Estimation of body water compartments in cirrhosis by multiple-frequency bioelectrical-impedance analysis.

Estimation of total body water by measuring bioelectrical impedance at a fixed frequency of 50 kHz is useful in assessing body composition in healthy populations. However, in cirrhosis, the distribution of total body water between the extracellular and intracellular compartments is of greater clinical importance. We report an evaluation of a new multiple-frequency bioelectrical-impedance analysis technique (MFBIA) that may quantify the distribution of total body water in cirrhosis. In 21 cirrhotic patients and 21 healthy control subjects, impedance to the flow of current was measured at frequencies ranging from 4 to 1012 kHz. These measurements were used to estimate body water compartments and then compared with total body water and extracellular water determined by isotope methodology. In cirrhotic patients, extracellular water and total body water (as determined by isotope methods) were well predicted by MFBIA (r = 0.73 and 0.89, respectively). However, the 95% confidence intervals of the limits of agreement between MFBIA and the isotope methods were +/-14% and +/-9% for cirrhotics (extracellular water and total body water, respectively) and +/-9% and +/-9% for cirrhotics without ascites. The 95% confidence intervals estimated from the control group were +/-10% and +/-5% for extracellular water and total body water, respectively. Thus, despite strong correlations between MFBIA and isotope measurements, the relatively large limits of agreement with accepted techniques suggest that the MFBIA technique requires further refinement before it can be routinely used to determine the nutritional assessment of individual cirrhotic patients.

Unequal synthesis and differential degradation of alpha and beta spectrin during murine erythroid differentiation.

Murine erythroleukemia (MEL) cells represent a valuable system to study the biogenesis of the cytoskeleton during erythroid differentiation. When attached to fibronectin-coated dishes MEL cells induce, upon addition of DMSO, a 7-d differentiation process during which they enucleate and reach the reticulocyte stage (Patel, V. P., and H. F. Lodish. 1987. J. Cell Biol. 105:3105-3118); they accumulate band 3, spectrin, and ankyrin in amounts equivalent to those found in mature red blood cells. To follow the biosynthesis of spectrin during differentiation, membranes and cytoskeletal proteins of cells metabolically labeled with [35S]methionine were solubilized by SDS and alpha and beta spectrins were recovered by specific immunoadsorption. In both uninduced and 3-d induced cells, the relative synthesis of alpha/beta spectrin is approximately 1:3. In uninduced MEL cells newly synthesized alpha and beta spectrins are degraded with a similar half-life of approximately 10 h. In contrast, in 3-d differentiated MEL cells newly made beta spectrin is much more unstable than alpha spectrin; the half-lives of alpha and beta spectrin chains are approximately 22 and 8 h, respectively. Thus, accumulation of equal amounts of alpha and beta spectrin is caused by unequal synthesis and unequal degradation. As judged by Northern blot analyses, the level of actin mRNA is relatively constant throughout the 7-d differentiation period. alpha and beta spectrin mRNAs are barely detectable in uninduced cells, increase during the first 4 d of induction, and remain constant thereafter. In contrast, band 3 mRNA is first detectable on day 4 of differentiation. Thus, most of the spectrin that accumulates in enucleating reticulocytes is synthesized during the last few days of erythropoiesis, concomitant with the onset of band 3 synthesis. To determine whether this was occurring in normal mouse erythropoiesis, we analyzed the rate of appearance of labeled membrane proteins in mature erythrocytes after a single injection of [35S]methionine. Our results show that most of the spectrin and band 3 in mature erythrocytes is synthesized during the last days of bone marrow erythropoiesis, and that, in the marrow, band 3 and protein 4.1 are synthesized at a somewhat later stage of development than are alpha and beta spectrin, ankyrin, and actin.

Characterization of bovine keratin genes: similarities of exon patterns in genes coding for different keratins.

Four different genomic clones which contain the genes coding for epidermal keratins Ia (mol. wt. approximately 68 000), Ib (68 000), III (60 000) and VIb (54 500) have been selected using cDNA probes and identified by hybrid-selection translation. The genes vary considerably in length, primarily due to differences in intron sizes: keratin Ia, 9.3 kb (approximately 2.55 kb total exons); keratin Ib, 6.0 kb (2.25 kb exons); keratin III, 6.0 kb (2.2 kb exons); keratin VIb, 4.4 kb (1.85 kb exons). The genes for all three representatives of the basic (type II) cytokeratin subfamily, i.e., keratins Ia, Ib and III, contain eight introns of variable sizes (0.1-1.8 kb) and their exon patterns are very similar. The gene coding for keratin VIb, a representative of the acidic (type I) subfamily, contains seven introns, and the size pattern of its five innermost exons closely resembles that of the genes of the type II keratins. Most of the introns are located in regions coding for the alpha-helical cores of these proteins. Mapping of the intron positions by the S1 nuclease technique and sequencing of some exon-intron boundaries has revealed that some of the introns of all four keratin genes have similar positions to each other and to those of the hamster vimentin gene.(ABSTRACT TRUNCATED AT 250 WORDS)