Physical Conditions of Fast Glacier Flow: 3. Seasonally-Evolving Ice Deformation on Store Glacier, West Greenland.

Temporal variations in ice sheet flow directly impact the internal structure within ice sheets through englacial deformation. Large-scale changes in the vertical stratigraphy within ice sheets have been previously conducted on centennial to millennial timescales; however, intra-annual changes in the morphology of internal layers have yet to be explored. Over a period of 2 years, we use autonomous phase-sensitive radio-echo sounding to track the daily displacement of internal layers on Store Glacier, West Greenland, to millimeter accuracy. At a site located ∼30 km from the calving terminus, where the ice is ∼600 m thick and flows at ∼700 m/a, we measure distinct seasonal variations in vertical velocities and vertical strain rates over a 2-year period. Prior to the melt season (March-June), we observe increasingly nonlinear englacial deformation with negative vertical strain rates (i.e., strain thinning) in the upper half of the ice column of approximately -0.03 a-1, whereas the ice below thickens under vertical strain reaching up to +0.16 a-1. Early in the melt season (June-July), vertical thinning gradually ceases as the glacier increasingly thickens. During late summer to midwinter (August-February), vertical thickening occurs linearly throughout the entire ice column, with strain rates averaging 0.016 a-1. We show that these complex variations are unrelated to topographic setting and localized basal slip and hypothesize that this seasonality is driven by far-field perturbations in the glacier's force balance, in this case generated by variations in basal hydrology near the glacier's terminus and propagated tens of kilometers upstream through transient basal lubrication longitudinal coupling.

Linear response of east Greenland's tidewater glaciers to ocean/atmosphere warming.

Predicting the retreat of tidewater outlet glaciers forms a major obstacle to forecasting the rate of mass loss from the Greenland Ice Sheet. This reflects the challenges of modeling the highly dynamic, topographically complex, and data-poor environment of the glacier-fjord systems that link the ice sheet to the ocean. To avoid these difficulties, we investigate the extent to which tidewater glacier retreat can be explained by simple variables: air temperature, meltwater runoff, ocean temperature, and two simple parameterizations of "ocean/atmosphere" forcing based on the combined influence of runoff and ocean temperature. Over a 20-y period at 10 large tidewater outlet glaciers along the east coast of Greenland, we find that ocean/atmosphere forcing can explain up to 76% of the variability in terminus position at individual glaciers and 54% of variation in terminus position across all 10 glaciers. Our findings indicate that (i) the retreat of east Greenland's tidewater glaciers is best explained as a product of both oceanic and atmospheric warming and (ii) despite the complexity of tidewater glacier behavior, over multiyear timescales a significant proportion of terminus position change can be explained as a simple function of this forcing. These findings thus demonstrate that simple parameterizations can play an important role in predicting the response of the ice sheet to future climate warming.

Sensitive response of the Greenland Ice Sheet to surface melt drainage over a soft bed.

The dynamic response of the Greenland Ice Sheet (GrIS) depends on feedbacks between surface meltwater delivery to the subglacial environment and ice flow. Recent work has highlighted an important role of hydrological processes in regulating the ice flow, but models have so far overlooked the mechanical effect of soft basal sediment. Here we use a three-dimensional model to investigate hydrological controls on a GrIS soft-bedded region. Our results demonstrate that weakening and strengthening of subglacial sediment, associated with the seasonal delivery of surface meltwater to the bed, modulates ice flow consistent with observations. We propose that sedimentary control on ice flow is a viable alternative to existing models of evolving hydrological systems, and find a strong link between the annual flow stability, and the frequency of high meltwater discharge events. Consequently, the observed GrIS resilience to enhanced melt could be compromised if runoff variability increases further with future climate warming.

Long term prognosis of fatty liver: risk of chronic liver disease and death.

BACKGROUND AND AIMS: Fatty liver is a common histological finding in human liver biopsy specimens. It affects 10-24% of the general population and is believed to be a marker of risk of later chronic liver disease. The present study examined the risk of development of cirrhotic liver disease and the risk of death in a cohort diagnosed with pure fatty liver without inflammation. METHODS: A total of 215 patients who had a liver biopsy performed during the period 1976-1987 were included in the study. The population consisted of 109 non-alcoholic and 106 alcoholic fatty liver patients. Median follow up time was 16.7 (0.2-21.9) years in the non-alcoholic and 9.2 (0.6-23.1) years in the alcoholic group. Systematic data collection was carried out by review of all medical records. All members of the study cohort were linked through their unique personal identification number to the National Registry of Patients and the nationwide Registry of Causes of Death, and all admissions, discharge diagnoses, and causes of death were obtained. RESULTS: In the non-alcoholic fatty liver group, one patient developed cirrhosis during the follow up period compared with 22 patients in the alcoholic group. Survival estimates were significantly (p<0.01) different between the two groups, for men as well as for women, with a higher death rate in the alcoholic fatty liver group. Survival estimates in the non-alcoholic fatty liver group were not different from the Danish population. CONCLUSIONS: This study revealed that patients with type 1 non-alcoholic fatty liver disease have a benign clinical course without excess mortality.

Serum YKL-40 is increased in patients with hepatic fibrosis.

BACKGROUND/AIMS: YKL-40, a mammalian member of the chitinase family, is a lectin that binds heparin and chitin. The function of YKL-40 is unknown, but it may function in tissue remodelling. The aims of this study were to assess the level of circulating YKL-40 in patients with various kinds and degree of chronic liver disease and its possible relation to liver fibrosis. METHODS: Serum YKL-40 levels were determined by radioimmunoassay in 129 patients with suspected liver disease and related to histological findings and immunohistochemical staining of YKL-40 in a liver biopsy taken simultaneously with the blood sample. RESULTS: The median serum YKL-40 was highest in patients with alcoholic cirrhosis (532 microg/l), in particular in patients with additional alcoholic hepatitis (740 microg/l). Patients with alcoholic cirrhosis, post-hepatitic cirrhosis (425 microg/l) and non-cirrhotic fibrosis (330 microg/l) had significantly higher serum YKL-40 than normal subjects (102 microg/l), patients with fatty liver (195 microg/l) or patients with viral hepatitis without fibrosis (174 microg/l). Serum YKL-40 was significantly (p<0.001) related to the degree of liver fibrosis with the highest levels in patients with moderate (466 microg/l) to severe (676 microg/l) fibrosis. Serum YKL-40 was also increased (p=0.018) in patients with slight fibrosis (270 microg/l) compared to patients without fibrosis. Immunohistochemical analysis demonstrated positive staining for YKL-40 antigen in areas with fibrosis, particularly areas with active fibrogenesis. YKL-40 staining was never found in hepatocytes. CONCLUSIONS: Our study indicates that the increased serum YKL-40 in patients with liver disease of various degree and aetiology seems to reflect fibrosis and fibrogenesis.

Distribution of liver haemosiderin iron in 187 patients with various types of hepatic diseases.

The purpose of this study was to evaluate the distribution of haemosiderin iron in various regions of the liver (central, intermediary and peripheral hepatocytes, Kupffer cells, portal macrophages and bile duct epithelial cells) in 174 patients with different hepatic diseases (alcoholic cirrhosis (n = 49), alcoholic steatosis (n = 60), non-alcoholic cirrhosis (n = 16), acute hepatitis (n = 20), clinically overt untreated hereditary haemochromatosis (n = 3), miscellaneous disorders (n = 26)), and in 13 subjects with a normal liver biopsy. Furthermore, the relationship between liver haemosiderin iron, biochemical iron status markers and biochemical liver tests was investigated. In haemochromatosis iron was consistently present in all examined regions of the liver, and in 43% of patients with alcoholic liver disease haemosiderin was present in at least one region of the liver lobule. In 65% of patients with acute hepatitis, haemosiderin was present in macrophages and Kupffer cells. In other hepatic diseases and in normal livers, haemosiderin was rarely seen. Regression analyses showed a correlation between iron status markers in most patients, except in those with high serum aspartate aminotransferase levels. In conclusion, haemosiderin iron is distributed in a typical pattern in haemochromatosis, alcoholic liver disease and acute hepatitis. Both histochemical liver iron and serum ferritin are of value as indirect markers of liver iron stores in patients with moderate hepatocellular damage.

Six billion neurons lost in AIDS. A stereological study of the neocortex.

Human immunodeficiency virus type 1 (HIV1) is neurotropic. One of the morphological changes that is seen in patients with acquired immunodeficiency syndrome (AIDS) is cerebral atrophy affecting various structures including the neocortex. The cause of atrophy is not known. The total number of neocortical neurons was estimated in formalin fixed brains of 12 males with AIDS and 12 male controls matched for age and height. The mean number of neocortical neurons was 16.0 x 10(9) (coefficient of variation = 0.11) in the AIDS patients compared with 21.9 x 10(9) (coefficient of variation = 0.22) in the controls, a difference of approximately six billion (p < 0.005, 2-tailed). The global neuronal loss was 37%, and affected all four neocortical lobes. Ten patients did not have a history of central nervous system symptoms; two patients had a history of dementia. The number of neurons in the AIDS cases was not associated with dementia. AIDS is the first disease in which a global loss of neocortical neurons has been demonstrated using unbiased stereological methods. The loss of more than one third of the neurons may partly explain the cortical atrophy. Focal neuron loss has been reported by several authors, but none have been based on unbiased methods. In this group of AIDS patients the severe loss of neurons did not correspond to neurological deficits.

Relationships among serum iron status markers, chemical and histochemical liver iron content in 117 patients with alcoholic and non-alcoholic hepatic disease.

Histochemical and chemical liver iron and iron status markers (serum (S-) ferritin, transferrin saturation) were determined in 109 patients with various types of liver disease (71 alcoholic, 38 non-alcoholic disease) and 8 normal subjects. In the series as a whole there was a significant correlation between histochemical hepatocyte iron and chemical iron (rho = 0.48, p = 0.0001). Of the iron status markers, only S-ferritin showed clinically significant correlations with histochemical liver iron (rho = 0.54, p = 0.0001) and chemical liver iron (r = 0.45, p = 0.0001) (log vs. log values). The highest correlation was found between S-ferritin and the product of chemical iron x ASAT (r = 0.61, p = 0.0001) (log vs. log values). None of the normal livers had stainable hepatocyte iron; median chemical iron content was 15 mumol/g dry weight (range 8-25). The entire group of alcoholics had a median liver iron content of 21 mumol/g; all patients had a hepatic iron index (hepatic iron/age) of under 1.4. In alcoholic liver disease, median chemical liver iron content was 15 mumol/g (range 3-36) in 35 subjects with grade 0 hepatocyte iron; 24 mumol/g (range 6-90) in 25 subjects with grade 1 + 2 hepatocyte iron; 30 mumol/g (range 14-74) in 11 subjects with grade 3 + 4 hepatocyte iron. Among subjects with alcoholic liver disease and normal liver iron (< 26 mumol/g), 39% had stainable hepatocyte iron vs. 70% in subjects with increased liver iron (> or = 26 mumol/g). The corresponding figures in subjects with non-alcoholic liver disease were 13% and 20%.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of liver fat using magnetic resonance spectroscopy.

Localized proton MR spectroscopy using stimulated echoes was used to quantify the liver fat concentration in patients with various degrees of fatty liver due to alcohol abuse. Ten patients underwent a liver biopsy followed by chemical triglyceride estimation of the fatty content. A statistically significant correlation was found between the fat concentration measured in the liver biopsies, and the concentration calculated from the spectroscopic experiments (r = 0.9, p < .001). Quantitative assessment of liver fat concentrations using localized spectroscopy is superior to methods based on differences in relaxation times, and can be used to estimate the fat concentration over the full range of fat content in contrast to the spectroscopic imaging methods. Localized spectroscopy may replace liver biopsy in the diagnosis of diffuse fatty infiltrations, and can be used for follow-up, due to its noninvasive nature.

Deposition of C3, the terminal complement complex and vitronectin in primary biliary cirrhosis and primary sclerosing cholangitis.

Characteristics of primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are bile duct destruction and portal inflammation. Increased levels of circulating complement activation products are also present. This raises the possibility of involvement of complement-dependent cytotoxic mechanisms in the pathogenesis. Therefore, we investigated liver biopsy specimens from 21 patients with PBC, six patients with PSC and six controls for complement deposits by immunohistochemistry using polyclonal and monoclonal antibodies against C3d, the terminal complement complex (TCC) and vitronectin (S-protein). We found C3d, TCC and vitronectin deposits only in the portal tracts. C3d and TCC were present in the walls of the hepatic arteries and in the connective tissue stroma but never around the bile ducts. We found vitronectin deposits throughout the connective tissue, often independent of the TCC deposits. When vitronectin and TCC were co-localized, the staining patterns were inverse; that is, intense staining for TCC accompanied weak staining for vitronectin and vice versa. Occasionally complete dissociation between TCC and vitronectin staining was observed. Deposits of TCC and vitronectin showed a focal distribution leaving many portal tracts free of TCC. Our results question whether complement-dependent cytotoxic mechanisms take part in the bile duct destruction in PBC and PSC.

Relation between bone marrow hemosiderin iron, serum iron status markers, and chemical and histochemical liver iron content in 82 patients with alcoholic and nonalcoholic hepatic disease.

Bone marrow hemosiderin iron was assessed in 48 patients with alcoholic, and in 34 patients with nonalcoholic liver disease (53 men, 29 women, median age 55 years, range 18-84) and correlated to serum (S)-iron status markers (iron, transferrin, ferritin), as well as to histochemical hepatocyte iron and chemical liver iron content. In a control group of 53 healthy subjects (23 men, 30 women, median age 28 years, range 18-90) marrow hemosiderin iron and iron status markers were evaluated as well. Among liver patients, the marrow iron grade was higher in men than in women (p = 0.03). Correlations were found between marrow iron and histochemical liver iron (rho = 0.38, p = 0.0001) as well as chemical liver iron (rho = 0.33, p = 0.01). Marrow iron was correlated to S-ferritin (rho = 0.53, p = 0.0001), mean red cell volume (rho = 0.34, p = 0.003), and S-transferrin (rho = -0.24, p = 0.02). Alcoholics had a higher marrow iron grade than nonalcoholics (p = 0.001) and controls (p = 0.0001). Among controls, the marrow iron grade was likewise higher in men than in women (p = 0.01). Correlations were found between marrow iron and ferritin (rho = 0.64, p = 0.0001), transferrin saturation (rho = 0.56, p = 0.001), transferrin (rho = 0.53, p = 0.001), S-iron (rho = 0.37, p = 0.01), and hemoglobin in women (rho = 0.38, p = 0.05). The results indicate that alcoholics either have increased marrow hemosiderin iron stores, or display a redistribution of iron in reticuloendothelial cells from soluble ferritin-bound iron to insoluble hemosiderin iron. Among patients with absent marrow hemosiderin iron, 81% had absent hepatocyte hemosiderin iron as well. Among patients with absent hepatocyte hemosiderin iron, 23% had absent and 77% normal or increased marrow hemosiderin iron. Therefore, in patients with iron depletion, assessment of marrow hemosiderin iron yields more relevant information of iron status than assessment of hepatocyte hemosiderin iron.

Cerebral atrophy in AIDS: a stereological study.

Stereological estimates of mean volumes, surface areas, and cortical thicknesses were obtained on formalin-fixed brains from 19 men with AIDS and 19 controls. Volumes of neocortex, white matter, central brain nuclei, ventricles and archicortex were estimated using point counting and Cavalieri's unbiased principle for volume estimation. In AIDS, the mean volume of neocortex was reduced by 11%, and that of the central brain nuclei by 18%. Mean ventricular volume was increased by 55%. Mean neocortical thickness was reduced by 12%. The mean volume of white matter was reduced by 13%. The findings in 6 clinically demented AIDS patients were not statistically different from the rest of the group.

Longitudinal study of influence of Helicobacter pylori on current risk of duodenal ulcer relapse. The Hvidovre Ulcer Project Group.

Seventy-four patients with duodenal ulcer were followed up longitudinally for 2 years after initial ulcer healing. Endoscopy including biopsy of the antral mucosa was performed every 3rd month and whenever clinical symptoms of relapse occurred. The presence of Helicobacter pylori in the biopsy specimens was scored as 0 (none), 1 (sporadic occurrence), 2 (clusters), and 3 (numerous bacteria found diffusely in the mucus layer). The incidence rates of ulcer relapse per patient-month, grouped in accordance with these scores, were (with 95% confidence intervals) 0.073 (0.048-0.111), 0.083 (0.052-0.133), 0.123 (0.096-0.157), and 0.069 (0.041-0.116), respectively. No significant differences in incidence rates across H. pylori scores were observed when taking into account the observation period after healing of the first ulcer, number of ulcer recurrence (1st, 2nd, 3rd), sex, age, smoking habits, peak acid output, time of healing of the preceding ulcer, treatment of the present ulcer (cimetidine, antacids, or no treatment), or type and degree of gastritis. Thus, although H. pylori is prevalent in patients with duodenal ulcer disease, the present study indicates that H. pylori does not have a substantial note in the precipitation of active duodenal ulcer.

Identification of patients with hereditary haemochromatosis by magnetic resonance imaging and spectroscopic relaxation time measurements.

A total of 4302 healthy blood donors were screened for elevated serum ferritin and transferrin saturation. Fifteen had increased serum ferritin at a follow-up examination. Five relatives of these donors also entered the study. Eleven patients had elevated liver iron concentrations, while five had normal liver iron concentrations. The R2 relaxation rate in the liver was first measured with a conventional multi-spin-echo imaging sequence, and then by a volume-selective spectroscopic multi-spin-echo sequence, in order to achieve a minimum echo time of 4 msec. No correlation was found between the relaxation rate R2 and the liver iron concentration, when R2 was calculated from the imaging data. Multi-exponential transverse relaxation could be resolved when the spectroscopic sequence was used. A strong correlation between the initial slope of the relaxation curve and the liver iron concentration was found (r = 0.90, p < 0.001). Signal intensity ratios between liver and muscle were calculated from the first three echoes in the multi-echo imaging sequence, and from a gradient echo sequence. A strong correlation between the logarithm of the signal intensity ratios and the liver iron concentration was found. Although both spectroscopic T2 relaxation time measurements and signal intensity ratios could be used to quantify liver iron concentration, the gradient echo imaging seemed to be the best choice. Gradient echo imaging could be performed during a single breath hold, so motion artifacts could be avoided. The accuracy of liver iron concentration estimates from signal intensity ratios in the gradient echo images was about 35%.

Hepatic effects of dietary weight loss in morbidly obese subjects.

This prospective study was carried out in order to evaluate the influence on liver morphology and function of a very-low-calorie formula diet. Fourty-one morbidly obese, non-alcoholic subjects had liver biopsy performed before and after a median weight loss of 34 kg. Fatty change improved (p less than 0.001), but 24% of the patients developed slight portal inflammation (p = 0.039) or slight portal fibrosis (p = 0.063). Patients developing portal fibrosis had a higher degree of fatty change at entry (p = 0.029), a more pronounced reduction of fatty change (p = 0.014) and a faster weight loss (p = 0.026). Liver biochemistry, which was of no individual diagnostic value, improved. It is concluded that morbidly obese subjects with a high degree of hepatic fatty change are at risk of developing portal inflammation and fibrosis when undergoing very fast dietary weight reductions.

The spectrum of alcohol induced liver disease. Histological features.

Alcohol may induce a variety of changes in the liver. None of the features are diagnostic, but some are relatively specific. Usually the simultaneous occurrence of one or more non-specific lesions in combination with other more specific changes leads to the correct diagnosis of alcoholic liver disease.

A reappraisal of Poulsen's disease (hepatic zone 1 sinusoidal dilatation).

The possible cause and pathogenesis of this disease are reviewed. The condition is rare, and there are only few reports which throw some light on this remarkable morphology. It is hypothesized that metabolic zonation in the functional liver acinus may be the basis of these changes, but lack of experimental and clinical studies still makes it enigmatic.

PIP: 3 types of possible causes of Poulsen's disease, also known as hepatic zone 1 sisusoidal dilatation, associated with oral contraceptives: hemodynamic, functional, and structural causes, are explored. Zone 1 is the peri-portal zone of Rappaport's classification: 4 cases of sinusoidal dilatation were described in oral contraceptive users in 1973. Despite developments in liver biopsy and laboratory investigations, no pathophysiology of this disorder has been proposed. It is not likely that aberrations in hemodynamics of the liver microcirculation or portal hypertension causes the problem. Swelling in zone 3 occurs in carbon tetrachloride toxicity and in alcoholic liver disease; but sinusoidal dilatation is not caused by congestive heart failure. There are several instances of functional differences in zonal distribution of toxic damage, such as metabolic concentration gradients in the liver sinusoids, for example for gluconeogenesis and bile acid transport. The structural causes of zone dilatation have been described in Poulsen's disease: sinusoids are empty and dilated, with detritus-filled dilated perisinusoidal spaces. Other instances of structural zonal damage are vinyl chloride toxicity and the zone 1 dilatation seen in toxicity from anabolic steroids. Zonal disease may be the unrecognized initial stages of a more general liver disease. No specific clinical or experimental data exists to pinpoint the pathophysiology of Poulsen's disease.

The pattern of fibrosis in the acinar zone 3 areas in early alcoholic liver disease.

The degree of fibrosis and the pattern of collagen distribution in the acinar zone 3, as well as the thickness of the terminal hepatic vein walls (THV) were analyzed in 48 consecutive liver needle biopsies from 48 alcoholics with preserved liver architecture. The fibrosis occurred to more or less the same degree in the whole circumference of each THV. A positive correlation was found between the degrees of perisinusoidal/pericellular fibrosis (PSF) and the occurrence of incomplete or complete septa. The thickness of THV walls (TTHV) varied from 1.0-12.5 microns with a median of 3.9 microns. No relationship was found between TTHV and PSF. The results were compared to similar data obtained in liver biopsies from 117 non-alcoholics with normal morphology or slight non-specific changes. No significant difference concerning TTHV and THV diameter was found between alcoholic and non-alcoholic patients. The results suggest that the initial liver fibrosis in alcoholics is slightly asymmetrical distributed in each acinar zone 3 area. With progression, the fibrosis tends to be more uniformly distributed and septa appear, eventually linking THV with portal tracts. Apparently, thickening of the THV walls does not occur in early alcoholic liver disease.

Prolonged T1 relaxation of the hemopoietic bone marrow in patients with chronic leukemia.

Eleven patients with chronic leukemia (7 with chronic lymphocytic leukemia and 4 with chronic myeloid leukemia) were evaluated with magnetic resonance (MR) imaging and T1 relaxation time measurements by use of a 1.5 tesla whole body MR scanner. Bone marrow biopsies were obtained from the posterior iliac crest (within 72 hours of the MR examination) in order to provide data on bone marrow cellularity and differential counts. The patients with chronic leukemia all showed a significant prolongation of the T1 relaxation times compared with the normal range for hemopoietic bone marrow.