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Biomedical subjects

F A de Wolff

Publications and source records attributed to F A de Wolff.

At least 37 records · Page 2Linked to original sources
PubMed1997

Dermal absorption of vaporous and liquid 2-methoxyethanol and 2-ethoxyethanol in volunteers.

OBJECTIVES: To estimate dermal absorption of vaporous and liquid 2-methoxyethanol (ME) and 2-ethoxyethanol (EE) in volunteers. METHODS: Five volunteers (two men and three women) were dermally exposed to vaporised and liquid ME and EE. Dermal exposure on an area of about 1000 cm2 (forearm and hand) to vapours of ME and EE (4000 mg/m3 ME and 3700 mg/m3 EE) lasted for 45 minutes. Duration of exposure to liquid ME and EE on an area of 27 cm2 (forearm) was 15 minutes. Dermal uptake was assessed by measurement of the main metabolites in urinary methoxyacetic acid (MAA) and ethoxyacetic acid (EAA). For each volunteer, excretion of metabolites was compared with a reference inhalatory exposure. RESULTS: Mean (SD) absorption rates of ME and EE vapour were 36 (11) and 19 (6) cm/h respectively. The mean (SD) absorption rates of the liquid ME and EE amounted to 2.9 (2.0) and 0.7 (0.3) mg/cm2.h. CONCLUSIONS: Vaporised and liquid ME and EE are readily absorbed through the skin. In the combined inhalatory and dermal exposure when whole body surface is exposed to vapour, the uptake through the skin is estimated to be 55% of the total uptake of ME and 42% of EE. Dermal uptake resulting from skin contact of both hands and forearms (about 2000 cm2) with liquid ME and EE for 60 minutes would exceed inhalatory uptake of the eight hour occupational exposure limit by 100 times at 16 mg/m3 of ME and 20 times at 19 mg/m3 of EE. The substantial skin uptake of ME and EE indicates that in assessing the health risks biological monitoring and use of biological exposure indices are preferable to environmental monitoring.

Acetates↗
PubMed1997

Serum aluminium levels of workers in the bauxite mines.

BACKGROUND/OBJECTIVE: Aluminium is produced from the mineral bauxite. Occupational exposure is reported during the industrial processing of aluminium and is associated with pulmonary and neurotoxicity. However, data on exposure and toxicity of workers in the open bauxite mining industry do not exist. Therefore, a study was performed to explore aluminium exposure in employees involved in this bauxite mining process in a Surinam mine. METHODS/DESIGN: A group of workers occupationally exposed to aluminium in an open bauxite mine were compared with a group of nonexposed wood processors. Serum aluminium was analyzed using atomic absorption spectrometry Data from the clinical chemistry of the blood and a questionnaire were used to explore determinants for aluminium exposure. RESULTS: No significant difference between serum aluminium in the exposed (4.4 +/- 2.0 micrograms/L, n = 27) and control group (5.1 +/- 1.5 micrograms/L, n = 27) was detected. For the serum concentration of the clinical chemical variables (calcium, citrate, and creatinine), a statistically significant difference was computed (p < or = 0.02) between the exposed and control group. All levels were slightly higher in the exposed group; no statistically significant correlations with serum aluminium were found. CONCLUSIONS: In this study, serum aluminium values were in the normal range, no significant difference between the groups could be detected despite long-term occupational exposure.

Adult↗
PubMed1997

[Relation between mercury and Alzheimer's disease?].

Mercury from dental silver amalgam has been suggested to be linked with Alzheimer's disease. The percentage in the population (formerly) possessing amalgam restorations exceeds that of Alzheimer patients. Therefore, low levels of mercury in the brain are unlikely to cause the disease. However, studies indicating increased levels of mercury in Alzheimer brains compared to controls have been criticised. In contrast, it has been proven that an inherited trait accounts for a minor proportion of Alzheimer's patients. Moreover, education--or related psychosocial factors--instead of amalgam has been found to be associated with the disease. Therefore, it does not seem warranted as yet to conclude that mercury is an etiological factor in Alzheimer's disease.

Alzheimer Disease↗
PubMed1996

Dermal absorption of cis-1,3-dichloropropene vapour: human experimental exposure.

1. The relevance of skin absorption of cis-1,3-dichloropropene (cis-1,3-DCP) vapour as a route of entry compared to inhalatory uptake has been assessed in human volunteers under controlled exposure conditions. 2. Five adults (four males and one female) were dermally exposed on the forearm and hand during 45 min to 86 mg/m3 cis-1,3-DCP. 3. Dermal uptake was assessed by determination of the main cis-1,3-DCP metabolite in urine: the mercapturic acid conjugate of cis-1,3-DCP (cis-1,3-DCP-MA). 4. When whole-body dermal exposure to vapour is compared to inhalatory exposure, the uptake through the skin is estimated to be about 2-5% of the inhalatory absorption.

Acetylcysteine↗
PubMed1995

Determination of 2,5-hexanedione, a metabolite of n-hexane, in urine: evaluation and application of three analytical methods.

Three methods for the determination of 2,5-hexanedione (2,5-HD) in urine were compared in order to assess their applicability for toxicokinetic studies and biological monitoring of occupational exposure to n-hexane. Two of them were based on derivatization, followed by gas chromatography and electron-capture detection. Of these two, one is a modification of the other, already published, method. The third one involves direct extraction of 2,5-HD followed by gas chromatography and flame-ionization detection. To determine 2,5-HD in urine of workers occupationally exposed to n-hexane, the most straightforward method, direct extraction of 2,5-HD from urine, has been proven to be the most suitable. However, in case of very low concentrations of 2,5-HD in urine, or analysis of small samples of blood, e.g. in kinetic studies, it is necessary to use a more sensitive procedure. The sensitivity of the methods based on the derivatization of 2,5-HD followed by electron-capture detection, was, as expected, much higher in terms of analytical reliability. By using these methods, however, precautions are necessary to avoid a matrix effect.

Chromatography, Gas↗
PubMed1995

Absorption of bismuth from several bismuth compounds during in vivo perfusion of rat small intestine.

Evaluation of the amount of bismuth (Bi) absorbed from the gastrointestinal tract is important for assessment of the possible risks associated with the use of Bi compounds in the treatment of gastrointestinal disorders. We compared the absorption of Bi from media containing the equivalent of 1 g of elemental Bi from either Bi subnitrate (BSN), Bi subsalicylate (BSS), colloidal Bi subcitrate (CBS), Bi chloride (BiCl3), or Bi citrate (BCit) by an in vivo perfusion system of rat small intestine. The intestinal absorption was < 1% for all compounds, but higher from BCit and CBS than from BSN, BSS, and BiCl3. The dose dependency of Bi absorption from both CBS and BiCl3 in citrate buffer showed a nonlinear relationship between the concentration of Bi in perfusate and the concentration of Bi in blood after 60 min.

Animals↗
PubMed1995

Sensitivity to 2,5-hexanedione of neurofilaments in neuroblastoma cell line SK-N-SH increases during differentiation.

The effect of 2,5-hexanedione (2,5-HD) on the distribution of the neurofilamental (NF) proteins and vimentin was examined in human neuroblastoma cell line SK-N-SH with immunocytochemical methods. Retinoic acid (10 microM) induced differentiation into neuronal cells resulting in the outgrowth of processes and synthesis of NF proteins in the majority of the cells. A minority (4%) differentiated as large fibroblasts. Cells were exposed to 0-10 mM 2,5-HD for 3 days. In neuronal cells a concentration-dependent accumulation of NF proteins was detected as a spherical structure in the perikaryon. Neurofilaments in differentiated SK-N-SH cells were more susceptible to 2,5-HD than NF in undifferentiated cells, as the effects were observed at much lower 2,5-HD concentrations. In contrast, no accumulation of vimentin was detected in the fibroblastic cells.

Cell Differentiation↗
PubMed1994

Phenytoin parahydroxylation is not impaired in patients with young-onset Parkinson's disease.

Impaired hepatic detoxification capacity by cytochrome P450 subsystems has been implicated in the pathogenesis of Parkinson's disease. We have demonstrated that hepatic parahydroxylation of phenytoin (PHT) is impaired in patients with late-onset Parkinson's disease. In the present study, we have investigated the hypothesis that PHT parahydroxylation is even more impaired in patients with young-onset Parkinson's disease (age at onset before 40 years). We determined PHT parahydroxylation capacity in 21 patients with young-onset Parkinson's disease and 15 healthy age-matched controls. PHT parahydroxylation capacity was assessed by measuring the ratio of PHT to its major metabolite p-hydroxyphenyl-phenylhydantoin in serum 6 h after an oral test dose of 300 mg PHT. PHT parahydroxylation did not differ significantly between patients and controls. These results argue against the hypothesis that impaired activity of the cytochrome P450 isoenzyme responsible for PHT parahydroxylation is involved in the etiology of Parkinson's disease.

Administration, Oral↗
PubMed1994

Giant axonal degeneration: scanning electron microscopic and biochemical study of scalp hair.

Tightly curled 'frizzy' hair is a pathognomonic sign of giant axonal degeneration (GAD). The present study compares the morphological structure of the scalp hair of a GAD patient with that of her parents and first-degree relatives with the aid of scanning electron microscopy. The comparison included plaited hair of two age-matched controls, in order to exclude mechanical plaiting artifacts. Trichorrhexis nodosa and fringing of the cut ends were exclusively found in the patient's hair. Longitudinal grooving was also frequently seen in hair of normal persons. Assay of carbon (C), sulfur (S) and nitrogen (N) contents of the patient's hair was normal, but the S:N ratio was significantly reduced, as compared with her relatives. However, comparison with a control group of non-related healthy volunteers showed no difference.

Adolescent↗
PubMed1993

Evaluation of biological monitoring parameters for occupational exposure to toluene.

A survey was conducted in a rotogravure printing plant with inhalatory and percutaneous exposure to toluene. Workers (n = 9) were followed for 2 consecutive days and the frequency and duration of skin contact with toluene were monitored. In order to assess percutaneous absorption an airstream helmet was worn during one day. Urine and exhaled air samples were collected simultaneously 5 times each day for toluene (urine and breath) and hippuric acid (urine). The mean (personal air sampling) exposure concentration was between 30 mg/m3 and 600 mg/m3. The best biological monitoring parameter of external exposure (without a helmet) was the concentration toluene in exhaled air 8 h after work (r = 0.99). While wearing the airstream helmet the relationship between external exposure (measured in the helmet) and concentrations in exhaled air and urine deviated from the preceding relations. This was likely the result of the high body burden and not of skin contact with toluene. Skin contact with toluene (usually by cleaning of the hands) was limited to 0-30 minutes a day, with an average of about 5 minutes. During experimental exposure (n = 6) in which the hands were washed with toluene for 5 minutes the toluene in exhaled air (max after 1040 min) clearly demonstrated skin absorption of toluene. The next morning 0.1 mg/m3 toluene was still detectable; this was less than the concentration measured the next morning in exhaled air of workers: between 0.5 and 10 mg/m3.

Adult↗
PubMed1993

Dermatitis in bulb growers.

A damaged skin forms a health hazard in flower-bulb growers as it enables higher permeation rates for pesticides than normal skin. Therefore, an investigation was performed into the skin condition of 103 bulb growers and 49 controls. Contact dermatitis of the hands was of the same order (11 and 10%) in both groups. However, minor signs of dermatitis were seen more often in bulb growers (30 versus 8%, p < 0.05). Most growers had contact with narcissus sap during the investigation. This irritant sap, as well as many other skin contacts with irritants such as hyacinth dust and pesticides, seemed to be responsible for many skin complaints. Contact sensitization was suspected in 19 growers and 3 controls. Patch tests showed that contact sensitization existed to pesticides in probably 10, and to flower-bulb extracts in 4 growers. Reactions to propachlor were not regarded as very reliable as the test concentration seemed to be marginally irritant. There were only a few allergic reactions to narcissus (3) and tulip (2) and none to hyacinth. This investigation showed that minor irritant contact dermatitis was frequent in bulb growers, and indicated that contact sensitization to pesticides and bulbs seemed to be a less frequent but important cause of dermatitis.

Adult↗
PubMed1993

Effect of aluminum chloride, -citrate, and -maltol on the calcium-mediated degradation of neurofilament proteins.

Aluminum (Al) has been observed to cause neurofilament protein accumulation in both experimental animals and cultured cells. Impairment of axonal transport is thought to be a mechanism of toxicity. Inhibition of the degradation of neurofilament proteins, however, resulting in accumulation of these proteins may be an alternative mechanism for Al toxicity. In the present study, the effect of calcium (Ca) on the proteolysis of the neurofilament triplet proteins by calcium-activated neutral proteases (CANP) was studied in the isolated sciatic nerve explants. The extent of the degradation was found to be dependent on the Ca concentration. The effect of Al chloride, -citrate and -maltol on the calcium-induced degradation was studied. No effect of any of the Al compounds was observed, suggesting that the metal may exert its neurotoxic effect via a mechanism other than impairment of neurofilament proteolysis. Maltol itself was found to enhance the effect of Ca on the degradation of neurofilament proteins, probably by facilitating the movement of Ca across the neuronal membrane.

Aluminum↗
PubMed1993

Effect of citric acid and maltol on the accumulation of aluminum in rat brain and bone.

Deposition of aluminum in the body is responsible for the development of dialysis-related diseases in patients with renal dysfunction and may play a role in the development of certain neurodegenerative disorders. Although citric acid is known to be a strong enhancer of gastrointestinal absorption of aluminum, its effect on aluminum distribution and accumulation is not yet clear. Maltol has been shown to increase the neurotoxicity of aluminum, but little is known about its effect on aluminum deposition in the body. To elucidate the role of citric acid and maltol in aluminum accumulation and toxicity, rats were loaded intraperitoneally during a 7-day period with different amounts of aluminum chloride in absence or presence of citric acid or maltol before analysis of aluminum in serum, brain, bone, and urine. Coadministration of citric acid led to relatively reduced serum levels, as compared with aluminum and aluminum-maltol treatment. This is explained by both tissue elimination and enhanced renal elimination. Only at the highest aluminum dose (8 mg/kg body weight) was an enhancing effect of citric acid on accumulation of aluminum in brain observed; no effect on bone aluminum was seen. Furthermore, it was seen that citric acid alters the distribution pattern of aluminum. This may be explained by the postulation of a characteristic aluminum citrate species in serum. Administration of citric acid may increase this aluminum fraction in serum, thereby inducing an alteration of the distribution pattern. Maltol was shown to be a strong enhancer of aluminum accumulation in serum, brain, and bone. The rise of aluminum in these target tissues was dose dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1993

Analysis for bismuth in tissue by electrothermal atomic absorption spectrometry.

We developed a simple method for the analysis of bismuth (Bi) in biological tissue, using wet digestion for sample pretreatment. Bi was determined by electrothermal atomic absorption spectrometry with platinum as a matrix modifier to decrease the volatility of Bi. The furnace program included a gas stop for sensitivity enhancement. Analytical performance was established for Bi in kidney, liver, brain, and bone. As little as 25 ng/g wet weight can be detected in the most concentrated digests. Homogenization of bone was necessary before digestion, and its matrix showed the strongest interference. In rats exposed orally to colloidal bismuth subcitrate for 14 days, the metal could be detected in liver, kidney, and spleen but not in brain and bone. In the tissues of 12 patients who died from non-Bi-related causes, no Bi were present in kidney in the other 2.

Adolescent↗