Composite sampling

In sampling certain types of materials, such as bags of fertilizer, or subsampling large quantities of water, as might be done in investigating the density of plankton in certain environmental situations, it is customary to composite the samples. That is, several samples are drawn, mixed into a composite sample, and a sample taken from the composite is then used to determine relevant characteristics of the population. In this paper the results of Brown and Fisher [1972] are extended to more complex situations (e.g., more than one variance component present).     

Operant autonomic conditioning and rod-and-frame test performance

Forty subjects were administered the portable rod-and-frame test (RFT) before and after operant autonomic conditioning training or control experiences. Ten subjects were assigned to each of four groups: a heart rate conditioning group; a false heart rate feedback group; a galvanic skin-response conditioning group; and a control group. Half of the subjects in the three experimental groups were informed of the response-reinforcement contingencies, and half were not informed. Informed subjects in the conditioning groups exhibited significantly lower portable RFT scores after conditioning. The results suggest that awareness of and control over autonomic functioning may be an important determinant of RFT performance.     

Pulmonary regurgitation in large atrial shunts without pulmonary hypertension

Seven patients with pulmonary regurgitation (PR), normal pulmonary artery (PA) pressures and large left-to-right atrial shunts are reported. Six had secundum atrial septal defects (ASD) and one had anomalous pulmonary venous drainage. These comprised 4% of 180 patients with atrial shunts and normal PA pressures. Pulmonary regurgitation was diagnosed clinically by mid-frequency diastolic decrescendo murmurs beginning after the pulmonic component of the second heart sound, and diagnoses were confirmed by catheterization. In two patients who had serial preoperative catheterizations over 8 and 16 years, PR progressed in one and was present only on the second study in the other. All patients underwent shunt correction, at which time the pulmonic anulus and artery appeared dilated, but the pulmonic valves were normal and did not require revision. In all patients the PR murmur disappeared after shunt correction alone, and on chest X-ray both PA and overall heart size decreased. Although it is known that pulmonary regurgitation occurs with atrial septal defects and pulmonary hypertension, the present study demonstrates that it also occurs with high flow atrial shunts, in which setting it has different implications and is reversible with shunt correction alone.     

The effect of various treatments in vitro and in vivo on the binding of 125I-labeled anti-rat serum albumin Fab'' to rat tissue polyribosomes

With 125I-labeled Fab' specific for rat liver serine dehydratase it has been possible to localize polyribosomes synthesizing the enzyme under several different environmental conditions. Evidence is presented to show that, following the administration of amino acids in vivo, the relative synthetic capabilities of free and membrane-bound polyribosomes synthesizing serine dehydratase vary with time. Early during the period of induction of the enzyme by administration of amino acids or by feeding a high protein diet the majority of the newly synthesized enzyme is derived from membrane-bound polyribosomes. Later in the induction process an increasing proportion of the enzyme is synthesized by the free polyribosomes. Subcellular localization studies clearly show that serine dehydratase is synthesized by both subclasses of hepatic membrane-bound polyribosomes, the loose and tight membrane-bound polyribosomes, as well as by the free polyribosomes. It was found that the membrane-bound polyribosomes are the preferential sites of synthesis of the majority of serine dehydratase molecules in the Morris hepatomas 5123C and 7800. It is concluded that the synthesis of the enzyme, serine dehydratase, in rat liver is not discretely compartmentalized in either class of free or membrane-bound polyribosomes. Rather, the relative proportions of the serine dehydratase synthesizing polyribosomes within these two classes of polyribosomes can vary depending on the metabolic and physiologic state of the liver cell.     

Racial difference in incidence of ABO hemolytic disease

In this review of 7,464 consecutive infants born at North Carolina Memorial Hospital, hemolytic disease from ABO incompatibility was found to be two to three times as common in black infants as in white infants. The statistical significance of the difference remained high as more restrictive criteria for ABO hemolytic disease were applied. ABO disease, serious enough to cause an indirect serum bilirubin of 15 mg/100ml or higher, had an incidence in black newborns as great as the incidence of Rh hemolytic disease in whites. In contrast, the general prevalence and severity of hyperbilirubinemia was not found to be higher in black newborns than in white infants. The difference cannot be attributed to differences in the prevalence of ABO blood groups between the two races. Policies of early discharge of newborns could be affected by the finding that ABO erythroblastosis is two to three times as common in black infants as in white infants.     

A deoxyribonucleic acid-replication intermediate in the growing mosquito

The arrangement of 18-S rRNA and 28-S rRNA within their 40-S common precursor molecule (pre-rRNA) of Xenopus laevis was investigated by electron microscopic analysis of secondary structure of nascent pre-rRNA chains of oocytes, and by 5'-end analysis of 18-S rRNA and 28-S rRNA hybridized to the EcoRI fragment of rDNA cloned as plasmid pCD42. Secondary structure mapping of phenol-extracted RNA from nucleolar cores revealed complete pre-rRNA chains or molecules at various stages of processing and pre-rRNA molecules apparently lacking one end. In this latter group, which was regarded as representing nascent chains, more than 90% of the molecules had no 28-S rRNA REGION. This shows that the 28-S rRNA sequence is transcribed after the 18-S rRNA region and hence must be located nearer to the 3' end of the pre-rRNA molecule. For 5' end-group determination [3H]uridine-labelled 18-S rRNA and 28-S rRNA were hybridized, as fragments of about 200 nucleotides, to the plasmid pCD42 containing coding sequences for four-fifths of the 18-S rRNA sequence, the external transcribed spacer, the non-transcribed spacer and a tenth of the 28-S rRNA sequence. The RNA was recovered from the hybrids and analyzed for uridine 3',5'-bisphosphate (pUp) after alkaline hydrolysis. The pUp content of the hybridized 18-S rRNA fragments was 20-fold higher than in those of 28-S rRNA, THUS DEMONSTRATING THAT THE 5' END OF THE 18-S rRNA is located next to the external spacer region. From these results it is concluded that the 18-S rRNA is located close to the 5' end of the 40-S pre-rRNA molecule.     

Regulation of nitrogen catabolic enzymes in chick liver -- effects of amino acids

It is well-known that in the chick, dietary protein increases the levels of several hepatic enzymes that are involved in nitrogen metabolism and excretion. However, the biochemical mechanism of this response is essentially unknown. The experiments presented in this paper show that the chick is responding to alpha-amino nitrogen and not to any specific amino acid. Furthermore, it is shown that this system responds to endogenous sources of nitrogen as well as dietary protein and that the xanthine dehydrogenase response involves regulation of enzyme synthesis without changing the rate of degradation.