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Biomedical subjects

K Wichmann

Publications and source records attributed to K Wichmann.

At least 19 recordsLinked to original sources
PubMed2006

European developments in standardisation of sludge physical parameters.

Characterisation is an important step in sludge management as it allows sludge properties to be evaluated and behaviour predicted. This is well recognised by the European Union (EU) countries which consider necessary the development of standardised sludge characterisation methods and procedures because objective and transparent regulations allow sludge management to be properly performed, legal requirements correctly fulfilled, and public confidence built. To this end, the European Committee for Standardization (CEN) established the Technical Committee 308 (TC308) whose scope is the production of Standards for sludge characterisation, and of Guides of good practice. In this field, physical properties are of great importance as they allow the prediction of sludge behaviour when handled and submitted to almost all treatment and utilisation/disposal operations. Activity of CEN/TC308 is developed in three Working Groups (WG) and several Task Groups (TG); in particular, TG3 of WG1 deals with physical parameters. In this paper developments regarding Standards for evaluation of capillary suction time, specific resistance to filtration, compressibility, settleability, thickenability, and calorific value, and Technical Reports dealing with a procedure for laboratory chemical conditioning and with sludge consistency (flowability/solidity) are briefly outlined. The results of relevant inter-laboratory tests for the validation of above standards are summarised.

European Union↗
PubMed2004

Sludge characterization: the rôle of physical consistency.

The physical consistency is an important parameter in sewage sludge characterization as it strongly affects almost all treatment, utilization and disposal operations. In addition, in many European Directives a reference to the physical consistency is reported as a characteristic to be evaluated for fulfilling the regulations' requirements. Further, in many analytical methods for sludge, different procedures are indicated depending on whether a sample is liquid or not, is solid or not. Three physical behaviours (liquid, paste-like and solid) can be observed with sludges, so the development of analytical procedures to define the boundary limit between liquid and paste-like behaviours (flowability) and that between solid and paste-like ones (solidity) is of growing interest. Several devices can be used for evaluating the flowability and solidity properties, but often they are costly and difficult to be operated in the field. Tests have been carried out to evaluate the possibility to adopt a simple extrusion procedure for flowability measurements, and a Vicat needle for solidity ones.

Chemistry, Physical↗
PubMed1986

Studies on structure-activity relationship of gossypol, gossypol ethers and three naphthaldehydes in the inhibition of spermatozoal metabolism.

Gossypol tetramethyl ether [C30 H24 O2(OCH3)4] and gossypol hexamethyl ether [C30 H24 O2(OCH3)6], which in contrast to gossypol are stable compounds, were tested for their ability to depress fructose degradation in fresh human sperm cells. Both ethers inhibited spermatozoal fructolysis, yet less effectively than did the parent compound. A synthetic compound, O-hydroxylnaphthaldehyde, and two commercially available preparations, 1- and 2-naphthaldehydes, were also tested under the same experimental conditions. These preparations represent about half of the gossypol molecule and possess a reactive aldehyde group in their molecules. Their inhibitory effect on fructose degradation in fresh human sperm cells, however, was considerably smaller than that of gossypol itself. It thus appears that the whole ring structure of gossypol rather than the intact aldehyde group is required for an effective inhibition of spermatozoal energy metabolism.

Aldehydes↗
PubMed1983

Vaginal contraception with gossypol: a clinical study.

A clinical study concerning the vaginal contraceptive efficacy of gossypol acetic acid was performed. Fifteen women who had undergone tubal sterilization volunteered for the study. The effect of vaginal gossypol-containing gel on spermatozoa was determined by postcoital tests performed in subjects without and after using gossypol gel. After gossypol application, the number of spermatozoa found in cervical mucus was greatly decreased and, in eleven of the fifteen women, all spermatozoa seen were immobilized. In four cases a few poorly motile spermatozoa were seen but they showed no forward progression. We have previously reported that gossypol has an inhibitory effect on herpes simplex virus type 2 in vitro. This anti-viral property of gossypol makes it particularly attractive as a topical barrier contraceptive. The present study shows that gossypol is also promising as a vaginal contraceptive agent in human in vivo experiments.

Adult↗
PubMed1983

Effect of gossypol on the motility and metabolism of human spermatozoa.

Gossypol, a polycyclic compound isolated from cotton seeds, had a dose-dependent inhibitory effect on human sperm motility. The drug also inhibited powerfully fructolysis and glycolysis by human spermatozoa. Both lactate and CO2 formation from the 14C-labelled sugars was inhibited, and the prevention of CO2 formation from [1-14C]pyruvate and [2-14C]pyruvate by gossypol indicated a direct effect on the tricarboxylic acid cycle. Repeated washing of the sperm cells after gossypol pretreatment failed to abolish the inhibitory effect on CO2 production. The profound disturbances of the sperm energy metabolism induced by gossypol were also reflected by a striking fall of the sperm ATP content. Gossypol had little effect on glucose utilization by minces of human vaginal mucosa, indicating the specificity of gossypol.

Adenosine Triphosphate↗
PubMed1977

Subcellular progesterone in human myometrium during late pregnancy.

Samples of myometrium were obtained from twenty-two patients undergoing caesarian sections for various obstetric indications. The myometrium was homogenized and divided into four subcellular fractions (crude nuclear, mitochondrial, microsomal and cytosol). The concentration of endogenous progesterone in these fractions was determined by radioimmunoassay. In addition the concentration of oestrone and oestradiol of fifteen cytosolic fractions was determined. The subcellular concentration of progesterone (pg/mg protein) in human myometrium was higher in samples taken during labour than in samples taken at elective caesarian sections. This finding was statistically significant in the crude nuclear (P less than 0.005) and the microsomal (P less than 0.05) fractions. The absolute concentration of progesterone was lowest in the nuclear and highest in the microsomal fraction. The relative progesterone concentrations in the four subcellular fractions were the same in both groups. The data show that there is no significant decrease in myometrial progesterone associated with labour in man. The mean concentration of oestrone was higher than the mean oestradiol concentration in the cytosol fraction of human myometrium in late pregnancy. This study shows that a completely different oestrogen ratio exists in myometrium than in plasma.

Estradiol↗