Association of hemoglobin Saint Etienne (alpha2beta295F8 His replaced by G1n) with hemoglobins A and F. Synthesis and subunit exchange in vitro

The unstable hemoglobin (Hb) Saint Etienne (alpha2beta295F8 His replaced by G1n) (betaSE) was found in the red blood cells of an 8-year-old boy. The composition of this hemoglobin was 26% Saint Etienne, 52% A, 3% A2 and 19% HbF. Studies of hemoglobin synthesis indicate: a) a balanced synthesis of alpha and non-alpha chains (alpha=betaA + betaSE + gamma), b) an increased pool of free alpha hemoglobin chains, and c) a rapid exchange of alpha chains between this pool and HbSE. The alpha chain pool resulted from the dissociation of HbSE and the greater instability of betaSE chains than alpha chains upon heating. Hemoglobin F is of the fetal type and is heterogeneously distributed among the red cells. Furthermore, two populations of red blood cells could be separated according to their i antigen content. Analysis of the hemoglobins revealed a heterogeneous distribution. Thus, F hemoglobin was preferentially associated with cells having low i antigen level, while Saint Etienne hemoglobin was increased in cells having a high i antigen level. HbF and HbSE were not present in the parents of the propositus. Study of the genetic markers confirmed the filiation. The parents were normal upon clinical and hematological examination; they exhibited a normal pattern and synthesis of hemoglobin. The Hb Saint Etienne case is compared with Hb Istanbul, which in spite of the same amino acid substitution is not associated with increased HbF level.     

Factors related to the formation of cytoplasmic crescents on milk fat globules

Cytoplasm from lactating cells is included with some milk fat globules at secretion. The objective was to search for factors causing this phenomenon. Globules bearing crescents of cytoplasm were selectively stained with the fluorescent dye, acridine orange, and their proportion in the globule population was obtained by counting from photomicrographs. Incidence of crescents on fat globules in milk samples of 50 human donors ranged from 1 to 29%, and the mean was 7.2%. Two bovine milk samples, both representing over 100 animals, contained 1% or less of globules with crescents. Globules in individual milkings of five beef cows showed the same low proportion of crescents. In addition to species, genetic and diurnal factors influenced numbers of crescents. Two sisters showed evidence within and between lactations of a persistent high proportion (greater than 25%) of globules with crescents. Samples collected in the a.m. contained a lower percentage of globules with crescents (6.5%) than those obtained in the p.m. (9.7%). Crescent incidence was not correlated with lipid or protein content of human milk, interval within a milking, days in lactation, or the donor's age. Evidence is presented to suggest that the concentration, distribution, and acylation of butyrophilin and xanthine oxidase, coat proteins of the apical plasma membrane, are important factors in globule crescent formation.     

Sequence analysis of the CCG polymorphic region adjacent to the CAG triplet repeat of the HD gene in normal and HD chromosomes

The CAG expansion responsible for Huntington's disease (HD) is followed by an adjacent polymorphic CCG repeat region which may interfere with a PCR based diagnosis. We have sequenced this region in 52 unrelated HD patients, from both normal and HD chromosomes. Fifty percent of the normal alleles were (CCG)7(CCT)2, 48% (CCG)10(CCT)2, and 2% (CCG)7(CCT)3. In contrast (CCG)7(CCT)2 was found in 85% of the HD alleles which represents significant linkage disequilibrium with the HD mutation.     

In-hospital malnutrition: indications of postoperative evolution

BACKGROUND: The question of the minimum number of Papanicolaou (Pap) smear slides that must be rescreened to draw statistically valid conclusions regarding the accuracy of screening often is raised. No method for generating answers in varying laboratory circumstances has achieved widespread application; standard statistical sample size calculations may represent such a resource. METHODS: A series of tables was constructed to display minimum required numbers of rescreens, with each table representing differing hypothetical laboratory circumstances. To use each table, assumptions must be specified in advance as to prevalence of abnormality, definition of error, baseline false-negative proportions (FNPs) of performance, and a degree of increase in FNPs that is considered a departure from baseline warranting concern, among others. RESULTS: The authors constructed four sample tables displaying minimum numbers of slides that must be rescreened in differing specified laboratory scenarios. Depending on assumed conditions and predetermined levels of satisfactory and unsatisfactory accuracy, the range of numbers is very broad (38-10,000). One example representing likely conditions indicates that 1040 slides must be reexamined; in another scenario, a sample size of 300 is sufficient. CONCLUSIONS: The minimum number of rescreened slides needed to draw statistically valid conclusions regarding Pap smear screening accuracy can be calculated using standard statistical methods. However, a number of assumptions must be detailed in advance. The authors offer this as a practical guide and a continuation of a general inquiry regarding Pap smear error rate measurement and display. The use of these tables raises at least as many questions as it answers, but still may represent a significant advance. Future efforts at further numeric characterization of aspects of Pap smear screening performance are warranted to enable rational decision making when performance is examined in the course of quality assurance, and during quality control and regulatory activities. [See editorial on pages 127-9, this issue.]     

DIRECT ELECTROCHEMICAL POWER GENERATION FROM CARBON IN FUEL CELLS WITH MOLTEN HYDROXIDE ELECTROLYTE

Historically, despite its compelling cost and performance advantages, the use of a molten metal hydroxide electrolyte has been ignored by direct carbon fuel cell (DCFC) researchers, primarily due to the potential for formation of carbonate salt in the cell. This article describes the electrochemistry of a patented medium-temperature DCFC based on a molten hydroxide electrolyte, which overcomes the historical carbonate formation.

An important technique discovered for significantly reducing carbonate formation in the DCFC is to ensure a high water content of the electrolyte. To date, four successive generations of DCFC prototypes have been built and tested to demonstrate the technology – all using graphite rods as their fuel source. These cells all used a simple design in which the cell containers served as the air cathodes and successfully demonstrated the ability to deliver more than 40 A with the current density exceeding 250 mA/cm². Conversion efficiency greater than 60% was achieved.     

Solvent-free copolymerization of rigid and flexible bis-1,3-benzoxazines: Facile tunability of polybenzoxazine network properties

We report the copolymerization of a flexible aliphatic-bridged bisphenol-based benzoxazine monomer comprising ten methylene units (BZ(10)BA) with two rigid benzoxazine monomers (commercially available Araldite 35600 and 35900) via a solvent-free cationic ring-opening polymerization process. The effects of monomer feed composition on polymerization behavior, thermomechanical transitions, and thermal degradation properties are reported. DSC of the ring-opening copolymerizations showed that the copolymerization behavior – in terms of polymerization onset temperature and total exothermic transition – depend greatly on the composition of the monomer feed. Samples containing larger concentrations of BZ(10)BA exhibited higher onset temperatures with lower polymerization enthalpies. The thermomechanical properties of the copolybenzoxazine networks, as evaluated by DMA, show a strong dependence on the monomer feed ratio, where higher Araldite content resulted in a higher T_g of the network. The most salient feature of benzoxazine copolymerization was revealed in the tailorability in thermomechanical properties, which were varied by 149 °C simply by changing the monomer feed ratio and the T_g was observed to be accurately predicted using the Fox equation.