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D L Miller

Publications and source records attributed to D L Miller.

At least 451 records · Page 25Linked to original sources
PubMed1981

Kinetics of calcium transport in the hamster duodenum and ileum.

Dietary calcium is absorbed chiefly from the small intestine, and characteristics of the transport process differ depending on site. Because transport behavior is crucial to calcium homeostasis, we characterized kinetics of duodenal and ileal calcium transport in vivo in the hamster. We measured net calcium transport with 40Ca and flux into the animal (influx) with 45Ca over the concentration range of 0- 25 mM. Nonmediated transport was twice as great in duodenum as in ileum. Mediated transport showed Michaelis-Menten kinetics. Kt for mediated transport (4.3 mM) was the same in duodenum and ileum, whereas Vmax (mumol/h per g) was twice as great in ileum (290) as in duodenum (137). Thus, Kt defines similar carrier function at both sites, but Vmax suggests calcium transport capacity is doubled in ileum. The lower nonmediated transport in ileum limits secretion and the higher Vmax absorbs calcium at a greater rate, permitting the ileum to move luminal calcium against a concentration gradient more effectively than the duodenum. Thus, ileal calcium transport, by its site and functional characteristics, makes a crucial contribution to calcium homeostasis in the hamster.

Animals↗
PubMed1980

alpha-Fetoprotein gene expression. Partial DNA sequence and COOH-terminal homology to albumin.

The DNA sequence corresponding to the 3'-terminal 540 bases of rat alpha-fetoprotein mRNA is reported. A protein synthesis termination codon lies 131 bases from the 3'-poly(A) segment. The 3'-noncoding region contains a purine-rich segment as well as the characteristic AAUAAA sequence. Analysis of the DNA-derived amino acid sequence shows extensive homology to mammalian albumins. Forty per cent of the residues are identical with no extensive additions or deletions and all of the cysteinyl residues that maintain the tertiary structure of albumin are conserved in the COOH-terminal domain of alpha-fetoprotein.

Amino Acid Sequence↗
PubMed1980

Nucleotide sequence of the mitochondrial genes coding for tRNAglyGGR and tRNAvalGUR.

Yeast mitochondrial DNA-pBR322 recombinant DNA molecules known to contain tRNA genes from a tRNA rich region of the yeast genome were used as a source of DNA for restriction mapping and tRNA gene sequence analysis. We report here restriction maps of two segments of yeast mitochondrial DNA and the sequence of mitochondrial genes coding for tRNAglyGGR and tRNAvalGUR. Both genes are flanked by A + T rich DNA and neither has an intervening sequence nor codes for a 3' CCA end. The tRNA structures deduced from the genes have the usual cloverleaf structures and invariant nucleotides. This combination of DNA sequencing and restriction mapping has enabled us to determine that the tRNAvalGUR and a previously sequenced tRNA, the tRNApheUUY are transcribed from the same strand of DNA.

Base Sequence↗
PubMed1980

Primary structure of elongation factor Tu from Escherichia coli.

The amino acid sequence of elongation factor Tu (EF-Tu) from Escherichia coli has been determined. EF-Tu is a single-chain polypeptide composed of 393 amino acids (Mr 43,225 for the species bearing COOH-terminal serine). The NH2-terminal serine is acetylated, and lysine-56 is partially methylated. The sites of facile tryptic cleavage are at arginines 44 and 58 and at lysine-263. The cysteinyl residues associated with aminoacyl-tRNA and guanosine nucleotide binding activities are residues 81 and 137, respectively. The COOH-terminal amino acid is heterogenous in that analyses of the COOH-terminal peptides isolated from different EF-Tu preparations gave position 393 as glycine and serine in ratios (Gly/Ser) ranging from about 0.7 to 3.

Amino Acid Sequence↗
PubMed1980

Estrogen-induced zonal changes in rat liver sinusoids.

Estrogen-containing oral contraceptives have been associated with changes in hepatic sinusoids in women. This association has not been studied systematically. To define, quantitate, and locate the estrogen-induced changes within the zones of the hepatic acinus. a morphometric analysis of sinusoids was performed in rat liver. Female rats received oral ethynyl estradiol, dissolved in corn oil, in doses of 0.125 mg/100 g body wt per day for either 2 or 6 wk. Control groups received corn oil in volumes equal to the ethynyl estradiol group or were untreated. After 2 or 6 wk, livers were fixed by perfusion with glutaraldehyde, and 5-microns sections were prepared and analyzed in an automatic image analyzer (Quantimet 720). The ratio of the volume fraction of the sinusoids in zone 1 to that in zone 3 was 2.04 +/- 0.15 (SE) after 2 wk of ethynyl estradiol administration, as compared with 0.87 +/- 0.5 (SE) in rats given corn oil and 0.76 +/- 0.3 (SE) in untreated controls. The differences between the two control groups and the ethynyl estradiol group were significant (P < 0.005). This greater zone 1/zone 3 ratio after ethynyl estradiol was due both to an increased volume fraction of sinusoids in zone 1 as well as to a decreased volume fraction of sinusoids in acinar zone 3, as compared with controls (P < 0.005). The surface to volume ratio of sinusoids, one of the parameters determining the probability of solute-sinusoidal wall interaction, was smaller in zone 1 (P < 0.005) and larger in zone 3 (P < 0.005) in animals treated with ethynyl estradiol than in controls. After 6 wk of ethynyl estradiol administration, the changes in volume fraction persisted. These results indicated that ethynyl estradiol, a synthetic estrogen contained in many oral contraceptives, induced selective zonal changes in rat liver sinusoids. These alterations resulted in the persistent dilatation of sinusoids of acinar zone 1, the acinar inlet, and in the sustained constriction of sinusoids of zone 3, the acinar outlet.

Animals↗
PubMed1979

Sequence analysis of two yeast mitochondrial DNA fragments containing the genes for tRNA Ser UCR and tRNA Phe UUY.

Two restriction enzyme fragments containing yeast mitochondrial tRNA genes have been characterized by DNA sequence analysis. One of these fragments is 320 base pairs long and contains a tRNA Ser gene. The corresponding tRNA SER was isolated from yeast mitochondria and its nucleotide sequence also was determined. This mitochondrial tRNA is 90 nucleotides in length, has a G + C content of 38%, and has UGA as the anticodon. A portion of a 680-base-pair DNA fragment containing a tRNA Phe gene was also sequenced. The portion of this gene which codes for the mature tRNA is 75 base pairs in length, has a G + C content of 33%, and contains the anticodon GAA. Neither gene contains an intervening sequence or codes for the 3' CCA terminus. Both are surrounded by regions of more than 90% A + T. The significance of these sequences is discussed.

Base Sequence↗
PubMed1979

alpha-Fetoprotein gene expression. Control of alpha-fetoprotein mRNA levels in cultured rat hepatoma cells.

The expression of alpha-fetoprotein (AFP) was infestigated in a cloned cell culture derived from Morris hepatoma 7777, which shows a density-dependent variation in the AFP synthesis rate. The rate of secretion of AFP was found to be governed by the level of cytoplasmic mRNAAFP. Saturation hybridization of pulse-labeled RNA to excess cloned cDNAAFP was used to illustrate quantitatively how mRNAAFP is regulated in these tumor cells. It was found that the mRNAAFP level is primarily determined by its rate of transcription and mRNAAFP declines to 40% of its maximum level, and it accumulates at 20% of its maximum rate. The half-life of mRNAAFP was found to be 40 h, 5 to 6 times that of poly(A)-containing RNA. This difference in stability, in cells doubling every 20 h, results in a 2 1/2-fold increase in the fraction of mRNAAFP above that expected from the relative transcription rate of mRNAAFP. During maximal synthesis of AFP, mRNAAFP accumulates in the cytoplasm at a rate 25 times greater than an average middle abundance mRNA and 1000 times greater than the average low abundance mRNA. These results and the relatively high translational efficiency of mRNAAFP explain how cells can optimize production of an abundant protein.

Animals↗
PubMed1979

Platelet aggregation induced by ultrasound under specialized conditions in vitro.

Human platelets were induced by 2.1-megahertz ultrasound to form aggregates around gas-filled pores in membranes immersed in platelet-rich plasma. The spatial peak intensities required were only about 16 to 32 milliwatts per square centimeter. Ultrasound generated by a medical Doppler device, whose intensity exceeded this, induced aggregate formation under the same conditions.

Blood Platelets↗
PubMed1979

Determining skin thickness with pulsed ultra sound.

A high frequency, high resolution ultrasonic echo technique is presented for determining the thickness of human skin. An experimental series is described in which the accuracy of this new technique is demonstrated by comparison with a radiological method of proven accuracy. The "ultrasonic biometric ruler" is shown to provide an accurate, simple, noninvasive method for measuring full-thickness human skin. In addition to the determination of skin thickness, it is demonstrated that the underlying subcutaneous fat and muscle can also be noninvasively "explored" with the possibility of identifying a variety of skin and underlying tissue lesions.

Adipose Tissue↗