Sympathetic dystrophies. Recognizing and managing a puzzling group of syndromes.

The sympathetic dystrophies are poorly understood and underdiagnosed, especially in their milder forms. Although the two major syndromes, causalgia and reflex sympathetic dystrophy, are similar in many aspects, significant differences remain in clinical presentation, pathogenesis, and management. This discussion of these syndromes focuses on clinical presentation and diagnosis for the primary care physician.

Changes in hepatic differentiation following treatment of rat fetuses with 5-azacytidine.

Rat fetuses of 20 days gestational age were treated in utero with 5-azacytidine. Within 14 to 18 h after treatment several significant changes in the fetal livers were observed, including a dramatic maturation of hepatocyte morphology with little alteration in hematopoietic elements. Assessment of mRNA levels by hybridization to cloned cDNAs, together with other measures of gene expression, established that the change in hepatocyte morphology was associated with strong activation of expression of genes normally activated later in development, including those coding for the liver enzymes tyrosine aminotransferase and phosphoenolcarboxykinase and a gene of unknown specificity that is regulated in liver much like the aminotransferase. Rates of transcription of two of these genes, measured in isolated nuclei, were significantly increased after 5-azacytidine treatment. Expression of alpha-fetoprotein, normally declining during the perinatal period of development, was reactivated following treatment with the drug, while albumin expression was somewhat enhanced. For the most part the changes observed reflect temporal advancement of events normally programmed to occur later in differentiation of the liver. These changes appear to be the consequence of multiple effects of 5-azacytidine, including enhanced gene transcription and stabilization of gene products.

Different mechanisms control developmental activation of transcription of genes subject to identical hormonal regulation in adult liver.

Developmental changes in expression of two genes subject to identical hormonal controls in adult liver were examined in livers of fetal and newborn rats. Both mRNA concentrations and transcription of tyrosine aminotransferase were very low throughout gestation and increased sharply at birth. The mRNA of gene 33 (Lee et al., J. Biol. Chem. 260: 16433-16438, 1985) and its transcription were also low in fetal liver until a significant increase occurred just prior to birth, followed by a further increase at birth. In mutant mice carrying a deletion that prevents developmental activation of aminotransferase transcription, that of gene 33 was not affected. The data indicate that different mechanisms control developmental activation of these genes, in contrast to hormonal regulation of their expression.

Molecular cloning of cDNAs cognate to genes sensitive to hormonal control in rat liver.

Poly(A)-RNAs were prepared from livers of rats treated with hydrocortisone and cycloheximide, then enriched for large mRNAs by successive sucrose gradients and gel electrophoresis. The size-selected RNAs were used as templates for synthesis of double-stranded cDNAs that were cloned in Escherichia coli using the pBR322 plasmid vector. Recombinant plasmids characterized as carrying inserts of potential interest were further analyzed by differential hybridization to mRNAs from untreated and hydrocortisone-treated rats. Seven of the cloned cDNAs were identified as complementary to mRNAs whose content in liver is sensitive to modulation by the steroid. Further screening for hormonal responsiveness revealed that two of the cloned cDNAs hybridize to a 3.4-kilobase mRNA that is rapidly induced in liver by treatment with insulin or cAMP as well as by hydrocortisone; restriction enzyme analysis demonstrated that the cDNAs from these two clones are derived from the same mRNA. In isolated nuclei, the rate of transcription of this mRNA is increased by each of the inducing hormones. This unusually regulated mRNA codes for a protein of 53 kDa on denaturing gels, undergoes rapid intracellular degradation that is prevented by cycloheximide, and appears to be the product of a single copy gene.

Activation of tyrosine aminotransferase expression in fetal liver by 5-azacytidine.

Rat fetuses of 20 days gestational age were treated in utero with the inhibitor of DNA methylation, 5-azacytidine. The liver enzyme tyrosine aminotransferase, normally expressed at very low levels until several hours after birth, was increased by the drug in the fetal livers after a lag period of about 9 hours, reaching a level 70-fold above control levels 18 hours after treatment. The high levels attained after 5-azacytidine treatment are comparable to those of glucocorticoid-treated adult livers, and were not further increased by administration of hydrocortisone to dams carrying treated fetuses. Cytidine and two other analogs, cytosine arabinoside and 6-azacytidine, were essentially without effect.

Development of tyrosine aminotransferase in perinatal rat liver: changes in functional messenger RNA and the role of inducing hormones.

Expression of the hepatic enzyme tyrosine aminotransferase was analyzed in the perinatal period of development in the rat, when this expression undergoes significant changes associated with hepatocyte differentiation. In late prenatal liver both enzyme and functional mRNA gene products are present at levels 10- to 15-fold below those in the fully differentiated adult liver. This low level of expression in fetal liver is refractory to induction by glucocorticoids, but both gene products are increased to a limited extent by cyclic AMP. This induction by cyclic AMP (cAMP) does not confer glucocorticoid-responsiveness on expression. By 3 hr after birth both functional mRNA and enzyme levels are significantly increased, an increase which continues until a peak is reached at 12 hr that is appreciably above the adult levels. Both gene products then decline until adult levels are reached by 24 hr. The postnatal shift in aminotransferase expression is accompanied by acquisition of the capacity to respond to glucocorticoids. Treatment of newborns with an antiglucocorticoid steroid or with glucose suppresses the postnatal overshoot of expression, but neither treatment affects the increase from fetal to adult levels of expression. The results indicate that prior to birth, expression of the aminotransferase gene is partially repressed, a repression that is lifted essentially immediately upon birth. The hormones capable of inducing aminotransferase synthesis have no apparent necessary role in this process.

Restriction map of the single-stranded DNA genome of Kilham rat virus strains 171, a nondefective parvovirus.

We constructed a physical map of Kilham rat virus strains 171 DNA by analyzing the sizes and locations of restriction endonuclease-generated fragments of the replicative-form viral DNA synthesized in vitro. BglI, KpnI, BamHI, SmaI, XhoI, and XorII did not appear to have any cleavage sites, whereas 11 other enzymes cleaved the genome at one to eight sites, and AluI generated more than 12 distinct fragments. The 30 restriction sites that were mapped were distributed randomly in the viral genome. A comparison of the restriction fragments of in vivo- and in vitro-replicated replicative-form DNAs showed that these DNAs were identical except in the size or configuration of the terminal fragments.