[18F]-2-fluoro-2-deoxyglucose transport kinetics as a function of extracellular glucose concentration in malignant glioma, fibroblast and macrophage cells in vitro

FDG-PET is used to measure the metabolic rate of glucose. Transport and phosphorylation determine the amount of hexose analog that is phosphorylated and trapped. Competition occurs for both events, such that extracellular glucose concentration affects the FDG image. This study investigated the effect of glucose concentration on the rate of FDG accumulation in three cell lines. The results show that extracellular glucose concentration has a greater impact on the rate of FDG accumulation than the relative abundance of GLUT transporter subtypes.

Immunophenotype of conjunctival melanomas: comparisons with uveal and cutaneous melanomas

OBJECTIVE

To characterize the immunophenotypic expression pattern of conjunctival melanomas, with the use of standard melanoma markers as well as microphthalmia transcription factor and p75 neurotrophin receptor.

DESIGN

Eleven conjunctival melanomas, including 1 caruncular melanoma, were immunolabeled with a panel of antibodies that included S100, tyrosinase, melan-A, HMB-45 and HMB-50 combination, microphthalmia transcription factor, and p75 neurotrophin receptor. The results were tabulated on the basis of intensity and pervasiveness of labeling and compared with a previous study of uveal melanomas.

RESULTS

Immunolabeling with S100 was at significantly higher levels in conjunctival melanomas than in uveal melanomas. Tyrosinase, HMB-45 and HMB-50 combination, melan-A, and microphthalmia transcription factor were expressed at high levels in conjunctival melanomas, whereas p75 neurotrophin receptor was not expressed.

CONCLUSIONS

Melanomas of the conjunctiva, including the caruncle, expressed S100, tyrosinase, melan-A, HMB-45 and HMB-50 combination, and microphthalmia transcription factor at high levels, suggesting that these are good markers for this melanoma subtype. Expression of S100 was significantly higher in conjunctival melanomas than in uveal melanomas. The immunophenotypic pattern of conjunctival melanomas is most similar to the epithelioid subtype of cutaneous melanomas.

Immunophenotypic differences between uveal and cutaneous melanomas

OBJECTIVE

To determine the immunophenotypic differences between uveal and cutaneous melanomas, employing standard melanoma markers as well as p75 neurotrophin receptor (p75NTR) and microphthalmia transcription factor (MITF).

DESIGN

Fifteen uveal melanomas (5 spindle, 5 epithelioid, and 5 mixed uveal subtypes) were immunolabeled with a panel of antibodies that included S100, tyrosinase, melan-A, HMB-45 and HMB-50 combination, MITF, and p75NTR. The results were tabulated on the basis of intensity and pervasiveness of the labeling and compared with a prior study on cutaneous spindle and epithelioid melanomas.

RESULTS

In contrast to its strong labeling of cutaneous melanomas, S100 immunolabeling of uveal melanomas was weak and variable. p75NTR, known to differentiate spindle from epithelioid melanomas of the skin, did not immunolabel uveal melanomas. HMB-45, HMB-50, tyrosinase, melan-A, and MITF immunolabeled all uveal melanomas strongly, irrespective of the histologic subtype, but not cutaneous melanomas. Microphthalmia transcription factor was especially clear in its labeling of uveal melanomas.

CONCLUSIONS

Although cutaneous and uveal melanomas share many molecular markers in common, there are differences between the 2 types of melanoma. First, the level of expression of S100 differs between cutaneous and uveal melanomas. Second, while cutaneous melanomas can be further subdivided into spindle and epithelioid types based on their immunophenotype, the uveal melanomas cannot.

The p75 neurotrophin receptor, relative to other Schwann cell and melanoma markers, is abundantly Expressed in spindled melanomas

Seventeen cases of spindled melanomas and eleven cases of epithelioid melanomas were immunolabeled with various melanoma and Schwann cell markers. Standard melanoma markers included S100, HMB45, HMB50, tyrosinase, and Melan A. Schwann cell markers included the p75 neurotrophin receptor (p75NTR), glial fibrillary acidic protein (GFAP), and the L1 adhesion protein. The degree of immunocytochemical labeling was scored by levels of both intensity and pervasiveness. The results confirmed a distinct difference in labeling between epithelioid and spindled melanomas. The p75NTR was strongly expressed in spindled melanomas and weakly expressed in the epithelioid melanomas. The usual melanoma markers, including HMB45, HMB50, MelanA, and tyrosinase had the reverse pattern, being strongly expressed in virtually all epithelioid melanomas, but rarely expressed in the spindled variants. S100 was unique among the markers in being expressed by both epithelioid and spindled melanomas. Glial fibrillary acidic protein and L1 adhesion protein were expressed moderately, with preferential labeling of the spindled melanomas. The greatest immunophenotypic difference between spindled and epithelioid melanomas was the high abundance of p75NTR expression in spindled melanomas. The functional significance of the high level of p75 neurotrophin receptor expression may contribute to the high predisposition of perineural extension in the desmoplastic subset of spindled melanomas.

Kinetic characterization of hexokinase isoenzymes from glioma cells: implications for FDG imaging of human brain tumors

Quantitative imaging of glucose metabolism of human brain tumors with PET utilizes 2-[(18)F]-fluorodeoxy-D-glucose (FDG) and a conversion factor called the lumped constant (LC), which relates the metabolic rate of FDG to glucose. Since tumors have greater uptake of FDG than would be predicted by the metabolism of native glucose, the characteristic of tumors that governs the uptake of FDG must be part of the LC. The LC is chiefly determined by the phosphorylation ratio (PR), which is comprised of the kinetic parameters (Km and Vmax) of hexokinase (HK) for glucose as well as for FDG (LC proportional to (Km(glc) x Vmax(FDG))/(Km(FDG) x Vmax(glc)). The value of the LC has been estimated from imaging studies, but not validated in vitro from HK kinetic parameters. In this study we measured the kinetic constants of bovine and 36B-10 rat glioma HK I (predominant in normal brain) and 36B-10 glioma HK II (increased in brain tumors) for the hexose substrates glucose, 2-deoxy-D-glucose (2DG) and FDG. Our principal results show that the KmGlc < KmFDG << Km2DG and that PR2DG < PRFDG. The FDG LC calculated from our kinetic parameters for normal brain, possessing predominantly HK I, would be higher than the normal brain LC predicted from animal studies using 2DG or human PET studies using FDG or 2DG. These results also suggest that a shift from HK I to HK II, which has been observed to increase in brain tumors, would have little effect on the value of the tumor LC.

Effect of cricoid pressure on the success of endotracheal intubation with a lightwand

BACKGROUND

The lightwand may be useful as an alternative for tracheal intubation during a rapid-sequence induction of anesthesia in the presence of a full stomach. This study was undertaken to assess the effect of application of cricoid pressure on the success of lightwand intubation.

METHODS

Sixty adult female patients presenting for abdominal hysterectomy were randomly allocated to lightwand intubation with and without cricoid pressure. The time to successful intubation and number of attempts were recorded.

RESULTS

All 30 patients allocated to intubation without cricoid pressure were intubated successfully at the first attempt within a median time of 28 s (95% confidence interval, 18-77 s). Lightwand intubation with cricoid pressure was successful in 26 of 30 patients at the first attempt, but the median time to successful intubation was significantly longer at 48.5 s (95% confidence interval, 36-78 s; P = 0.001). Three patients required two attempts for successful intubation, and one could not be intubated with the lightwand while cricoid pressure was being applied.

CONCLUSIONS

The lightwand cannot be recommended for the first attempt at intubation where cricoid pressure is being applied because the time to successful intubation is significantly prolonged, and the failure rate for the first attempt at lightwand intubation is 13%.

The application of direct immunofluorescence to intraoperative neurosurgical diagnosis

A diagnostic problem can occur at the time of intraoperative consultation of neurosurgical tumors as to whether the tumor is of neuroectodermal origin or whether it represents an epithelial metastasis from another site. Intraoperative diagnoses based on hematoxylin and eosin stained frozen sections are often later confirmed by immunocytochemical analysis of formalin-fixed, paraffin-embedded tissue sections that are not available at the time of surgery. The objective of the current study was to demonstrate that the application of direct immunofluorescence to the intraoperative diagnosis of neurosurgical tumors would provide unequivocal, and nearly immediate results. This report describes a new application of an existing technique for an optimized, rapid procedure utilizing direct immunocytochemistry with fluorescence-labeled primary antibodies to analyze surgical biopsies intraoperatively. The examination of five neurosurgical biopsies established a neuroectodermal origin of three tumors via immunolabeling for glial fibrillary acidic protein (GFAP) and lack of labeling with keratin markers, whereas several metastatic lung carcinomas were identified by immunostaining for keratin, but not GFAP, markers. The results of the direct immunolabeling method were unequivocal and required only minutes. The same diagnoses were confirmed by standard immunocytochemical labeling of formalin-fixed, paraffin-embedded sections, though it required several days to obtain the results. Direct immunofluorescence using fluorescently conjugated primary antibodies is a practical and rapid method for deciding whether a neurosurgical tumor is a primary glial or an epithelial metastatic tumor in origin. It is the first reported application of the technique for this aspect of rapid neurosurgical diagnosis.

Eph receptors and ephrins in the developing chick cerebellum: relationship to sagittal patterning and granule cell migration

Spatiotemporal expression patterns of six members of the Eph gene family (EphA4, EphA3, EphB2, ephrin-B1, ephrin-A2, and ephrin-A5) were characterized immunocytochemically at various stages of chick cerebellar development. EphA4 expression is observed in the cerebellar anlage as early as embryonic day 5 (E5) and continues in the posthatch cerebellum. During the early period of cerebellar development (E3-E8), complementarity is observed between EphA4 and ephrin-A5 expression within the cerebellar-isthmal region. By E8, differential expression of EphA4 in parasagittal Purkinje cell bands is evident, and the expression remains banded in the posthatch cerebellum. Banded expression of the ephrin-A5 ligand complements EphA4 expression during the middle period (E9-E15). During this period, ephrin-A2 and EphA3 are coexpressed in a banded pattern and with variable correlation to EphA4. Variability in the banding expression is observed for EphA4, EphA3, ephrin-A5, and ephrin-A2 across different lobes, and graded complementarity in the expression pattern of EphA3 and ephrin-A5 is observed in the external granular layer between the posterior and anterior lobes. Analysis of Purkinje cell birth date in correlation with Eph-ephrin expression during the middle period reveals that early-born cells express EphA4, whereas late-born cells express ephrin-A5. Finally, EphA4 expression domains are respected by migrating granule cell ribbons, which express both ephrin-B1 and EphB2. These expression patterns suggest multiple roles for the Eph-ephrin system in cerebellar development, including demarcation/enforcement of boundaries of the cerebellar anlage, formation/maintenance of Purkinje cell compartments, and restriction of the early phase of granule cell migration to ribbons.

Postnatal decrease in transforming growth factor alpha is associated with enlarged ventricles, deficient amygdaloid vasculature and performance deficits

It is well established that transforming growth factor alpha is involved prenatally in development of the nervous system, but its role in the postnatal brain is less well understood. Here, we document the occurrence of late-onset, morphological and behavioral deficits in the naturally occurring murine mutant, Waved-1 (Wa-1), whose transforming growth factor alpha levels decrease naturally between early postnatal and adolescent ages. Morphological analyses suggest that reduction in the growth factor postnatally is associated temporally with the onset of enlarged lateral ventricles, a reduction in vasculature in the region of the amygdala and a reduction in size of the central nucleus. Onset of the morphological deficits corresponds to the appearance of a performance deficit in contextual fear conditioning. In contrast, the transforming growth factor alpha gene-targeted null mutants exhibit neither morphological nor performance deficits. These data suggest that transforming growth factor alpha during postnatal maturation of the brain may contribute to maintenance of limbic morphology and vasculature, which may in turn affect some behaviors associated with these specific brain structures.

Mechanisms of progenitor maturation are conserved in the striatum and cortex

We recently reported that developmental changes in the expression of epidermal growth factor receptors (EGFRs) by cortical progenitor cells regulate their fate and migration. Higher levels of EGFRs are expressed by later embryonic progenitor cells and are required for several responses to EGF family ligands, including astrocyte differentiation and migration. Progenitor cells in the ganglionic eminence (GE), the forerunner of the striatum, also exhibit a developmental increase in EGFR expression. The striatum differs from the cortex in several respects, including cytoarchitecture, the timing of changes in EGFRs, and the level of transforming growth factor-alpha (TGFalpha) expression. To determine whether signaling mediated by EGFRs in GE progenitors regulates their fate and migration as observed in cortex, we used a retrovirus to increase EGFR expression in embryonic GE progenitor cells prematurely. As in cortex, premature elevation of EGFRs promoted the departure of GE progenitors from the ventricular zone and their differentiation into astrocytes. Settling patterns of infected cells in the striatum, however, differed from the patterns observed in cortex. In addition, the extent of premature astrocyte differentiation reached similar levels in striatal cells, even in the presence of greater endogenous TGFalpha. These findings suggest that additional factors play an important role in modulating EGFR-mediated changes in cell fate. Together with previous studies in cortex, these observations in the striatum indicate that a conserved mechanism involving developmental changes in EGFR expression regulates cell fate and the timing of migration.

Analgesia and sedation in the critically ill--a practical approach

Advancements in intensive care therapy have progressed rapidly over the last two decades. Associated with this have been scientifically unsubstantiated sedation and analgesia practices in the intensive care unit. There is little consensus as to which agents are the most suitable, let alone when and how to use them. There are few, if any, placebo-controlled trials involving sedative drugs in critically ill patients. In an analysis of the literature, we have attempted to present a practical approach to sedation and analgesia practices in the critically ill patient. The aim is to present a framework upon which medical personnel managing critically ill patients can develop a strategy for their own circumstances.

Response diversity and the timing of progenitor cell maturation are regulated by developmental changes in EGFR expression in the cortex

Early cortical progenitor cells of the ventricular zone (VZ) differ from later progenitor cells of the subventricular zone (SVZ) in cell-type generation and their level of epidermal growth factor receptors (EGFRs). To determine whether differences in their behavior are causally related to EGFR number/density, we introduced extra EGFRs into VZ cells with a retrovirus in vivo and in vitro. This results in premature expression of traits characteristic of late SVZ progenitor cells, including migration patterns, differentiation into astrocytes, and proliferation of multipotential cells to form spheres. The choice between proliferation and differentiation depends on ligand concentration and progenitor cell age and may reflect different thresholds of stimulation. The level of EGFRs expressed by progenitor cells in the cortex may therefore contribute to the timing of their maturation and choice of response to pleiotropic environmental signals.

De facto gatekeeping and informed consent in intensive care

Medical decision-making is based on the doctrine of informed consent which is, in turn, based on autonomy, which represents one of four pillars of medical ethics, the others being beneficence, non-malfeasance and social justice. Decision-making in intensive care with respect to the withdrawal of treatment, in particular ventilator therapy, is often extremely difficult for patients or their relatives and they would rather not make any decision other than to insist on the maintenance of therapy in spite of sound, reasonable medical advice that such therapy is of no value to the patient. Aside from issues of a dignified death, this is likely to be to the detriment of other patients who might be refused admission to intensive care and thus is counter to the dictates of social justice. Under these circumstances, there would appear to be a need to give authority to the reasonable medical decision to discontinue resuscitation.

Effects of prenatal alcohol exposure on the postnatal morphology of the rat oculomotor nucleus

Morphological development of the rat oculomotor nucleus was investigated on postnatal day 15 following a prenatal ethanol exposure. Analysis of toluidine blue stained plastic sections showed that the prenatal alcohol exposure caused a decrease in the density of neurons and an increase in the density of astrocytes in the center of the nucleus. There was an alcohol-induced reduction in the overall size of the cross-sectional region of the oculomotor nucleus, but no effect on the number of neurons per unit area of that total oculomotor region, indicating a delay or alteration of the migration of neurons to their normal clustered position in the center of the nucleus. The areas of the neuronal cell nucleus and nucleolus were not affected by the alcohol exposure. Analysis of Golgi-Cox-impregnated multipolar neurons showed that the alcohol exposure caused a reduction in area of the cell soma; a reduction in the number of dendritic branches; and a reduction in the complexity of the dendritic arbor relative to distance from the soma, based on concentric ring analysis. The results of this study demonstrate that gestational alcohol exposure can retard the maturation of the oculomotor nucleus.

Combined pre- and postnatal ethanol exposure alters the development of Bergmann glia in rat cerebellum

The development and maturation of Bergmann glial cells in the rat cerebellum was evaluated on postnatal day 15 by glial fibrillary acidic protein (GFAP) immunocytochemistry, following combined gestational and 10-day postnatal ethanol exposure (a full three trimester human equivalency). GFAP-positive Bergmann glial fibers of lobules I, III, VIb, VII and X of the cerebellar vermis were examined and counted in the molecular layer (ML), the external granular layer (EGL) and the external limiting membrane (ELM). Ethanol exposure reduced: (1) the number of GFAP-positive fibers (per unit length of folia surface) at all three levels; (2) the percentage of mature fibers; and (3) the cross-sectional area in all lobules examined. When data from the five lobules were pooled, there were 7% fewer GFAP-positive fibers in the ML, 15% fewer in the EGL and 20% fewer in the ELM; the percentage of mature fibers was reduced by 16%; and the cross-sectional areas of lobules were reduced by 16%. The altered development of Bergmann glia could be one of the factors causing delayed migration of granular neurons and reductions in the number of granule cells reported in other studies following developmental ethanol exposures and could help to explain some of the motor dysfunctions reported in FAS victims.

Alterations in neuronal development in the substantia nigra pars compacta following in utero ethanol exposure: immunohistochemical and Golgi studies

The effects of gestational ethanol exposure on the development of dopaminergic neurons of substantia nigra pars compacta were investigated in the rat. Pregnant rats were either fed an ethanol-containing liquid diet (6.7% v/v) or pair-fed an isocaloric diet throughout gestation. The morphology of neurons in both ethanol-exposed and pair-fed control offspring was assessed on postnatal day 15 by using tyrosine hydroxylase immunohistochemistry and Golgi impregnation methods. Alterations in the development of neurons were indicated in ethanol-exposed offspring compared with control offspring by the following: (i) tyrosine hydroxylase-positive cell bodies were smaller and appeared more closely packed; (ii) the numbers of second-, third- and fourth-order dendrites and total dendritic segments per cell were reduced; (iii) the dendritic branching pattern relative to distance from the soma was altered; and (iv) some dysmorphic neurons with irregular cell body contours and spheroidal enlargements in the dendrites were encountered in both tyrosine hydroxylase-immunostained and Golgi-stained specimens. The results of the present study suggest that gestational ethanol exposure causes retardation in the development of substantia nigra pars compacta neurons, especially in their dendritic growth and branching, and also causes pathological changes in some neurons. The underdevelopment of dendrites could result in altered development of neuronal circuitry which, in turn, could result in abnormal motor function.

Early operative management of chylothorax by thoracic duct ligation

Chylothorax following mediastinal mobilisation for carcinoma of the oesophagus can be devastating, especially in malnourished, debilitated patients. Early surgical management in significant chylothorax (+ 500 ml/d) is suggested before nutritional degeneration occurs. Conservative management should be reserved for those patients who drain less than 500 ml/d.