Sea urchin actin gene subtypes. Gene number, linkage and evolution.

The actin gene family of the sea urchin Strongylocentrotus purpuratus was analyzed by the genome blot method, using subcloned probes specific to the 3' terminal non-translated actin gene sequence, intervening sequence and coding region probes. We define an actin gene subtype as that gene or set of genes displaying homology with a given 3' terminal sequence probe, when hybridized at 55 degrees C, 0.75 M-Na+. By determining the often polymorphic restriction fragment band pattern displayed in genome blots by each probe, all, or almost all of the actin genes in this species could be classified. Our evidence shows that the S. purpuratus genome probably contains seven to eight actin genes, and these can be assigned to four subtypes. Studies of the expression of the genes (Shott et al., 1983) show that the actin genes of three of these subtypes code for cytoskeletal actins (Cy), while the fourth gives rise to a muscle-specific actin (M). We denote the array of S. purpuratus actin genes indicated by our data as follows. There is a single CyI actin gene, two or possibly three CyII genes (CyIIa, CyIIb, and possibly CyIIc), three CyIII actin genes (CyIIIa, CyIIIb, CyIIIc), and a single M actin gene. Comparative studies were carried out on the actin gene families of five other sea urchin species. At least the CyIIa and CyIIb genes are also linked in the Strongylocentrotus franciscanus genome, and this species also has a CyI gene, an M actin gene and at least two CyIII actin genes. It is not clear whether it also possesses a CyIIc actin gene, or a CyIIIc actin gene. The genome of a more closely related congener, Strongylocentrotus dröbachiensis, includes 3' terminal sequences suggesting the presence of a CyIIc gene. In S. franciscanus and S. dröbachiensis the first intron of the CyI gene has remained homologous with intron sequences of both the CyIIa and CyIIb genes, indicating a common origin of these three linked cytoskeletal actin genes. Of the four S. purpuratus 3' terminal subtype probe sequences only the CyI 3' terminal sequence has been conserved sufficiently during evolution to permit detection outside of the genus Strongylocentrotus. An unexpected observation was that a sequence found only in the 3' untranslated region of the CyII actin gene in the DNA of S. dröbachiensis and S. purpuratus is represented as a large family of interspersed repeat sequences in the genome of S. franciscanus.

Nonhyperoxic retrolental fibroplasia.

Retrolental fibroplasia (RLF) has most often been observed in preterm infants exposed to high ambient oxygen concentrations. This case report describes an infant near term who was never exposed to supplemental oxygen but in whom stage 4 RLF developed. The etiologic role of exchange transfusion is discussed.

Management of patent ductus arteriosus in the premature infant: indomethacin versus ligation.

A previous report from our institution analyzed the results of pharmacological (indomethacin) closure of patent ductus arteriosus (PDA) in 82 neonates. Closure was achieved in 54 patients. However, gastrointestinal complications occurred in 21, necrotizing enterocolitis in 13, and focal perforation in 8. Overall mortality in the indomethacin group was 40%. This paper compares the results of that pharmacological experience with our subsequent surgical experience with 86 low-birth-weight neonates for whom gestational age, size, illness, and mode of diagnosis were comparable. Mean weight at operation for this study was 1.1 kg; mean gestational age was 29.1 weeks. All infants required endotracheal-assisted ventilation for severe radiographic and clinical hyaline membrane disease. Range-gated Doppler study, retrograde flush aortography, and echocardiographic measurement of the ratio between the left atrium and the aortic root were used to confirm the diagnosis of PDA. Ligation was done in the neonatal intensive care unit using local anesthesia supplemented with morphine. Ventilation was controlled by an inhalation therapist; drug and blood administration were controlled by the infant's nurse. Surgical ligation was employed in all infants except for 7 in whom hemoclip ductal closure was chosen because of extreme instability, coagulopathy, or ductal perforation. There were no operative deaths. Surgical morbidity included ductal perforation (2 patients), wound infection (1), and phrenic nerve injury (1). Necrotizing enterocolitis occurred in 9 patients. The overall mortality was 17%. Patients with preoperative pneumo-thorax had a 32% overall mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Regionalization: a time for new solutions.

We are at a time when solutions must be found to the problems of facilities, personnel, transportation, and re-imbursement which face us in the delivery of neonatal health care. No one system can be perfect for each situation or area. Each city, country, state, or region must implement systems which will bring us to our goal. Simply stated, that goal is the provision of appropriate care for high-risk newborns as close to their place of birth as is medically and financially feasible.

4p- phenotype in an infant with t(4p-;19p or q+)mat translocation.

Four family members had an apparently balanced t(4p-;19p or q+) translocation indentified by Giemsa banding. One of these individuals, a male infant, has a 4p- phenotype with seizures, large bilateral cleft palate, abnormal anterior fontanel, abnormally shaped ears, hypertelorism, small penis with third-degree hypospadias, and bilateral simian creases. It is theorized that 4p material containing loci essential for normal development was lost in this infant by a simple deletion or "aneusomy by recombination."

Acute transplacental ethanol intoxication.

With the use of ethanol in hyperalimentation regimens and for the inhibition of premature labor, there is increased opportunity for exposure of the fetus to this potentially toxic substance. We reviewed the literature regarding the effects of ethanol on the fetus and neonate, and illustrate its potential toxicity by the report of a case of neonatal depression secondary to acute maternal ethanol ingestion.

Prophylaxis against hypocalcemia in low-birth-weight infants requiring bicarbonate infusion.

Forty-eight low-birth-weight infants with varying degrees of respiratory distress were studied with respect to serum calcium concentration and urinary calcium excretion. Serum calcium decreased over the 24-hour study period in infants who did not receive calcium infusion. The decrease was greater in those receiving bicarbonate therapy for acidosis. Continuous calcium infusion at 1 mg/kg/hr sustained relatively normal serum calcium concentration, even in those infants who required bicarbonate. Since the changes in estimated extracellular calcium could not be accounted for by urinary excretion, a shift of calcium into bone was postulated.

Differential expression of the actin gene family of Strongylocentrotus purpuratus.

Molecular probes that individually recognize the 3' nontranslated regions of six actin genes were utilized in RNA gel blot hybridizations to detect RNAs complementary to each gene in embryonic and adult tissues of Strongylocentrotus purpuratus. In addition the probes were used in DNA excess filter hybridizations to estimate the relative contribution of the different actin genes. All six genes produce relatively stable mRNAs, and each displays a characteristic and distinct pattern of expression. On the basis of their expression in the egg, early embryos, or in adult coelomocytes, it is concluded that genes termed CyI, CyIIa, CyIIb, CyIIIa, and CyIIIb encode cytoskeletal actin proteins. Actin gene M gives rise to mRNAs that are found only in tissues containing muscle. Actin genes CyI, CyIIa, CyIIb, and M are expressed in both adult and embryonic tissues, giving rise to transcripts 2.1-2.2 kb in length. Expression of genes CyIIIa and CyIIIb is confined to the embryo. Gene CyIIIa provides the major embryonic actin mRNA, which is 1.8 kb in length. Three of the cytoskeletal actin genes are linked over a 30-kb distance in the S. purpuratus genome. We show that the actin genes included in this linkage group are not coordinately expressed.