Evaluation of hepatocyte injury following partial ligation of the left portal vein

BACKGROUND/AIMS

Total ligation of the left portal vein is thought to induce both hepatocyte apoptosis and necrosis. The pathological impact of partial ligation of a branch of the portal vein has not yet been evaluated.

METHODS

We studied the degree of hepatocyte injury following 0, 43, 48, 59, 68, 72, 78 and 100% left portal vein stenosis in 200-g Sprague-Dawley male rats. Serum alanine aminotransferase levels, total body weight, and left and right liver lobe weights were measured at 2 and 7 days. Mitosis and 3H-thymidine labelling indices were measured as markers of proliferation; the apoptotic index and TUNEL stain were used as markers to measure apoptotic cell death. Necrosis was assessed morphologically. All these parameters were evaluated 2 days after ligation.

RESULTS

There was a direct relation between the increase in weight of the right lobes and the reduction in weight of the left lobes. The degree of weight change correlated significantly with the degree of stenosis. In the right lobes, mitosis and 3H-thymidine labelling were increased in proportion to the degree of stenosis. In the left lobes, the decrease in volume of hepatocytes correlated with the degree of ligation, especially in the pericentral areas. Necrosis was identified only when ligation was > or = 68%, this being associated with an increase in alanine aminotransferase levels. On the other hand, apoptotic cells were identified in increasing numbers, starting from the lowest degree of ligation to 100% ligation. This was found both morphologically and with TUNEL stain.

CONCLUSIONS

Partial ligation of the left portal vein induces left liver atrophy through hepatocyte volume loss and apoptosis. Necrosis is found only when the degree of ligation is severe.

Cell cycle gene regulation in reversibly differentiated new human hepatoma cell lines

Several novel differentiated cell lines have been derived from a human hepatocarcinoma named HBG. Analysis of their functional properties evidenced a gradual differentiation process as they became confluent and a remarkable stability of the whole quiescent population for at least 6 weeks. However, when replated at low density after several weeks of quiescence, the differentiated cells were able to rapidly reverse to active proliferation, accompanied by transient dedifferentiation. Demonstration that the differentiated hepatic cells were growth-arrested in G1 phase was provided by the increased number of cells with 2C DNA content and decreased expression of S-phase markers. Characteristic features of oncogenes and cell cycle genes were defined during the differentiation process: (a) a biphasic expression of c-myc, with the latter wave covering the quiescence period; (b) opposite kinetics of c-Ki-ras and of N-ras expression with a pattern of changes paralleling that of c-myc; and (c) a decrease of cyclin D1 protein expression and of the cyclin D1-associated kinase activity. The mechanisms by which quiescent differentiated cells might reinitiate active proliferation were analyzed by studying several genes involved in cell growth and death regulation. We found: (a) a point mutation and loss of the specific activity of the tumor suppressor gene p53 without alteration of the apoptotic response to transforming growth factor beta1; (b) a gradual decrease of retinoblastoma protein, which was constantly present, mainly in a hyperphosphorylated form; and (c) an increase of cyclin-dependent kinase inhibitor p27 expression in confluent differentiating cells, as expected, whereas, surprisingly, a disappearance of the p21 protein was observed in parallel. These data may reflect specific mechanisms of cell cycle regulation in liver parenchymal cells through which these cells can proceed to control their reversible differentiation program.

Task-dependent effect of limb immobilization on the fatigability of the elbow flexor muscles in humans

Because short-term limb immobilization produces selective adaptations in the neuromuscular system that probably interact with the task-dependent expression of muscle fatigue, the purpose of this study was to determine the effects of limb immobilization on the ability of human subjects to sustain isometric contractions at low and moderate submaximal forces. Four weeks of elbow joint immobilization caused a substantial decrease in the daily activity of biceps brachii during immobilization, a significant reduction in the cross-sectional area and volume of the elbow flexor muscles as measured by magnetic resonance imaging, and a decline in the maximum voluntary contraction (MVC) activation and force of the elbow flexor muscles. Immobilization had a task-dependent effect on muscle fatigue with a substantially increased endurance time (reduced fatigability) at a low force (20% MVC) and no statistical effect at a moderate force (65% MVC). Despite atrophy of the elbow flexor muscles due to the immobilization, the twitch force elicited in biceps brachii by electrical stimulation was greater after immobilization. The selective improvement of fatigue resistance for the low-force contraction and the absence of a change in the time course of the twitch suggests that the immobilization-induced adaptations included an improved efficacy of some excitation-contraction processes and underscored the major role of these mechanisms in determining the endurance time for low-force, long-duration contractions.

Variability in hepatic iron concentration measurement from needle-biopsy specimens

BACKGROUND/AIM

Quantitative measurement of hepatic iron by biochemical analysis of liver biopsy samples is required to assess hepatic iron stores accurately. Cirrhotic livers, however, contain variable amounts of fibrous tissue and the distribution of iron within the hepatic parenchyma is not always uniform. The aim of this study was to assess the variability in hepatic iron concentration measurement from needle-biopsy specimens.

METHODS

The livers from eight patients with cirrhosis selected because of elevated serum ferritin were obtained at the time of liver transplantation (n = 6) or at autopsy (n = 2). Multiple needle biopsies were done, and hepatic iron concentration was measured by atomic absorption spectroscopy. The hepatic iron index was calculated as iron concentration divided by age.

RESULTS

Four cases had a mean hepatic iron index above 2.0, in the range of that reported in patients with homozygous genetic hemochromatosis, whereas the other four had an hepatic iron index of less than 2.0. The intra-individual coefficient of variation for hepatic iron concentration ranged from 11.3 to 43.7%, averaging 24.9%. The coefficient of variation was smaller in biopsy samples > 4 mg dry weight than in samples < 4 mg (19.8% vs 28.6%, p < 0.05). Histological examination of surgical biopsies from these livers showed large amounts of fibrous tissue, and inhomogeneous distribution or iron in the hepatic parenchyma.

CONCLUSIONS

This study demonstrates an important variability in the measurement of hepatic iron content from needle biopsy specimens in patients with severe cirrhosis.

Growth factor dependence of progression through G1 and S phases of adult rat hepatocytes in vitro. Evidence of a mitogen restriction point in mid-late G1

Several hepatocyte mitogens have been identified, but the signals triggering the G0/G1 transition and cell cycle progression of hepatocytes remain unknown. Using hepatocyte primary cultures, we investigated the role of epidermal growth factor/pyruvate during the entry into and progression through the G1 phase and analyzed the expression of cell cycle markers. We show that the G0/G1 transition occurs during hepatocyte isolation as evidenced by the expression of early genes such as c-fos, c-jun, and c-myc. In culture, hepatocytes progress through G1 regardless of growth factor stimulation until a restriction point (R point) in mid-late G1 beyond which they cannot complete the cell cycle without mitogenic stimulation. Changes in cell cycle gene expression were associated with progression in G1; the cyclin E mRNA level is low early in G1 but increases at the G1/S boundary, while the protein is constantly detected during cell cycle but undergoes a change of electrophoretic mobility in mid-late G1 after the R point. In addition, a drastic induction of cyclin D1 mRNA and protein, and to a lesser extent of cyclin D2 mRNA, takes place in mitogen-stimulated cells after the R point. In contrast, cyclin D3 mRNA appears early in G1, remains constant in stimulated cells, but accumulates in unstimulated arrested cells, paralleling the cyclin-dependent kinase 4 mRNA expression. These results characterize the different steps of G1 phase in hepatocytes.

Hypocalcemia decreases the early and late responses to epidermal growth factor in rat hepatocytes

Extreme variations in extracellular Ca2+ concentrations ([Ca2+]e) modify the signaling generated by many hormones and growth factors. However, the influence of physiological changes in [Ca2+]e on the response to hepatic mitogens remains largely unknown. To study the influence of [Ca2+]e on the response to epidermal growth factor (EGF), hepatocytes from normal rat livers were equilibrated in vitro at [Ca2+]e similar to those observed in normocalcemia or hypocalcemia. To further investigate the effect of hypocalcemia in vivo, hepatocytes were obtained from chronically hypocalcemic rats and kept in vitro at the [Ca2+]e prevailing in vivo. Intracellular Ca2+ concentrations ([Ca2+]i) and DNA synthesis were evaluated after increasing doses of EGF. [Ca2+]e strongly influenced the [Ca2+]i response to EGF with significantly smaller [Ca2+]i increases in hepatocytes of normal rats kept in low [Ca2+]e compared with those kept in normal [Ca2+]e. In hypocalcemic rat hepatocytes, the response was further decreased and found to be significantly lower than that obtained in control cells kept in vitro at either 1.25 mmol/L or 0.8 mmol/L [Ca2+]e. In normal [Ca2+]e, the EGF-induced increases in [Ca2+]i were abolished by inhibiting EGF receptor autophosphorylation and by blocking calcium channels. Low in vitro [Ca2+]e significantly dampened the EGF-mediated DNA synthesis in normal rat hepatocytes but hypocalcemia in vivo further reduced the proliferative response compared with that obtained in control rat hepatocytes maintained in normal, or low [Ca2+]e. Furthermore, the blunted responses in [Ca2+]i mobilization and DNA synthesis associated with hypocalcemia could not be overcome by increasing concentrations of EGF nor by normalization of [Ca2+]e in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-term immobilization has a minimal effect on the strength and fatigability of a human hand muscle

The purpose of this study was to determine the association between reduced fatigability typically observed in disused muscle and an improved resistance to the impairment of neuromuscular propagation. Endurance time of an isometric contraction sustained at 35% of maximum voluntary contraction (MVC) force and the fatigue-induced change in the evoked compound muscle action potential (M wave) were measured in the first dorsal interosseus muscle of human subjects before, during, and after 3 (n = 9) or 5 wk (n = 2) of immobilization. The immobilization procedure caused a substantial decline in the chronic electromyographic (EMG) activity (to 4% of control value) of the first dorsal interosseus muscle. Endurance time was found to be significantly correlated to the maintenance of M-wave amplitude during the fatigue task. However, neither of these variables was significantly affected by immobilization. Also, immobilization had no significant effect on the prefatigue values of MVC force and EMG or twitch contraction time or on the postfatigue changes in MVC force and EMG, M wave duration, twitch amplitude, and contraction time. In the unfatigued muscle, immobilization did cause an increase in twitch force (153%) and a decrease in M-wave amplitude (67%). It appears, therefore, that a healthy first dorsal interosseus muscle is generally resistant to adaptation when its use has been reduced for 3-5 wk by immobilization.

Changes in the electromyographic spectrum power distribution caused by a progressive increase in the force level

The purpose of the present study was to determine the specific changes occurring in the power spectrum with an increasing force level during isometric contractions. Surface electromyographic signals of the triceps brachii (TB) and the anconeus (AN) of 29 normal subjects were recorded during isometric ramp contractions performed from 0 to 100% of the maximum voluntary contraction (MVC) in a 5-s period. Power spectra were obtained at 10, 20, 30, 40, 50, 60, 70, 80 and 90% MVC. Changes in the shape of these spectra were evaluated visually and with the calculation of several statistical parameters related to the distribution of power along the frequency axis, such as median frequency and mean power frequency, standard deviation, skewness, first and third quartiles and half-power range. For the AN, the behaviour of the spectrum was relatively similar across subjects, presenting a shift toward higher frequencies without any major change in the shape of the spectrum. For the TB, subjects with a thin skinfold thickness presented similar behaviours. In subjects with a thicker skinfold, however, a loss of power in the high frequency region paralleled the increase in the force level. Significant correlations were obtained between the extent of the change in the value of higher order statistical parameters across force and the thickness of the skin. This points out the importance of the skinfold layer when recording with surface electrodes. Furthermore, the use of a combination of several parameters appears to provide a better appreciation of the changes occurring in the spectrum than any single parameter taken alone.

EMG power spectrum of elbow extensors: a reliability study

In order to be considered a potential tool for the characterization of muscle activity, the reliability of EMG power spectral analysis should be demonstrated. In this study, the reliability of the mean power frequency (MPF) and of the median frequency (MF) of power spectra (triceps brachii (TB), anconeus (AN)) obtained at different force levels from both ramp and stepwise isometric contractions was tested across three similar sessions performed on three different days (N = 9). Two-way ANOVAs for repeated measures did not disclose any significant differences (p > 0.05) in the value of either the MF or the MPF across the different sessions for either type of contraction. In contrast, significant changes (p < 0.05) in both the MF and the MPF were found across force levels. No significant interactions (p > 0.05) were found between the session and the force factors, for any of the analyses performed. The present results indicate that the MPF and the MF of the EMG power spectrum, taken at a specific force level, are reliable measures across sessions performed on different days. Consequently, this supports the possible use of power spectral analysis of EMG signals as an evaluation technique that could monitor changes in the neuromuscular system that can occur over a given period.

Comparison of the EMG power spectrum of the human soleus and gastrocnemius muscles

The purpose of this study was to compare the behaviour of electromyographic (EMG) power spectrum statistics, mean power frequency (MPF) and median frequency (MF), across increasing force levels of the soleus (SO), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) muscles. Surface EMG signals of these three muscles were recorded in 12 men and 10 women during both (1) ramp (single ongoing contractions with the force increasing linearly from 0 to 100% of the maximum voluntary contraction (MVC); and (2) step (steady force levels: 10, 20, 30, 40, 60 and 80% MVC) static (isometric) plantar flexions. Power spectral analysis of these signals was performed on single 256-ms windows at all of the above-mentioned force levels, for both types of contraction. The MF and MPF were calculated from each of the obtained spectra. A less pronounced increase in the MF or MPF was expected for the SO because of its higher type I fibre content. The main results are as follows: (1) similar behaviours were found in the value of MPF and MF across increasing force for the SO and GL muscles, while the GM gave rise to a different behaviour; (2) no difference was found between ramp and step contractions in the behaviour of either MF or MPF across force levels; and (3) different behaviours were observed between the MF and MPF across increasing force levels, for both ramp and step contractions. Our initial expectations were thus not confirmed. It is concluded that the present results support the hypothesis that the EMG power spectrum may be more sensitive to the diameter of the fibres than to the fibre type proportion of the triceps surae muscles. Furthermore, the sensitivity of the power spectrum statistics of a given muscle to the low-pass filter effect of its skin layer was also emphasized.

Transjugular intrahepatic portacaval stent shunt as a rescue treatment for life-threatening variceal bleeding in a cirrhotic patient with severe liver failure

Variceal bleeding in cirrhotic patients with severe liver failure that is not controllable by endoscopic sclerotherapy is a life-threatening situation. We report the case of a patient with decompensated cirrhosis (Pugh class C) who bled repeatedly from gastric varices despite multiple sessions of sclerotherapy. The portal vein was catheterized by a transjugular approach. A tract between a hepatic vein and the portal vein was created after balloon dilatation, and this opening was stented with an expandable stainless steel Palmaz stent. The portal vein pressure decreased from 35 mm Hg to 19 mm Hg after shunting. Gastric varices also were embolized. Two months later, bleeding had not recurred; the shunt remained opened and the marked decrease in portal pressure still persisted. Endoscopy showed the disappearance of gastric varices. This procedures could become a life-saving therapeutic option for such critically ill cirrhotic patients.

Clinical significance of the V-shaped space in the subluxed shoulder of hemiplegics

Recently, it has been proposed that shoulder subluxation in hemiplegia is accompanied by 1) the appearance of a V-shaped articular configuration occurring between the humeral head and glenoid fossa and 2) the presence of chronic pain. The main purpose of this study was to investigate the validity of these statements. We evaluated 40 hemiplegic subjects over 3 months. Radiographs of the affected and nonaffected shoulders were taken at both a frontal plane (0 degree) and a 45 degree incidence. From these patients, subluxed (n = 19) and nonsubluxed (n = 21) groups were formed. Pain was evaluated using the Present Pain Intensity index of the McGill Pain Questionnaire. On these x-ray films, measurements were taken of the V-shaped space, abduction of the arm, and rotation of the scapula. The statistical analysis (analysis of variance for repeated measures) contrasted the results obtained from the nonaffected side with those from the affected side over the 3 months studied. At the 45 degree angle, which better exposes the articular configuration of the shoulder, the difference in the V angle between the affected and nonaffected shoulders was significant for the subluxed group (p less than 0.01), indicating that such a V-shaped space can be identified. The measures taken also indicate that a downward subluxation of the humeral head occurs relative to the scapula without any systematic abduction of the humerus or downward rotation of the scapula. None of the results obtained from the frontal plane x-ray films was significant. Finally, no significant relation was found between subluxation and shoulder pain.

EMG power spectra of elbow extensors during ramp and step isometric contractions

The goal of the present study was to compare electromyogram (EMG) power spectra obtained from step (constant force level) and ramp (progressive increase in the force level) isometric contractions. Data windows of different durations were also analysed for the step contractions, in order to evaluate the stability of EMG power spectrum statistics. Fourteen normal subjects performed (1) five ramp elbow extensions ranging from 0 to 100% of the maximum voluntary contraction (MVC) and (2) three stepwise elbow extensions maintained at five different levels of MVC. Spectral analysis of surface EMG signals obtained from triceps brachii and anconeus was performed. The mean power frequency (MPF) and the median frequency (MF) of each power spectrum were obtained from 256-ms windows taken at 10, 20, 40, 60 and 80% MVC for each type of contraction and in addition on 512-, 1024- and 2048-ms windows for the step contractions. No significant differences (P greater than 0.05) were found in the values of both spectral statistics between the different window lengths. Even though no significant differences (P greater than 0.05) were found between the ramp and the step contractions, significant interactions (P less than 0.05) between these two types of contraction and the force level were found for both the MPF and the MF data. These interactions point out the existence of different behaviours for both the MPF and the MF across force levels between the two types of contraction.

The influence of an increase in the level of force on the EMG power spectrum of elbow extensors

It has been proposed that the mean power frequency (MPF) of the electromyogram (EMG) power spectrum increases gradually with force of contraction and that this increase is a function of the fiber-type content of the muscle investigated and the inter-electrode distance (IED) used when recording the EMG signals. In order to test these hypotheses, the values of the MPF of two elbow extensor muscles, triceps brachii (TB, 65% fast twitch fibers) and anconeus (AN, 65% slow twitch fibers), were compared at different levels of contraction. Subjects (n = 13) produced ten static ramp elbow extensions [0-100% maximum voluntary contraction (MVC)]. EMG signals of each muscle were recorded with two pairs of surface miniature electrodes having IEDs of 6 mm and 30 mm respectively. MPFs were obtained at each of the following levels: 10, 20, 40, 60, 80 and 100% MVC. Statistical analyses indicated that the MPF of AN increased significantly (P less than 0.05) up to 60% MVC. In contrast, the MPF values for TB showed no significant change across different levels of contraction (P greater than 0.05). Since skinfold was on average 3.2 times thicker over TB than over AN it is suggested that the low-pass filtering effect of the skin could have prevented the observation of an increase of the MPF for TB. It thus appears that changes of the MPF with the level of force, as disclosed by surface electrode recordings, is specific to each muscle. Consequently one has to account for factors such as thickness of the skinfold when it comes to the determination of the fiber-type content of different muscles within a subject.

Modulation of chylomicron remnant metabolism by an hepatic hydroxymethylglutaryl coenzyme A reductase inhibitor

This study was designed to test the hypothesis that in patients with elevated plasma low-density lipoprotein (LDL) apolipoprotein-apoB, chylomicron remnant clearance can be modulated by therapy with a hepatic hydroxymethyl glutaryl coenzyme A reductase inhibitor. Accordingly, chylomicron triglyceride and remnant clearance were determined following a vitamin-A fat load in 12 such patients, before and after therapy with Lovastatin (Merck, Sharp & Dohme, Rahway, NJ). Such therapy had no significant overall effect on plasma triglyceride clearance, although there was a trend to lower levels of Sf greater than 400 triglycerides at the later time points. By contrast, retinol clearance in plasma and Sf greater than 400 lipoproteins was markedly increased (30% and 40%, respectively). The data indicate, therefore, that following therapy with Lovastatin in this group of patients, chylomicron plasma remnant clearance was significantly enhanced. The exact mechanisms responsible remain to be explicated.

Dyslipoproteinemias after heart and heart-lung transplantation: potential relation to accelerated graft arteriosclerosis

Plasma lipid, lipoprotein lipid, and low-density lipoprotein (LDL) apolipoprotein B (Apo B) levels were measured in 34 patients who had undergone heart transplantation and in two patients who had undergone heart-lung transplantation. In contrast to initial reports, atherogenic dyslipoproteinemias were common, with 14% of patients having increased LDL cholesterol levels, 16.7% increased triglyceride levels, 8.3% decreased high-density lipoprotein (HDL) cholesterol levels, and 22.2% increased LDL Apo B levels. Of interest, 14% of patients had an HDL cholesterol level greater than the 95th percentile of the general population. In four patients coronary arteriosclerosis developed after transplantation. All had an atherogenic dyslipoproteinemia. One had type II hypercholesterolemia, and one had isolated low HDL cholesterol levels. Two had hyperapobetalipoproteinemia, one of whom also had low HDL cholesterol levels. The results establish that atherogenic dyslipoproteinemias are frequent in patients after heart transplantation and suggest that these dyslipoproteinemias, along with rejection, may play a role in the pathogenesis of arteriosclerosis after transplantation.

Study of the use of lincomycin aerosols in dogs

This paper reports studies on different aspects of the administration of lincomycin by aerosol in dogs.The purpose of the study was to determine the depth of penetration of the drug into the lungs and its transfer into the blood, urine and tissues when administered as an aerosol.Special consideration was given to the possibility of side effects at the level of the bronchial mucosa, since this study was viewed as preliminary to the use of the antibiotic in humans.