No changes in lung function after a saturation dive to 2.5 MPa with intermittent reduction in $$ P_{{{{\rm O}}_{{{\rm 2}}} }} $$ during decompression

Decompression stress and exposure to hyperoxia may cause a reduction in transfer factor of the lung for carbon monoxide and in maximal aerobic capacity after deep saturation dives. In this study lung function and exercise capacity were assessed before and after a helium-oxygen saturation dive to a pressure of 2.5 MPa where the decompression rate was reduced compared with previous deep dives, and the hyperoxic exposure was reduced by administering oxygen intermittently at pressures of 50 and 30 kPa during decompression. Eight experienced divers of median age 41 years (range 29-48) participated in the dive. The incidence of venous gas microemboli was low compared with previous deep dives. Except for one subject having treatment for decompression sickness, no changes in lung function or angiotensin converting enzyme, a marker of pulmonary endothelial cell damage, were demonstrated. The modified diving procedures with respect to decompression rate and hyperoxic exposure may have contributed to the lack of changes in lung function in this dive compared with previous deep saturation dives.

Increased oxygen before and during decompression reduces bubble formation in rats

The aim of this study was to test the hypothesis that increased oxygen partial pressure shortly before and during decompression from hyperbaric pressures would decrease venous gas bubble formation. Bubbles were detected by an ultrasound Doppler technique in conscious, freely moving rats. All rats were exposed twice to 6 bar for 2 hours. In exposure A, the breathing gas mixture was 1 bar O2 and 5 bar N2. In exposure B, the breathing gas was changed to 2 bar O2 and 4 bar N2, 5 min prior to decompression. The decompression rate was 0.1 bar x s(-1) in both groups. Significantly fewer bubbles were detected after decompression in exposure B compared to A. The angiotensin converting enzyme (ACE) concentration in serum was measured as an indicator of possible damage to the pulmonary endothelium induced by bubbles. However, no correlation between ACE and bubble amount was found. In conclusion, this study in conscious rats indicates that safer decompression may be obtained by increasing the oxygen partial pressure before and during decompression.

[Muscle enzymes in differential diagnosis of acute myocardial infarction and rhabdomyolysis. Evaluation of the parameter creatine kinase isoenzyme MB index (CKMB index)]

Both serum creatine kinase activity (CK) and creatine kinase isoenzyme MB mass concentration (CKMB) may be elevated in patients with either skeletal muscle damage or myocardial infarction. In a prospective study we evaluated the parameter CKMB index in discriminating these different events in 70 hospitalised patients with elevated CK-values, of whom 38 satisfied the WHO criteria for acute myocardial infarction. The sensitivity and specificity of the index for diagnosing myocardial infarction with various cut-off values between negative and positive tests are presented. A maximal CKMB index in a series of blood samples exceeding 5.0 is diagnostic of myocardial infarction, while a maximal value lower than 3.0 virtually excludes this diagnosis. An index of more than 3.0 in a single test makes rhabdomyolysis improbable and is strongly indicative of acute myocardial infarction. We conclude that CKMB index may be a valuable diagnostic tool in the differential diagnosis of myocardial infarction versus muscle damage.

Single-dose pharmacokinetics of lomefloxacin in patients with normal and impaired renal function

The quinolone antibiotic lomefloxacin was administered as a 400 mg single oral dose to 12 subjects with renal impairment (creatinine clearance 5-65 mL/min/1.73 m2) and to 13 healthy subjects (creatinine clearance 80-135 mL/min/1.73 m2). The concentrations of lomefloxacin in plasma and urine were determined by high-pressure liquid chromatography up to 48 hours post-administration. Linear correlations were found between lomefloxacin plasma and renal clearances and creatinine clearance. The mean nonrenal clearance of lomefloxacin (approximately 32 mL/min/1.72 m2) was not influenced by renal function. The mean plasma clearances of lomefloxacin in healthy subjects and in a subgroup of patients with severe renal impairment (creatinine clearance 5-15 mL/min/1.73 m2) were 209 and 43 mL/min/1.73 m2, respectively. The decrease in plasma clearance of lomefloxacin was explained fully by the decrease in renal clearance. The elimination half-life of lomefloxacin increased significantly with the degree of renal impairment, from 7.5 hours in normal subjects to 26.9 hours in subjects with severe renal impairment. The maximum serum concentration and the time to maximum serum concentration were not significantly affected by renal function. The pharmacokinetics of lomefloxacin are dependent on renal function, and appropriate dosage adjustment is necessary when creatinine clearance is less than 30 mL/min/1.73 m2.

Automated method for the determination of angiotensin-converting enzyme in serum

A method for the determination of angiotensin-converting enzyme in serum (S-ACE; EC 3.4.15.1.) with use of 3-(2-furylacryloyl)-L-phenylalanyl-glycyl-glycine (FAPGG) as substrate has been adapted for the Cobas Bio microcentrifugal analyser. The method allows 24 determinations per hour in a sample volume of 28 microliters with a within run precision of less than 3% and a between run precision of less than 5%. The reaction is linear up to at least 470 U/l. The reference interval in 92 blood donors has been determined to 14-110 U/l. The method correlates well with the manual method of Hurst & Lovell-Smith (r = 0.982). We have found the method excellently suited for routine assay.

Smoking during pregnancy--effects on the fetal thyroid function

Infants delivered at term by mothers smoking at least 10 cigarettes daily during pregnancy (n = 46) were found to be growth retarded compared to infants of non-smoking mothers (n = 49), birthweights 3,445 +/- 385 (SD) g and 3,667 +/- 392 g respectively (p less than 0.05) in the two groups. Cord serum thyrotropin (TSH) was significantly decreased (8.2 +/- 4.0 U/l vs. 10.3 +/- 4.9 U/l) and free thyroxine index (FT4I)/TSH ratio significantly increased (18.8 +/- 9.0 vs. 14.4 +/- 7.6) (p less than 0.05) in the smoking group compared to infants of non-smokers. Cord serum thyroxine (T4) and FT4I were higher in the smoking group (149.0 +/- 22.4 nmol/l and 125.5 +/- 14.9 respectively) compared to infants of non-smoking mothers (140.6 +/- 21.6 nmol/l and 120.0 +/- 16.5 respectively), with borderline statistical significance (0.05 less than p less than 0.10). The results indicate that infants of smoking mothers may have a hyperfunction of the thyroid gland at birth compared to infants of non-smokers, with a negative feed-back on TSH production from the pituitary gland. Increased metabolic rate and oxygen consumption caused by fetal thyroid hyperfunction may be pathogenetic factors for the fetal growth retardation caused by maternal smoking.

Accumulation of pyroglutamic acid (5-oxoproline) in homocystinuria

A 12-year-old boy with homocystinuria due to a cystathionine synthetase defect was shown to accumulate large amounts of pyroglutamic acid (pyroglu). In four different urine samples the concentration ranged between 4.1 and 9.7 mol/mol of creatinine. The pyroglu concentration in plasma was 1.6 mmol/l, and in erythrocytes 750 nmol/g cells. Normally only trace amounts are present. The pyroglu levels normalized during treatment with pyridoxine and folic acid. Accumulation of pyroglu has not previously been described in homocystinuria. Homocysteine can replace cysteine as a substrate for gamma-glutamylcysteine synthetase, an enzyme involved in the biosynthesis of glutathione, giving gamma-glutamylhomocysteine. This dipeptide is efficiently split by gamma-glutamylcyclotransferase to pyroglu and homocysteine. This reaction sequence most likely explains the accumulation of pyroglu in our patient. Ten other homocystinuria patients, who all had lower plasma levels of homocysteine, did not accumulate pyroglu. Our patient might either be a new variant, or more likely the pyroglu formation occurs only high levels of homocysteine.

Disulphide reduction in glutathione-deficient erythrocytes from a patient with pyroglutamic acidemia

Erythrocytes from a patient with pyroglutamic acidemia, containing about 5% of the normal content of glutathione, were able to reduce cystamine at a relatively high rate (about 50% that of normal cells) at low concentrations of the disulphide. Compared to normal cells, the reduction of disulphide by the patient's cells were highly sensitive to inhibition by high concentrations of the disulphide. This inhibition was noted whether glucose or inosine were used as carbohydrate substrate, and was also present when hemolysates were used and NADPH was added directly to the reaction mixture. The "disulphide poisoning" is assumed to be due to the formation of mixed disulphides at the expense of oxidized glutathione available for reduction by glutathione reductase. The glutathione/glutathione reductase system is probably the only disulphide reducing system of importance in human erythrocytes.

Studies of amino acid content and transport in glutathione-deficient erythrocytes from a patient with pyroglutamic acidemia (5-oxoprolinemia)

Repeated biochemical studies of the erythrocytes of a patient with pyroglutamic acidemia have shown a varying biochemical disorder in these cells. Whereas earlier studies demonstrated absence of glutathione and massive amino acid loading in erythrocytes, these cells later contained small but readily measurable amounts of glutathione and had a relatively normal amino acid content. The marked increase in amino acids after acid hydrolysis of erythrocytes had also disappeared. Transport studies showed a significant increase in the active transport of glycine, while the transport of other amino acids was comparable to that of normal cells. We are unable to detect any activity of gamma-glutamyl transpeptidase in human erythrocytes. Our observations suggest a role for glutathione in the transport of amino acids by erythrocytes, but at present no definite conclusion can be drawn with regard to the participation of the gamma-glutamyl cycle in this process. The biochemical variability in our patient's erythrocytes is unexplained and should be searched for in other patients with pyroglutamic acidemia.

Studies on the accumulation of L-pyroglutamic acid in guinea pig epidermis

The activities and properties of the enzymes involved in the formation and degradation of pyroglutamic acid (2-pyrrolidone-5-carboxylic acid, 5-oxoproline) in guinea pig epidermis have been studied. The enzyme pattern was characterized by an extremely high activity of gamma-glutamyl cyclotransferase. The epidermal extracts possessed a measurable, but rather low activity of pyroglutamate hydrolase. It is suggested that the only major pathway by which pyroglutamate may be formed in epidermal tissue is from L-glutamate by a 2-step reaction, the first involving the formation of a gamma-glutamyl peptide by the action of gamma-glutamyl-cysteine synthetase, and the second cyclization of the gamma-glutamyl moiety by the action of gamma-glutamyl cyclotransferase. Abundant substrate supply, the extremely high cyclotransferase activity and the rather low capacity to degrade pyroglutamate may be the factors responsible for the accumulation of this compound in epidermal tissue. A relatively low content of reduced glutathione may also be a contributing factor.

The cerebral lesions in a patient with generalized glutathione deficiency and pyroglutamic aciduria (5-oxoprolinuria)

The clinical and pathologic features of a male patient with generalized glutathione deficiency and pyroglutamic aciduria are presented. The patient died at the age of 28 years. He was mentally retarded from infancy and developed progressive tremor, retardation of movement, and ataxia as from the age of 16. Neuropathologic examination of the brain disclosed a selective atrophy of the granule cell layer of the cerebellum and focal lesions in the visual cortex and the thalamus. The type and distribution of the lesions resembled those seen after mercury intoxication. However, in our patient the damage was probably caused by the lack of protection of glutathione against oxidative damage in the brain. Possible treatment of this rare metabolic disorder might include external supply of an antioxidant, e.g., a thiol capable of penetrating the blood brain barrier.