Neurological manifestations of decompression illness in recreational divers - the Cozumel experience.

Neurological signs and symptoms are common in recreational divers with decompression illness (DCI). The spectrum of neurological manifestations, temporal profile, and laboratory findings are described in a large series of 200 consecutive recreational divers treated for DCI. The Hyperbaric Medicine Unit charts of 200 recreational divers treated for DCI were reviewed and analyzed. The cohort was mainly male, with a median age of 40 years, and quite experienced, with a median of 100 prior dives. In 44 divers (22%) a rapid ascent was documented. The median time to onset of neurological symptoms was 60 minutes after surfacing. One hundred seventy-seven of 200 divers (88.5%) had at least one symptom of neurological DCI at presentation. The most common neurological manifestations were paresthesia, dysesthesia, incoordination, motor weakness, and dizziness. Paresthesias were associated with significantly younger (p = 0.003) and less experienced (p = 0.03) divers. Similar but less significant correlations were noted for dysesthesias. Female divers were significantly more likely to experience painful skin symptoms (p < 0.001). Neurological manifestations are common in recreational divers treated for DCI. Neurological DCI and paresthesias are more likely to occur in younger and less experienced divers.

Growth inhibition of cultured human glioma cells by beta-interferon is not dependent on changes in ganglioside composition.

This investigation tested the hypothesis that the growth inhibiting effects of human beta-interferon on cultured human glioma cells involves changes in the ganglioside composition of these cells. Four cell lines derived from human malignant gliomas (12-18, U-251 MG, I29-A, 7-24) and two lines from human fetal brain (CHI, CHII) were cultured in the presence and in the absence of human beta-interferon (HuIFN-beta), 1,000 units per ml medium for three days before harvesting. Human beta-interferon had an inhibitory effect on growth of glioma but not fetal brain cells. Total ganglioside sialic acid for all cell lines ranged between 3.5 and 13.8 micrograms/10(7) cells (0.6-3.9 micrograms/mg protein). No distinct difference in the amount of total ganglioside per cell was observed between neoplastic and non-neoplastic cells, but the latter had more ganglioside per mg total protein. All cell lines displayed different patterns of gangliosides determined by high performance thin layer chromatography, but there was no distinct difference between glioma and fetal brain cells. Human beta-interferon increased the total amount of ganglioside per cell in one fetal brain and two glioma lines, but on a protein basis in only one glioma cell line (I29-A); HuIFN-beta had only minor effects on ganglioside patterns. There was a slight shift towards a greater proportion of structurally simpler gangliosides in both fetal brain and two glioma cell lines exposed to HuIFN-beta, but the reverse occurred in glioma U-251 MG. None of these changes strongly correlated with the degree of growth inhibition due to HuIFN-beta.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of crush lesion on ganglioside radiolabelling patterns in rat sciatic nerve.

Left sciatic nerves in rats were crushed and allowed to regenerate for variable periods of time up to 14 days; uncrushed right nerves from the same animals were used as controls. Two days before killing the rats, both L-5 dorsal root ganglia (DRG) were injected with 100 microcuries [3H]glucosamine. Gangliosides were purified separately from sciatic nerve (SN) distal to the crush site, lumbosacral trunk (LST) proximal to the crush site, and the injected DRG. Changes in major glycoconjugate classes were previously reported; in this study total gangliosides were separated by high performance thin layer chromatography, located by autofluorography and radioactivity was measured by liquid scintillography. In control DRG, major radiolabelled gangliosides were GM3 and LM1; in control LST and SN, GD1b and GT1b were the major ones. During day two and four following crush, GM3 and LM1 decreased in DRG, but at one and two weeks were at normal and elevated levels, respectively; there were inverse changes in GD3, GT1b and GQ1b. GD1b, GT1b and GQ1b were lower in crushed than in control LST and SN between days zero and four. In LST, GM3 and LM1 remained constant for four days, but were elevated at one and two weeks, whereas GD1a was elevated at all times. Indeed, GD1a is the major recently synthesized ganglioside that is transported into LST and SN two to four days after trauma, suggesting that it may play an important role in regeneration. Indices of oligosaccharide complexity and degree of sialylation indicated that between two and four days following crush, gangliosides in DRG had more complex oligosaccharides and more sialic acid residues than in either controls or in DRG of crushed nerves at one and two weeks post-crush. The degrees of ganglioside sialylation and oligosaccharide complexity in crushed LST and SN were lower than in control specimens between one and seven days after crush. Changes in the ganglioside composition of peripheral nerve following trauma may be important for axonal regeneration.

Glycolipid markers of astrocytomas and oligodendrogliomas.

Neutral glycolipids and gangliosides were analyzed in 149 astrocytomas (A), 46 oligodendrogliomas (O), and 21 oligoastrocytomas (OA) to determine if specific glycolipids correlate with histologic diagnosis and grade. Positivity for asialoGM1 (GA1) and negativity for paragloboside by immuno-TLC correlated with histological diagnosis of O and OA, whereas the reverse pattern correlated with A. High levels (over 5 microg hexose per mg dry weight) of CMH generally correlated with an O component, but the association was not as strong as for either GA1 presence or paragloboside absence. Pilocytic astrocytomas and pleomorphic xanthoastrocytomas had high proportions (> 15%) of globoside, low ratios (< 0.5) of GD1a: GD1b, and identifiable ceramide trihexoside (CTH). Three gangliosides of the 1b pathway were progressively lost with increasing grade of A, but a similar correlation with grade was not seen in O or OA. A high proportion of cases expressing sialosylparagloboside (3'LM1; 6'LM1) were grade 4 A. Glycolipids are synthesized by glycosyltransferases that add specific sugars to the nascent oligosaccharide. Correlation of specific glycolipids with histological diagnoses and grades indicate that these tumor types express specific patterns of glycosyltransferases, several of which have been cloned. It is possible that critical genes coding for these enzymes are deleted, overexpressed, or mutated in certain tumor types and grades, thus leading to the patterns of glycolipids that we found to be associated with these tumors.

Small cell architecture--a histological equivalent of EGFR amplification in glioblastoma multiforme?

Although there is much written about the molecular definitions of "primary" glioblastomas (GBM), there is little known about the histological features of this predominant subtype. We hypothesized that the "small cell architecture" would represent a histological feature of most primary GBMs. This was tested by comparing the presence of the small cell phenotype with the presence or absence of amplification of the epidermal growth factor receptor (EGFR), a common event in primary GBMs. After a pilot study that found a correlation between this small cell phenotype and EGFR amplification, we selected 9 pure small cell GBMs (SCGBM) and 12 non-SCGBMs to be studied for EGFR amplification by fluorescence in situ hybridization (FISH). In this set of 21 cases, 8 of 9 SCGBMs and 5 of 12 non-SCGBMs were amplified for EGFR. We then correlated the EGFR status of 79 GBMs unselected for their histological features from a set that had been previously characterized in regard to EGFR amplification. Fourteen of 21 (67%) exclusively small cell neoplasms, 8 of 25 (32%) GBMs with both small cell and non-small cell areas, and 3 of 33 (9%) non-small cell GBMs were amplified for EGFR (p = 0.0004 with an exact test). We conclude that EGFR amplification is associated with a small cell phenotype in GBMs and that SCGBMs are an important component of "primary" GBMs.

The influence of academic stress and season on 24-hour concentrations of growth hormone and prolactin.

Stress has been considered a physiological regulator of GH and PRL secretion in humans. The stressors used in studies have often been extreme. The influence of commonplace stressors on the endocrine system has not been clarified. Therefore, to better define the role of commonplace stressors on GH and PRL secretion, we evaluated the effect of examination stress on GH and PRL secretion in 37 male medical students. We performed hourly sampling for 24 h for GH and PRL 4 weeks before, during exam week, and 2 weeks after major examinations in the fall and spring of their first year. Stress, as evaluated by the Perceived Stress Scale (PSS), increased as expected during examination weeks, but there was no correlation between the PSS scores and mean day or night GH and PRL secretion. Twenty-four-hour GH and PRL secretion was not significantly altered during examinations in either fall or spring. A significant seasonal influence, however, was noted on GH secretion, with both daytime and nocturnal GH secretion being consistently higher in the Fall than in the Spring. We conclude that examination stress does not significantly influence mean daytime or nocturnal GH and PRL concentrations. We suggest that serum GH and PRL levels may not be significantly altered in man by commonplace stressors. Also, seasonal effects may be operative in the control of human GH secretion.

Immunohistochemical staining for ganglioside GD1b as a diagnostic and prognostic marker for primary human brain tumors.

Immunohistochemical staining intensity for ganglioside GD1b was determined for 108 human neuroectodermal tumors. Most of the tissue elements that immunostained were tumor cells; only a few axons and occasional neurons reacted in some specimens. All pilocytic astrocytomas stained very positively, whereas none of the ependymomas and only 11% of primitive neuroectodermal tumors, 20% of glioblastomas, and 28% of anaplastic astrocytomas showed more than faint staining. A similar association between grade and immunostaining was seen in tumors containing an oligodendrogliomatous component, but reactivity was not as strong as in astrocytic tumors or primitive neuroectodermal tumors. Results of Cox regression showed significant associations between immunostaining intensity and survival for all cases taken together (P = 0.007); for the group consisting of astrocytomas, oligoastrocytomas, and oligodendrogliomas (P = 0.002); and for astrocytomas alone (P = 0.04). Results were also significant using a proportional hazards model controlling for patient age (all cases P = 0.005; astrocytomas only P = 0.02), but not when controlling for tumor grade. Our results indicate that immunohistochemical staining for GD1b is correlated with tumor grade and that it may be of prognostic utility in some primary human brain tumors, especially astrocytomas.

Gangliosides and neutral glycolipids in ependymal, neuronal and primitive neuroectodermal tumors.

Neutral glycolipid and ganglioside compositions were determined on 11 ependymal tumors, 12 medulloblastomas, 6 other neuronal tumors of the brain, 4 peripheral neuroblastomas, 1 cerebral primitive neuroectodermal tumor (PNET), and 1 PNET of the thoracic wall. Within the group of tumors that can demonstrate neuronal phenotypes, there was an association between the degree of neuronal differentiation usually demonstrated by these tumors and the proportions of both GD1a and 1b-pathway gangliosides. The amount of globoside also correlated with the amount of 1b pathway gangliosides. Patients with medulloblastomas whose 1b gangliosides made up over 15% of the total gangliosides survived longer that those with lower proportions of 1b gangliosides. The only gangliosides in the choroid plexus papilloma were GM3 and GD1a, but other ependymal tumors had significant amounts of GD1b and its metabolic precursors. Ependymoma and anaplastic ependymoma had similar neutral glycolipid compositions, which were different from subependymoma, which lacked ceramide monohexoside and ceramide dihexoside. These differences in glycolipid compositions suggest that there may be fundamental biological differences between these types of ependymal tumors.

Plasma cortisol levels and reactivation of latent Epstein-Barr virus in response to examination stress.

In this study, we explored the possibility that glucocorticoid hormones, known to increase under stress, might be one component of the mechanism involved in induction of latent Epstein Barr virus (EBV). We obtained blood samples from 45 male medical students during examinations and approximately 3-4 weeks before the examinations (baseline) and measured antibody titers to EBV and plasma cortisol levels. We found reproducible changes in EBV, virus capsid antigen (VCA) antibody titers, with higher antibody titers observed in the examination blood samples consistent with the reactivation of latent virus. However, we found no evidence that day and night plasma cortisol values across the sampling points changed significantly from baseline to examinations. Therefore, academic stress did not elevate cortisol levels, but increases in EBV VCA antibody titers were still observed. The data suggest in these subjects that other neuropeptides or hormones were involved in the induction of latent EBV.

Influence of academic stress and season on 24-hour mean concentrations of ACTH, cortisol, and beta-endorphin.

We investigated the influence of a common stressful event, i.e., academic examinations, on the 24-h mean concentration of adrenocorticotropic hormone (ACTH), cortisol, and/or beta-endorphin. In addition, we evaluated the effect of season on the endocrine response to this stressor. We studied medical students (n = 55), screened for a variety of health and life style factors, from three consecutive medical school classes 1 month before, during, and 2 weeks following examinations. Hourly blood samples were obtained from an indwelling catheter and two serum pools were made (0800-2200h = day and 2300-0700h = night). Examinations produced a significant (p < .001) increase in perceived stress scores. In addition, we found a significant (p < .001) effect of examination stress on the increase in mean daytime but not nocturnal ACTH levels during autumn, but not during the spring. In contrast, the examination stress did not significantly affect day or night mean cortisol levels from baseline to examination week. We further divided the students by whether their perceived stress scores increased during examination week and fell during recovery (Group 1) or whether their perceived stress scores did not follow the expected pattern (Group 2). We found that in the Group 1 students who perceived the most stress, cortisol levels significantly increased (p < .001) from baseline to examination. Therefore, the nature of the stressor and the state of the responder were of equal importance in the observed cortisol response during examinations among these students. Further, academic stress had no significant effect on beta-endorphin levels. Finally, we found that the mean day and night ACTH levels were higher (p < .001) in the spring than in the fall; a seasonal influence on cortisol and beta-endorphin concentrations, however, was not observed. In summary, we have demonstrated that stress associated with the taking of examinations produces a dissociation among mean 24-h levels of ACTH, cortisol, and beta-endorphin. In addition, daytime cortisol levels increased during examinations only in the group of students whose perceived stress scores increased. Further, a seasonal influence on ACTH secretion was suggested by these results with higher levels observed in the spring than in the fall.

The anatomical distribution of skin cancers.

The relative density of skin tumours by anatomical site has been drawn from a variety of clinical studies and tumour registry investigations. The data sources are remarkably consistent and support current theories implicating chronic solar exposure in the development of non-melanoma and intense exposure for melanoma tumours.

GM1 ganglioside and darkly staining neurons in brains of rats subjected to neonatal hypoxia-ischemia.

Rat pups, seven days old, with right carotid artery ligations were exposed to an atmosphere of oxygen 8% remainder nitrogen for 2 hr. The animals that survived for three weeks after the hypoxic-ischemic episode had clusters of darkly stained (hematoxylin-eosin) neurons in the cortex and reduced uptake of dopamine (frontal cortex) and choline (frontal cortex, hippocampus and striatum) in preparations of synaptosomes. Treatment with GM1 ganglioside partially corrected the loss of uptake activity and increased the number of darkly stained neurons.

The incidence of the gene for thermolabile methylene tetrahydrofolate reductase in African Americans.

Increased levels of homocysteine have been linked to both arterial and venous thromboembolic problems (1,2). Homocystinuria is a relatively rare disorder caused by a deficiency of cystathione synthase and is characterized by markedly increased levels of homocysteine and premature vascular disease (3-5). Epidemiological studies have suggested that mild elevations of homocysteine are also associated with vascular disease (2). Recent evidence suggests that a polymorphism of the gene encoding for 5,10-methylene tetrahydrofolate reductase (MTHFR) gives rise to a thermolabile form of the enzyme that is associated with increased levels of homocysteine when inherited as a homozygous trait (6). This polymorphism is due to a C --> T substitution at nucleotide 677 which converts an alanine to valine in a conserved portion of the molecule (6). The allele frequency for the thermolabile form of the enzyme was quite high (0.38) in a population of French Canadians. This polymorphism thus appears to be a common risk factor for increased plasma levels of homocysteine and vascular diseases. As the incidence of such genetic polymorphisms often varies among ethnic populations, we were interested in comparing the incidence of this polymorphism in Caucasians and African Americans.

The prognostic significance of Ki-67 labeling indices for oligodendrogliomas.

OBJECTIVE: The prognostic significance of quantitative measurement of tumor proliferative activity was evaluated for oligodendroglial tumors. METHODS: Ki-67/MIB-1 immunochemistry was used to measure proliferative activity in 81 oligodendrogliomas and oligoastrocytomas. The relationship among survival, proliferation, histological features, and clinical variables were evaluated using a Cox proportional hazards analysis. RESULTS: After stratifying by histological grade and adjusting for age at diagnosis, there was a significant association between the Ki-67/MIB-1 labeling index (LI) (percentage of positive cells) and survival (P = 0.04). This association was illustrated further by the significantly different survival of two groups based on LI ranges of less than or equal to 5 and greater than 5 (P < 0.0001). CONCLUSION: The poor correlation between mitotic figures and survival in oligodendrogliomas that has been reported previously emphasizes the need for an accurate method to measure proliferative activity. Our study demonstrated the usefulness of the Ki-67/MIB-1 LI and demonstrated that LI ranges can be defined for clinical application.

Prognostic significance of flow cytometry deoxyribonucleic acid analysis of human astrocytomas.

Flow cytometry was used to determine the deoxyribonucleic acid ploidy and proliferative activity of 230 astrocytomas. The relationships among survival, ploidy, proliferation, histological features, and clinical variables were analyzed. Multivariate analysis confirmed the independent prognostic significance of the S-phase fraction (P < 0.01), ploidy (P = 0.04), age at diagnosis (P < 0.001), extent of surgery (P < 0.01), and sex (P = 0.03). Three groups with significantly different survival were defined based on S-phase fraction ranges of < 3%, 3%-5.9%, and > or = 6%. The strong correlation between the S-phase fraction and survival confirmed the importance of quantitative proliferation assays in predicting tumor behavior and demonstrated that specific reference ranges can be defined for clinical application. The weaker association between ploidy and survival leaves the usefulness of the determination of ploidy with flow cytometry in doubt.

Prognostic significance of flow cytometry deoxyribonucleic acid analysis of human oligodendrogliomas.

Flow cytometry was used to determine the deoxyribonucleic acid ploidy and proliferative activity of 60 oligodendrogliomas and oligoastrocytomas. The relationships among survival, ploidy, proliferation, histological features, and clinical variables were analyzed. Survival was strongly associated with the S-phase fraction (P < 0.001). Three groups with significantly different survival rates were defined, based on S-phase fraction ranges of < 3%, 3 to 5.9%, and > 6%. Significant associations between survival and age at diagnosis (P < 0.001), tumor grade (P < 0.001), and extent of surgery (P < 0.01) were found also. The poor correlation between mitotic figures and survival in oligodendrogliomas that has been reported previously emphasizes the need for an accurate method to measure proliferative activity. Our study demonstrated the usefulness of the flow cytometry-determined S-phase fraction in this regard and demonstrated that specific reference ranges could be defined for clinical application. In contrast, the determination of ploidy by flow cytometry was not useful in the evaluation of oligodendrogliomas.

Sex- and age-related differences in ceramide dihexosides of primary human brain tumors.

Neutral glycolipids (NGL) are promising diagnostic markers of human gliomas, but differences in NGL with age and sex have not been examined. Previous work demonstrated that ceramide dihexosides (CDH) levels in mouse kidney are age- and sex-dependent, probably due to levels of sex hormones. We quantitated CDH in 181 human gliomas and found significant differences with sex and age, particularly menopause and male puberty. This emphasizes the importance of assessing results of studies on glycolipids in disease states with respect to age and sex in order to avoid erroneous conclusions concerning the relationship of glycolipid composition with diagnosis and pathogenesis.

Bayesian modelling of the dynamics of hepatotoxicity.

Hepatotoxicity (liver damage) is a common problem in drug treatment trials but is observed only indirectly through biomarkers measured in the blood. This creates the need to infer an individual's unobserved liver function dynamically using blood tests and other patient baseline characteristics. Major statistical challenges include high dimensionality, irregular time observation points over patients, presence of missing observations, and noise involved in measurement and biological processes. This article introduces a class of multivariate Bayesian dynamic stochastic models for detecting and forecasting changes in an individual's liver function in two situations: without and with drug. These models separate measurement error from variation inherent in a biological process, and describe the underlying process of liver detoxification, whereby, drug affects liver function which in turn induces changes in observed analytes. We apply the Bayesian methodology to make an inference. A clinical toxicity study is examined, together with simulated data. The results suggest that changes in observed analytes can be captured by the proposed models.

Diagnostic and prognostic value of glycosyltransferase mRNA in glioblastoma multiforme patients.

Glioblastoma multiforme (GBM) is the most common and aggressive primary human brain tumour in adults with an average survival of 11 months. The 2-year survival is less than 10%, and only a small proportion of patients are alive at 3 years. Despite improved treatment strategies and aggressive therapy, the prognosis of GBM has changed little in past decades. Thus, any test that can reliably and rapidly diagnose the tumour and predict patient survival could be a valuable tool. Herein we report the use of quantitative real-time polymerase chain reaction (PCR) to quantify five glycosyltransferase transcripts in gliomas. Our results indicate that measuring GM1 synthase (beta-1,3 galactosyltransferase) mRNA may provide a useful method for segregating GBMs from other types of gliomas. In these studies, 97% of gliomas (36/37 tumours) below a threshold value had a diagnosis of GBM compared with 49% (52/106 tumours) above the threshold. More importantly, the increased expression of GD3 synthase mRNA in combination with decreased GalNAcT message correlated with increased survival in 79 GBM patients (proportional hazards model controlling for age, P = 0.02). These data were further corroborated by a data analysis from one of our previous studies on gangliosides of 80 GBMs, in which increased amounts of GM3 and GD3 (which accumulate in the absence of GalNAcT) correlated with a longer survival (P < 0.01). Thus, measuring GalNAcT and GD3 transcripts may provide a rapid method to assess prognosis in GBM patients. In summary, the data indicate that measuring glycosyltransferase mRNA levels by real-time PCR may be clinically useful for determining both diagnosis and prognosis in GBM patients.

Stochastic search strategy for estimation of maximum likelihood phylogenetic trees.

The maximum likelihood (ML) method of phylogenetic tree construction is not as widely used as other tree construction methods (e.g., parsimony, neighbor-joining) because of the prohibitive amount of time required to find the ML tree when the number of sequences under consideration is large. To overcome this difficulty, we propose a stochastic search strategy for estimation of the ML tree that is based on a simulated annealing algorithm. The algorithm works by moving through tree space by way of a "local rearrangement" strategy so that topologies that improve the likelihood are always accepted, whereas those that decrease the likelihood are accepted with a probability that is related to the proportionate decrease in likelihood. Besides greatly reducing the time required to estimate the ML tree, the stochastic search strategy is less likely to become trapped in local optima than are existing algorithms for ML tree estimation. We demonstrate the success of the modified simulated annealing algorithm by comparing it with two existing algorithms (Swofford's PAUP* and Felsenstein's DNAMLK) for several theoretical and real data examples.