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Biomedical subjects

P Hemmersbach

Publications and source records attributed to P Hemmersbach.

7 recordsLinked to original sources
PubMed1998

Determination of benzodiazepines in human urine and plasma with solvent modified solid phase micro extraction and gas chromatography; rationalisation of method development using experimental design strategies.

Solid phase micro extraction (SPME) and gas chromatographic analysis was used for the analysis of several benzodiazepines (oxazepam, diazepam, nordiazepam, flunitrazepam and alprazolam) in human urine and plasma. Several factors likely to affect the analyte recovery were screened in a fractional factorial design in order to examine their effect on the extraction recovery. Parameters found significant in the screening were further investigated with the use of response surface methodology. The final conditions for extraction of benzodiazepines were as follows: Octanol was immobilised on a polyacrylate fibre for 4 min. The fibre was placed in the sample and extraction took place at pH 6.0 for 15 min. Urine samples were added to 0.3 g ml(-1) sodium chloride. In plasma, the extraction recovery was less than in urine and releasing the benzodiazepines from plasma proteins followed by protein precipitation was found necessary prior to sampling. The method was validated and found linear over the range of samples. The limits of detection in urine were determined to be in the range 0.01-0.45 micromol l(-1). The corresponding limits of detection in plasma were in the range 0.01-0.48 micromol l(-1). Finally, the method developed was applied to determine some benzodiazepines after administration of a single dose. This method offers sufficient enrichment for bioanalysis after a single dose of high dose benzodiazepines as diazepam, but for low dose benzodiazepines as flunitrazepam, further sensitivity is needed.

Alprazolam↗
PubMed1998

Bone mineral density and menstrual irregularities. A comparative study on cortical and trabecular bone structures in runners with alleged normal eating behavior.

Bone mineral density (BMD), and associated biochemical and endocrine markers were compared in a group of runners with menstrual dysfunction (IR, n=13), and a group of performance matched eumenorrheic runners (R, n=15). All subjects claimed to have normal eating habits. Body height and weight, body mass index, and amount of body fat were similar. The IR group consisted of 5 presently oligomenorrheic (O) and 8 presently amenorrheic (A) runners. The BMD values of the athletes were additionally compared with corresponding values in a reference group (C) of healthy age matched controls (n=54). BMD values were significantly lower in IR compared with R on all measuring sites: Total body (-9%, p=0.03), femoral neck (-11%, p=0.01), lumbar spine (-12%, p=0.001), lower leg (-6.5%, p=0.03) and arms (-7%, p=0.01). In addition, IR athletes had lower total body (-5%, p=0.01), and lumbar spine BMD (-10%, p=0.001) than C. No differences were observed in serum IGF-1, SHBG, testosterone and cortisol, or in the biochemical marker of bone formation (osteocalcin) and bone resorption (1 CTP). Values of serum E2, FSH and LH were low in IR and normal in R. TSH was in the normal range in both groups, but f-T4 was significantly lower in IR than in R. The athletes were furthermore grouped according to past and present menstrual dysfunction severity. At all measuring sites, with the exception of the lower leg, increasing menstrual dysfunction severity was linearly associated with declining BMD values (p<0.05). In conclusion, even highly conditioned cortical bone tissue seems to be negatively related to menstrual disorders, which may serve to explain the high incidence of stress fractures in athletes with menstrual disorders. Single measurements of biochemical markers of bone resorption and formation may not reflect the current bone status.

Adipose Tissue↗
PubMed1997

Blood sampling in doping control. First experiences from regular testing in athletics.

We report the results from blood sampling taken for the first time during doping control in athletics. The study includes samples from 99 athletes tested during IAAF-meetings in 1993-94. Blood doping with allogenic blood was not detected. The distribution of haemoglobin levels in athletes did not differ markedly from that found in controls. Erythropoietin (EPO) values were markedly lower in athletes than in controls, and 58% had EPO lower than the detection limit for the assay. This may be due to high-altitude residence prior to testing. Measurements of growth hormone (GH) and insulin-like growth factor 1 did not suggest GH-misuse in any athlete tested. One third of the male athletes had testosterone levels that were lower than the normal reference interval. This may at least partly be due to the combination of sampling at night and after strenuous exercise. One female athlete was found to have a grossly elevated testosterone level. In conclusion, the present results show the importance of taking into account the special circumstances during sampling when interpreting results from blood testing in athletes. Future research should focus on developing more sensitive and specific tests to detect doping with endogenous substances such as GH and EPO.

Bilirubin↗
PubMed1996

Stimulants, narcotics and beta-blockers: 25 years of development in analytical techniques for doping control.

More than 25 years of developing doping control methods have led to comprehensive screening and confirmation procedures for stimulants, narcotics and beta-blockers. Much of this work has been initiated and/or improved by the late Prof. Dr. Manfred Donike. The methodological approach covered in this overview was applied to doping control procedures during the XXV Summer Olympics in Barcelona, Spain, in 1992 and the XVII Winter Olympics in Lillehammer, Norway, in 1994. Urine samples are screened through a combination of two analytical methods that are complementary: (a) gas chromatographic analysis of the parent compound and unconjugated metabolites, following single-step sample extraction and detection by a nitrogen-specific detector based on a retention index identification system and (b) gas chromatographic analysis including also conjugated drugs and metabolites after hydrolysis, solid-phase extraction, derivatisation and mass spectrometric detection. Confirmation and identification is always performed by gas chromatographic separation and full scan mass spectrometric detection. These methods facilitate the rapid screening and confirmation of more than 100 stimulants, narcotic analgesics and beta-blockers in urine for at least 24 h after the intake of a pharmaceutical dose. Application of the methods ensures high quality standards for the unequivocal identification of doping agents as well as a rapid turnaround time for sample analyses.

Adrenergic beta-Antagonists↗
PubMed1995

Chemometric evaluation of urinary steroid profiles in doping control.

Ten endogenous steroid hormones and metabolites were determined according to the screening procedure for anabolic steroids in spot urine samples from 105 healthy young male athletes (control samples) and 23 males that tested positive for anabolic steroids in the doping control (positive samples). The GC-MS peak areas for each sample were normalized to total area. Multivariate data analysis by Partial Least Square Regression (PLSR) and using a coded Y-variable (positive samples: +1 and control samples -1) allows projection of the most systematic profile structures into a 2D plot revealing a clear distinction between the control and misuser groups. The most important determinants of the location in the loading plot were the ratios of testosterone to epitestosterone and androsterone to etiocholanolone. The ratio between 11-beta-hydroxyandrosterone and 11-beta-hydroxy-etiocholanolone was less important, in accordance with the fact that anabolic-androgenic steroid intake primarily affects the excretion of testosterone from the testis and to a much lesser degree adrenal steroid genesis. We present a preliminary validation of this model (PLS1-DISCRIM) for analysing steroid profiles in doping control samples from several categories of athletes, some of which are suspected for drug misuse, and results from a one dose excretion study in healthy volunteers. Our findings suggest that use of multivariate PLS-regression may give valuable information about anabolic androgenic steroid misuse in sport. When appropriately calibrated, this methodology may delineate drug misusers directly from the screening procedure for anabolic steroids in spot urine tests.

Adolescent↗
PubMed1994

[Endocrine effects of doping with androgenic anabolic steroids].

We describe two case histories that highlight some of the endocrine effects of doping with androgenic anabolic steroids. The main endocrine effect observed after use of androgenic anabolic steroids is the development of hypogonadotrope hypogonadism, characterized by low levels of gonadotrophins, suppression of testosterone production and azoospermia. If testosterone is used alone, or in combination with synthetic anabolic steroids, the circulating levels of testosterone are normal or high. Oestrogen levels may be elevated owing to aromatization of testosterone. The level of sex hormone binding globulin is suppressed. These endocrine parameters are of practical use in evaluating patients misusing androgenic anabolic steroids.

Adult↗