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Biomedical subjects

R A Malt

Publications and source records attributed to R A Malt.

At least 163 records · Page 9Linked to original sources
PubMed1976

Alien cancers of the duodenum.

Invasion of the duodenum by contiguous cancer or an isolated metastasis can manifest itself with the signs and symptoms of primary cancer of the duodenum. Fourteen patients were identified with this type of diagnostic confusion. All of their tumors were in the second or third portion of the duodenum. Although the median length of survival after excision of the tumor or palliative bypass operations in these patients was nine months, considerably longer survival times have also been described. Barium enema examinations and excretory urograms should be considered as diagnostic tests for any patient with a tumor of the duodenum to identify the contiguous carcinomas of the colon and kidney subject to long palliation.

Adult↗
PubMed1976

Onset of cell proliferation in the shortened gut: growth after subtotal colectomy.

Cell proliferation and remodeling of the small intestine were studied after subtotal colectomy in the rat. After an initial fall in nucleic acid contents, there was a trend to increasing amounts of RNA throughout the intestine on the fourteenth postoperative day; by the thirtieth day RNA and DNA contents were increased about 20 percent. DNA synthesis increased after 5 days. Although initially villi became shorter and crypts shallower, higher villi, deeper crypts, and an increased rate of cell migration were present after 14 days. Subtotal colectomy stimulates nucleic acid synthesis and remodeling of the small bowel within 2 weeks. Changes are more marked in ileum.

Animals↗
PubMed1975

Methylated messenger RNA in mouse kidney.

Polyadenylated messenger RNA from mouse kidney labeled in vivo exhibited a pattern of methylation distinct from that of rRNA and tRNA. After mice were given L-[methyl-3H]methionine, 4% of the polyribosomal RNA label was bound to oligo (dT)-cellulose; 20-24% of orotate- or adenine-labeled polyribosomal RNA eluted in the poly(A)+ RNA fraction under similar conditions. [3H]Methyl radioactivity was not incorporated into low molecular weight (5-5.8 S) rRNA, indicating the extent of nonmethylpurine ring labeling was negligible. [3H]Methyl-labeled poly(A)+ RNA sedimented heterogeneously in sodium dodecyl sulfate containing gradients similarly to poly(A)+ mRNA labeled with [3H]orotic acid. Based on an average molecular length of 2970 nucleotides, renal mRNA was estimated to contain 8.6 methyl moieties per molecule. Analysis of alkaline-hydrolyzed RNA sampled by DEAE-Sephadex-urea chromatography provided estimates of the relative amounts of base and ribose methylation. Although 83% of the [3H]methyl radioactivity in rRNA was in the 2'-0-methylnucleotide fraction, no methylated dinucleotides were found in mRNA. In poly(A)+ mRNA 60% of the [3H]methyl label was in the mononucleotide fraction; the remainder eluted between the trinucleotide and tetranucleotide markers and had a net negative charge between -4 and -5. The larger structure, not yet charcterized, could result from two or three consecutive 2'-0-ribose methylations and is estimated to contain 2.6 methyl residues. Alternatively, the oligonucleotide could be a 5'-terminal methylated nucleotide species containing 5'-phosphate(s) in addition to the 3'-phosphate moiety resulting from alkaline hydrolysis. Either structure could have a role in the processing or translation of mRNA in mammalian cells.

Animals↗
PubMed1975

Messenger ribonucleoprotein complexes isolated with oligo(dT)-cellulose chromatography from kidney polysomes.

As an initial step towards understanding the role of mRNP complexes in translational regulation during compensatory renal hypertrophy, characteristics of polysome-associated mRNP isolated by affinity chromatography were studied. Renal mRNP contained 15-30 percent of the counts after a 1 hr pulse with -3H-orotic acid; it sedimented mainly between 10S and 100S and had a buoyant density of 1.42-1.44 g/cm-3. RNA derived from the mRNP sedimented between 5S and 40S on sucrose density gradients, with the greatest radioactivity in the region of 15S. After labeling with -3H-adenine for 1 hr, up to 17 percent of the radioactivity present in the mRNP-associated RNA was resistant to digestion by pancreatic and T1 ribonucleases. The mRNP protein moiety contained six polypeptides with molecular weights 69,000, 75,000, 80,000, 100,000, 109,000, and 118,000 daltons, which were undetected in the material not binding to oligo(dT)-cellulose.

Animals↗
PubMed1975

Differential labeling with orotic acid and uridine in compensatroy renal hypertrophy.

Using [5-3H]orotic acid and [5-3H]uridine as precursors, we compared the efficiency of labeling and the localization of labeled RNA during compensatory hypertrophy of the mouse kidney. [5-3H]orotic acid in tubules labeled RNA 15 times more intensely that [5-3H]uridine, presumably because of greater incorporation of orotic acid into tubular cells. Of the orotic acid label, 97% was in tubular cells, mostly in the proximal tubules. Only about 80% of the uridine label was in the tubules; the ratio in proximal tubules compared with that in distal tubules was 2:1. No changes in distribution within the nephron were produced during compensatory hypertrophy. [5-3H]uridine should be used as the precursor of generalized labeling is desired, but [5-3H5orotic acid is the better precursor of RNA for many studies of compensatory hypertrophy since it is more efficient and concentrates in the segments of greatest biologic activity.

Animals↗
PubMed1975

Compensatory renal hypertrophy in the absence of androgen binding.

As a direct test for a role of androgens, compensatory renal hypertrophy was studied in normal male mice, in androgen-insensitive Tfm/Y mice, and in sibling normal female mice. Fifteen days after unilateral nephrectomy, although the kidneys of the normal male mice were larger, relative increases in renal weight were similar in all groups (33-43%). The magnitude of the increase and the contents of protein, RNA, and DNA were the same in the Tfm/Y mice and the female mice. Androgens are not essential to compensatory renal hypertrophy, but they promote larger mice with larger kidneys.

Androgens↗
PubMed1975

Rapid reversal of compensatory renal hypertrophy after withdrawal of the stimulus.

The permanence of the early phases of compensatory renal hypertrophy was tested by interrupting vascular parabiosis between an anephric rat and a normal rat after 48 hours. At the time of interruption, the weights and the ratio of ribonucleic acid (RNA) content to deoxyribonucleic acid (DNA) content of the kidneys were the same as those of the remaining kidney in a single rat subjected to unilateral nephrectomy, previously reported. Within 12 hours after parabiosis was stopped, renal mass and nucleic acid concentrations returned to normal. Compensatory hypertrophy could be produced again by unilateral nephrectomy. Regression of the early phase of compensatory hypertrophy appears to be faster than muscular atrophy produced by disuse or denervation. Compensatory hypertrophy can be activated at least twice.

Animals↗
PubMed1974

Ribonucleic acid labelling and nucleotide pools during compensatory renal hypertrophy.

During the first 48h of compensatory renal hypertrophy induced by unilateral nephrectomy, RNA content per cell increased by 20-40%. During this period, rates of RNA synthesis derived from the rates of labelling of UTP and RNA after a single injection of [5-(3)H]uridine showed no change in the rate of RNA synthesis (3.1nmol of UTP incorporated into RNA/min per mg of RNA). ATP and ADP pools were not changed. The rate of RNA synthesis was considerably in excess of the increment of total RNA appearing in the kidneys. With [5-(3)H]uridine as label, only continuous infusion for 24h could produce an increase (60%) in the specific radioactivity of renal rRNA in mice with contralateral nephrectomies. With a single injection of [methyl-(3)H]methionine used to identify methyl groups inserted into newly synthesized rRNA, the specific radioactivity of this rRNA was unchanged 5h after contralateral nephrectomy, increased by 60% at 9-48h, and returned to normal values at 120h. Most RNA synthesized in both nephrectomized and sham-nephrectomized mice has a short half-life. Since total cellular RNA content increases in compensatory hypertrophy despite unchanged rates of rRNA synthesis, the accretion of RNA might involve conservation of ribosomal precursor RNA or a change in rate of degradation of mature rRNA.

Adenine Nucleotides↗
PubMed1973

Cable from Cathay.

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Acupuncture Therapy↗