Biomedical subjects

D R Hilbelink

Publications and source records attributed to D R Hilbelink.

12 recordsLinked to original sources

PubMed1992

A novel model to assess developmental toxicity of dihaloalkanes in humans: bioactivation of 1,2-dibromoethane by the isozymes of human fetal liver glutathione S-transferase.

Glutathione S-transferase (GST) isozymes from human fetal liver (16-18 weeks gestation) were purified by affinity chromatography followed by ion-exchange high performance liquid chromatography (HPLC). The purified isozymes were used to investigate toxicity of 1,2-dibromoethane(EDB) in an in vitro model of rat embryos in culture as passive targets. At least five isozymes of GST were found in the human fetal liver. Two anionic forms [pI values 5.5 (P-2) and 4.5 (P-3)] and one basic form [pI value 8.7 (P-6)] were clearly separated. The presence of two near-neutral forms was also identified. All the isozymes of the human fetal liver GSTs tested metabolized EDB (specific activities were 2.1, 7.0, and 2.0 mumol of GSH consumed/min/mg protein for P-2, P-3, and P-6 isozymes, respectively). Covalent binding of EDB to DNA and protein was 144% and 212% higher, respectively, with the P-3 anionic isozyme when compared to the P-6 basic isozyme of GST. No covalent binding to either protein or DNA was observed with the P-2 isozyme. EDB bioactivation by the GST isozyme P-3 (15 units; 1 unit = 1 nmol of GSH consumed/min) resulted in toxicity to cultured rat embryos. Significant reductions of crown rump length, yolk sac diameter, and the composite score of morphological parameters (Brown and Fabro method) were observed. The central nervous system, optic and olfactory systems, and the hind limb were most significantly affected. The results of this investigation suggest that EDB may be classified as a suspected developmental toxicant in humans.

Animals↗

PubMed1992

Rat hepatic glutathione S-transferase-mediated embryotoxic bioactivation of ethylene dibromide.

The embryotoxic effects of ethylene dibromide (EDB) bioactivation, mediated by purified rat liver glutathione S-transferases (GST), were investigated using rat embryos in culture. Significant EDB metabolism was observed with rat liver GST purified by affinity chromatography (specific activity of 188 +/- 11.3 nmol/min/mg protein). The reaction was enzymatic in nature and the conjugation rate was proportional to the concentration of EDB (up to 0.75 mM) and the enzyme present in the reaction medium. EDB activation by 100 units (1 unit = 1 nmol of glutathione consumed per min) of purified rat liver GST caused a significant reduction in general development as measured by crown-rump length, yolk sac diameter, somite number, and the composite score for different morphological parameters (Brown and Fabro methodology). Structures most significantly affected were the central nervous and olfactory systems as well as the yolk sac circulation and allantois. The results of this study clearly indicate that under in vitro conditions, bioactivation of EDB by GST can lead to embryotoxicity.

Animals↗

PubMed1992

Statistical analysis of the effect of cadmium and zinc on hamster teratogenesis.

Maternal smoking is correlated with lower average birth weights and an increase in malformations in some studies. Increased maternal cadmium levels and reduction of zinc levels in certain tissues from fetuses of women who smoke suggest a biological association during pregnancy. Zinc has a protective effect on hamster teratogenesis caused by cadmium. To determine whether this protective effect is additive or synergistic (interactive), pregnant golden Syrian hamsters were injected (iv) on Day 8 of gestation with a test solution based on maternal body weight (0.5 ml per 100 g). Five doses were given: 2 mg/kg zinc chloride, 2 mg/kg cadmium chloride, 3 mg/kg cadmium chloride, 2 mg/kg zinc chloride plus 2 mg/kg cadmium chloride, and 2 mg/kg zinc chloride plus 3 mg/kg cadmium chloride. Fifty dams were randomly placed into one of the groups, for a total of 10 pregnant dams in each group. Twenty other dams were randomly placed into untreated or saline control groups. Fetuses were recovered on Day 15 and weighed, crown-rump length was measured, and fetuses were examined for viability and external malformations. Resorptions were noted. Statistical analyses included one- and two-way nested ANOVA, and logistic regression adjusted for litter effect. Zinc's protective effect on acute cadmium embryonic/fetal toxicity and teratogenicity was confirmed. The protective effect was of the same magnitude relative to the dose-dependent effect of the cadmium exposure, indicating that the effect was statistically additive and not synergistic. This suggests that the effect depends on competition of the two elements at some common binding site(s).

Abnormalities, Drug-Induced↗

PubMed1991

Carpal orientation from computed reference axes.

Carpal instability is usually diagnosed by abnormal two-plane radiographic angles. These angles are often unreliable. A method that eliminates interpretation of overlapping shadows and uses all of the carpal geometry should improve clinical diagnoses. The digital data from computed tomography scans can be manipulated to describe the carpal orientation in the normal wrist. The digital data from the computed tomography scans of twenty-two normal wrists were used to compute distances with and without directions between the volumetric centroids of the carpal bones. An expansion technique also extracted from the computed tomography data an orthogonal set of vectors, the principal axes. The first principal axis describes the longest dimension of each bone. The average angle produced by the first principal axes of the scaphoid and lunate was 23.6 degrees, scaphoid and capitate was 73.2 degrees, and the capitate and the lunate was 93.5 degrees. These computations represent new carpal axes and intercarpal angles that are not related to the commonly measured two-plane radiographic angles. They should prove helpful in the study of kinematics and pathomechanics in the wrist joint.

Carpal Bones↗

PubMed1991

Computed analyses of the pathomechanics of scaphoid waist nonunions.

The computed tomography scans of both the injured and the normal wrists of nine patients with a scaphoid nonunion of 5 to 120 months' duration were used to create three-dimensional computer models. When the computer images of the normal and the contralateral fractured scaphoids were superimposed, it was possible to calculate the volume of bone that was lost as a result of the injury and its failure to heal, as well as the angular relationship of the fracture components to one another. The amount of the scaphoid bone that was lost varied from 6% to 15% of bone volume and did not show a linear correlation with the duration of the nonunion. The configuration of the missing bone was consistent and exhibited a prismatic shape whose base is quadrilateral and faces palmarly. The proximal scaphoid fracture component is extended, radially deviated, and supinated in relation to its distal fracture component. The consistent fracture deformity and the configuration of the bony defect in the scaphoid waist nonunions should be helpful in the understanding and treatment of the condition.

Adult↗

PubMed1991

Regional changes in hemodynamics and cardiac myocyte size in rats with aortocaval fistulas. 1. Developing and established hypertrophy.

The effects of a large arteriovenous fistula on left and right ventricular hemodynamics and cardiac myocyte size were examined in adult rats at 1 week and 1 month after surgery. Cardiac output, left ventricular function, and right ventricular function were evaluated before obtaining isolated myocytes for cell size measurements. Average heart weight increased 35% at 1 week and 86% at 1 month in rats with fistulas. In general, myocyte hypertrophy was due to a proportional increase in length and width (length/width ratio remained constant). This change was more evident in the large hearts from rats with 1-month fistulas. At both the 1-week and 1-month intervals, the hypertrophic response of right ventricular myocytes was slightly greater than that observed in the left ventricle or interventricular septum. Left ventricular systolic pressure and dP/dtmax were significantly reduced at 1 week but returned to normal after 1 month of overloading. Left ventricular end-diastolic pressure was increased approximately fivefold and twofold at 1 week and 1 month, respectively. Right ventricular systolic pressure and dP/dtmax were increased at both intervals examined. We conclude that severe volume overloading from a large aortocaval fistula in the rat is characterized by 1) depressed left ventricular function at 1 week followed by a large compensatory hypertrophy and near normal function at 1 month, 2) right ventricular pressure overload, and 3) changes in myocyte shape that resemble normal physiological growth.

Animals↗

PubMed1991

Regional changes in hemodynamics and cardiac myocyte size in rats with aortocaval fistulas. 2. Long-term effects.

Regional changes in hemodynamics and cardiac myocyte size were examined in adult rats 5 months after creating a large aortocaval fistula. At that time, cardiac output, left and right ventricular pressures, and left and right ventricular dP/dtmax were measured. Subsequently, isolated cardiac myocytes were collected from the left ventricle, right ventricle, and septum for cell size measurements. Compared with sham-operated controls, percent dry weight was reduced in the liver and kidney but was unchanged in the lung. Heart rate, left ventricular systolic pressure, left ventricular dP/dtmax, and systolic aortic pressure were not changed in rats with fistulas. However, cardiac output, stroke volume, left ventricular end-diastolic pressure, and all measured parameters in the right ventricle were significantly increased. Mean cell volume and the ratio of heart weight to body weight were both elevated 92%. Cell volume, cell length, and cross-sectional area increased significantly in each heart region examined. Hypertrophy was more pronounced in cells from the right ventricle and the endomyocardium of the left ventricle. The percentage of cells with mononucleation or binucleation was not changed in any heart region of rats with fistulas. In summary, despite evidence of renal and hepatic congestion, most indexes of cardiac function were normal or elevated 5 months after creation of a large volume-overload-induced hypertrophy. Data from isolated cardiac myocytes suggested that cellular hypertrophy, rather than hyperplasia, was responsible for the increased cardiac mass.

Animals↗

PubMed1988

Mathematical analysis of computed carpal models.

The computed carpal models from digital computed tomography (CT) data obtained in this study compare favorably to natural anatomy. A new application of algebraic analysis of this data provides mathematical markers from which to calculate the position and orientation of each carpal bone. When the origin of the spatial coordinates of a carpal bone is transferred to the centroid of the bone, the data can be treated as three-dimensional pattern vectors describing its surface. It is then possible to calculate vectors that are the principal axes of the geometry. These axes provided references that were used to calculate position and orientation of the carpal bones in three wrist specimens. Comparisons of volumes, surface areas, and sizes and proportions of five computed images of each carpal bone from two of these wrists demonstrate the reliability of the technique. The analysis of CT scans of ceramics with known boundaries allows an estimation of its accuracy. The technique is well suited to the future study of normal wrist kinematics and pathological conditions.

Carpal Bones↗

PubMed1988

Structural remodeling of cardiac myocytes in rats with arteriovenous fistulas.

Structural changes in the heart associated with chronic volume overloading have not been adequately documented. In anesthetized adult rats, microsurgical techniques were used to produce two types of arteriovenous shunts. The end of a femoral artery was connected to the side of a femoral vein to produce a femoral shunt. Aortocaval fistulas were produced by placing a venous graft (femoral vein) between the abdominal aorta and inferior vena cava. A polyethylene ring was placed around the venous graft to control the size of the shunt. After 10 weeks, rats were anesthetized and hearts were excised, weighed, and perfused with collagenase to obtain isolated myocytes. Heart weight/body weight of rats increased 15% (p less than 0.005) with unilateral femoral fistulas and 41% (p less than 0.001) with aortocaval fistulas. Length of isolated cardiac myocytes was measured directly with a microscope. Cell volume was measured with a Coulter Channelyzer. Myocyte cross-sectional area was calculated from cell volume/cell length. Cell volume increased in proportion to heart weight in each experimental model. With both types of shunts, the majority of myocyte hypertrophy was due to an increase in cell length. There was a trend toward an increase in cross-sectional area in each region of both fistula groups, although this change was not statistically significant. These results indicate that eccentric cardiac hypertrophy was associated with enlargement of individual myocytes primarily as a result of increased length.

Animals↗

PubMed1986

Endotoxin-induced hyperthermia in pregnant golden hamsters.

The degree of elevation and the duration of induced fever following endotoxin treatment of pregnant golden hamsters were examined. A radiothermistor was surgically implanted in the abdomen of each animal on day 6 of pregnancy. The animals were intravenously treated with a bolus injection of saline or endotoxin (1, 10, 20, or 200 micrograms/kg) on the morning of day 8 of gestation. Abdominal temperatures were monitored at 15-minute intervals on days 8 and 9 and at 1-hour intervals on days 10 through 14 of gestation. The mean temperature of the saline-treated control animals was 37.2 degrees C with a range from 36.5 to 38.2 degrees C. The total number of viable fetuses, and the mean fetal weight of the 1-microgram/kg group were not significantly different from those of the saline controls, although a statistically significant monophasic temperature elevation did occur between 3 and 9 hr post-treatment. Three of seven females that received 10 micrograms/kg had viable litters and exhibited a monophasic fever. The remaining four animals exhibited a biphasic fever and total resorption of all implanted fetuses. The first phase began 2.5 hr post-treatment and lasted for 3-6 hr. The second phase began 12-15 hr post-treatment and lasted for 15 to 25 hr. All animals receiving 20 or 200 micrograms/kg demonstrated similar multiple temperature elevations. Treatment of animals with greater than 20 micrograms/kg resulted in total resorption of all implanted fetuses and maternal weight loss. Nonpregnant females treated with 20 micrograms/kg of endotoxin exhibited a biphasic temperature elevation; thus the second phase of the fever response can not be attributed to embryo death and resorption.

Animals↗

PubMed1986

Sirenomelia: analysis in the cadmium- and lead-treated golden hamster.

Sirenomelia, a fusion of the lower extremities, is believed to result from a median, bilateral symmetric defect of the caudal portion of the embryo at a very early stage in development. Anomalies of the gastrointestinal and urogenital systems are commonly associated with this malformation. Sirenomelia is not an embryo-lethal condition but typically is incompatible with postnatal life when combined with the associated malformations. In this study, intravenous treatment of hamsters with a combination of cadmium and lead on the morning of the eighth day of gestation resulted in 1.4, 22.2, and 35.6% of the viable fetuses displaying sirenomelia in litters recovered on days 15, 12, and 10 of gestation, respectively. With the exception of several fetuses with exencephaly, most structures cranial to the level of the umbilicus were normal. Caudal abdominal and pelvic structures were severely affected, with agenesis or dysgenesis of the kidneys, bladder, umbilical arteries, and external genitalia frequently noted. The administration of a combination of cadmium and lead has proven to be an effective and consistent means of inducing sirenomelia in the golden hamster.

Animals↗

PubMed1978

Fast green staining of whole embryos for examination and photography.

Immersion for 15 seconds in a 1:1 solution of 0.25% fast green and 95% ethyl alcohol facilitates the examination of normal and abnormal embryos for gross surface morphology and renders their surface detail highly photogenic. The method does not interfere with subsequent histological staining when the embryos are sectioned.

Animals↗