BACKGROUND: Previous studies have found considerable interobserver variability in the roentgenographic diagnosis of pneumonia. In this study we determined the impact of experience on interobserver variability in the interpretation of chest roentgenograms of patients with pneumonia and defined the characteristics of chest roentgenograms interpreted as pneumonia by all groups. METHODS: The chest roentgenograms of 15 consecutive patients with a clinical and roentgenographic diagnosis of pneumonia were read by a convenience sample of 10 first-year and 20 fourth-year medical students, 21 medical residents, and 21 staff physicians from the department of medicine. Three board-certified radiologists served as the gold standard. The majority rule decision and logistic regression analysis were used to analyze agreement among the various groups of observers. RESULTS: Agreement with the majority decisions of the gold-standard radiologists on the presence or absence of pneumonia for all observations of the various groups were as follows: original radiologist, 87%; first-year medical students, 59%; fourth-year medical students, 54%; medical residents, 66%; and attending staff, 72%. Chest roentgenograms with dense lobar or segmental opacities were generally interpreted as pneumonia by all observers. Patchy opacities caused major disagreements and were usually read as not being due to pneumonia. Bronchopneumonia was not diagnosed by any of the observers. Air bronchograms, atelectasis, and chronic obstructive lung disease were usually not recognized by the nonradiologists. CONCLUSIONS: There is considerable interobserver variability in the roentgenographic diagnosis of pneumonia. This variability does not improve with increasing experience. Dense lobar or segmental opacities are uniformly recognized as pneumonia while patchy opacities result in a variety of interpretations.

Aged↗

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Sulfhemoglobinated erythrocytes as an optical intravascular tracer in the lung.

Sulfhemoglobinated erythrocytes (SHb-RBC's) were examined for utility as an optical multiple indicator dilution tracer in lung studies. A device was developed to measure this tracer optically in flowing blood. Arterial blood was sampled from cannulated, anesthetized dogs and pumped through the device that measured the optical density (OD) of blood at 620 nm. This system was calibrated for increasing SHb-RBC concentrations using an unsteady-state indicator dilution procedure. Areas under optical density (delta OD) profiles were well correlated with injected SHb-RBC volumes using linear regression (r2 > 0.9). This linearity was independent of blood oxygenation, hematocrit, or pH. In vivo lung indicator dilution studies in the intact dog were performed and compared to radioisotope indicator studies using 51Cr labeled erythrocytes. Coefficient of variation (CV) between the two curves was 0.065 under baseline conditions, 0.085 for studies performed during hypoxia, and 0.073 after pH was lowered. We conclude that this device linearly measured SHb-RBC content in whole blood and that SHb-RBC is as accurate a lung indicator dilution tracer as 51Cr-erythrocytes.

Animals↗

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Classics revisited: researches on pre-natal life by Sir Joseph Barcroft.

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Embryology↗

PubMedDate not supplied

Conference report: IVth meeting of European Placenta Group (EPG): joint with the Rochester Trophoblast Conference (RTC), 22-26 September 1991.

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Animals↗

PubMedDate not supplied

Evidence that recombination between reiterated sequences in the Bacillus subtilis chromosome does not occur via unequal crossing over.

An experimental system was designed to permit the detection of recombination events occurring via unequal crossing over between sister bacterial chromosomes in Bacillus subtilis. It exploits the fact that during spore development, genetic and metabolic cooperation occurs between two different cell types, only one of which survives. During the early stages of sporulation, the two chromosomes of the developing sporangiole lie in the same cell and recombination between them is possible, in principle. Internal duplications flanking a selectable antibiotic-resistance gene have been introduced into the spoIIIC, spoIVA and spoVJ genes, whose correct expression in the mother cell (non-surviving compartment) is necessary for completion of spore development. After incubation in a sporulation-inducing medium in the absence of selective pressure, these strains sporulate at a low frequency and up to 30% of the progeny are Spo-. They result from mosaic sporangioles, in which only the chromosome segregated into the mother cell compartment of the developing sporangiole contains a reconstituted spo gene. In mosaic sporangioles generated by unequal crossing over between sister bacterial chromosomes, the insertionally inactivated spo gene, segregated into the pre-spore compartment, would carry an extra copy of the duplication initially present. Analysis of the products of 124 independent recombination events giving rise to mosaic sporangioles provided no evidence for the occurrence of unequal crossing over.

Bacillus subtilis↗

PubMedDate not supplied

The uptake of naturally occurring amino acids by the plasma membrane of the human placenta.

The characteristics of the uptake of four naturally occurring amino acids, alanine, leucine, lysine and aspartate, by microvesicles prepared from the plasma membrane on the maternal surface of the human placenta were studied. Electron microscopy showed that a variety of fragments was interspersed between the vesicles and this heterogeneity probably accounted for the considerable variation in the results. Nevertheless, the properties of the uptake of amino acids were similar to those of vesicle preparations from other tissues. Insulin did not enhance the uptake of any of the amino acids.

Alkaline Phosphatase↗

PubMedDate not supplied

Protein synthetic rate in the sheep placenta in vivo: the influence of insulin.

The metabolic gradient between the placenta and maternal tissues is large when expressed as fractional protein synthesis rate; the half-life of the mixed placental proteins is one-fifth of these in the maternal liver, but a little longer than those of the fetal liver and heart. This high turnover rate provides the priority of the uptake of the feto-placental unit for nutrients, to satisfy the genetic growth potential, enabling equivalent weights of the conceptus to take up amino acids in greater quantities than the maternal liver, the adult organ with the highest protein synthetic rate. The results suggest that fractional synthesis rate of the placental proteins was increased when fetal plasma insulin concentrations were raised. Should this enhancement of protein synthetic rate occur in the human subject, it might be responsible for the heavy placentae found in diabetic subjects whose blood sugar is uncontrolled, and account for their apparently large functional capacity.

Animals↗

PubMedDate not supplied

Transplacental arteriovenous gradients for glucose, insulin, glucagon and placental lactogen during normoglycaemia in human pregnancy at term.

The potential contributions of placental extraction and degradation to glucoregulatory hormone turnover in late pregnancy were assessed by measuring arteriovenous differences for glucose, insulin, glucagon and human placental lactogen (hPL) across the uterine and fetal circulation in ten pregnant women at the time of elective caesarean section. The observations were made during stable conditions of euglycaemia; values for maternal arterial glucose, insulin, glucagon and hPL were 78.8 +/- 5.0 mg/dl, 10.1 +/- 2.1 microU/ml, 72.0 +/- 8.5 pg/ml and 5.18 +/- 0.59 micrograms/ml, respectively. The glucose decrements observed consistently across the uterus and fetus indicated uptake by the placenta and fetus, and in the maternal circulation the arterial-uterine vein increment for hPL was 2.10 +/- 0.44 micrograms/ml. However, within the limits of analytical accuracy, no significant gradient could be demonstrated for insulin across the uterine (maternal) or umbilical (fetal) circulations. A small (8.5 per cent) but significant arteriovenous difference for glucagon was observed across the uterus but none was found on the fetal side of the placenta. The findings indicate that detectable gradients for insulin cannot be demonstrated under basal conditions of metabolism and at normal rates of placental blood flow. The results do not exclude the possibility of more significant extraction ratios under other physiological conditions or at higher concentrations of glucoregulatory hormones.

Adult↗

PubMedDate not supplied

A direct method for investigating the transfer of endogenous nitrogen from maternal body protein to fetal protein.

Maternal body protein was labelled with [15N]glycine during the last third of pregnancy in the rat; the label was found in fetal protein, demonstrating that amino acids derived from maternal protein had crossed the placental membrane. The enrichment of fetal carcass protein was greater than that of maternal skeletal muscle, expressed as atoms per cent excess but similar to that of her liver. Enrichment of both fetal body and maternal liver declined during the period studied, while that of maternal skeletal muscle remained constant. The capture of label by fetal protein increased gradually at a rate which was the same as its rate of decline in the maternal liver, suggesting that the latter was a major source of the fetal label. The average [15N] content of the maternal liver was 2.3 per cent of that injected, while the total conceptus content was more than twice this value, 5.6 per cent, indicating that more than half was contributed from other maternal sources as well as her liver. The results were not influenced by maternal food restriction of two-thirds.

Animals↗