Heterogeneity of neural tube defects in Europe: the significance of site of defect and presence of other major anomalies in relation to geographic differences in prevalence.

In the period 1980-1987, neural tube defects were two to three times more prevalent in populations covered by EUROCAT registries in the United Kingdom and Ireland (UKI) than in Continental Europe and Malta (CEM). 1864 NTD cases in a total population of 580,000 births in UKI and 455 cases in a population of 380,000 births in CEM were analysed to find if there were differences in the ratio of prevalence rates between UKI and CEM according to site of the defect and association with non-central nervous system (CNS) anomalies. The prevalence rate ratio was high for anencephaly with accompanying spina bifida, iniencephaly, and upper spina bifida, and low for encephalocele, lower spina bifida, and anencephaly without other neural tube defects. There was a greater female excess for anencephaly with accompanying spina bifida, iniencephaly, and upper spina bifida than for other defects in both geographic areas. There was a female excess for encephalocele in UKI but a male excess in CEM. Certain sites (anencephaly with accompanying spina bifida, iniencephaly, and encephalocele) were more likely to have accompanying non-CNS anomalies. The prevalence rate ratio of multiply malformed NTD was in general lower than for isolated NTD but showed the same pattern by site. The prevalence rate ratio was high for multiply malformed anencephaly with accompanying spina bifida, iniencephaly, and upper spina bifida. The sex ratio was similar between isolated and multiply malformed cases when site of the defect is taken into account. It is concluded that the geographic prevalence pattern and sex ratio differ according to site of NTD but do not differ substantially according to whether NTD is isolated or associated with non-CNS anomalies.     

Analysis of the duplicated human C4/P450c21/X gene cluster

Gene duplications, deletions and rearrangements occur with an unusually high frequency in the region of the P450c21 genes encoding 21-hydroxylase. In the human genome, the locus contains at least 6 genes, oriented 5′ C4A, P450c21A, XA, C4B, P450c21B, XB 3′. Sequence analysis of the XA gene, of the 5′ flanking DNA of the C4A gene, and of part of the XB gene revealed that this gene cluster was duplicated by nonhomologous recombination at a CAAG tetranucleotide. The location of this duplication suggests that it may have occurred after mammalian speciation. The XA gene is abundantly expressed in the human adrenal as a stable 2.6 kb RNA, but it is not known if that RNA serves a biological function. Knowledge of the anatomy of the XA gene facilitates genetic analysis of disease-causing lesions in the P450c21B gene. Southern blotting data show that about 76% of disordered P450c21B alleles bear gene microconversions that resemble point mutations; the remaining alleles are equally distributed between gene deletions and large gene conversions.     

Release of acetylcholine by Xenopus oocytes injected with mRNAs from cholinergic neurons.

Xenopus laevis oocytes were injected with poly(A)+ mRNAs extracted from the electric lobes of Torpedo marmorata. The electric lobes contain the perikarya of approximately 120,000 cholinergic neurons that innervate the electric organs and are homologous to motor neurons. The injected oocytes accumulated acetylcholine and were able to synthesize [14C]acetylcholine from 1-[14C]acetate. With KCl depolarization and upon treatment with a Ca2+ ionophore, they released their endogenous as well as the radiolabelled neurotransmitter in a Ca(2+)-dependent manner. No synthesis or release were obtained from control oocytes. With respect to their dependency upon Ca2+ concentration, the oocytes injected with Torpedo electric lobe mRNAs released acetylcholine in a manner which closely resembled that found in the native synapses. In contrast to the controls, primed oocytes were also able to release [14C]acetylcholine that was injected a few hours prior to the release trial. Immunoblot analysis demonstrated that the 15 kd proteolipid antigen of the purified mediatophore, a 200 kd presynaptic protein able to translocate acetylcholine, was expressed in the ACh-releasing oocytes but not in the controls. The present observation may provide a useful approach for investigating the proteins involved in the release of acetylcholine and of other neurotransmitter substances.     

Mechanisms of heat protection by cycloheximide or puromycin: Involvement of polyamines?

1. 1.|When Chinese hamster ovary cells are treated with cycloheximide (10 μg/ml) or puromycin (100 μg/ml) for 2 h before and during heating at 43°C for 3 h, there is protection from hyperthermic killing; i.e. the plating efficiency increases 2000-fold from 3.7 × 10⁻⁵ to (6–9) × 10⁻².

2. 2.|The total intracellular levels of spermidine and spermine are not altered by the hyperthermic or drug treatments.

3. 3.|The small 30% decrease in intracellular putrescine observed after heating is not altered by drug treatment.

4. 4.|Heat protection by treatment with cycloheximide or puromycin cannot be attributed to changes in levels of total intracellular polyamines.

Properties of the estrogen receptors contained in the MtTF4 tumor whose growth is inhibited by estradiol: 17 beta-estradiol, 17 alpha-estradiol and DNA bindings

The steroid and the DNA bindings of the estrogen receptor of the MtTF4 tumor whose growth is inhibited by estradiol where characterized and compared to those of uterine estrogen receptors. In the tumor cytosol: E protects its binding sites against thermal denaturation, depending on the effects of sodium molybdate upon the dissociation rate of [3H]E at 20 degrees C and the ability of receptor to bind to DNA, the activation (or transformation) process, supposed to be necessary for the full action of estrogen ligand, occurs on estrogen receptor complexes and the calf thymus DNA interacts with estrogen receptor with an affinity similar to that of uterine estrogen receptor. Kinetic and equilibrium studies with 17 alpha-[3H]E both in uterus and tumor indicate that this ligand is fast-associating, fast-dissociating and that its affinity for ER is 2- to 4-fold lower than that of 17 beta-[3H]estradiol one. Competition experiments between 17 beta-[3H]estradiol and the unlabelled 17 alpha epimer reveal, in both uterus and tumor, a time-dependent decrease of the apparent potency of 17 alpha-E to inhibit the binding of [3H]E. It is concluded that the estrogen receptors are very similar in MtTF4 tumor and uterus and the diversity of the response of cell growth to E is due rather to differences at the post-receptor level.     

Natural Selection VS. Random Drift: Evidence from Temporal Variation in Allele Frequencies in Nature

We have obtained monthly samples of two species, Drosophila pseudoobscura and Drosophila persimilis, in a natural population from Napa County, California. In each species, about 300 genes have been assayed by electrophoresis for each of seven enzyme loci in each monthly sample from March 1972 to June 1975. Using statistical methods developed for the purpose, we have examined whether the allele frequencies at different loci vary in a correlated fashion. The methods used do not detect natural selection when it is deterministic (e.g., overdominance or directional selection), but only when alleles at different loci vary simultaneously in response to the same environmental variations. Moreover, only relatively large fitness differences (of the order of 15%) are detectable. We have found strong evidence of correlated allele frequency variation in 13-20% of the cases examined. We interpret this as evidence that natural selection plays a major role in the evolution of protein polymorphisms in nature.     

Evidence for the Neurotrophic Regulation of Collagen-Tailed Acetylcholinesterase in Immature Skeletal Muscle by β-Endorphin

Abstract: Acetylcholinesterase (AChE) was extracted in a high-saline medium from gastrocnemius muscles of rat embryos and young rats aged 14 days'gestation to 40 days post partum. The molecular forms of the enzyme were separated by low-salt precipitation, followed by velocity sedimentation. During gestation, all molecular forms increased in activity, particularly the 16 S (A₁₂) form. During the first 2 weeks of life, there was a large increase in the activity of soluble AChE (G forms), whilst the activity of insoluble AChE (A forms) was reduced. Denervation of the muscle reversed the change in the relative proportions of the molecular forms. The embryonic pattern of activities of AChE forms persisted in cultures of myotubes obtained at 20 days'gestation and maintained in the absence of spinal cord. When myotubes were maintained in medium previously conditioned by developing spinal cord explants, 16 S AChE declined while the soluble (4 and 6 S) forms increased in activity in a manner resembling that seen in early postnatal muscles in vivo . β-Endorphin (β-EP) immunoreactivity was detected in the spinal cord-conditioned medium and was identified by HPLC and ion-exchange chromatography as β-EP-(l–31) plus its shortened and N -acetylated forms. Cultivation of myotubes in the presence of synthetic camel β-EP resulted in a reversible change in the pattern of AChE forms which was similar to that seen with spinal cord-conditioned medium. These studies provide evidence for the neuroregulation of AChE A and G forms in immature skeletal muscle. A major candidate for this role is β-EP, produced and released by developing spinal cord.     

Characterization of Cholecystokinin from the Human Brain

Human forms of cholecystokinin have not previously been characterized chemically. In this study, we have extracted and purified the predominant molecular form of cholecystokinin present in human cerebral cortex. The peptide was characterized by amino acid analysis, automated peptide sequencing, and fast atom bombardment mass spectrometry. It appears to be identical to porcine cholecystokinin-octapeptide, with the sequence of Asp-Tyr(SO3)-Met-Gly-Trp-Met-Asp-Phe(NH2). This structural identity is consistent with the observations that the peptide in human brain and porcine cholecystokinin-octapeptide are recognized similarly by a battery of antisera to porcine cholecystokinin; that they coelute from several chromatographic systems, including gel filtration, ion exchange, and reversed-phase; and that they possess similar biological activities.