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Biomedical subjects

S L Smith

Publications and source records attributed to S L Smith.

At least 235 records · Page 13Linked to original sources
PubMed1979

Ecdysone 20-monooxygenase: characterization of an insect cytochrome p-450 dependent steroid hydroxylase.

Ecdysone 20-monooxygenase, the enzyme system that hydroxylates ecdysone at C-20 of the side-chain to form ecdysterone, has been characterized in the fat body of early last instar larvae of the tobacco hornworm, Manduca sexta, using a radioenzymological assay. Ecdysterone was demonstrated to be the product of the enzyme system by high-pressure liquid chromatography, gas-liquid chromatography and mass spectrometry. Differential centrifugation, sucrose-gradient centrifugation, electron microscopy and organelle-marker enzyme analysis revealed that ecdysone 20-monooxygenase activity is associated with the mitochondria. The enzymatic properties of ecdysone 20-monooxygenase are that it is most active in a 0.05 M phosphate buffer, is inhibited by Mg2+ and exhibits pH and temperature optima at 7.5 and 30 degrees C, respectively. The enzyme complex has an apparent Km for ecdysone of 1.60 x 10(-7) M and is competitively inhibited by its product, ecdysterone, with an apparent Ki of 2.72 x 10(-5) M. The cytochrome P-450 nature of this insect steroid hydroxylase was initially suggested by its obligate requirement for NADPH and its inhibition by carbon monoxide, p-chloromercuribenzoate, metyrapone and p-aminoglutethimide but not by cyanide. Difference spectroscopy revealed the presence of cytochrome P-450 in the fat-body mitochondrial fraction. A photochemical action spectrum of ecdysone 20-monooxygenase activity confirmed the involvement of cytochrome P-450 in this monooxygenase system.

Animals↗
PubMed1978

Kinetic determination of the genome size of the pea.

Renaturation of pea (Pisum sativum) DNA has been used to estimate the size of the pea genome and the fraction of pea DNA containing repeated DNA sequences. Pea DNA renaturation and single copy tracer renaturation indicate that the size of the pea genome is 0.5 picograms. More than 70% of pea DNA sequences are repeated from 100 to 5,000 times.

Journal Article↗
PubMed1978

Gas-chromatographic determination of polyol profiles in cerebrospinal fluid.

We describe a simple method for collectively determining polyols in the cerebrospinal fluid. The method consists of protein removal, sample derivatization, and gas chromatography of the trimethylsilylated polyols, with use of glass capillary columns. Nine major polyol constituents, the structures of which were verified by combined gas chromatography/mass spectrometry, can be simultaneously assayed. The presence of three polyols in the cerebrospinal fluid is reported here for the first time.

Chromatography, Gas↗
PubMed1977

Vocalizations of the black-tailed prairie dog, Cynomys ludovicianus.

Seven variable vocal displays of Cynomys ludovicianus were studied in a captive colony, and checked through limited field work and literature reports. The form of each display makes available information identifying its user. In addition, since each display correlates probabilistically with a consistent set of activities, it makes available information about the behaviour in which the communicator is, or may become, engaged. At least five different kinds of behaviour can be specified through the use of these displays.

Animals↗
PubMed1977

Carbon-13 nuclear magnetic resonance investigations into the interactions of bisulfite with pyrimidine nucleosides and nucleotides.

Carbon-13 NMR is utilized to demonstrate the attack of bisulfite anion on uridine, 5-fluorouridine, and uridine 5'-monophosphate. The attack produces a pair of diastereomeric adducts similar in structure to those seen in the uracil series. Intensity data from the equilibrium system give an estimate for the individual equilibrium constants. Thymidine and thymidine 5'-monophosphate show no evidence of nucleophilic attack by bisulfite. This evidence indicates that bisulfite addition to nucleosides and nucleotides models the enzymatic methylation of uridine by the enzyme thymidylate synthetase better than the uracil bisulfite system.

Chemical Phenomena↗
PubMed1975

Mechanical cleansing of contaminated wounds with a surfactant.

Mechanical cleansing of a wound with a sponge soaked in a surfactant has prevented the development of experimental wound infection. The surfactant utilized for wound cleansing is Pluronic F-68, a member of a family of block copolymers called Pluronic polyols. Long-term toxicity studies and clinical trials suggest that this surfactant is safe for human use. Pluronic F-68 is a nonionic detergent that does not have any intrinsic antibacterial activity. Although mechanical cleansing with saline-soaked sponges effectively removes bacteria, it damages the wound and impairs its resistance to infection. The severity of the damage to the skin exerted by the sponge can be correlated with its porosity. Sponges with a low porosity are abrasive and exert more damage to skin than do sponges with a higher porosity. The addition of Pluronic F-68 to even the most abrasive sponges ensures that the bacterial removal efficiency of the sponge scrub is maintained, while tissue trauma is minimized. This dual effect of the surfactant results in a dramatic reduction in the infection rate of contaminated wounds. On the basis of these results, a clinical trial with surfactant-soaked sponges would appear to be indicated.

Animals↗
PubMed1975

Variations in ovarian steroid levels during the luteal phase of the menstrual cycle.

1. Six subjects were investigated during the luteal phase of the menstrual cycle to determine whether the ovarian steroids, estrogen and progesterone were released in an episodic manner. 2. Analysis of plasma obtained every 20 min. during a normal working day provided no evidence for pulsatile release of either steroid although values were lower in the afternoon than in the morning (p less than 0.001). A good correlation (r=0.908) was obtained for the release of both hormones. 3. Cortisol secretion was inversely related to that of the ovarian steroids.

Circadian Rhythm↗
PubMed1975

T-tube tract dilatation for removal of large biliary stones.

A technique used for removal of residual biliary tract stones, too large to be withdrawn through a T-tube tract, is reported. Telescoping Teflon catheters were used in one patient to dilate the tract sufficiently to remove the stone with the Dormia type wire basket.

Adult↗