Search PubMed⌕ Search

Biomedical subjects

S Daniels

Publications and source records attributed to S Daniels.

At least 91 records · Page 5Linked to original sources
PubMed1984

Tissue-specific and pretranslational character of variants of the rosy locus control element in Drosophila melanogaster.

Prior reports from this laboratory have described the experimental basis for our understanding of the genetic organization of the rosy locus (ry:3-52.0) of Drosophila melanogaster, as a bipartite genetic entity consisting of a structural element that codes for the xanthine dehydrogenase (XDH) peptide and a contiguous, cis-acting control element. The present report describes our progress in the analysis of the control element and its variants. Characterization of the control element variants reveals that, with respect to late third instar larval tissue distribution of XDH activity and cross-reacting material, i409H is associated with a large, tissue-specific increase in fat body which is not observed in malpighian tubules. Further data are presented in support of the inference that this differential expression must reflect differential production of XDH-specific RNA transcripts.--Gel blot analyses are described which demonstrate that the phenotypic effects associated with variation in the rosy locus control element relate to differences in accumulation of XDH-specific poly-A+ RNA and do not relate to differences in rosy DNA template numbers.--Experiments are described that provide for unambiguous mapping of control element sites through the use of half-tetrad recombination experiments and the recovery and phenotypic characterization of the reciprocal products of exchange between control element site variants. Thus, we are able to order the sites as follows: kar-i1005 i409-ry.

Animals↗
PubMed1980

The detection of gas bubbles in guinea-pigs after decompression from air saturation dives using ultrasonic imaging.

1. Bubble formation in the hind limb of anaesthetized guinea-pigs, after decompression from two different saturation exposures to air, 0.69 and 0.83 MPa gauge, has been studied using an ultrasonic pulse--echo imaging technique. 2. A qualitative analysis of the bubble formation, observed over a 30 min period after decompression, showed that profuse, largely stationary bubble formation occurred within 3 min of the decompression from 0.83 MPa gauge but that extensive stationary bubble formation was not observed until 17 min after decompression from 0.69 MPa gauge. Electrocardiogram changes appeared coincidently with the appearance of major bubble formation after the 0.83 MPa decompression but after the 0.69 MPa decompression changes were not observed until the end of the 30 min surveillance period, considerably later than the occurrence of a large number of bubbles. 3. A quantitative analysis of the echo patterns recorded during the 60 sec decompression and for 60 sec after the decompression demonstrated that the increase in severity of the decompression corresponded to an increase of 152% in the number of bubbles observed. The echoes observed during this period have been identified as either transient or persistent and their distribution of size, location and times of appearance and duration have been described. 4. From the quantitative analysis approximate estimates of the contribution by mobile, intravascular gas bubbles to the elimination of the excess gas have been made. These estimates range from 0.01 to 0.9% after the 0.69 MPa decompression and from 0.06 to 6% after the 0.83 MPa decompression. 5. It is concluded that the pulse--echo ultrasonic imaging technique provides a powerful means of analysing the distributions of bubble formation, both qualitatively and quantitatively, after decompression; it has the important attribute of being able to monitor both moving and stationary bubbles simultaneously in a variety of tissue types.

Animals↗
PubMed1979

The effects of some hydrophobic gases on the pulmonary surfactant system.

1. Decompression from exposures to raised ambient pressure of sulphur hexafluoride, carbon tetrafluoride, hexafluoro-ethane and nitrous oxide results in the formation of dense foam and pulmonary oedema. 2. The degree of pulmonary oedema produced is dependent on the exposure pressure, although the exposure time required is short in comparison to tissue saturation times. 3. The effect is not prevented by atropine, ephedrine or hydrocortisone. 4. The effect is also produced in vitro by saturated solutions of halothane, chloroform and ether. 5. It is suggested that the mechanism of action is physical with physico-chemical factor involved being a differential partition of these gases within the surfactant: membrane complex.

Animals↗
PubMed1979

Portion sizes, preparation and cooking yields, and plate waste in school meals.

Available portion sizes for a wide range of menu items were measured in seven junior schools and three senior schools in one local authority area. Serving waste was also measured and used as a criterion of acceptability. Portion sizes for entrees, desserts and potatoes were generally acceptable except for a few unpopular items. Custard was the most acceptable milky sauce. A small range of vegetables was acceptable in small quantities, but excess was rejected while others were almost totally rejected. Peeling, trimming and cooking yields for vegatables, trimming and cooking yields for meat, and plate waste were measured over one year in 180 schools in eight local authority areas. Results for vegetables compared favourably with previously published data except for new potatoes where the yield after machine peeling was lower. Cooking yields for pork, beef and lamb were slightly lower than previously published values. Trimming waste from meat for stewing was substantially greater than the 5 per cent visible fat which is the catering specification for ordering. The mean plate waste was 33 g per child meal (excluding bones).

Adolescent↗
PubMed1979

Ultrasonic imaging system for the study of decompression-induced gas bubbles.

An high-resolution pulse echo ultrasonic imaging system has been developed to study decompression-induced gas bubbles. It was considered necessary that the system be capable of detecting gas bubbles with a diameter of 10 micrometer and up and be able to monitor the growth of these bubbles. In addition the system needed to be capable of distinguishing separate gas bubbles from within an area containing a number of bubbles and allowing their position to be accurately located. The current system is capable of detecting bubbles as small as 10 micrometer and of resolving bubbles separated by 0.8 mm in azimuth and 0.4 mm in range, and these values correspond to the maximum accuracy of location. Finally, it has been shown that the technique is extremely unlikely to induce any bubble formation by means of cavitation or thermal mechanisms. It is concluded that the system represents a powerful method for studying the factors controlling bubble formation.

Decompression↗
PubMed1978

Potency of mixtures of general anaesthetic agents.

The anaesthetic potencies of binary mixtures of the gases argon (Ar), nitrous oxide (N2O) and sulphur hexafluoride (SF6) have been measured using mice. The mixtures SF6-N2O and N2O-Ar showed additive behaviour, whereas the constituents of the mixture SF6-Ar were non-additive, having a smaller total potency than expected. Further experiments on this mixture with Italian Great Newts and on the carbon tetrafluoride mixtures CF4-Ar and CF4-SF6 with mice suggested that the anomalous potencies may arise from specific pulmonary effects associated with the breathing of SF6 accompanied by a high pressure of some other gas.

Anesthesia, Inhalation↗
PubMed1975

Pole cells of Drosophila paulistorum: embryologic differentiation with symbionts.

The pole cells of young D. paulistorum embryos are destined to form the germinal cells of both male and female imagoes. In addition, specialized portions of the midgut may be derived from pole cell progenitors. In this initial study of their embryogenesis by means of electron microscopy, various stages of pole cell development are shown in both non-hybrid (potentially fertile) and intersemispecific hybrid (potentially sterile as males) materials. Originally, approximately 5 or 6 cells emerge to form the early polar cap and subsequently divide asynchronously until the 35-50 cells of the late polar cap are derived. Unlike other Drosophila species, however, mycoplasma-like symbionts, apparently an hereditary infection, have been traced to locations within the cytoplasm of these pole cells. They are depicted as arriving there after transmission via the egg cytoplasm, implicating this as their probable route of entry into the future germinal tissues of adult flies. It is postulated that these microorganisms function as an infectious reproductive isolating mechanism fostering hybrid male sterility between D. paulistorum semispecies.

Animals↗
PubMedDate not supplied

Reference range and repeatability of a combined intestinal permeability and function test in clinically healthy Irish setter dogs.

A reference range was determined for a combined test of differential sugar permeability, using lactulose (L) and rhamnose (R), and intestinal function, using D-xylulose (X) and 3-O-methylglucose (G), in clinically healthy adult Irish setter dogs. Urinary L/R ratios in 48 Irish setters from one to 12 years old varied from 0.03 to 0.18, with a mean (SEM) of 0.10 (0.01); X/G ratios varied from 0.46 to 0.81, with a mean (SEM) of 0.59 (0.01). There were no significant differences between L/R or X/G ratios of dogs of different sex (P > 0.2) or age (P > 0.5), using analysis of covariance. Lactulose/rhamnose ratios of > or = 0.18 and X/G ratios > or = 0.43 were considered normal, defined by the respective mean +/- 2SD. Repeatability was established by performing three permeability and function tests at monthly intervals in twelve of the dogs. Analysis of repeated L/R and X/G ratios by means of linear models procedure revealed no significant differences between measurements made on successive occasions (P > 0.15), confirming the repeatability of this test.

Aging↗