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Biomedical subjects

M Fried

Publications and source records attributed to M Fried.

At least 325 records · Page 18Linked to original sources
PubMed1986

Gene activation properties of a mouse DNA sequence isolated by expression selection.

The MES-1 element was previously isolated from restricted total mouse cellular DNA by "expression selection"--the ability to reactivate expression of a test gene devoid of its 5' enhancer sequences. Mes-1 has been tested in long-term transformation and short-term CAT expression assays. In both assays MES-1 is active independent of orientation and at a distance when placed 5' to the test gene. The element is active with heterologous promoters and functions efficiently in both rat and mouse cells. MES-1 activates expression by increasing transcription from the test gene's own start (cap) site. Thus the expression selection technique can be used for the isolation of DNA sequences with enhancer-like properties from total cellular DNA.

Acetyltransferases↗
PubMed1986

Large inverted duplications are associated with gene amplification.

Amplified DNA can be found in arrays of large repeated units, with each repeat unit containing a marker gene and surrounding DNA sequences. Amplified DNA sequences from established cell lines were assessed for the presence of repeat units in the form of inverted duplications. Inverted duplicated DNA was detected by virtue of its concentration-independent resistance to S1 hydrolysis after denaturation and rapid renaturation. Using this assay, inverted duplications were detected in amplified DNA (both DM and HSR configurations) containing the myc gene (16-50 copies/cell) in four human tumor cell lines and in amplified DNA containing the CAD gene (30-200 copies/cell) in three PALA-resistant BHK cell lines. The widespread association of inverted duplications with amplified DNA must bear on the amplification mechanism.

Animals↗
PubMed1986

A frameshift at a mutational hotspot in the polyoma virus early region generates two new proteins that define T-antigen functional domains.

A frameshift mutation, arising from the deletion of any one of nine consecutive cytidines in the region of Py DNA encoding both the midregion of large T-Ag and the C-terminal region of middle T-Ag, yields unstable flat cell revertants that synthesize two novel viral proteins in which shuffling of the different domains of the Py T-Ags has occurred. The first protein (37 kd) is a hybrid containing the N-terminus of large T-Ag and the hydrophobic C-terminus of middle T-Ag. The latter domain is responsible for membrane association, even in the 37 kd hybrid protein. The second protein (43 kd), which contains the N-terminal 75% of middle T-Ag, has an associated protein kinase activity and forms a complex with c-src, but cannot induce a transformed phenotype.

Animals↗
PubMed1986

Polymeric dyes: limitations in their use as reference markers in postcibal studies.

Polyporphyre and polycyanine are polymeric dyes which were recently described as useful markers for intestinal perfusion studies. The dyes were examined in this study in regard to their suitability for postcibal studies. In comparison with polyethylene glycol (PEG) 4000, a widely used nonabsorbable marker, both dyes were quantitatively adsorbed to cooked liver particles. This in vitro finding was confirmed in dogs with midgut fistulas. After a meat meal, we observed complete uptake of polycyanine to food particles. Polycyanine furthermore showed color instability below pH 3. These results indicate that the dyes are inferior to PEG 4000 when solid food is present in the intestinal lumen.

Absorption↗
PubMed1986

Gastric processing and emptying of fat.

This study was undertaken to determine whether fat leaves the stomach within or bound to the surface of particles of solid food. We studied gastric emptying of fat in 6 human subjects and in 6 dogs with Roux-en-Y duodenojejunostomies so that chyme leaving the stomach could be collected free of bile and pancreatic enzymes. Humans were studied with a duodenal multilumen tube so that phase-specific, nonabsorbed markers in the meal could be tracked with corresponding, phase-specific markers perfused into the duodenum. In this way, we observed the separate time-courses of gastric emptying of the aqueous and solid phases, as well as the extracellular fat (ECF) and intracellular fat (ICF) phases of the meal. In the dogs, all chyme leaving the stomach was collected from a Roux-en-Y fistula and was analyzed directly for aqueous, solid, ECF, and ICF markers in the meal. In both the humans and the dogs, the aqueous phase emptied promptly, whereas the solid, ECF, and ICF phases emptied together, in parallel, after an initial lag. In humans, 22% of the ECF versus 51% of the ICF (p less than 0.02) emptied on or in the solid food particles. In dogs, 81% of the ECF emptied as an oil, 13% emptied on the solid particles, and only 6% emptied as a stable, aqueous emulsion. Sixty-six percent of the ICF emptied in the solid food particles, 20% as a stable, aqueous emulsion, and 14% as an oil. We conclude that most of the ICF empties within the solid food phase, whereas most of the ECF empties as an oil phase.

Animals↗
PubMed1986

The MES-1 murine enhancer element is closely associated with the heterogeneous 5' ends of two divergent transcription units.

The location in the mouse genome of the 149-base pair MES-1 element, previously isolated by its ability to restore expression to an enhancerless selectable gene, was analyzed. The active moiety of the single-copy MES-1 element is located between the 5' ends of two divergent transcription units, SURF-1 and SURF-2, both of which specify more than one mRNA species by differential splicing. The heterogeneous 5' ends of the SURF transcripts are separated by only 50 to 75 base pairs, and this sequence possesses a high G + C content (65%) and contains neither the TATA and CAAT box motifs normally associated with many highly expressed genes nor the GC box motif (Sp1-binding site) associated with a number of housekeeping genes. Although MES-1 appears to have enhancerlike properties when linked to heterologous genes, its normal genomic location suggests that it functions as a bidirectional promoter. Thus, MES-1 may represent a new class of enhancer-promoter element.

Amino Acid Sequence↗
PubMed1986

Inverted duplication-transposition event in mammalian cells at an illegitimate recombination join.

Illegitimate recombination events in mammalian cells often contain extraneous nucleotides or filler DNA at the recombinant joins. The polyomavirus-transformed cell line 7axB has previously been found to contain 37 base pairs (bp) of filler DNA at one virus-host join of the single insert of integrated viral DNA (A. Hayday, H. E. Ruley, and M. Fried, J. Virol. 44:67-77, 1982). By using a synthetic oligomer of these 37 bp as a probe, we demonstrated that this filler DNA is an inverted duplication of a single-copy rat sequence found 650 bp upstream from this virus-host join. The other virus-host join appears to be the result of a simple illegitimate recombination event between viral and host sequences. This is the first identification of filler DNA as a transposed copy of a chromosomal sequence. The relevance of the recombination events studied to cellular rearrangements and viral integration is discussed.

Animals↗
PubMed1986

Human pharmacological effects of SMS 201-995 on gastric secretion.

The inhibition of pentagastrin-stimulated-(3 micrograms kg-1 h-1) gastric acid secretion by various doses of intravenous and subcutaneous SMS 201-995, a somatostatin analogue, was investigated in healthy volunteers by means of gastric aspiration, using phenol red as a volume marker. The intravenous doses were compared with the standard dose of somatostatin-14, 3.5 micrograms kg-1 h-1. Similarly, SMS 201-995-induced inhibition of gastric acid secretion was compared with that of exocrine pancreatic secretion assessed by gastroduodenal aspiration. The results can be summarized as follows: SMS 201-995 is a potent inhibitor of gastric acid secretion, exerting near maximal inhibition at a dose of greater than or equal to 0.56 micrograms kg-1 h-1. Near maximal inhibition equals that achieved with SST-14 (3.5 micrograms kg-1 h-1). Pancreatic enzyme secretion appears to be strongly inhibited by lower doses of SMS 201-995 than gastric secretion. Single subcutaneous injections of SMS 201-995 produce an inhibition of gastric acid secretion lasting for many hours. Near maximal inhibition was obtained with a dose of 100 micrograms.

Adult↗
PubMed1985

Isolation of a gene enhancer within an amplified inverted duplication after "expression selection".

We have attempted to isolate and identify cellular expression sequences from F9 teratocarcinoma DNA by utilizing their ability to reactivate a selectable gene devoid of its own expression sequences (expression selection). Restriction nuclease-digested F9 cellular DNA was ligated to a polyoma virus (Py) DNA fragment which contains an intact transforming region but is incapable of inducing transformation because it lacks the viral 5' enhancer sequence. The ligation mixture was used to transfect Rat-1 cells and a transformed cell line, 3B, was isolated. The 3B cell line contained a single type of Py DNA insert, which was molecularly cloned as an 18-kilobase BglII fragment. A weak cellular enhancer was identified in a 4.7-kilobase BamHI fragment upstream from the Py sequences. Both the Py DNA and the enhancer sequences were found to be present in an inverted duplication in the 3B clone. The presence of this structure in 3B genomic DNA was confirmed by the analysis of selectively isolated inverted duplicated sequences, and the structure was found to be at least 22 kilobases long. In the 3B cell line, the inverted duplicated sequences containing the Py and enhancer sequences are quite stable and are amplified 20- to 40-fold. The strongly transformed phenotype of the 3B cells may be a result of this amplification. The formation of inverted duplications as a part of the amplification mechanism as well as a general strategy for the cloning of inverted duplicated (amplified) sequences is discussed.

Animals↗
PubMed1985

Pancreatic enzyme response to a liquid meal and to hormonal stimulation. Correlation with plasma secretin and cholecystokinin levels.

Pancreatic trypsin output and plasma secretin and cholecystokinin (CCK) levels were measured in five healthy volunteers to investigate the mechanisms involved in regulating postprandial pancreatic secretion. The pancreas was stimulated by a liquid test meal or by either intravenous secretin (1-82 pmol/kg-1 per h-1) or caerulein, a CCK analogue (2.3-37 pmol/kg-1 per h-1), or by a combination of secretin and caerulein. Pancreatic secretion was assessed by a marker perfusion technique (polyethylene glycol [PEG 4000]), plasma secretin, and CCK by specific radioimmunoassays. Increasing doses of secretin produced increasing bicarbonate output (P less than 0.01), whereas trypsin was not stimulated over basal. Graded caerulein produced a stepwise increase in trypsin and bicarbonate output (P less than 0.01). Potentiation occurred for bicarbonate secretion between secretin and caerulein, but not for trypsin output. Postprandial trypsin secretion averaged 29.1 IU/min-1 over 150 min (equal to 55% of maximal response to caerulein). The peak trypsin response amounted to 90% of maximal caerulein. Significant increases of plasma secretion (P less than 0.05) and CCK (P less than 0.01) were observed after the meal. Comparison of enzyme and CCK responses to the testmeal or to exogenous caerulein suggested that the amount of CCK released after the meal could account for the postprandial trypsin secretion. We conclude that (a) the postprandial enzyme response in man is submaximal in comparison to maximal exogenous hormone stimulation; (b) CCK is a major stimulatory mechanism of postprandial trypsin secretion, whereas secretin is not involved; and (c) Potentiation of enzyme secretion is not a regulatory mechanism of the postprandial secretory response.

Adult↗
PubMed1984

Effect of proglumide, a cholecystokinin receptor antagonist, on caerulein-stimulated pancreatic enzyme secretion and pancreatic polypeptide release in the dog.

In five conscious dogs we studied the effect of proglumide, a cholecystokinin (CCK) antagonist, on caerulein-stimulated pancreatic secretion and release of pancreatic polypeptide (PP). Graded doses of caerulein (15-240 ng/kg per h) were infused intravenously. Experiments were repeated with a fixed infusion of proglumide (40 mg/kg per h). Release of PP following increasing doses of caerulein was significantly inhibited by proglumide (P less than 0.01). However, proglumide did not significantly affect caerulein-stimulated pancreatic protein secretion. Proglumide might be useful in defining the physiological role of CCK.

Animals↗
PubMed1984

Demonstration of Isospora belli by acid-fast stain in a patient with acquired immune deficiency syndrome.

Isospora belli, like Cryptosporidium sp., a sporozoan parasite of the small intestine, has been isolated from both immunodeficient and immunologically normal persons. In immunocompetent persons the infection may be asymptomatic; it frequently causes mild and self-limited diarrhea. The spectrum of the disease in persons with acquired immune deficiency syndrome is not well established. I. belli did not stain well with the methods usually used for intestinal protozoa and was difficult to see unstained. However, it stained well with the acid-fast technique used for Cryptosporidium sp. and was easily identified by such stains. A case of combined infection with Cryptosporidium sp. and I. belli is reported.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Plasma secretin and pancreatic response to various stimulants including a meal.

In dogs with gastric and duodenal Thomas cannulas, we investigated the threshold dose range of exogenous secretin and intraduodenal HCl for pancreatic bicarbonate secretion and, with a recently developed radioimmunoassay, measured the increase in plasma secretin concentrations. Synthetic secretin (2.5, 7.5, and 22.5 ng X kg-1 X h-1) was dissolved in saline or 0.1% dog albumin and given with or without a background infusion of 30 ng X kg-1 X h-1 of caerulein. The minimal dose of secretin that elicited a significant pancreatic bicarbonate response as well as an increase in plasma secretin concentration was 7.5 ng X kg-1 X h-1 when administered with albumin and 22.5 ng X kg-1 X h-1 without albumin. The threshold dose for duodenal HCl was 2 mmol X h-1. The threshold secretin dose for bicarbonate secretion and for an increase in plasma secretin levels was unchanged with a background caerulein infusion. Furthermore, postprandial secretin concentrations were measured. After a meat meal plasma secretin release appeared to occur in spikes up to 10 pmol X l-1 corresponding to secretin levels seen during infusion of 7.5 ng X kg-1 X h-1 of secretin and intraduodenal acid perfusion at a dose of 2 mmol X h-1.

Animals↗