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S Smith

Publications and source records attributed to S Smith.

At least 937 records · Page 52Linked to original sources
PubMed1982

Path dependence of adsorption behavior of mixtures containing dipalmitoyl phosphatidylcholine.

The adsorption of aqueous phospholipid dispersions containing dipalmitoyl phosphatidylcholine (DPPC) is investigated at 35-37 degrees C as a function of dispersion preparation technique. Systems studied in terms of surface pressure-time (pi-t) adsorption behavior were pure DPPC, 9:1 DPPC:dipalmitoyl phosphatidylethanolamine, 7:3 DPPC:egg phosphatidylglycerol (PG), and lipids extracted from cow lung lavage. The results show that pi-t characteristics can differ significantly depending on the technique by which the DPPC-containing mixtures are initially dispersed in 0.15 M NaCl solution. Examples of path dependence include the fact that DPPC, which will not adsorb at T = 35 degrees C when placed in powdered crystals on the subphase surface, exhibits measurable pi-t changes after subphase dispersion by sonication or by mechanical vortexing. For 7:3 DPPC:PG, dispersion by sonication on ice or by mechanical vortexing gives faster adsorption than dispersion by sonication without temperature control. The effect of heating to T = 45 degrees C, which is greater than the gel to liquid crystal transition temperature of DPPC (Tc = 41 degrees C), is found to be particularly detrimental to the adsorption of 7:3 DPPC:PG. Of the phospholipid mixtures studied, extracted cow lung lipids exhibited by far the greatest adsorption capability and also showed less path dependence than 7:3 DPPC:PG. Similarly, in terms of dispersion techniques investigated, sonication on ice tended to give the most rapid adsorption for a given phospholipid mixture.

Adsorption↗
PubMed1982

Localization of thioesterase II, the chain-length regulatory enzyme of milk fatty acid synthesis, in rat mammary gland epithelial cells.

Two approaches were used to establish the intercellular distribution of fatty acid synthetase and thioesterase II in the lactating rat mammary gland. Thioesterase II is the chain-length regulatory enzyme in the biosynthesis of the medium-chain fatty acids characteristic of milk fat. Using immunohistochemical techniques, immunoreactive fatty acid synthetase was found in both mammary adipocytes and epithelial cells; in contrast, immunoreactive epithelial cells were isolated from lactating rat mammary glands after digestion with collagenase and thermolysin, and their lipogenic activity was studied using isotopically labelled acetate. Consistent with the immunohistochemical data, adipocytes synthesized exclusively long-chain fatty acids whereas epithelial cells synthesized predominantly chain fatty acids. The results indicate that the capacity for synthesis of medium-chain fatty acids is a unique property of the epithelial cell component of the mammary gland.

Animals↗
PubMed1982

Bifid blind-ending ureter.

Six patients with bifid blind-ending ureter diagnosed at excretory urography are presented. In four of six patients the blind ureter was an incidental discovery. All had a characteristic appearance on urography consisting of an elongated contrast-filled tubular structure which usually terminated in a bulbous proximal tip. Demonstration of the rounded tip at excretory urography is important as it indicates the entire blind ureter has been opacified, obviating the need for retrograde pyelography.

Adult↗
PubMed1982

The development of monosomy 19 mouse embryos.

In general, autosomal monosomy is lethal much earlier in mammalian development than autosomal trisomy. In an attempt to understand why monosomy is so deleterious, we have begun to characterize the development of mouse embryos monosomic for chromosome 19. A dramatic loss of monosomy 19 embryos was found to occur between days 3 and 4 of development. This loss occurred both in vivo and in vitro and with intact blastocysts or isolated inner cell masses. Experiments with inbred strains showed that this loss was not due to the expression of recessive lethal genes. While monosomic embryos were found to have fewer cells than normal and trisomic litter-mates beginning at the early morula stage, the ability to form blastocysts is not interfered with. Electron microscopy revealed no difference in the cellular ultrastructure of monosomic when compared with diploid embryos. Furthermore, two-dimensional gel electrophoresis did not reveal any differences in the proteins synthesized by monosomic, trisomic or diploid litter-mates when examined at day 3 of development. These results indicate a lack of gross genomic disturbances in monosomic embryos. When monosomy in equilibrium diploid chimaeras were made, viable monosomic cells were found in day-9 post-implantation embryos, well past the lethal period. Thus, in chimaeric embryos, the normal cells appear to be able to provide whatever is lacking, suggesting that monosomy 19 is not a cell lethal. Instead, death may be due to a dosage alteration in specific gene products needed during early development.

Aneuploidy↗
PubMed1981

Purification and properties of fatty acid synthetase from a human breast cell line.

A human mammary epithelial cell line (SKBr3) has been identified in which fatty acid synthetase constitutes up to 28%, by weight of the cytosolic proteins. The enzymes has been purified to near homogeneity from this cell line and some of its properties studied. In common with fatty acid synthetases from other animal tissues, the enzyme is a 480 000 dalton dimer of similar molecular weight subunits, it synthesizes predominantly palmitic acid and is inactive in the absence of free coenzyme A. The kinetic properties and amino acid composition of the enzyme are also similar to those of fatty acid synthetases from various tissues of other animals. Appreciable structural resemblance between human and rodent fatty acid synthetases is indicated by studies on the immunological cross-reactivities of these enzymes.

Amino Acids↗
PubMed1981

Development of the capacity of mouse mammary glands for medium chain fatty acid synthesis during pregnancy and lactation.

The time-course for appearance of fatty acid synthetase and thioesterase II, enzymes required for the synthesis of medium chain (C8--C12) fatty acids by the mammary gland, has been studied in the mouse and compared with that in the rat. The development of high levels of fatty acid synthetase in the mouse mammary gland during the early days of lactation coincided with an observed increase in the overall lipogenic capacity of the gland, assessed by measuring the incorporation of radioactive acetate into fat in tissue slices. Both the level of thioesterase II in the gland and the proportion of medium chain fatty acids synthesized from acetate by tissue slices began to increase in late gestation but did not reach a maximum until lactation was well established. In this regard the mouse is distinctly different from the rat, which establishes maximum levels of thioesterase II in the mammary gland prior to parturition. The significance of this difference as it relates to mammary gland development is discussed.

Acetates↗
PubMed1981

DNA sequence of the rat growth hormone gene: location of the 5' terminus of the growth hormone mRNA and identification of an internal transposon-like element.

The present communication describes the molecular cloning and DNA sequence determination of the rat growth hormone (rGH) gene. The rGH gene was cloned on an 11 kilobase EcoRI fragment of total rat DNA; it has four intervening sequences which correspond in position to those of the human growth hormone (hGH) gene. One of the intervening sequences in the rGH gene contains a possible transposable element: a 200 base pair direct repeat that is itself flanked by an exact 15 base pair direct repeat. The DNA sequence was used to estimate the location of the 5' end of the mature growth hormone mRNA. By S1 nuclease mapping it was located approximately 25 bases "downstream" from a TATAAA sequence presumed to play a role in initiation of transcription of the rGH gene.

Animals↗
PubMed1981

Amino acid analysis of elastin hydrolysates using a lithium citrate gradient: quantification of elastin from whole lung.

A method to quantitate the elastin content in lungs is described. Desmosine and isodesmosine, the cross-linking amino acids unique to elastin, were measured directly from acid hydrolysates of hamster and human lungs by amino acid analysis. A Durrum D-500 (Dionex) amino acid analyzer, with a modified lithium citrate buffer gradient was used. Results compared favorably with those obtained by gravimetric and microenzymatic techniques, and the method described could be used for the quantification of elastin in biopsy specimens

Amino Acids↗
PubMed1981

Small-bowel mucosa in asymptomatic children with celiac disease. Mucosal changes with gluten-free diets.

Even though children with celiac disease may appear to be progressing satisfactorily while taking gluten-free diets, dietary lapses and persisting mucosal abnormalities are common. Of 32 children with celiac disease proven by biopsy only ten kept regularly to their diet, and 11 continued to ingest gluten regularly. Despite satisfactory clinical progress, intestinal biopsy specimens obtained after at least one year of a gluten-free diet were markedly abnormal in eight and were normal in only 14 children. Laboratory criteria also failed to detect those with persisting mucosal abnormalities. The only way to ensure that the small-bowel mucosa returns to normal and remains so is by intestinal biopsy.

Adolescent↗
PubMed1981

Neonatal perirenal urinary extravasation with posterior urethral valves.

Renal dysplasia and atrophy are associated with congenital urinary tract obstruction, such as posterior urethral valves, and are thought to result from the increased pressure in the developing obstructed urinary system. This increased pressure is likely to be alleviated by perirenal urinary extravasation and urinary ascites. Whether this relief of pressure in the obstructed developing kidney results in a lessened degree of renal abnormality is likely to depend on the time during the period of gestation when the urinary leak occurs and the degree of renal dysplasia and atrophy at the time of the urinary leak.

Ascites↗
PubMed1981

Prenatal diagnosis of fetal urinary tract abnormalities by ultrasound.

The prenatal detection of renal enlargement and sonolucent "cystic" lesions in 4 fetal abdomens by ultrasound is described. These were later proved to be congenital urinary tract anomalies. Only one of the other 4,628 mothers who had ultrasound gave birth to a child with a congenital urinary tract anomaly that was missed, and 1 fetus was falsely diagnosed as having a congenital urinary tract anomaly based on the ultrasound. Obstruction in the developing urinary tract is associated with renal dysplasia and insufficiency. More experience and improved ultrasonography may enable an accurate diagnosis of urinary tract obstruction; and early relief of the obstruction may be a possible method of management to minimize the renal damage.

Abnormalities, Multiple↗
PubMed1981

Mortality of nickel workers: experience of men working with metallic nickel.

The mortality of men employed in a plant manufacturing nickel alloys from metallic nickel and other metals has been examined. The plant has operated since May 1953, and 1925 men were identified who had been employed in the operating areas at the plant, other than as members of the staff, for a total of five or more years, excluding breaks. Analysis of samples of air obtained from personal samplers showed that since 1975 most of the men are likely to have been exposed to average concentrations of nickel of between 0.5 and 0.9 mg Ni/m3. All but 22 (1.1%) of the men were successfully traced to 1 April 1978 or until they died or emigrated. One hundred and seventeen had died. The numbers of deaths observed from cancers of respiratory and other sites, other respiratory disease, ischaemic heart disease, and other causes of death were compared with the numbers expected from national and local mortality rates. No evidence of the existence of any occupational hazard was obtained. The number of deaths from lung cancer (15) in men employed for five years or more is small. At 98% of the number expected at local rates it is statistically compatible with risks of between 0.5 and 2.2 times "normal."

England↗