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Biomedical subjects

G Froese

Publications and source records attributed to G Froese.

At least 19 recordsLinked to original sources
PubMed1994

Effects of in utero exposure to low dose ionizing radiation on development in the rat.

Most studies of in utero effects of ionizing irradiation involve high doses and examination at postnatal intervals. Little information is available on the effects of low levels of ionizing radiation on embryogenesis. The developmental effects of in utero exposure to 50 cGy gamma radiation on gestational day-9.5 was investigated using Sprague-Dawley rats. Irradiated rats and appropriate controls were killed at prenatal intervals of 4h, 48h and 10 days after exposure. Fetuses were examined for abnormalities and random samples of tissues were prepared for microscopic study. With the exception of the neuroepithelium, no histopathological changes were observed in embryos 4h after exposure to 50 cGy. In irradiated embryos, mitoses were reduced within the neuro-epithelium; pyknosis and some necrosis of cells were apparent at this gestational interval. Among the gross developmental abnormalities observed in embryos 48h after irradiation, excessive flexion of the embryo and abnormal flexion of the head were the only ones that appeared to be radiation-induced. The mean numerical score (42.3 +/- 0.2, controls; 42.4 +/- 0.1, irradiated) for 17 morphological parameters examined in fetuses at this gestational period compares favorably with other studies. Controls, however, showed greater variability in the extent of development of their forebrain, olfactory system, midbrain, hindbrain, and caudal neural tube. In all cases, there was evidence of slower development in these regions compared to their irradiated counterparts. At term, no significant differences in litter size or resorption rates were observed in irradiated animals compared to the controls, but there was a higher incidence of defective eye development, spinal curvature and visceral anomalies.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Radiation-Induced↗
PubMed1993

Postnatal development of the rat CNS following in utero exposure to a low dose of ionizing radiation.

In utero exposure to ionizing radiation is of importance because of its potential health risks. The developing nervous system is particularly vulnerable and the consequences of exposure to low levels of radiation (< or = 1 Gy) are not well established. The developmental effects of maternal exposure to 50 cGy gamma-radiation on gestational days (GD) 9.5, 15, and 18 were investigated in Sprague Dawley rats. Rats exposed on GD-9.5 along with appropriate controls were killed at 4 h, 48 h, and 10 days post-irradiation while those irradiated on GD-15 and GD-18 were killed postnatally (PN) on days 7 and 26. All were examined for developmental anomalies and representative samples of brains were processed for microscopic study. No significant developmental differences were observed between irradiated and control embryos killed 48 h after irradiation on GD 9.5. However, in irradiated fetuses a larger number of developmental anomalies were observed at term. Defects of the eye and of spinal curvature were the most common malformations encountered. Mitoses were reduced within the neuroepithelium of embryos irradiated on GD-9.5 and evidence of pyknosis and necrosis was seen 4 h after irradiation. The capacity of surviving primitive neural cells for repair, however, was such that by 48 h after exposure the irradiated nervous system no longer differed from controls. Rats irradiated on GD-15 and GD-18 and examined on PN-26 exhibited clusters of small, dark, pyknotic neurons within the hippocampal and dentate gyri, often bilaterally.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Radiation-Induced↗
PubMed1991

The sensitivity of the thoracolumbar spinal cord of the mouse to hyperthermia.

Twelve millimeters of the thoracolumbar spinal cord of mice has been treated with a radiofrequency heating system which has been shown previously to produce localized and controllable elevation of temperature. The severity of neurological damage was assessed by measuring the reduction in the reflex leg extension of the hind legs of the mice from video-recorded images and by scoring the performance of the mice by a negative geotaxis test. The response to treatment was rapid with maximum paralysis occurring within a few days after treatment. Only minor symptoms were observed in those animals which had not developed paralysis within 2 weeks. A 40% reduction in the reflex leg extension was chosen as an end point, and the percentage of mice having reached the end point for different thermal doses was determined in groups of nine mice. The ED50 for heating for 1 h was 43.1 degrees C and for heating at 45 degrees C was 10.8 min. An increase in temperature by 1 degree C required a decrease in time by a factor of 2.25 to produce the same effect. Thermotolerance was observed 24 h after preheating at 45 degrees C for 1.9 min with a thermotolerance ratio of 1.7. The rapid response and high sensitivity of the spinal cord will have to be taken into consideration in the clinical application of hyperthermia.

Acclimatization↗
PubMed1989

Effect of rioprostil, an oral prostaglandin E1 analogue, on lower oesophageal sphincter pressure and on the motility of the distal oesophagus in healthy volunteers.

The influence of rioprostil on the resting pressure of the lower oesophageal sphincter (LESP) and on the bolus-stimulated contraction wave amplitude of primary peristalsis is investigated in 9 healthy male volunteers receiving placebo or 300 micrograms and 600 micrograms of rioprostil orally in a randomized, double-blind, threefold crossover study. Manometry is performed using the low-compliance pneumohydraulic infusion system. The results show that: rioprostil, 600 micrograms, slightly increases LESP (ns) and contraction wave amplitudes, measured 10 cm above the lower oesophageal sphincter (LES) (p = 0.0039); rioprostil in both doses does not change the contraction wave amplitudes of the distal oesophagus, 5 cm above the LES; the duration of the peristaltic contractions is not altered. We conclude that rioprostil, in doses which effectively inhibit gastric acid and pepsin secretion and heal peptic ulcers, has no inhibitory effects on oesophageal motility. Studies are warranted, therefore, to establish the efficacy of rioprostil in the treatment of reflux oesophagitis.

Adult↗
PubMed1988

Effect of rioprostil, an oral prostaglandin E1 (PGE1) analogue, on lower esophageal sphincter pressure and on the motility of the distal esophagus in healthy volunteers.

The influence of rioprostil on the resting pressure of the lower esophageal sphincter (LESP) and on the bolus-stimulated contraction wave amplitude of primary peristalsis was investigated in 9 healthy male volunteers receiving placebo or 300 and 600 micrograms of rioprostil orally in a randomised, double-blind, threefold cross over study. Manometry was performed using the low-compliance pneumohydraulic infusion system. Rioprostil in a dose of 600 micrograms slightly increased LESP and contraction wave amplitudes measured 5 cm and 10 cm above LES. The duration of the peristaltic contractions was not altered. We conclude that rioprostil in doses which inhibit effectively gastric acid and pepsin secretion and heal peptic ulcers has no inhibitory effects on esophageal motility. Thus rioprostil may be a candidate to treat reflux esophagitis and studies are warranted to establish its efficacy.

Adult↗
PubMed1982

Tumour cell-antibody interactions. II. In vitro studies.

The interaction of L5178Y thymic lymphoma cells syngeneic to DBA/2 mice and of normal thymocytes with goat IgG antibodies was studied in vitro. Viable tumour and normal cells exerted a rapid, continuous and temperature-dependent destruction of antibody activity. Fractionation studies of culture supernatants from antibody-coated cells revealed that a significant portion of the antibody was completely degraded to amino acids. Tumour cells digested antibody more effectively than did normal lymphocytes. This observed degradation of antibody was most extensive at 37 degrees, significantly less at room temperature (23 degrees) and not detectable at 0 degrees. Undegraded antibody released from antibody-coated cells had also lost its antibody activity to a considerable extent. This was due to the formation of soluble antigen-antibody complexes, which was observed even at 0 degrees. Cells fixed with 10% formalin bound maximum amounts of antibody were incapable of digesting antibody even at 37 degrees and did not release immune complexes. These findings are of relevance to cancer immunodiagnosis and immunotherapy.

Animals↗
PubMed1982

Tumour cell-antibody interactions. I. In vivo experiments.

Goats were immunized with membrane fractions of the L5178Y tumour syngenic to DBA/2 mice. IgG fractions of this antiserum were made tumour specific by repeated in vitro and in vivo absorptions with normal cells and concentrated by adsorption to and elution from tumour cells. In vivo studies indicated that the accumulation of 125I-labelled antibody in tumour tissue could not be improved by extensive purification and concentration. The observed clearance rates of radioactivity from tumours and whole animals showed that the metabolism of antibodies was significantly accelerated in the presence of target cells. It is suggested that a rapid neutralization and degradation of antibody by the target tissue prevents its accumulation in tumour nodules.

Animals↗
PubMed1980

Antigen(s) expressed on cultured cells of various species that crossreact with tumor antigens(s).

Antibodies eluted from a methycholanthrene induced sarcoma (MC-D) of strain 13 guinea pigs were examined for reactivity against 11 cultured cell lines derived from unrelated tumors and 11 cell lines originating from normal tissues of various species by radioimmunoassay. Six tumor-derived lines of mouse, hamster, rat, guinea pig and man and five "normal" cell lines of guinea pig, human and fish origin showed significant reaction.

Animals↗
PubMed1978

Comparisons of the chemical and biologic properties of triaziquone and triaziquone-protein conjugates.

Prepared with nonimmunospecific proteins were covalent conjugates of triaziquone [2,3,4-tris(1-aziridinyl)-p-benzoquinone] (hereafter referred to by the tradename, Trenimon). The bound Trenimon that absorbs maximally at 350 nm (epsilon = 8,200) was assayed by titration of the acid uptake during alkylation of thiosulfate ion and by the color produced during alkylation of 4-(p-nitrobenzyl)pyridine. Conjugates of Trenimon with nonimmune IgG were toxic to cells in culture, although no firm binding of conjugate to cell surface could be measured by fluorescein labeling. Inhibition of cellular pinocytotic activity with cytochalasin B had no effect on the cytotoxic response. Polyoma virus-transformed baby hamster kidney (BHK) cells that were threefold more resistant to the action of a conjugate than was the parent cell line were as sensitive as normal BHK cells when grown in the presence of dibutyryl cyclic AMP or when acted on in suspension by the conjugate. These conditions did not affect the response of the parent BHK line. Cysteine acted to protect both cell lines. The results suggest that Trenimon bound to nonimmmune protein reacted primarily with a component of the cell surface. The reaction did not appear to depend on a firm attachment of the conjugate to the cell.

Bucladesine↗
PubMed1975

A microradioimmunoassay for antibodies to tumor-associated antigens.

A versatile microradioimmunoassay for the detection of antibodies to tumor-associated and other tissue antigens was described. The method involved: a) the preparation of solid-phase antigen with cultured (already adhered) or noncultured cells (sedimented by centrifugation) fixed to Micro-Test plates with neutral buffered formaldehyde or absolute methanol; b) the incubation of the antigen with test or control sera; and c) the incubation of the antigen with radioiodinated antiglobulin antibody. The nonspecific background of radioactivity was reduced to an acceptable level by the fixed cells being precoated in the wells with 0.5% bovine serum albumin in phosphate-buffered saline which was also used for the dilution of sera and labeled antiglobulin antibody. Tumor cells in primary cultures gave a high background, as compared to long-term cultures, which was due to the presence of immunoglobulins (most likely tumor-specific antibody). The specific antibody response to a syngeneic mouse tumor was demonstrated by this technique.

Animals↗