In-vitro teratogenicity of retinoids.

Mid-gestation rat conceptuses were cultured for 48 h in serum containing the retinoids all-trans-retinoic acid (TRA), 13-cis-retinoic acid (13-CRA), etretinate (ETR), etretin or one of six retinamides at concentrations ranging from 0.5 to 400 micrograms/ml. TRA was toxic at a concentration of 0.5 microgram/ml. 13-CRA and etretin caused abnormal development at 1.0 microgram/ml. However, the six retinamides were less toxic and adverse developmental effects were only evident at concentrations of 50 or 100 micrograms/ml. ETR was without effect at 100 micrograms/ml, the highest dose level of this compound tested. In vivo, TRA, 13-CRA and ETR are highly teratogenic. In this culture system, TRA and 13-CRA caused abnormal development at very low concentrations but in contrast, ETR was non-toxic at 100 micrograms/ml. Therefore these findings indicate that in vivo, maternal pharmacokinetics, and bioactivation in particular, play a major role in inducing abnormal development. Cis/trans isomerization was not a major determinant of toxicity. However, there appeared to be a relationship between abnormal development and the actual or estimated pKa values of the 10 retinoids tested.     

Comparative teratogenicity of nine retinoids in the rat.

he comparative teratogenicity of nine retinoids in Wistar rats was investigated. The compounds studied and dose levels tested (mg/kg) were: all-trans-retinoic acid (TRA), 6.25, 12.5, 25, 50, 100; etretinate (ETR), 25, 50; acitretin (ACIT), 25, 50; 13-cis-retinoic acid (13CRA), 100, 200; and five retinamides, each at 300 and 600 mg/kg, N-(4-hydroxyphenyl)-retinamide (4HPR); N-tetrazol-5-ylretinamide (TZR); N-butylretinamide (NBR); N-ethylretinamide (NER); 13-cis-N-ethylretinamide (13CNER). Retinoids were administered by oral intubation on days 10 and 11 post coitum (p.c.). Dams were killed on day 22 p.c. and examinations carried out to assess teratogenic potential. TRA, ETR, ACIT, 13CRA and 4HPR increased the incidence of resorptions. The incidence of abnormal fetuses, irrespective of the specific abnormalities induced, was markedly increased (50-100%) by TRA, ETR, ACIT, 13CRA and 4HPR, whereas TZR and NBR caused moderate increases (20-50%), and NER and 13CNER induced mild increases (10-20%). The incidences of CNS, craniofacial and urinogenital defects were generally high with TRA, ETR, ACIT and 13CRA. Cardiac vessel defects were markedly increased by 4HPR. Using a number of criteria, a generalized ranking order of the toxicity of the compounds was drawn up: TRA > ETR > ACIT > 13CRA > 4HPR > TZR identical to NBR > NER identical to 13CNER. The ranked order of relative in-vivo teratogenicity for the nine retinoids is compared with a previously reported in-vitro assessment of the compounds using a rat whole embryo culture technique.     

The teratogenicity of anticonvulsant drugs

BACKGROUND: The frequency of major malformations, growth retardation, and hypoplasia of the midface and fingers, known as the anticonvulsant embryopathy, is increased in infants exposed to anticonvulsant drugs in utero. However, whether the abnormalities are caused by the maternal epilepsy itself or by exposure to anticonvulsant drugs is not known. METHODS: We screened 128,049 pregnant women at delivery to identify three groups of infants: those exposed to anticonvulsant drugs, those unexposed to anticonvulsant drugs but with a maternal history of seizures, and those unexposed to anticonvulsant drugs with no maternal history of seizures (control group). The infants were examined systematically for the presence of major malformations, signs of hypoplasia of the midface and fingers, microcephaly, and small body size. RESULTS: The combined frequency of anticonvulsant embryopathy was higher in 223 infants exposed to one anticonvulsant drug than in 508 control infants (20.6 percent vs. 8.5 percent; odds ratio, 2.8; 95 percent confidence interval, 1.1 to 9.7). The frequency was also higher in 93 infants exposed to two or more anticonvulsant drugs than in the controls (28.0 percent vs. 8.5 percent; odds ratio, 4.2; 95 percent confidence interval, 1.1 to 5.1). The 98 infants whose mothers had a history of epilepsy but took no anticonvulsant drugs during the pregnancy did not have a higher frequency of those abnormalities than the control infants. CONCLUSIONS: A distinctive pattern of physical abnormalities in infants of mothers with epilepsy is associated with the use of anticonvulsant drugs during pregnancy, rather than with epilepsy itself.     

Anti-cancer action of retinoids.

The anti-cancer action of retinyl acetate (Vitamin-A acetate, VAA), chosen as a representative retinoid substance, is attributed to its power to exercise immunopotentiation, though other possibilities are considered. The reasons for forming this opinion were: (1) chronic administration of VAA brought about enlargement of the thymus and peripheral lymph nodes; (2) the administration of VAA curtailed the life of skin allografts though (3) its action could be reversed by the concomitant administration of immunosuppressive agents.     

In-vitro platelet-neutrophil adherence.

The specific adherence of platelets to neutrophils in vitro has been noted with increasing frequency and with increasing interest, but its significance remains obscure. Two cases in which this event occurred are presented, and the literature is reviewed.     

Rubella virus replication and links to teratogenicity

Rubella virus (RV) is the causative agent of the disease known more popularly as German measles. Rubella is predominantly a childhood disease and is endemic throughout the world. Natural infections of rubella occur only in humans and are generally mild. Complications of rubella infection, most commonly polyarthralgia in adult women, do exist; occasionally more serious sequelae occur. However, the primary public health concern of RV infection is its teratogenicity. RV infection of women during the first trimester of pregnancy can induce a spectrum of congenital defects in the newborn, known as congenital rubella syndrome (CRS). The development of vaccines and implementation of vaccination strategies have substantially reduced the incidence of disease and in turn of CRS in developed countries. The pathway whereby RV infection leads to teratogenesis has not been elucidated, but the cytopathology in infected fetal tissues suggests necrosis and/or apoptosis as well as inhibition of cell division of critical precursor cells involved in organogenesis. In cell culture, a number of unusual features of RV replication have been observed, including mitochondrial abnormalities, and disruption of the cytoskeleton; these manifestations are most probably linked and play some role in RV teratogenesis. Further understanding of the mechanism of RV teratogenesis will be brought about by the investigation of RV replication and virus-host interactions.     

In-vitro development of refrozen mouse embryos

To evaluate the effects of sequential, repetitive freezing on their in- vitro development, mouse embryos at the eight- to 16-cell stage were subjected to one of five treatments. They were (i) cultured as unfrozen controls, (ii) frozen once and cultured, (iii) subjected to two consecutive freeze-thaw cycles, (iv) frozen and thawed, and then cultured for 18-30 h before being frozen a second time, and (v) frozen three times in succession without being cultured. To assess their functional survival after freezing and thawing, all embryos were cultured in vitro to the hatched blastocyst stage in Whitten's medium. In one experiment, hatched embryos that developed after one, two or three cycles of freezing and thawing were stained with Hoechst 33342 to determine their mean cell number. More embryos of the culture control group and the once-frozen group developed into hatching blastocysts than those of the refrozen groups. There was no difference in the second post-thaw rate of in-vitro development for embryos refrozen with the culture-refreeze or direct-refreeze procedure. Furthermore, there was no difference among in-vitro development rates for embryos frozen two or three times. However, among those embryos subjected to repeated cycles of freezing and thawing that did not survive, there was a considerable amount of damage to their zonae pellucidae. Furthermore, frozen mouse embryos had fewer cells per embryo at the time of hatching than the unfrozen embryos. Nevertheless, these results demonstrate that mouse embryos can survive even three successive freeze-thaw cycles yet still be capable of in-vitro development.      

生物材料血液相容性体外评价的研究进展

体外实验因其快捷、方便、特点 ,通常被用作生物材料血液相容性评价的初步筛选实验。在体外血液相容性评价中 ,需选用合理的血液与材料接触模型、敏感而又特异的检测指标 ,在整个实验中尽量避免外界非待测材料对血液的激活作用。另外接触时间、接触方式、切变率以及参照材料的选择等均是重要的影响因素。近年来 ,体外评价方法虽已取得很大进展 ,但仍有待于标准化 ,以更有效地评价生物材料的血液相容性。     

In-vitro genetic modification of mitochondrial function

Defects of mitochondrial (mt) DNA cause a diverse group of incurable, progressive diseases that often lead to severe disability and premature death. Most patients with pathogenic mtDNA defects have a mixture of mutant and wild-type mtDNA (heteroplasmy), and the clinical defect is only expressed when the percentage of mutant mtDNA exceeds a critical threshold. Since mtDNA is continually replicating and being turned over, we have proposed an approach to the treatment of these disorders that utilizes sequence-specific antigenomic peptide nucleic acids (PNAs) to hybridize and specifically inhibit the replication of mutant mtDNA under physiological conditions. By allowing the selective propagation of wild-type molecules, it may be possible to correct the cellular biochemical defect and to prevent the progression of disease. This paper summarizes the experimental progress in this area, including the cellular uptake of PNA molecules and their import into mitochondria both in vitro and in cell culture by the addition of a nuclear-encoded mitochondrial targeting sequence. The possibilities of extending this strategy to the treatment of mtDNA deletion disorders are discussed.     

In-vitro fertilization; the ethics

This paper is addressed to practitioners. It seeks to acquaintthem with ‘ethical’ arguments against their workwhich, because they are simple and plausible, persuade manypeople. These arguments are briefly rehearsed and as brieflyexamined. A more positive ethics of in-vitro fertilization ispresented which seeks to respect (a) what is known in the relevantscience and done in developing practice; (b) the inseparabilityof research from clinical application; (c) a moral traditionof long-standing which relates the protection of fetal lifepan passu with its own morphological growth towards maturity;(d) the moral sense of properly informed persons whose judgementswe trust in other areas of life. Practitioners themselves areto be defended as the proper moral agents (that is, to be entrustedwith decisions) provided that they are careful (a) to keep publicconfidence by means of a corporate self-discipline; (b) to keepfaith with patients and research subjects; (c) to maintain mutualtrust between research scientists and clinical practitioners;(d) to safeguard the liberty of disciplined enquiry, of purposefulcuriosity, as being inherent in the notion of a science, necessaryto therapeutic advance, and proper to the nature of man. Theauthor writes from within the theological tradition of the Churchof England.     

In-vitro demonstration of a complicated atherosclerosis-like lesion

Smooth muscle cells derived from the media of adult rat aorta were grown on elastin membranes for up to 3 weeks in cell culture. Cell degeneration was evident by the 4th day and increased with time. At the end of the experiment necrotic and calcified areas were prominent. The basic feature of cell degeneration was dissolution of myofilaments; the disintegrating cytoplasm usually contained numerous glycogen granules. Increased electron density of the mitochondrial matrix and fat globules were seen and nuclei showed dilution of chromatin or pyknosis. Abundant cellular debris, vesicular structures and microfibrils were found in the extracellular space.     

Evolving knowledge of the teratogenicity of medications in human pregnancy

A majority of pregnant women take at least one medication during pregnancy, although the safety of such drugs during pregnancy is not always known. We reviewed the safety during pregnancy of 172 drugs approved by the US Food and Drug Administration (FDA) from 2000 to 2010 using the TERIS risk rating system. We also reviewed safety information for 468 drugs approved by the FDA from 1980 to 2000 to determine if revisions in risk categories had been made in the last 10 years. The teratogenic risk in human pregnancy was “undetermined” for 168 (97.7%) of drug treatments approved between 2000 and 2010. Furthermore, the amount of data available regarding safety in pregnancy was rated as “none” for 126 (73.3%) of these drugs. For those drugs approved between 1980 and 2000, only 23 (5%) changed a full risk category or more in the past 10 years. Sources of data that led to a revised risk were derived from exposure cohort studies performed through record linkage studies, teratogen information services, large population-based case-control studies, and pregnancy registries. The mean time for a treatment initially classified as having an “undetermined” risk to be assigned a more precise risk was 27 years (95% confidence interval 26–28 years). The lack of information needed to assess the safety of drug treatments during human pregnancy remains a serious public health problem. A more active approach to post-marketing surveillance for teratogenic effects is necessary. © 2011 Wiley-Liss, Inc.     

Antiinflammatory aspects of systemic and topically applied retinoids

Conclusions Evidence is presented that retinoids have topical and systemic antiinflammatory actionsin vivo. This degree of antiinflammatory activity, as assessed in different model systems is often similar to that observed for standard reference antiinflammatory agents of both the non steroidal or corticosteroidal type.These new classes of polycyclic substances not only share the ability of retinoids to modulate cellular differentiation, but in addition have a general antiinflammatory action. The mechanism of this activity is at present unknown but under investigation in our laboratories.