Search PubMed⌕ Search

Biomedical subjects

L Larsson

Publications and source records attributed to L Larsson.

At least 415 records · Page 23Linked to original sources
PubMed1978

Detection of alcohols and volatile fatty acids by head-space gas chromatography in identification of anaerobic bacteria.

A head-space gas chromatographic technique for the analysis of volatile bacterial metabolites is described. Bacteroides fragilis, Clostridium perfringens, and Propionibacterium acnes, cultured in a glucose-containing peptone yeast extract medium, were studied. The head-space technique was compared with the injection of the complete liquid culture medium, and solvent extracts thereof, into the gas chromatograph. Volatile fatty acids could be detected by all three methods, whereas alcohols produced by C. perfringens and P. acnes were detectable only in the head-space chromatograms. Both FFAP and Porapak Q were used as gas chromatography stationary phase. Porapak Q was found more suitable than FFAP for the separation of alcohols. The head-space technique requires a minimum of preparation before the analysis and is well suited to automation.

Alcohols↗
PubMed1978

A biochemical basis for grouping of patients with urolithiasis.

The urinary excretion of calcium, magnesium, oxalate, creatinine, phosphate and urate was investigated in patients with urolithiasis and in normal subjects. The excretion of oxalate and urate per mole creatinine and the quotients calcium/magnesium, calcium X oxalate/magnesium and calcium X oxalate/(magnesium X creatinine) were significantly higher in stone formers than in normal subjects. The mean creatinine-correlated urinary excretion of calcium was higher and of magnesium lower in patients with urolithiasis, but the differences were statistically not significant. The urine investigation was supplemented with analysis of calcium, magnesium, creatinine, urate, bicarbonate and chloride in serum and a qualitative analysis of stone composition. A simple schedule for a biochemical grouping of patients with urolithiasis is presented and on the basis of the analytical findings it was possible to classify 67% of patients with so-called 'idiopathic stone disease' according to these principles.

Adult↗
PubMed1978

Muscle glycogen depletion and lactate concentration during downhill skiing.

Skilled and unskilled skiers were studied during downhill skiing. Muscle glycogen and muscle lactate concentrations in the vastus lateralis muscle were determined following different skiing conditions. Heavy glycogen utilization was found in the groups studied during a day of skiing. The skilled and unskilled skiers differed with respect to selective glycogen depletion pattern and the skilled subjects demonstrated greater depletion of slow twitch fibers than the unskilled subjects. Lactate concentrations ranged from approximately 5-26 mmoles x kg-1 wet muscle after approximately one minute of maximal skiing. This wide range was not found to be related to the level of skiing proficiency. However, skiing with varyingly angled boots, resulting in different knee angles, did affect lactate concentration. Lactate concentration was positively correlated to individual muscle fiber composition expressed as a percent of fast twitch fibers. The results suggest more pronounced involvement of aerobic energy metabolism in skilled skiers than in unskilled skiers.

Adult↗
PubMed1978

Serum ionized calcium and corrected total calcium in borderline hyperparathyroidism.

We studied 25 borderline-hyperparathyroidism patients whose total serum calcium concentration was within normal limits (reference range: 2.25--2.75 mmol/liter) but whose concentrations of serum ionized calcium were above normal (reference range: 1.03--1.23 mmol/liter). Their hyperparathyroidism was histopathologically verified. To compare the discriminating value of corrected serum calcium with ionized calcium, we studied the serum calcium and albumin concentrations in a reference group of 2098 patients. After patients from endocrine and dialysis departments were excluded from the reference group, we obtained the range (mean +/- 2 SD) 2.05--2.71 mmol/liter for uncorrected serum calcium and 2.11--2.63 mmol/liter for corrected serum calcium. The correction factor for calcium on albumin was 20 mumol/g. Even with this limit for corrected serum calcium, 13 of 25 borderline hyperparathyroidism patients had values that fell within the reference range. We conclude that correcting total serum calcium values for serum albumin concentration improves discrimination of borderline hyperparathyroid patients, but that measurement of ionized calcium in serum discriminates better.

Calcium↗
PubMed1978

Parathyroid localization in patients with previous neck surgery.

The results of parathyroid arteriography and venous parathyroid hormone assay were evaluated in thirteen patients reexplored for persistent or recurrent hyperparathyroidism. The operative findings in these patients were ten adenomas and eight hyperplastic parathyroid glands. Angiography disclosed eight of the adenomas and failed to visualize one. Only two of the hyperplastic glands were disclosed by angiography. By venous sampling the correct side was predicted in seven out of eight cases of unilateral lesions--in one case of an adenoma no hormonal maximum was found. In two cases of bilateral lesions a maximum was found on one side only, while in three cases of unilateral two-lesions the maximum was correct in two cases and contralateral in one. We conclude that a combination of angiography and venous sampling gave localization or lateralisation in 12/13 patients with previous neck surgery for hyperparathyroidism and found the methods to be complementary to each other and prefer both done in these cases.

Adenoma↗
PubMed1977

Pyrolysis gas chromatography of microorganisms. Influence of various pyrolysis parameters on the yield of volatile organic products.

Bacteroides fragilis was analysed by pyrolysis gas chromatography (PGC). The influence of temperature rise time, pyrolysis temperature and pyrolysis time on the yield of volatile organic pyrolysis products was studied. The use of short pyrolysis time (8 msec) and a high pyrolysis end temperature (1300 degrees C) was found to provide a high yield. In consecutive analyses of the test organism, under the pyrolysis conditions indicated, the standard deviation of the total yield of volatile organic products was +/- 7%. The pyrolysis technique described suggests that few secondary reactions of the pyrolysis fragments occur.

Bacteroides fragilis↗
PubMed1977

Application of gas chromatography to diagnosis of microorganisms and infectious diseases.

Gas chromatography (GC) can be used to characterize microorganisms chemically. Microbial whole cells and cell extracts can be analysed by GC after being thermally or chemically degraded, i.e. pyrolysed or hydrolysed. Microbial metabolic products can be detected by GC analysis of culture media or the atmosphere above such media, i.e. headspace analysis. Pyrolysis products can be analysed direct, while hydrolysis products and non-volatile metabolites must be derivatized before being chromatographed. Differences in the chromatographic patterns can be used to differentiate between microorganisms. Detection of metabolic products in body fluids by means of GC constitutes a potential technique for the rapid diagnosis of infectious diseases.

Chromatography, Gas↗
PubMed1977

Muscle strength and fiber composition in athletes and sedentary men.

Members of Swedish national teams in track and field events (sprinting and jumping), downhill skiing, race walking, orienteering, and a group of sedentary men were studied to examine the relationship between muslce fiber characteristics in needle biopsy samples form m. vastus lateralis and muscle strength measured as peak torque during isokinectic knee extensions. In comparison with the sedentary group the following differences were found: a) percentage fast twitch fibers was lower in the endurance athetes, b) fast to slow twitch muscle fiber area ratio was higher in the track athletes, c)track athletes and downhill skier attained higher peak torque values at all angular velocities examined. The track athletes had, however, higher torque values at the fastest angular velocity as compared to the downhill skiers, whereas there was no differnce under isometric conditions. The proportion of fast twitch fibers was related to torque produced, especially at high motion velocity. The training also appeared to affect the force-velocity relationship.

Adult↗
PubMed1976

Mechanisms of fluid absorption during proximal tubule development.

UNLABELLED: Passive permeation characteristics and paracellular pathway ultrastructure were studied in vitro by perfusion of rabbit isolated proximal convoluted tubules during postnatal ontogenesis. The influence upon net volume flow (Jv) of transepithelial hydrostatic and protein osmotic pressure was significantly higher during early postnatal maturation than in the mature tubule. Hydraulic hydrostatic conductance (X10(-3) ml - cm-2 - min-1 - cm H2O-1) was 0.0367 +/- 0.0048 during early postnatal maturation (N = 99) and 0.0052 +/- 0.002 at maturity (N = 78). Hyperoncotic serum (12.7 +/- 0.4 g/100 ml) in the bath increased Jv by 67.5 +/- 21.1% from 0.31 +/- 0.06 to 0.52 +/- 0.08 nl-mm-1-min-1 in the neonatal proximal tubule, whereas an increase of only 25.7 +/- 20.4% from 1.08 +/- 0.15 to 1.32 +/- 0.18 nl-mm-1-min-1 was noted in the mature proximal tubule during this elevated bath protein-osmotic pressure. Electron microscopic observations showed that microperoxidase passed from tubule lumen through the basement membrane via intercellular spaces in immature tubules perfused at an increased transtubular pressure gradient. This suggests that a transepithelial shunt pathway may participate in changes of conductance during ontogenesis, although length and ultrastructural configuration of tight junctions did not vary with these variables. CONCLUSIONS: 1) Hydrostatic and oncotic water conductance of the rabbit proximal tubule changes with postnatal development. 2) Ultrastructural tracer studies suggest that the change in conductance is due to alteration of the paracellular pathway. 3) Isotonic absorption of the neonatal proximal tubule may depend more on transepithelial pressure gradients than in the mature tubule.

Absorption↗
PubMed1976

Gas chromatographic characterization of mycobacteria: analysis of fatty acids and trifluoroacetylated whole-cell methanolysates.

Mycobacterium avium, M. bovis strain Bacillus Calmette-Guerin (BCG), M. kansasii, and M. tuberculosis were studied by gas-liquid chromatography. Methylated fatty acids of the mycobacterial lipids and trifluoroacetyl (TFA) derivatives of whole-cell methanolysates were analyzed. Both the fatty acid and the TFA chromatograms showed reproducible differences between the various mycobacteria studied. Chromatograms from different strains of one and the same species showed negligible differences. Fatty acid methyl esters and TFA methyl glycosides are probably the main constituents of the TFA chromatograms. TFA derivatives are easily prepared and the method provides a potential tool for species indentification of mycobacteria.

Fatty Acids↗
PubMed1976

Grouping of patients with hyperparathyroidism by clinical signs, correlated to some biochemical findings.

Serum parathormone (S-PTH), total and free fractions of serum calcium (Cat and Caf), urinary excretion of cyclic 3',5'-adenosine monophosphate (cAMPu), serum phosphate and serum magnesium were analysed in 68 patients with hyperparathyroidism verified by operation and PAD. The diagnostic significance of the analyses was examined. It was shown that Caf was consistently above normal even in patients in whom the other tests were normal. The best diagnostic sensitivity was thus found for Caf followed by Cat, S-PTH and cAMPu. The results of these tests were generally correlated to each other except in patients with impaired renal function in whom S-PTH increased out of porportion to the other tests. Cat and Caf were significantly correlated to each other. However, Caf was pathologic even when Cat was normal. It is concluded that for hypercalcemic patients Cat and Caf are the most reliable tests. S-PTH is elevated only in some hypercalcemic patients. In normocalcemic patients all tests except Caf show normal values.

Adult↗
PubMed1975

Partition of an organophosphorus compound, dichlorvos, between liquid and liquid crystalline phases.

The partition coefficients for an organophosphorus compound, dichlorvos (2,2-dichlorovinyl dimethyl phosphate), between pure liquids, micellar solutions, and liquid crystalline phases were determined by spectrometric analysis of the dichlorvos content after equilibration and separation of the phases. The results demonstrated the pronounced importance of associated colloid structures on the partition coefficient and showed that the partition coefficient did not display a simple concentration dependence.

Chemistry, Pharmaceutical↗