Development of hexachlorobenzene porphyria in rats: time sequence and relationship with lipid peroxidation

The relationship between the development of porphyria and free-radical formation induced by hexachlorobenzene was studied in iron-overloaded rats. The first sign of porphyria, an increase in porphyrins in the liver, was detected at day 22. Liver malondialdehyde was also increased at day 22. During the following weeks, liver porphyrins and malondialdehyde increased simultaneously, accompanied by a decrease in uroporphyrinogen decarboxylase activity and glucose-6-phosphate activity in liver, and a high excretion of porphyrins in the urine. In the rats given hexachlorobenzene, changes were detected in the pattern of lipids in the liver microsomes. In comparison with the controls, there were decreases in C20:4 and C22:5 fatty acids, whereas the fatty acid C20:3w6 was increased. In this study of hexachlorobenzene-induced liver damage there was no difference in the time course of the development of porphyria and that of lipid peroxidation.

Blood exchange and transfusion therapy for acute cholestasis in protoporphyria

Acute cholestasis is a rare complication of EPP with a high mortality rate despite extensive treatment with corticosteroids, cholestyramine, and antioxidants. A single survivor, reported in the literature, was treated with blood exchange transfusions. We treated two EPP patients with blood exchange and additional blood transfusions which resulted in full clinical and biochemical recovery from the cholestasis and accompanying hepatitis. Recurrences of the cholestasis and hepatitis could repeatedly be corrected by additional blood transfusions.

Automating the quantification of heme in feces

We present a modification of the HemoQuant assay, a good but lengthy and tedious method for determining heme in feces by means of its transformation to porphyrins. The laborious extraction procedure was replaced by a simple centrifugation procedure. The nonhomogeneous hot oxalic acid suspension was replaced by acetic acid. We observed no significant difference in results between samples analyzed by the older method vs the present modification (r = 0.996, n = 52). Mean (and SD) analytical recoveries of added hemoglobin and protoporphyrin were 99% (7%) and 93% (6%), respectively. The analytical procedure can now be automated by using discrete samplers and a flow-through fluorometer. Initial sampling and dilution of feces are still done manually, however. The excellent specificity, sensitivity, and overall analytical performance of the original method are retained, while circumventing the practical inconveniences of this reliable screening test for occult blood in feces.

Automating the quantification of heme in feces

We present a modification of the HemoQuant assay, a good but lengthy and tedious method for determining heme in feces by means of its transformation to porphyrins. The laborious extraction procedure was replaced by a simple centrifugation procedure. The nonhomogeneous hot oxalic acid suspension was replaced by acetic acid. We observed no significant difference in results between samples analyzed by the older method vs the present modification (r = 0.996, n = 52). Mean (and SD) analytical recoveries of added hemoglobin and protoporphyrin were 99% (7%) and 93% (6%), respectively. The analytical procedure can now be automated by using discrete samplers and a flow-through fluorometer. Initial sampling and dilution of feces are still done manually, however. The excellent specificity, sensitivity, and overall analytical performance of the original method are retained, while circumventing the practical inconveniences of this reliable screening test for occult blood in feces.

Elevated protein requirements in cirrhosis of the liver investigated by whole body protein turnover studies

1. In patients with cirrhosis of the liver and in healthy control subjects, the rates of nitrogen flux, protein synthesis and protein breakdown were studied, using a single oral dose of 200 mg of [15N]glycine as a tracer. The nitrogen flux through the amino acid pool was measured separately with both urinary ammonia and urinary urea as end products; the average value was used for further calculations. 2. Subjects were studied in the fed state, both on an adequate and a protein-restricted diet, and also in the fasting state. 3. The rates of protein synthesis were markedly increased in the patients, not only in the fed but also in the fasting state. Protein breakdown rates were increased in the patients in the fed state. 4. The nitrogen balance in steady-state conditions in the fed state was more positive in the patients, while their nitrogen loss in the fasting state was no higher than that of control subjects. 5. A hypothesis is put forward that the high protein requirements of cirrhotic patients could be caused by small and inadequate liver glycogen stores; due to these small stores, gluconeogenesis from amino acids will take place and lead to an extra amino acid loss even during short-term fasting. This increased amino acid loss could explain the elevated protein requirements in cirrhotic patients.

Standardization of heparins by means of high performance liquid chromatography equipped with a low angle laser light scattering detector

This study shows that HPLC-LALLS (high performance liquid chromatography with a light-scattering detector) is a convenient and reliable method for the characterization of standard heparin samples, provided that polyelectrolyte artefacts are suppressed by a suitable dialysis procedure. The method has been successfully applied to the assessment of calibrated relations like the Mark-Houwink relation and the calibration curve of gel permeation chromatography. Furthermore, this study confirms that gel permeation chromatography for heparins cannot be calibrated with dextranes or polyethyleneglycols, but in addition to this well known fact it is shown that even the universal (hydrodynamic volume) calibration procedure does not work. Moreover, in addition to the familiar conclusion that heparins should be calibrated with heparins, it is shown that calibrated relations are valid only when the calibration has been made with heparin samples of the same origin (i.e. same tissue source, same animal source, and same purification scheme).

Determination of haemoglobin in gastric aspirates

The haemoglobin content of gastric aspirates can be quantitated by conversion of non-fluorescent haem to fluorescent porphyrins by heating gastric aspirates with oxalic acid and ferrous sulphate. Recovery of haemoglobin added to gastric aspirates was 92 +/- 9%, variation coefficient, n = 52, day to day variation less than 8%. This method was used to calculate blood (haemoglobin) loss in 211 (24 hours) gastric aspirates obtained from 58 intensive care patients. Gastric blood loss was also measured by the 51Cr radiolabelled erythrocytes method in the same samples. There was a good linear correlation (r = 0.942, p less than 0.001) between the two methods. The fluorimetric method of quantitating haem is therefore suitable for detecting and measuring blood loss in gastric contents.

Bile acid malabsorption in cystic fibrosis; membrane vesicles, a tool for revealing the role of the ileal brush border membrane

Increased fecal bile acid loss in cystic fibrosis (CF) may result from ileal dysfunction. A method to quantitate in vitro Na+-dependent taurocholate uptake into brush border membrane vesicles prepared from frozen ileum and ileal biopsy specimen is described. This transport across the ileal brush border membrane can be measured selectively, in contrast to in vivo measurements which represent a complex overall process. Preliminary results obtained with ileal specimen of 2 CF patients, suggest that in vitro bile acid uptake is low but not abnormal.

Venous capacity, venous refill time and the effectiveness of the calf muscle pump in normal subjects

With strain gauge plethysmography various procedures to assess the competence of the venous system in the lower leg were compared in 10 normal subjects. The reproducibility and ease of use were established, and normal values were obtained. It is concluded, that measurements in the sitting position are preferable to those in the standing position. To measure the venous capacity, the dependency test is the method of choice. Rhythmic exercise to assess the effectiveness of the calf muscle pump can be restricted to five successive contractions. The refill time after exercise is not a suitable parameter to assess the competence of the venous valves.

Endogenous bile acid tolerance test for liver function

Fasting and postprandial (stimulated) serum conjugated bile acids (CBA) were measured by a solid-phase radioimmunoassay in 329 patients undergoing liver biopsy, and the results were analyzed for 231 who fitted into 10 diagnostic categories. In healthy volunteers the mean fasting CBA of 1.8 +/- 0.7 mumol/liter rose to 3.0 +/- 0.8 mumol/liter postprandially. In patients mean fasting and stimulated CBA were only significantly raised in moderate to severe chronic and acute liver disease. Diagnostic sensitivity was poor in mild liver disease. Individuals with normal results were found in 8 of 11 disease categories. The ratio of stimulated to fasting CBA expressed in a stimulation quotient did not rise in more advanced liver disease. These findings are best explained by a constant fractional clearance of bile acids by the liver. We conclude that the serum conjugated bile acid determination as a test of liver cell function is not sensitive enough to identify all cases of biopsy-proven liver disease.

Familial porphyria cutanea tarda: the pattern of porphyrins formed from porphobilinogen by hemolysates

Porphyria cutanea tarda is thought to result from an inherited deficiency of uroporphyrinogen decarboxylase (EC 4.1.1.37) in some patients. Present methods for determining uroporphyrinogen decarboxylase activity are time consuming, so we examined the pattern of porphyrins formed from porphobilinogen by hemolysates as a possible marker for hereditary porphyria cutanea tarda. After the hemolysates are incubated with porphobilinogen, the porphyrins are converted to their methyl esters and examined by liquid chromatography, with fluorometric detection. The porphyrinic patients examined, and some of their relatives, showed a characteristic pattern of porphyrin production, with high uroporphyrin/coproporphyrin and (uroporphyrin + heptacarboxylic porphyrins)/coproporphyrin ratios, at least partly ascribable to increased uroporphyrinogen I synthetase (EC 4.2.1.8) activity in patients' hemolysates, and also to a relative deficiency of uroporphyrinogen decarboxylase. Examination of the pattern of porphyrins produced from porphobilinogen by hemolysates is a suitable technique for detecting asymptomatic individuals with porphyria cutanea tarda.

Familial porphyria cutanea tarda: the pattern of porphyrins formed from porphobilinogen by hemolysates

Porphyria cutanea tarda is thought to result from an inherited deficiency of uroporphyrinogen decarboxylase (EC 4.1.1.37) in some patients. Present methods for determining uroporphyrinogen decarboxylase activity are time consuming, so we examined the pattern of porphyrins formed from porphobilinogen by hemolysates as a possible marker for hereditary porphyria cutanea tarda. After the hemolysates are incubated with porphobilinogen, the porphyrins are converted to their methyl esters and examined by liquid chromatography, with fluorometric detection. The porphyrinic patients examined, and some of their relatives, showed a characteristic pattern of porphyrin production, with high uroporphyrin/coproporphyrin and (uroporphyrin + heptacarboxylic porphyrins)/coproporphyrin ratios, at least partly ascribable to increased uroporphyrinogen I synthetase (EC 4.2.1.8) activity in patients' hemolysates, and also to a relative deficiency of uroporphyrinogen decarboxylase. Examination of the pattern of porphyrins produced from porphobilinogen by hemolysates is a suitable technique for detecting asymptomatic individuals with porphyria cutanea tarda.

A continuous wave Doppler velocimeter for monitoring blood flow in the popliteal artery, compared with venous occlusion plethysmography of the calf

A transcutaneous Doppler velocimeter has been used for monitoring changes in blood flow in the popliteal artery during and after exercise of the calf muscles on a calf-ergometer. The instrument and the positioning of the probe are described. The validity of the Doppler measurements has been assessed by comparing results after exercise and after 5 min arterial occlusion with venous occlusion plethysmography. For 10 healthy volunteers calibration lines were found which are curved. This can be ascribed partly to alinearity of the Doppler instrument and partly to changes of the diameter of the popliteal artery. Displacement of the probe with respect to the artery, which influences the measured velocity signal, can be detected and to a certain extent corrected by taking into account the intensity of the Doppler signal. The largest deviation of a data point from the corresponding calibration line varies for the ten subjects between 90 and 170 Hz in the high flow range (mean Doppler frequency around 1000 Hz) and between 20 and 60 Hz in the low flow range (mean Doppler frequency below 200 Hz).