Risk factors for vancomycin-resistant enterococcus bacteremia and its influence on survival after allogeneic hematopoietic cell transplantation

Vancomycin-resistant enterococcus (VRE) is a well-known infectious complication among immunocompromised patients. We performed a retrospective analysis to identify risk factors for the development of VRE bacteremia (VRE-B) within 15 months after allogeneic hematopoietic cell transplantation (alloHCT) and to determine its prognostic importance for other post-transplant outcomes. Eight hundred consecutive adult patients who underwent alloHCT for hematologic diseases from 1997 to 2011 were included. Seventy-six (10%) developed VRE-B at a median of 46 days post transplant. Year of transplant, higher HCT comorbidity score, a diagnosis of ALL, unrelated donor and umbilical cord blood donor were all significant risk factors on multivariable analysis for the development of VRE-B. Sixty-seven (88%) died within a median of 1.1 months after VRE-B, but only four (6%) of these deaths were attributable to VRE. VRE-B was significantly associated with worse OS (hazard ratio 4.28, 95% confidence interval 3.23-5.66, P<0.001) in multivariable analysis. We conclude that the incidence of VRE-B after alloHCT has increased over time and is highly associated with mortality, although not usually attributable to VRE infection. Rather than being the cause, this may be a marker for a complicated post-transplant course. Strategies to further enhance immune reconstitution post transplant and strict adherence to infection prevention measures are warranted.

Protracted haemangioblastic proliferation and differentiation in von Hippel-Lindau disease

Von Hippel-Lindau (VHL) disease is caused by germline mutation of the VHL tumour suppressor gene. Patients frequently develop multiple nervous system tumours, denominated haemangioblastomas. Analysis of affected autopsy tissues suggests that tumourigenesis propagates from developmentally arrested, embryonic cells and progresses with consistent architectural, cytological, and molecular sequences similar to haemangioblastic formation and differentiation in the embryo. In this study, we analysed 156 nervous system tumours, 139 of which had been surgically resected from 83 VHL patients. We demonstrate that large tumours consistently contain epithelioid components characteristic of haemangioblastic differentiation in comparison to small tumours that solely display a poorly differentiated, mesenchymal structure. We further show exclusive activation of HIF2alpha in both small mesenchymal tumours and the mesenchymal component of large tumours, whereas activation of HIF1alpha is associated with epithelioid structure. We also show that the MIB1 proliferative index is variably increased in the epithelioid component of large tumours, with extramedullary haematopoiesis foci within the epithelioid component at 100%. These data provide compelling evidence that nervous system tumourigenesis in VHL disease represents a protracted process of haemangioblastic proliferation and differentiation that parallels haemangioblastic formation and differentiation in the embryo.

Glycomics analysis of serum: a potential new biomarker for ovarian cancer?

We recently reported the use of matrix-assisted laser desorption ionization (MALDI) Fourier transformation mass spectrometry (FTMS) techniques to identify unique glycan markers in ovarian cancer cell lines which may be biomarkers for diagnosis of ovarian cancer. Glycan markers and CA125 levels are compared in a series of ovarian cancer patients and normal control subjects. Oligosaccharides (OS) were cleaved from the serum glycoproteins and isolated using solid phase extraction. MALDI-FTMS was then used to identify unique mass spectrometry (MS) peaks. Sensitivity, specificity, and the area under the receiver operating characteristic (ROC) curve were calculated to measure the test performance of glycan markers. Sixteen unique OS MS signals were identified in ovarian cancer patient sera. Their additive mass/charge intensities were used to determine their presence or absence. The ovarian cancer patients varied in their disease status, with initial cancer stages ranging from IC to IV. Forty-four of 48 patients had detectable OS signals, with CA125 values between 2 and 17,044. Four patients had undetectable signals and their CA125 ranged between 7 and 10. Twenty-three of 24 control subjects had no detectable glycan markers, with CA125 levels between 10 and 64. Sensitivity and specificity values were determined to be 91.6% and 95.8%, respectively. The area under the ROC curve for all 72 samples was 0.954 (95% CI: 0.896, 1.0) using the glycomics assay, which was superior to CA125 in discriminating between cases and controls. This preliminary study suggests that glycomics profiling may be useful for the detection of ovarian cancer.

Urgent endovascular revascularization for symptomatic intracranial atherosclerotic stenosis

BACKGROUND

Endovascular revascularization for intracranial atherosclerotic stenoses is being increasingly performed at major medical centers and has been reported to be technically feasible and safe. The authors report their experience with patients who underwent such a procedure for impending stroke and neurologic instability.

METHOD

All 18 patients (21 intracranial lesions) treated between 1997 and 2002 at the authors' institution with endovascular revascularization were retrospectively reviewed. Each patient had failed maximal medical therapy and was thought to be at high risk for an imminent stroke.

RESULTS

Endovascular revascularization was performed on eight distal internal carotid artery lesions, six middle cerebral artery lesions, four intracranial vertebral artery lesions, and three basilar artery lesions. Recanalization was complete in 5 arteries (Thrombolysis in Myocardial Infarction [TIMI] Grade III), partial in 14 arteries (TIMI Grade II), and complete occlusion (TIMI 0) developed in 1 artery. In a patient with a tight basilar stenosis, no angioplasty could be performed because of the inability to cross the stenosis with the guidewire. Major periprocedural complications occurred in 9 (50%) patients: intracranial hemorrhage in 3 (17%), disabling ischemic stroke in 2 (11%), and major extracranial hemorrhage in 4 (22%). Three patients died: one from intracerebral hemorrhage and two from cardiorespiratory failure.

CONCLUSIONS

Endovascular revascularization of intracranial vessels is technically feasible and may be performed successfully. However, periprocedural complication and fatality rates in neurologically unstable patients are high. The results suggest that patient selection, procedure timing, and periprocedural medical management are critical factors to reduce periprocedural morbidity and mortality.

In nonhuman primates intracarotid adenosine, but not sodium nitroprusside, increases cerebral blood flow

Intracarotid infusion of short-acting vasodilators, such as adenosine and nitroprusside, in doses that lack significant systemic side effects, may permit controlled manipulation of cerebrovascular resistance. In this experiment we assessed changes in cerebral blood flow (CBF) after intracarotid infusion of nitroprusside and adenosine. The study was conducted on six adult baboons under isoflurane anesthesia and controlled ventilation. Intracarotid drug infusion protocol avoided hypotension during nitroprusside infusion and tested for autoregulatory vasoconstriction. CBF (intraarterial (133)Xe technique) was measured four times during infusions of 1) intracarotid saline, 2) IV phenylephrine (0.2 microg x kg(-1) x min(-1)) aimed to increase mean arterial pressure by 10-15 mm Hg, 3) IV phenylephrine and intracarotid nitroprusside (0.5 microg x kg(-1) x min(-1)), and 4) intracarotid adenosine (1 mg/min). IV phenylephrine increased mean arterial pressure (69 +/- 8 to 91 +/- 9 mm Hg, P < 0.0001, n = 6), and concurrent infusion of intracarotid nitroprusside reversed this effect. However, compared with baseline, CBF did not change with IV phenylephrine or with concurrent infusion of IV phenylephrine and intracarotid nitroprusside. Intracarotid adenosine profoundly increased CBF (from 29 +/- 8 to 75 +/- 32 mL x 100 g(-1) x min(-1); P < 0.0001). In nonhuman primates, intracarotid adenosine increases CBF in doses that lack significant systemic side effects, whereas intracarotid nitroprusside has no effect. Intracarotid adenosine may be useful for manipulating cerebrovascular resistance and augmenting CBF during cerebral ischemia.

IMPLICATIONS

Intraarterial (133)Xe cerebral blood flow (CBF) measurements suggest that intracarotid adenosine, in a dose that lacks significant systemic side effects, profoundly increases CBF, whereas nitroprusside has no effect.(5-12)

SUB1, an Arabidopsis Ca2+-binding protein involved in cryptochrome and phytochrome coaction

Cryptochromes and phytochromes are the major photosensory receptors in plants and often regulate similar photomorphogenic responses. The molecular mechanisms underlying functional interactions of cryptochromes and phytochromes remain largely unclear. We have identified an Arabidopsis photomorphogenic mutant, sub1, which exhibits hypersensitive responses to blue light and far-red light. Genetic analyses indicate that SUB1 functions as a component of a cryptochrome signaling pathway and as a modulator of a phytochrome signaling pathway. The SUB1 gene encodes a Ca2+-binding protein that suppresses light-dependent accumulation of the transcription factor HY5.

Radiographic evidence and surgical confirmation of a saccular aneurysm on a hypoplastic duplicated A1 segment of the anterior cerebral artery: case report

OBJECTIVE AND IMPORTANCE

True duplication of the A1 segment of the anterior cerebral artery is extremely rare, as is finding a true A1 segment saccular aneurysm. We report the angiographic and surgical findings of such a case with the additional association of a hypoplastic ipsilateral M1 segment of the middle cerebral artery.

CLINICAL PRESENTATION

A 68-year-old man presented with a Hunt and Hess Grade II subarachnoid hemorrhage and symptoms of headache, nuchal rigidity, and facial paresis.

INTERVENTION

Angiographic evaluation with superselective exploration revealed a small ruptured aneurysm located on a duplicated hypoplastic A1 segment of the left anterior cerebral artery with associated middle cerebral artery stenosis and secondary early moyamoya changes. Surgical clipping of the aneurysm was performed successfully while sparing the hypoplastic A1 segment.

CONCLUSION

A1 aneurysms occurring on a duplicated anterior cerebral artery segment probably develop from a congenital weakness of the parent vessel and increased local shear stress. Superselective angiography was helpful in the preoperative planning and facilitated the decision to treat with surgical clipping instead of embolization.

Direct sequencing of RAPD fragments using 3'-extended oligonucleotide primers and dye terminator cycle-sequencing

Random amplified polymorphic DNA (RAPD) markers are used widely to develop high resolution genetic maps and for genome fingerprinting. Typically, single oligomers of approximately 10 nucleotides are used to PCR amplify characteristic RAPD marker fragments. We describe an efficient method for the direct end-sequencing of gel-purified RAPD fragments using one primer from a set of four 3'-terminal extended (A, T, C or G) oligonucleotides, identical to the RAPD primer but for the single nucleotide extension. Strand-specific DNA sequence could be independently read from each of the RAPD fragments without recourse to strand separation or fragment cloning. Informative RAPD fragments could be readily converted into mapped STS or SCAR loci using this technology. The 3'-extended primers may also be used to amplify independent genomic RAPD markers.

The Arabidopsis blue light receptor cryptochrome 2 is a nuclear protein regulated by a blue light-dependent post-transcriptional mechanism

Cryptochrome 2 is a flavin-type blue light receptor mediating floral induction in response to photoperiod and a blue light-induced hypocotyl growth inhibition. cry2 is required for the elevated expression of the flowering-time gene CO in response to long-day photoperiods, but the molecular mechanism underlying the function of cry2 is not clear. The carboxyl domain of cry2 bears a basic bipartite nuclear localization signal, and the cry2 protein was co-fractionated with the nucleus. Analysis of transgenic plants expressing a fusion protein of CRY2 and the reporter enzyme GUS (GUS-CRY2) indicated that the GUS-CRY2 fusion protein accumulated in the nucleus of transgenic plants grown in dark or light. The C-terminal domain of cry2 that contains the basic bipartite nuclear localization signal was sufficient to confer nuclear localization of the fusion protein. Phenotypic analysis of transgenic plants expressing the fusion protein GUS-CRY2 demonstrated that GUS-CRY2 acts as a functional photoreceptor in vivo, mediating the blue light-induced inhibition of hypocotyl elongation. These results strongly suggest that cry2 is a nuclear protein. Although no obvious light regulation was found for the nuclear compartmentation of GUS-CRY2 fusion protein, the abundance of GUS-CRY2 was regulated by blue light in a way similar to that of cry2.

Antagonistic actions of Arabidopsis cryptochromes and phytochrome B in the regulation of floral induction

The Arabidopsis photoreceptors cry1, cry2 and phyB are known to play roles in the regulation of flowering time, for which the molecular mechanisms remain unclear. We have previously hypothesized that phyB mediates a red-light inhibition of floral initiation and cry2 mediates a blue-light inhibition of the phyB function. Studies of the cry2/phyB double mutant provide direct evidence in support of this hypothesis. The function of cryptochromes in floral induction was further investigated using the cry2/cry1 double mutants. The cry2/cry1 double mutants showed delayed flowering in monochromatic blue light, whereas neither monogenic cry1 nor cry2 mutant exhibited late flowering in blue light. This result suggests that, in addition to the phyB-dependent function, cry2 also acts redundantly with cry1 to promote floral initiation in a phyB-independent manner. To understand how photoreceptors regulate the transition from vegetative growth to reproductive development, we examined the effect of sequential illumination by blue light and red light on the flowering time of plants. We found that there was a light-quality-sensitive phase of plant development, during which the quality of light exerts a profound influence on flowering time. After this developmental stage, which is between approximately day-1 to day-7 post germination, plants are committed to floral initiation and the quality of light has little effect on the flowering time. Mutations in either the PHYB gene or both the CRY1 and CRY2 genes resulted in the loss of the light-quality-sensitive phase manifested during floral development. The commitment time of floral transition, defined by a plant's sensitivity to light quality, coincides with the commitment time of inflorescence development revealed previously by a plant's sensitivity to light quantity - the photoperiod. Therefore, the developmental mechanism resulting in the commitment to flowering appears to be the direct target of the antagonistic actions of the photoreceptors.

Adenosine-induced cardiac pause for endovascular embolization of cerebral arteriovenous malformations: technical case report

OBJECTIVE

Extremely high flow through arteriovenous malformations (AVMs) may limit the safety and effectiveness of endovascular glue therapy. To achieve a more controlled deposition of glue, we used transient but profound systemic hypotension afforded by an intravenously administered bolus of adenosine to induce rapidly reversible high-degree atrioventricular block.

METHODS AND CASE REPORT

A patient with a large high-flow occipital AVM fed primarily by the posterior cerebral artery underwent n-butyl cyanoacrylate glue embolization. Nitroprusside-induced systemic hypotension did not adequately reduce flow through the nidus, as determined by contrast injection in the feeding artery. In a dose-escalation fashion, boluses of adenosine were administered to optimize the dose and verify that there was no flow reversal in the AVM and no other unexpected hemodynamic abnormalities by arterial pressure measurements and transcranial Doppler monitoring of the posterior cerebral artery feeding the AVM. Thereafter, 64 mg of adenosine was rapidly injected as a bolus to provide 10 to 15 seconds of systemic hypotension (approximately 20 mm Hg). Although there were conducted beats and some residual forward flow through the AVM during this time, the mean systemic and feeding artery pressures were roughly similar and remained relatively constant. A slow controlled injection of n-butyl cyanoacrylate glue was then performed, with excellent filling of the nidus.

CONCLUSION

Adenosine-induced cardiac pause may be a viable method of partial flow arrest in the treatment of cerebral AVMs. Safe, deep, and complete embolization with a permanent agent may increase the likelihood of endovascular therapy's being curative or may further improve the safety of microsurgical resection.

Recurrent abrupt occlusion after transluminal angioplasty for basilar artery stenosis: case report

OBJECTIVE AND IMPORTANCE

Angioplasty for basilar artery stenosis is often complicated by recurrent abrupt vessel closure. The clinical results can be catastrophic. In this case report, we assess the effects of intra-arterial papaverine (American Regent Laboratories Inc., Shirley, NJ) on rebound occlusion.

CLINICAL PRESENTATION

The patient presented with crescendo transient ischemic attacks from atherosclerotic narrowing of the midbasilar artery despite maximal medical treatment.

INTERVENTION

Angioplasty of the midbasilar artery was performed with serial balloon inflations. The patient was treated successfully with intra-arterial papaverine and achieved a nearly full recovery, with only mild dysarthria, by the time of the 7-month follow-up examination.

CONCLUSION

Using intra-arterial papaverine, we were able to reverse the effects of this potentially life-threatening complication of basilar artery angioplasty.

Cerebral arteriovenous malformation feeding artery aneurysms: a theoretical model of intravascular pressure changes after treatment

OBJECTIVE

A quantitative model may be used to estimate the magnitude of expected pressure changes along the vascular tree with shunt ablation and may provide information to assess the hemodynamic risk of arteriovenous malformation (AVM) treatment.

METHODS

A computer model of the cerebral circulation was applied to estimate the changes in intravascular pressure, velocity, biomechanical stress, and shear stress that might be expected from either endovascular or surgical ablation of AVMs. Two AVM sizes and two feeding artery constellations were simulated. The effect of different shunt flows on vascular pressure was modeled. In each simulation, AVMs were occluded in a stepwise fashion. The effects of systemic hypertension and hypotension in various vascular zones were also simulated.

RESULTS

As large (1000 ml/min) AVMs were occluded, the mean feeding arterial pressure increased from 18 to 68 mm Hg; the percent-occlusion at half-maximal pressure increase was 92%. For medium (500 ml/min) AVMs, feeding arterial pressure increased from 37 to 66 mm Hg; the percent-occlusion at half-maximal pressure increase was 71%. During manipulation of systemic pressure, hemodynamic changes in the circulation close to the nidus were proportionally less than changes in systemic pressure; the degree of proportionality depended on the magnitude of AVM shunt flow.

CONCLUSION

In this simulation, shunt obliteration increased pressure in the nidus and feeding arteries with little effect on the proximal circulation. The shunt provided a "buffering" effect, i.e., higher flow fistulas were exposed to smaller variations in intravascular pressure in feeding artery and nidal pressures during manipulation of systemic pressure.

Treatment of inoperable carotid aneurysms with endovascular carotid occlusion after extracranial-intracranial bypass surgery

OBJECTIVE

Hunterian ligation of the internal carotid artery (ICA) is an accepted treatment for inoperable carotid aneurysms. Preliminary extracranial-intracranial (EC-IC) bypass surgery is required in some patients. The reported incidence of thromboembolic and ischemic complications remains significant for these patients, despite a variety of advocated management strategies. We present our treatment paradigm.

METHODS

Between April 1992 and March 1997, nine patients with inoperable ICA aneurysms were treated using EC-IC bypass surgery and then permanent endovascular ICA occlusion. All of the patients except one had been selected for bypass surgery on the basis of failing results of the ICA test occlusion with hypotensive challenge. ICA occlusion was performed by endovascular means and was delayed after bypass surgery was performed by a mean of 6 days (range, 2-20 d). All patients were managed in the intensive care unit after ICA occlusion.

RESULTS

Clinical improvement was noted in all patients (mean follow-up, 21 mo; range, 3-42 mo). There were no major complications. Aneurysmal thrombosis was confirmed in all patients. Although ICA occlusion was delayed after bypass surgery, only one bypass was noted to be occluded. The occluded bypass occurred in a patient who subsequently underwent successful ICA occlusion. This patient was thought to have been improperly selected for bypass surgery.

CONCLUSION

Certain carotid aneurysms can be effectively managed with hunterian ICA ligation. After preliminary identification of patients with borderline cerebrovascular reserve as candidates for EC-IC bypass surgery, close attention to the following points may help enhance clinical outcome: 1) excellence in surgical technique for EC-IC bypass surgery, 2) occlusion of the parent vessel as close to the aneurysm neck as possible by endovascular means, and 3) judicious postoperative combination of anticoagulation, fluid, and pressure management.

Risk of spontaneous haemorrhage after diagnosis of cerebral arteriovenous malformation

BACKGROUND

A small proportion of strokes are caused by cerebral arteriovenous malformations (AVM). Treatment to prevent intracranial haemorrhage itself carries risks, and untreated AVM may in many cases have a good prognosis. We investigated the risk of subsequent symptomatic bleeding in the clinical course of AVM in patients with and without an initial haemorrhage.

METHODS

281 unselected, consecutive, prospectively enrolled patients with cerebral AVM were grouped according to their initial clinical presentation--142 presented with and 139 without haemorrhage. The frequency of AVM haemorrhages during the subsequent clinical course (before the start of endovascular, surgical, or radiation treatment) in the two groups was compared by means of Kaplan-Meier life-tables, log-rank test, and multivariate proportional-hazards regression models. Haemorrhage was defined as a clinically symptomatic event with signs of acute bleeding on computed tomography or magnetic resonance brain imaging.

FINDINGS

During mean follow-up of 8.5 months for the haemorrhage group and 11.9 months for the non-haemorrhage group, haemorrhages occurred in 18 (13%) of the former patients and in three (2%) of the latter (p=0.0002). The annual risk of haemorrhage was 17.8% and 2.2%, respectively. In the multivariate regression model, the adjusted hazard ratio for haemorrhage at initial presentation was 13.9 (95% CI 2.6-73.8; p=0.002). Deep venous drainage (hazard ratio 4.1 [1.2-14.9], p=0.029) and male sex (9.2 [2.1-41.3], p=0.004) were also significantly associated with subsequent haemorrhage, but no significant association was found for age or AVM size. The annual rate of spontaneous haemorrhage was 32.6% for men and 10.4% for women in the haemorrhage group compared with 3.3% for men and 1.3% for women in the non-haemorrhage group. Among patients with haemorrhage at initial presentation, the risk of haemorrhage fell from 32.9% in year 1 to 11.3% in subsequent years (34.2% to 31.0% in men; 31.1% to 5.5% in women).

INTERPRETATION

In AVM, patients initially presenting with haemorrhage have a higher risk of subsequent bleeding than those presenting with other symptoms. The risk is higher in men than in women.

Intra-arterial nitrovasodilators do not increase cerebral blood flow in angiographically normal territories of arteriovenous malformation patients

BACKGROUND AND PURPOSE

The mechanism of adaptation to chronic cerebral hypotension in normal brain adjacent to cerebral arteriovenous malformations (AVMs) is unknown. To clarify these mechanisms, we performed cerebral blood flow (CBF) studies in structurally and functionally normal vascular territories during 53 distal cerebral angiographic procedures in 37 patients with AVMs.

METHODS

CBF was measured using the superselective intra-arterial 133Xe method before and after a 3-minute infusion of either verapamil (1 mg.min-1, n = 23), acetylcholine (1.33 micrograms.kg-1.min-1, n = 7), nitroprusside (0.5 microgram.kg-1.min-1, n = 16) or nitroglycerin (0.5 microgram.kg-1.min-1, n = 7).

RESULTS

Mean +/- SD systemic (76 +/- 13 mm Hg) and distal cerebral arterial (55 +/- 16 mm Hg; range, 20 to 97 mm Hg) pressures were not different among groups. Verapamil increased CBF (45 +/- 12 to 65 +/- 21 mL.100 g-1.min-1, P < .001). There was no effect of acetylcholine (no change [46 +/- 9 to 46 +/- 9 mL.100 g-1.min-1], NS) or nitroglycerin (36 +/- 14 to 36 +/- 13 mL.100 g-1.min-1, NS). Nitroprusside decreased CBF (40 +/- 12 to 31 +/- 11 mL.100 g-1.min-1, P < .001). The percent change in CBF after drug administration was proportional to cerebral arterial pressure for verapamil only (r = .57, P = .0051).

CONCLUSIONS

When infused intra-arterially in clinically relevant doses in both hypotensive and normotensive normal vascular territories remote from an AVM nidus, calcium channel blockade caused vasodilation, but there was an absence of response to nitric oxide-mediated vasodilators. These data suggest that (1) the nitric oxide pathway probably is not involved in the adaptation to chronic cerebral hypotension in AVM patients and (2) if our findings in vessels remote from or contralateral to the AVM are applicable to vessels of patients with other forms of cerebrovascular disease, clinically relevant doses of intra-arterial nitrovasodilators may not be useful in the manipulation of cerebrovascular resistance.

Strain differences in tissue repair response to 1,2-dichlorobenzene

Fischer 344 (F344) rats are reportedly 75-fold more sensitive than Sprague Dawley (S-D) rats to 1,2-dichlorobenzene (o-DCB) hepatotoxicity. Lethality studies were conducted since no information was available regarding the ultimate consequence of this sensitivity in terms of animal survival in the two strains. LD50S for o-DCB (1.66 ml/kg and 1.76 ml/kg in male F344 and S-D rats, respectively) did not differ. Several studies have shown the importance of tissue repair on animal survival following exposure to toxic chemicals. The objective of this study was to investigate if differential rates of cell division and tissue repair might explain the lack of difference in LD50 dose between the two strains despite higher hepatotoxic injury in F344 rats. Age-matched male S-D and F344 rats were administered o-DCB (0.2, 0.6, 1.2 ml/kg, i.p.); injury and tissue repair occurring as two dynamic but opposing events were measured over time. Liver injury was assessed by measuring plasma alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) activities and by liver histopathology. Higher plasma ALT elevations were observed in F344 rats following administration of 0.2 and 0.6 ml o-DCB/kg. Using SDH as a marker of liver injury, the strain difference was evident only at 0.2 ml o-DCB/kg. Liver regeneration was estimated by 3H-thymidine incorporation into hepatonuclear DNA and via proliferating cell nuclear antigen (PCNA) assay. Prompt and significantly higher hepatocellular regeneration beginning at 36 h was evident in F344 rats following administration of 0.2 and 0.6 ml o-DCB/kg. The significantly higher depletion of hepatic glycogen observed in F344 rats following administration of 0.2 and 0.6 ml o-DCB/kg occurred without significant changes in plasma glucose and is consistent with highly stimulated tissue repair seen in these rats at the corresponding doses. However, increasing the dose further to 1.2 ml o-DCB/kg results in a delayed (S-phase synthesis begins at 48 h) and diminished response to o-DCB. These findings suggest that a significantly higher rate of tissue repair in F344 rats helps them overcome higher liver injury inflicted by o-DCB. This differential in tissue repair in the two strains may play a vital role in equalizing the ultimate outcome of toxicity in the two strains.

Varicella-zoster virus DNA in CSF and arteries in delayed contralateral hemiplegia: evidence for viral invasion of cerebral arteries

A 78-year-old woman presented with a right basal ganglia infarct 6 weeks after a left herpes zoster ophthalmicus. MR angiography showed focal segmental stenosis of the proximal segments of the anterior, middle, and posterior cerebral arteries. Varicella DNA was detected in the CSF by polymerase chain reaction (PCR). Treated with dexamethasone and acyclovir without improvement, she died 1 month later. There was focal endarteritis in the left anterior, middle, and posterior cerebral arteries at autopsy. Varicella DNA was detected by PCR of extracts from these vessels but not from the arteries on the right side. This study provides further evidence that the vasculopathy after herpes zoster ophthalmicus results from direct viral invasion of the vessel wall.

The negative angiogram in subarachnoid haemorrhage

Our purpose was to review the incidence of negative cerebral panangiography in acute nontraumatic subarachnoid haemorrhage (SAH); to document the amount and distribution of subarachnoid blood on CT and determine its relationship to findings on repeat angiography; and to study the outcome of these patients from the time of presentation to hospital discharge. From 1983 to 1992, 295 patients underwent cerebral angiography for acute SAH at our institution. The CT, angiographic and MRI findings and clinical course of patients with initially negative angiograms were reviewed retrospectively. The overall incidence of negative cerebral panangiography was 31% (92/295). An aneurysm was disclosed on a second angiogram in 4 cases, and on a third angiogram in 1, giving a total false negative rate of 5%. In 55% of cases, only a small amount of SAH was present on CT. The distribution of the subarachnoid blood was nonspecific and resembled the pattern seen in aneurysmal SAH. Ninety-four percent of the patients presented in Hunt-Hess grades I and II. The complications of conservative treatment were few: a rebleed rate of 4%, delayed cerebral ischemia in 4%, cerebral infarcts in 8% and hydrocephalus requiring shunting in 3%. On discharge, 93% of patients had recovered completely and the others were left with moderate disability. There were two deaths related to massive rebleeding. Patients with perimesencephalic SAH (35%) fared particularly well; none developed complications during their hospital stay and repeat angiograms never revealed an underlying aneurysm. In such cases, further angiographic investigations do not seem warranted.

Tophaceous gout of the lumbar spine mimicking an epidural abscess: MR features

We present the MR findings in a case of tophaceous gout of the lumbar spine with cauda equina compression, mimicking an epidural abscess. The diagnosis was clinically unsuspected and confirmed at laminectomy. Tophus material in the paraspinal soft tissues appeared intermediate in signal intensity and showed heterogeneous contrast enhancement.

Magnetic resonance imaging of lateral ventricular tumours

The authors review their experience with magnetic resonance imaging (MRI) of giant lateral ventricular tumours, placing special emphasis on the imaging features that aid in the differential diagnosis. The tumours illustrated include astrocytoma, oligodendroglioma, neurocytoma, subependymoma, metastatic lesions and subependymal giant cell astrocytoma. Because of their large size, most of these lesions cause hydrocephalus. The presence of associated edema indicates direct brain invasion or a higher grade of tumour differentiation. The degree and pattern of contrast enhancement, as well as the signal characteristics before administration of contrast agent, are nonspecific. The location of the tumour within the lateral ventricles and the patient's age are the most helpful diagnostic clues. Giant lateral ventricular tumours are uncommon, and the patients usually come to clinical attention with symptoms related to increased intracranial pressure. MRI assists in surgical planning by defining the exact location of the lesion and its relation to adjacent structures. Although the signal characteristics and patterns of contrast enhancement are nonspecific, preoperative diagnosis is possible in most cases if the imaging findings are correlated with the patient's age and the specific location of the tumour within the lateral ventricles.

A learned odor evokes an enhanced Fos-like glomerular response in the olfactory bulb of young rats

Young rats exposed to peppermint odor and reinforcing tactile stimulation from postnatal days (PND) 1-18 increase their preference for that odor relative to controls. This early olfactory memory is accompanied by an 80% increase in the density of glomerular-layer cells displaying Fos-like immunoreactivity in response to the learned odor on PND 19. The difference is observed in midlateral portions of the olfactory bulb that align with foci of 2-deoxyglucose (2-DG) uptake in adjacent sections. Trained and control animals are not different in the Fos-like response of juxtaglomerular cells within ventrolateral 2-DG foci. Ratios of midlateral/ventrolateral response differ significantly between trained and control animals and include differences among cells of three staining intensities. These ratios are correlated with ratios of 2-DG uptake (midlateral/ventrolateral foci), which also differ significantly between trained and control rats. Juxtaglomerular cells associated with 2-DG foci also express Egr-1-like immunoreactivity. However, the midlateral Egr-1 response does not differ between trained and control rats. These results show that early memories can be associated with an increased Fos-like response in a primary sensory area of the CNS. They also suggest that only specific regions within the olfactory bulb are modified following the learning of a given odor in early life.

Herpes zoster vasculitis: demonstration by MR angiography

A patient presented with multiple cerebral infarcts in various vascular territories after having been treated for herpes zoster ophthalmicus. Magnetic resonance angiography demonstrated multiple focal stenoses involving the proximal intracranial vessels which corresponded to endarteritis at autopsy.

Intramedullary schwannoma

OBJECTIVE

To present the imaging findings for two cases of intramedullary schwannoma involving the thoracic cord and the conus medullaris.

PATIENTS AND METHODS

a 34-year-old man and a 53-year-old woman presented with symptoms of weakness and pain in the lower limbs. Myelography and magnetic resonance imaging as well as other examinations, were performed.

RESULTS

The imaging failed to indicate the correct diagnosis in either patient. However, intramedullary schwannoma was confirmed pathologically in both patients. Subtotal excision resulted in local tumour recurrence at 5 and 3 years, respectively.

CONCLUSIONS

Intramedullary schwannoma should be considered in the differential diagnosis of spinal cord tumours. The importance of accurate diagnosis from frozen sections at surgical biopsy is emphasized .

Alveolar epithelial cells express and secrete parathyroid hormone-related protein

Parathyroid hormone-related protein (PTHrP) was discovered as a hypercalcemia-inducing product of malignant cells and has since been demonstrated to be a product of many tissues. Although it is robustly expressed in fetal lung, PTHrP expression has not been assigned to alveolar epithelial cells in adult lung. We have shown that PTHrP is expressed in the adult rat lung and by cultured rat alveolar type II epithelial cells with sensitive and specific immunoassays and immunohistochemical techniques. Immunoassay of cell extracts demonstrated that freshly isolated type II cells contained PTHrP (136 pg/10(7) cells), whereas freshly isolated alveolar macrophages and cultured macrophages did not express PTHrP. Cultured type II cells secreted PTHrP into medium, 202 +/- 11 fg PTHrP/micrograms cell protein in 24 h. Basal secretion remained stable up to 7 days in culture. Treatment with phorbol myristate acetate or 1-oleoyl-2-acetyl-sn-glycerol produced a dose-related, 2- to 4-fold increase in PTHrP secretion. However, forskolin, ionomycin, ATP, phenylephrine, capsaicin, and bradykinin had no effect. Thus, PTHrP secretion appeared to be regulated by a protein kinase C-dependent pathway. PTHrP could also be demonstrated in pulmonary lavage fluid. Although the function of PTHrP in the adult lung is unknown, it could involve control of cell growth and differentiation or control of surfactant lipid secretion. Further studies are necessary to elucidate the function of PTHrP in the lung.

Transcranial Doppler ultrasonographic changes after embolization of cerebral arteriovenous malformations

The authors assessed the potential role of transcranial Doppler ultrasonography (US) in monitoring hemodynamic changes induced by embolization of cerebral arteriovenous malformations. Transcranial Doppler US was performed in eight patients with such lesions before and after embolization with n-butyl cyanoacrylate [corrected]. Changes in mean flow velocity and pulsatility index were analysed in all feeding and nonfeeding arteries. Anatomic and hemodynamic observations were also correlated with the results of digital subtraction angiography. A consistent trend was observed in all treated feeding arteries after embolization: the flow velocity decreased by a mean of 26% or 33 cm/s (p = 0.01, paired t-test), and the pulsatility index increased by a mean of 27% or 0.15 (p = 0.005). Although these changes did not correlate with the degree of angiographic reduction of the nidus (r = -0.31), they were most marked in malformations with a lower Spetzler grade or a higher degree of shunt obliteration. After embolization, recruitment of untreated feeding arteries was documented in two cases and a decrease in the "steal effect" from contralateral nonfeeding arteries in three. Changes in the nonfeeding arteries ipsilateral and contralateral to the malformation were variable. The authors conclude that transcranial Doppler US is a convenient and reliable method to evaluate quantitatively the hemodynamic effects of embolization of cerebral arteriovenous malformations.

Multiple intracerebral cavernous angiomas

Eight patients (seven women and one man) with multiple intracerebral cavernous angiomas (cavernomas), also known as angiomatosis cerebri, were examined with high-field magnetic resonance imaging (MRI). Although previous articles have referred to such cases, a series similar to the one reported here has apparently not been described in the radiology literature. The patients presented with seizures, progressive neurologic deficit or cerebral hemorrhage. In all eight cases the multiplicity of the lesions was an incidental finding in the magnetic resonance images. The MRI appearance of the cavernomas, although characteristic, is similar to that of other angiographically occult intracranial vascular malformations, in particular thrombosed arteriovenous malformations and mixed vascular malformations, as well as that of hemorrhagic metastases. Additional criteria, such as the absence of edema, the presence of calcifications and the temporal evolution of the cavernomas on serial scans, should allow cavernomas to be differentiated from hemorrhagic metastases. The exquisite sensitivity in detecting angiomatosis cerebri and the ability to show the evolution of internal hemorrhage in individual lesions make MRI the method of choice for diagnosing and following this condition.