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Biomedical subjects

F Beck

Publications and source records attributed to F Beck.

At least 109 records · Page 6Linked to original sources
PubMed1988

The effect of epidermal growth factor, insulin and transferrin on the growth-promoting properties of serum depleted by repeated culture of postimplantation rat embryos.

Homologous serum, when repeatedly used for the culture of postimplantation rat embryos, rapidly loses its capacity to support growth and development. Replenishment of the 'exhausted' serum with glucose and vitamins (MEM vitamin concentrate--Flow Laboratories) together with gentle dialysis to remove small molecular weight toxic metabolites (lactate etc) fails to restore the growth-promoting properties of the serum. This suggests that 'recycled' serum has been depleted of specific growth-promoting factors. Such serum that has been subjected to dialysis can be completely replenished by addition of 30% normal rat serum. It is therefore probable that the growth promoters are originally present at very low concentrations and become rate limiting when serum is recycled. Many growth factors and hormones fall into this category and it is likely that a considerable number are involved when serum is 'exhausted' by repeated use. When insulin, epidermal growth factor or rat transferrin are added to dialysed 'exhausted' serum each effects a partial restoration of growth of rat embryos.

Animals↗
PubMed1988

Histochemical localization of IGF-I and IGF-II mRNA in the rat between birth and adulthood.

We describe the postnatal ontogeny and localization of insulin-like growth factors I and II (IGF-I and -II) in the rat. We have used oligodeoxyribonucleotide probes for in situ hybridization (hybridization histochemistry) and for Northern blotting. IGF-II mRNA is strongly expressed in liver, skeletal muscle, perichondrium, leptomeninges and choroid plexus of the newborn. Demonstrable levels fall dramatically in the liver at 18-20 days postnatally but persist for longer periods in muscle and remain undiminished throughout life in the pia/choroid plexus, indicating that different control mechanisms operate in these tissues. IGF-I mRNA is predominantly found in the liver. Its level in this organ rises well before levels of IGF-II fall. This suggests that distinct factors govern the expression of IGF-I and -II genes.

Animals↗
PubMed1988

The localization of laminin mRNA and protein in the postimplantation embryo and placenta of the mouse: an in situ hybridization and immunocytochemical study.

In situ hybridization (ISH) and immunocytochemistry were used to localize sites of synthesis and deposition of the basement membrane glycoprotein laminin during development in the postimplantation mouse embryo and extraembryonic membranes. In addition, similar studies were performed on postnatal viscera during the first 20 days after birth. Up to 10 days post coitum, embryonic laminin synthesis was confined to parietal endoderm. In maternal tissue, intense laminin mRNA expression was detected in decidual cells in the mesometrial and antimesometrial endometrium at 5-7 days. At 10 days, uniform expression was still seen within the mesometrial endometrium, with higher levels around migrating trophoblast, but in the antimesometrial aspect expression was restricted to the basal zone. High levels of mRNA expression persisted in parietal endoderm throughout gestation but much lower levels were detected in visceral yolk sac. In the mature placenta, laminin mRNA expression was also found associated with fetal vessels in the labyrinth and giant cells at the fetal/maternal boundary. In the embryo, the external limiting membrane of the cerebral vesicles and spinal cord stained for laminin protein and detectable mRNA was found in the pia mater. Growing peripheral nerves and dorsal and ventral root fibres expressed laminin mRNA and stained for laminin protein. Laminin mRNA expression was found in ureteric buds and nephrogenic vesicles (but not in metanephric blastema) during early prenatal kidney development, and in glomeruli, Bowman's capsule, loops of Henle and collecting duct cells at later stages of development, and after birth. All these structures possessed laminin-rich basement membrane (BM). Laminin mRNA expression fell to below detectable levels in the kidney around weaning. In the gut, laminin expression and protein staining was confined to the muscularis externa and the lamina propria during embryogenesis. After birth, the muscularis externa, muscularis mucosa and lamina propria cells corresponding to fibroblasts had detectable laminin mRNA, but in adult gut no laminin mRNA could be demonstrated in any cell type. In liver, low levels of laminin mRNA were seen in the capsule and in periportal connective tissue. After birth, laminin mRNA was associated with intrahepatic bile channels; no laminin mRNA was detected in the parenchyma and protein deposition was restricted to blood sinus BM. In the adult liver, no laminin mRNA was detected in any cell type. The developing heart showed uniform expression of laminin mRNA from 12 days to before birth. Postnatally, labelling was restricted to connective tissue cells.

Animals↗
PubMed1988

Control of IGF-II mRNA levels by glucocorticoids in the neonatal rat.

Insulin-like growth factor-II (IGF-II) is thought to be a major growth factor during fetal and neonatal development. Levels of IGF-II mRNA fall dramatically in the liver - the major site of endocrine production - between 18 and 20 days post-natally. No information concerning the control of gene expression post-natally has hitherto been available. Using Northern blotting and in-situ hybridization, we show here that cortisone acetate rapidly extinguishes IGF-II mRNA expression in the neonatal rat liver. The effect at putative autocrine/paracrine locations such as skeletal muscle and choroid plexus is much less marked or absent. The repression by cortisone acetate is discussed in the light of the available IGF-II gene sequence.

Animals↗
PubMed1987

The effects of mannose on rat embryos grown in vitro.

Rat embryos have been cultured in vitro from 9.5 days of gestation for different times in serum containing mannose, and the embryos have been observed by scanning electron microscopy. Embryos cultured in 3 mg/ml (1.7 X 10(-2) M) or 6 mg/ml (3.3 X 10(-2) M) mannose for 48 h showed inhibition of the expansion of the yolk sac and were smaller than the control embryos. Mannose-treated embryos also showed delayed development according to morphological criteria, and a range of abnormalities including abnormalities of the neural tube. Embryos cultured in 6 mg/ml mannose for 24 h also showed significant inhibition of yolk-sac expansion and were smaller and less advanced than the control embryos. Abnormalities were seen, including a delay in the closure of the neural folds. Abnormalities were also observed in embryos cultured in mannose for 10 h; embryos at the neural groove stage showed irregularities in the neural groove. Mannose did not inhibit the re-elevation of neural folds which had been caused to collapse by exposure to medium containing low calcium. These results are compatible with the idea that mannose retards development and thereby perturbs the morphogenesis of the neural tube.

Animals↗
PubMed1987

A stage-dependent effect of ethanol on 9.5-day rat embryos grown in culture and the role played by the concomitant rise in osmolality.

The effects of ethanol on the rat embryo undergoing organogenesis in vitro have been studied. We have shown that embryopathy is dependent on the stage of development at which explanted embryos were treated. The early neural plate (presomite) stage was highly sensitive to a 4-hour exposure of 300 mg/% ethanol, whereas embryos explanted 5 hours later, at the late head-fold (two to six somites) stage grew normally under the same conditions. We have also established that raised serum osmolality, associated with ethanol in serum, is responsible for some but not all of the teratogenic effect. This was shown by mimicking the rise in osmolality with hyperosmotic serum, containing glycerol, NaCl, or concentrated Hanks' salts. Dilution of this osmotic effect by the addition of distilled water in part reversed these embryopathic effects.

Abnormalities, Drug-Induced↗
PubMed1987

Histochemical localization of IGF-I and -II mRNA in the developing rat embryo.

We describe the histological localization of embryonic and fetal tissues whose cells express the genes coding for insulin-like growth factors I and II (IGF-I and IGF-II) in the developing rat. Our studies span the period between early somite stages and full term. We have used oligodeoxyribonucleotide probes and obtained results which are both topographically precise and highly reproducible. The gene coding for IGF-II is predominant throughout development. It is strongly expressed in the liver and yolk sac. A variety of other tissues also expresses the IGF-II gene, especially many mesodermally derived structures in the process of differentiation. Many tissues do not express IGF genes. Thus no IGF mRNA was demonstrable in ectodermally derived structures, including the central and peripheral nervous systems as well as the skin and its derivatives.

Animals↗
PubMed1987

Effect on rat embryos of in vitro culture in sera from human diabetic patients.

Recently conditions have been established whereby rat embryos can be cultured in vitro in human serum over the period of their major morphogenesis. By standardizing the amount of glucose in sera from diabetic subjects prior to culture, it has been possible to investigate factors other than hyperglycemia which might account for the increased incidence of congenital defects seen in infants of diabetic mothers. The incidence of abnormalities in rat embryos cultured in sera from chlorpropamide-treated diabetics was not significantly different from that using control sera from normal subjects. On the other hand, sera from insulin-dependent diabetics produced more defects in rat embryos than sera from either normal subjects or diabetics on oral agents. The incidence of abnormal rat embryos does not appear to be correlated with patient age, with the original blood glucose concentration or with the concentration of hemoglobin A1 or, in the insulin group, with the total daily insulin dosage.

Animals↗
PubMed1986

The giant yolk sac: a model for studying early placental transport.

Nine and a half day rat embryos can be cultured for 48 hours in whole heat-inactivated rat serum using the roller culture method described by New, Coppola & Terry (1973). We have prolonged the culture period, usually by seven days. Although the embryo dies almost immediately during this extended culture period, the yolk sac continues to grow and reaches a diameter of approximately 2 cm; we have called this the giant yolk sac. The morphology of the giant yolk sac is very similar to that of control yolk sacs (17 1/2 or 18 1/2 days in vivo), the main difference being the greatly enlarged vacuolar volume in the endodermal cells of the giant yolk sac, which have been studied morphometrically. The pinocytic nature of the giant yolk sac has been demonstrated by its ability to take up colloidal gold. Its rate of uptake of 125I-polyvinylpyrrolidone in whole serum gassed with 95% O2; 5% CO2 has been shown to be similar to the rate of uptake found in control yolk sacs under the same incubation conditions. Acid phosphatase activity was found to be similar in the giant yolk sac and control yolk sacs using both histochemical and biochemical methods. Giant yolk sacs without a contained dead embryo can be produced by removing the embryonic pole of the egg cylinder prior to incubation. They exhibit all the features detailed above. Finally it is shown that the fluid from within the extra-embryonic coelom of the giant yolk sac has some capacity to support the growth and development of 9 1/2 day rat embryos when a source of bulk protein is also provided. This model, therefore, seems to be very useful for the study of transport in a placental system. Its full potential requires further study.

Acid Phosphatase↗
PubMed1985

Effects of diltiazem on hormonal and hemodynamic responses to lower body negative pressure and tilt in patients with mild to moderate systemic hypertension.

Mean arterial blood pressure, forearm vascular resistance, plasma norepinephrine, plasma renin activity and aldosterone responses to graded lower body negative pressure and tilt at 80 degrees were examined in 10 men with mild to moderate essential hypertension before and after 12 weeks of diltiazem (240 to 360 mg/day) therapy. Diltiazem therapy lowered basal supine systolic and diastolic blood pressures without affecting basal heart rate. Mean arterial blood pressure and forearm vascular resistance were decreased from 114 +/- 1.5 to 105 +/- 1 mm Hg, p less than 0.01 and from 29.3 +/- 3.5 to 18.9 +/- 2.1 units, p less than 0.01, respectively. Diltiazem therapy had no effect on basal supine levels of norepinephrine, plasma renin activity or aldosterone, nor on the responses of these hormones to lower body negative pressure. Diltiazem did decrease the forearm vascular resistance responses to lower body negative pressure and tilt. Diltiazem abolished an orthostatic increase (10 +/- 0.3 mm Hg) in mean arterial blood pressure and this was associated with a greater plasma norepinephrine response to tilt. These results suggest that diltiazem decreases vascular resistance through a reduction in the postjunctional effects of norepinephrine on vascular smooth muscle.

Adult↗
PubMed1985

Effects of beta-hydroxybutyrate on rat embryos grown in culture.

In order to investigate further the relationship between maternal diabetes and fetal malformation, rat embryos were grown in vitro in the presence of beta-hydroxybutyrate, one of the ketone bodies produced by diabetics. At 10 mM, beta-hydroxybutyrate produced minor abnormalities and at 20 mM it produced major abnormalities in rat embryos.

Abnormalities, Drug-Induced↗
PubMed1985

Cl transport across the basolateral membrane in frog skin epithelium.

Cellular Cl concentrations were determined by electron microprobe analysis to obtain further insight into the Cl transport across the basolateral membrane of the frog skin epithelium. Cl-free media on the serosal side led in all epithelial layers within 1 h to a decrease in cellular Cl concentration from about 40 to 15 mmol/kg wet wt, whereas the application of Cl-free solutions or amiloride to the apical side had no effect. Na-free media, furosemide or bumetanide on the serosal side had little effect on cellular Cl but abolished the Cl-reuptake into Cl-depleted cells. It is concluded that cellular Cl concentration is maintained above electrochemical equilibrium by a co-transport system, which is relatively silent under control conditions.

Animals↗