectively, as estimated by using either the viability or the protein assay. The uptake of cyanate-modified poly(D-lysine) ligands in cultured L929 cells was not reduced, while the uptake of poly(D-lysine)/Heparin complex was reduced by 80%, as compared to that of unmodified poly(D-lysine). The in vivo biodistribution of cyanate-modified poly(D-lysine) ligands in the lungs and the liver of mice was not altered in comparison to that of unmodified poly(D-lysine), whereas the poly(D-lysine)/Heparin complex was only accumulated in the liver but not in the lungs. The data in this paper indicate that a 50% decrease in the positive charge density of poly(D-lysine) reduces the toxicity, but not the carrier potential of this polycationic ligand.

Location of N2,N2-dimethylguanosine-specific tRNA methyltransferase

Most steps in the maturation of nuclear coded tRNAs occur in the nucleus in eukaryotic cells, but little is known as to the intranuclear location of this RNA maturation pathway. Indirect immunofluorescence experiments using antibody to N2,N2 dimethylguanosine-specific tRNA methyltransferase, a tRNA processing enzyme, and to Nup1p, a nuclear pore protein, show that both locate to the nuclear periphery in wild type cells. Staining of the nuclear membrane is more uniform with anti-Trm1p than the punctate staining observed with antibodies recognizing Nup1p. Biochemical fractionation experiments comparing fractionation of Trm1p with Nup1p, tRNA splicing ligase, and tRNA splicing endonuclease show that Trm1p behaves more like the known peripheral nuclear membrane proteins, Nup1p and tRNA splicing ligase, than like the integral membrane protein, tRNA splicing endonuclease. Cells overproducing Trm1p also concentrate it to the nuclear periphery. Thus, the site(s) of interaction of Trm1p are not easily saturable and are likely to be in excess to Trm1p. Trm1p is shared by mitochondria and the nucleus. Cells transformed with a gene coding Trm1p with a mutant nuclear targeting signal display cytoplasmic staining and an enzyme with increased solubility when compared to the solubility of wild type enzyme. Thus, mutations that prevent the enzyme from entering the nucleus result in an increase in its cytosolic but not mitochondrial concentration suggesting that the mitochondrial/nuclear distribution of Trm1p is not due solely to competition of mitochondrial and nuclear targeting information.

Percutaneous transluminal angioplasty of neck vessels

BACKGROUND

Although surgical endarterectomy or bypass is regarded as the treatment-of-choice for extracranial cerebral vascular stenosis, percutaneous transluminal angioplasty (PTA) has its role as an alternative procedure for symptomatic patients refractory to medical therapy and/or for whom surgical treatment is contraindicated.

METHODS

Occlusive blood vessels were first identified by neurologic, ultrasonic and angiographic studies. Patients were premedicated with heparin and corticosteroid. From a transfemoral approach, double lumen balloon dilatation catheter was guided across the area of stenosis, and inflated two or three times to produce dilatation. Following PTA, patients received anticoagulants and corticosteroid for a period, and were followed by clinical examination, Doppler blood-flow and angiographic studies.

RESULTS

Seventeen patients undergoing 26 procedures were included in this study. The lesions involved subclavian artery in nine cases, common carotid artery in seven, internal carotid artery in five and proximal vertebral artery in five. Digital subtraction angiography (DSA) was done immediately after PTA and showed improvement of stenotic segment (residual stenosis < 30%) in 22 vessels. Restenosis occurred in two cases of subclavian artery PTA six months later. There were three complications, including TIA in two cases and hematoma at the puncture site in one case. Clinically, symptomatic improvement was obtained in 13 cases.

CONCLUSIONS

In patients with significant atherosclerotic stenosis of neck vessels, PTA is a beneficial procedure for improving blood flow to brain circulation and for alleviating symptoms.

Transepithelial transport of tyramine across filter-grown MDCK cells via a poly(D-lysine) carrier

In order to investigate the advantage of using membrane-adsorptive carriers to mediate drug transport across epithelial tissue, we have prepared disulfide- and thioether-linked conjugates of tyramine (tyn) as a model drug to a cationic, nondegradable carrier, poly(D-lysine) (PDL). The transport properties were evaluated using microporous filter-grown Madin-Darby canine kidney (MDCK, strain I) epithelial cells, and we have determined that: (a) the [125I]tyn-SS-PDL conjugate predominantly transported [125I]tyn in the apical-to-basal direction (20-fold greater transport vs. basal-to-apical); (b) [125I]tyn-SS-PDL elicits a 10-fold greater degree of [125I]tyn transport than [125I]tyn-S-PDL, thus demonstrating the importance of the reducible disulfide linkage for [125I]tyn transport to occur; (c) 125I-radioactivity recovered in the basal media was determined to be 95% [125I]tyn-containing small molecules, thus demonstrating the release of [125I]tyn from its PDL carrier; (d) the apical addition of an anionic species, heparin, completely blocks apical-to-basal transport of [125I]tyn, indicating the importance of PDL-mediated binding to the apical membrane for transport to occur; (e) apical-to-basal transport proceeds via non-lysosomal pathways, as lysosomal inactivation by NH4Cl exposure does not inhibit transport, and (f) the addition of a membrane-impermeable inhibitor of disulfide reduction, bisdithionitrobenzoic acid (DTNB), to the apical media inhibits transport by approximately 70%, indicating the importance of apically-localized disulfide reducing reactions for transport of [125I]tyn. Pulse-chase studies indicate that there is no paracellular leakage of conjugate, and the ratio of recycled:membrane-associated:transported [125I]tyn fragment following chase is 4:2:1.

CT of sebaceous adenoma of the parotid gland

We report a large sebaceous adenoma of the parotid gland. CT showed soft-tissue mass in the lateral portion of the adenoma corresponding to the histologic finding of proliferation of sebaceous glands and fibrous stromal tissue. There were numerous fatty cysts (-65Hu). Some of the cystic component ruptured, and CT demonstrated leaking of fatty material into the parapharyngeal space.

Subcellular locations of MOD5 proteins: mapping of sequences sufficient for targeting to mitochondria and demonstration that mitochondrial and nuclear isoforms commingle in the cytosol

MOD5, a gene responsible for the modification of A37 to isopentenyl A37 of both cytosolic and mitochondrial tRNAs, encodes two isozymes. Initiation of translation at the first AUG of the MOD5 open reading frame generates delta 2-isopentenyl pyrophosphate:tRNA isopentanyl transferase I (IPPT-I), which is located predominantly, but not exclusively, in the mitochondria. Initiation of translation at a second AUG generates IPPT-II, which modifies cytoplasmic tRNA. IPPT-II is unable to target to mitochondria. The N-terminal sequence present in IPPT-I and absent in IPPT-II is therefore necessary for mitochondrial targeting. In these studies, we fused MOD5 sequences encoding N-terminal regions to genes encoding passenger proteins, pseudomature COXIV and dihydrofolate reductase, and studied the ability of these chimeric proteins to be imported into mitochondria both in vivo and in vitro. We found that the sequences necessary for mitochondrial import, amino acids 1 to 11, are not sufficient for efficient mitochondrial targeting and that at least some of the amino acids shared by IPPT-I and IPPT-II comprise part of the mitochondrial targeting information. We used indirect immunofluorescence and cell fractionation to locate the MOD5 isozymes in yeast. IPPT-I was found in two subcellular compartments: mitochondria and the cytosol. We also found that IPPT-II had two subcellular locations: nuclei and the cytosol. The nuclear location of this protein is surprising because the A37-->isopentenyl A37 modification had been predicted to occur in the cytoplasm. MOD5 is one of the first genes reported to encode isozymes found in three subcellular compartments.

MR imaging evaluation of bone marrow signal change in post-irradiation patients with nasopharyngeal carcinoma

BACKGROUND

The normal distribution of red and yellow marrow can be altered by therapeutic irradiation, which causes a well-documented sequence of bone marrow changes. This study measured the T1 signal intensity of the clivus and cervical vertebral bodies of NPC patients who had received a complete course of radiation therapy.

METHODS

There were 3 categories of patients: Group I: NPC patients who had radiation myelitis; 14 persons which a total 20 times of MRI. Group II: NPC patients, without radiation myelitis; 6 patients, which a total 6 times of MRI. Group III (control group): patients who received MRI of the cervical spine because of cervical spondylosis or HIVD, were total of 45 patients. In the sagittal section of T1WI, the signal intensity of the bone marrow of clivus and C2 to T1 vertebral bodies was measured.

RESULTS

1). There were homogeneous increases of signal intensity of the bone marrow of clivus and C2 to T1 in Groups I and II. 2). There was no statistical difference between Groups I and II. 3). The increased signal intensity of bone marrow after radiation showed no difference in short and long duration between radiation therapy and MR examinations, indicating that bone marrow signal intensities were increased in NPC patients whether or not they had radiation myelitis.

CONCLUSIONS

Signal change in bone marrow may have occurred soon after radiation therapy, and may have persisted for several years. The radiation myelitis always involved the low medulla oblongata to C5 level; however, the bone marrow signal change always extended downward to the T1 level, so bone marrow is more sensitive than the spinal cord and is prone to be affected by irradiation.

MRI of Joubert's syndrome

OBJECTIVE

To report five cases of the rare Joubert's syndrome.

SUBJECTS

All five cases were studied by 1.0-Tesla MRI. All the patients showed typical clinical manifestations of Joubert's syndrome including neonatal respiratory abnormalities, developmental delay, ataxia, retinal atrophy and nystagmus.

RESULTS

The T1WI of MRI showed characteristic MRI features of Joubert's syndrome including dilatation of the fourth ventricle with some appearing bat-wing shaped, elongation and stretching of the superior cerebellar peduncles, dysphasia of the vermis, widening of the foramen of Magendie and the posterior cistern. One case was associated with encephalomeningocele.

CONCLUSIONS

MRI can provide characteristic findings of Joubert's syndrome and confirm the clinical diagnosis.

The establishment of polarity and enhanced transcytosis of transferrin receptors in enterocyte-like Caco-2 cells

The effect of enterocyte-like differentiation on the transferrin receptor (TfR) polarity in filter-grown Caco-2 cells was studied. The ratio of apical to basolateral TfRs which was found to be approximately 1:1 on the first day after the cells had reached confluence, changed to 1:40 eight days after reaching confluence. The transepithelial electrical resistance (TEER), transport of horseradish peroxidase (HRP) across the monolayer, and total cellular TfR number remained constant over this period. However, the activity of brush border membrane-associated alkaline phosphatase, an established marker for enterocyte differentiation, increased over this 8-day period concurrent with a decrease in apical TfR number. These results suggest that enterocyte-like differentiation rather than tight junction formation is most likely responsible for the polarized distribution of TfRs in Caco-2 cells. The effects of the fungal metabolite brefeldin A (BFA) on TfR distribution and TfR-mediated transcytosis in Caco-2 cells were also studied. BFA caused a marked decrease in the number of basolateral TfRs along with a slight increase in the number of apical TfR. BFA enhanced the TfR-mediated transcytosis of both 125I-Tf and the horseradish peroxidase-Tf conjugate across Caco-2 cells in both apical-to-basolateral and basolateral-to-apical directions. These findings imply a potential application of BFA as an enhancer for TfR-mediated delivery of protein drugs across the intestinal epithelium.

[MRI of postmortem brains]

We studied 18 formalin-fixed brains using MRI, and correlated our data with subsequent gross and microscopic examinations. 9 of our patients died from brain diseases (stroke due to infarction 4, stroke due to hemorrhage 1, encephalitis 2, head injury 1, brain tumor 1). 9 of our patients died from non-CNS diseases (stomach cancer 1, colon cancer 1, liver cirrhosis 1, myocardial infarction 2, trauma 4). In MRI of postmortem brain, T1WI and T 2WI was able to clearly show the myelination process of brainstem, basal ganglia, internal capsule and optic radiation in a 2 months-old-boy. The findings were similar to MRI of live infants. In normal adult postmortem brains, the T1WI showed a relatively low signal intensity of white matter as compared to gray matter. The pictures were similar to proton density images, not T1WI of normal adult brains. The reason why the signal intensity of the white matter was lower than the gray matter may have been due to lysis of lipid of myelin sheath in the formalin solution. Postmortem MRI was able to detect the periventricular hyperintensity (corresponding to arteriosclerotic encephalopathy) and subcortical hyperintensity spots (which corresponding to the widening of the Virchow-Robin perivascular space because of arteriosclerosis) in the brains of our elderly patients. Postmortem MRI detected the intracerebral hemorrhage, which appeared as a dark signal in both short and long TR images. However, MRI did not show blood in the ventricles, sulci, or superficial hemorrhages in the cortex of brain. Brain edema was revealed in the postmortem MRI and appeared as low signal intensity in T1WI and hyperintensity in T2WI. It was associated with a significant mass effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Gadolinium-DTPA enhanced magnetic resonance imaging of dural sinus occlusion in dural arteriovenous malformation: a case report

A case of dural arteriovenous malformation of the transverse sinus, is presented, with dural sinus occlusion imaged with gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). The patient, a 59-year-old man, had developed easy forgetfulness and frequent misreading over a four-month period; he had had episodic vertiginous attacks since 3 January 1992. Magnetic resonance (MR) imaging done on 21 January 1992 showed abnormally dilated subcortical vessels and a non-hemorrhagic venous ischemia in the subcortical white matter of the left posterior temporal lobe. Thrombosis of the left sigmoid sinus was seen. After administration of intravenous Gd-DTPA, dense enhancement in the left sigmoid sinus and abnormal serpiginous enhancement in the left temporal lobe were revealed. Left carotid angiography showed dural arteriovenous malformation in the posterior fossa, with non-opacification of the left transverse and sigmoid sinuses, plus forward venous drainage into left superior petrosal sinus. The focal neurologic deficits in this case from non-hemorrhagic venous ischemia in the subcortical white matter of the left posterior temporal lobe, and were secondary to venous hypertension.

Regulation of pathways within cultured epithelial cells for the transcytosis of a basal membrane-bound peroxidase-polylysine conjugate

A conjugate of horseradish peroxidase (HRP) to poly(L-lysine) (PLL) was used as a non-specific adsorptive probe to study transcytosis in MDCK strain I and Caco-2 epithelial cells. As we have shown previously, HRP-PLL transcytosis proceeds via an intracellular, non-lysosomal proteolytic compartment in MDCK cells; yet, this compartment is utilized for transcytosis only in the basal-to-apical direction (Taub, M. E. and Shen, W.-C. J. Cell. Physiol., 150, 283–290, 1992). Using size exclusion chromatography, we demonstrate that the PLL moiety of the conjugate is effectively cleaved during transcytosis, thus releasing free HRP from the apical surface of the cells. Pulse-chase studies indicate that approximately 6% of basolateral surface-associated HRP-PLL conjugate in Transwell-grown cell monolayers enters the basal-to-apical transcytotic pathway. Brief (1 hour) treatment with 160 nM phorbol ester (PMA), a protein kinase C stimulator, elicits a 2-fold increase in the rate and amount of HRP-PLL transcytosis following a 1 hour lag time. Treatment with 1.6 micrograms/ml brefeldin A (BFA) inhibits HRP-PLL transcytosis by approximately 30%; additionally, BFA is able to abolish completely the PMA stimulatory effect. Removal of BFA causes a re-establishment of the normal rate of transcytosis within 2 hours, demonstrating the reversibility of BFA inhibition with respect to HRP-PLL transcytosis. Thus, PMA most likely elicits an increase in the amount of basally internalized conjugate delivered to BFA-sensitive transcytotic compartments.(ABSTRACT TRUNCATED AT 250 WORDS)

A clinical and MRI study of cerebellar infarctions

The frequency of cerebellar infarctions over two and a half years was 2.7% of the 1300 hospitalized patients over that period. Sixteen patients with cerebellar infarctions were studied by using clinical manifestations and magnetic resonance imaging (MRI). Ages ranged from 41-87 (mean 63.5) years; 13 were men and 3, women. Risk factors included: hypertension (50%), diabetes (44%), prior stroke (44%), cardiac disease (38%), and hyperlipidemia (19%). Common symptoms and signs were dizziness/vertigo (75%), unsteadiness (69%), dysarthria (69%), and nausea/vomiting (50%). Infarcts mainly involved the posterior inferior cerebellar artery (PICA) territory and tended to be associated with brainstem infarcts in 14 of the 16 patients. Most cerebellar infarctions had a benign course, especially the small ones. No mortality was noted in this series. The short-term outcome of the cerebellar infarctions seemed to depend on the size of the infarcts and the sites of the artery occlusion. It was concluded that diagnosis of cerebellar infarctions requires a high index of clinical suspicion, especially when patients present with a sudden onset of ataxia, dizziness/vertigo, nausea/vomiting and dysarthria; and that MRI is a useful tool for the detailed study of cerebellar infarctions and can elucidate associated brainstem infarcts.

Magnetic resonance imaging of cerebral hemiatrophy

Twenty-one cases of cerebral hemiatrophy were studied using 1.0 T magnetic resonance imaging (MRI). In addition to showing the generalized decrease in volume of the cerebral hemisphere, three patterns of cerebral hemiatrophy were noted: pattern I, diffuse cortical and subcortical atrophy (six cases):pattern II, diffuse cortical atrophy associated with expanded porencephalic cysts (10 cases); pattern III, old infarction with necrosis in the territory of the middle cerebral artery (five cases). Pattern I and pattern II were believed to have resulted from hypoxic-ischemic encephalopathy with subcortical leukomalacia (SCL). In all 21 cases, MRI also showed Wallerian degeneration, hyperintensive signals in the posterior limb of the internal capsule on the T2-weighted images, and unilateral atrophy of the cerebral peduncle as far as the pyramid of the medulla oblongata. Structural changes such as thickness of the calvarium, dilatation of the ipsilateral side of the frontal and ethmoid sinus, and reduced size of the middle cranial fossa, were found in 13 cases. Thus, MRI is a useful method of examination in the diagnosis of cerebral hemiatrophy as it has the ability to highlight changes in the cerebral hemisphere, basal ganglion, thalamus and brainstem as well as highlighting bony structural changes.

The Saccharomyces cerevisiae LOS1 gene involved in pre-tRNA splicing encodes a nuclear protein that behaves as a component of the nuclear matrix

Mutations of the Saccharomyces cerevisiae LOS1 gene cause the accumulation of end matured intron-containing pre-tRNAs at elevated temperatures. In an effort to decipher the role of the LOS1 protein in pre-tRNA splicing, we have analyzed the LOS1 gene and its protein product. The LOS1 gene is located on the left arm of chromosome XI and the order of genes in this area of the chromosome is .... URA1 ... SAC1 TRP3 UBA1 STE6 LOS1 .... FAS1..... The LOS1 open reading frame encodes a putative protein of 1100 amino acids that shows no significant homology to other genes. The LOS1 open reading frame was tagged with the influenza virus hemagglutinin epitope recognized by the 12CA5 antibody. The 12CA5 antibody recognizes an epitope-tagged protein of the size predicted by the LOS1 open reading frame. Using this antibody for indirect immunofluorescence and cell fractionation studies we show that the LOS1 protein is located in nuclei. Los1p cannot be extracted from nuclei by treatment with nucleases, salts, or Triton X-100. This insolubility suggests that Los1p is a component of the nucleoskeleton. We propose that LOS1 mutations may affect pre-tRNA processing via alteration of the nuclear matrix.

Wallenberg's lateral medullary syndrome with loss of pain and temperature sensation on the contralateral face: clinical, MRI and electrophysiological studies

Thirteen patients with Wallenberg's lateral medullary syndrome (WLMS) were studied. Clinical and magnetic resonance imaging (MRI) evidence demonstrated infarction in the dorsolateral medulla which produced loss of pain and temperature sensation on one side of the face ipsilateral to the lesion in seven patients. However, in another six patients, the infarction in a similar location produced the same sensory loss on the contralateral face. This is the first report of an analysis comparing these two conditions in WLMS patients, confirmed by MRI. The finding of normal blink reflex and somatosensory evoked potentials (stimulation on median nerve) in the two groups of patients may indicate that the impulses travel along the central pathways of touch, vibration and joint position sensation instead of the pathways for pain and temperature, because the patients had normal sensation of touch, vibration and joint position but impairment of pain and temperature sensation. In addition, it is suggested that the pathways of late blink reflex (R2) pass through the medial lemniscus in the ventromedial medulla instead of the spinal trigeminal tract in the dorsolateral medulla. Further, the observation of the much longer lantencies (about 29 ms) of the normal R2 raises the possibility that the impulses may travel along the longer pathways through the opposite medial lemniscus and up to the thalamus or cortex where they project to bilateral motoneurons of the orbicularis oculi muscles. Although the alternative of R2 travelling only by the shorter pathways through the brain stem is not excluded, this is not supported by current data.

[The chemical shift imaging of liver]

Tissue characterization of different pathologies of the liver can be achieved by differences of relaxation time on changing of pulse sequences in magnetic resonance imaging (MRI). The usefulness of MRI for detection of liver disease is limited when the pathological change is subtle. Chemical shift is a fundamental characteristics in nuclear magnetic resonance (NMR). Chemical shift imaging (CSI) in MRI is based on the different Larmor frequency of proton in water and fat; and therefore it was able to enhance the effectiveness of pathology. For this study, Dixon's method was used to detect liver pathologies and compare its detectability with conventional pulse sequences. Forty cases were enrolled for study; they included 5 health volunteers, 15 hepatomas, 1 cholangiocarcinoma, 5 metastatic hepatic tumors and 14 fatty livers. In hepatic tumors, the lesion number, tumor margination and lesion-to-liver contrast in images were read and analyzed. Signal intensities, signal-to-noise ratio and contrast-to-noise ratio were compared, after measurement, from stored data. In fatty livers, the relative change of signal intensities in different areas of the liver in in-phase and out-phase images were compared with the back muscle and spleen to find where the fatty metamorphosis happened. CSI in spin echo or gradient echo pulse sequences was found to be adequate and valuable for detecting fatty liver, when compared with conventional MRI. CSI not only identified the extension of disease itself but also characterized the fatty change in liver parenchyma. Though CSI affords no further advantages than conventional pulse sequences for detection of hepatic tumors, occasionally, when the image quality of the conventional pulse sequences is not satisfactory or equivocal in lesion detection, the use of CSI might be attempted.