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Biomedical subjects

S A Jackson

Publications and source records attributed to S A Jackson.

At least 73 records · Page 4Linked to original sources
PubMed1988

Glycolysis in permeabilized L-929 cells.

Mouse L-929 cells permeabilized with dextran sulphate (DSP cells) carry out glycolysis when supplemented with glucose, ATP and NAD+ in a suitable incubation buffer. Glycolytic rates were linear and generally independent of cell density over the range examined (1 x 10(6)-10 x 10(6) cells/ml). Electron microscopy revealed characteristic changes in DSP cell ultrastructure, notably for nuclei and mitochondria. Some cells lacked plasma membranes, while others appeared intact. In the latter case, estimates of the lesion size in plasma membranes were obtained from volume of distribution studies using 14C-labelled proteins, and infiltration of fluorescein isothiocyanate dextran. The results indicated the presence of lesions large enough to allow globular proteins of about 400 kDa to cross the cell surface. In spite of that, only about 10% of total cell protein exited from DSP cells during a 30 min incubation period. We propose that none of the glycolytic enzymes in DSP cells can exist completely in solution in the 'cytosol', suggesting extensive enzyme organization. The results are interpreted within the broader picture of metabolic organization in animal cells and the nature of the 'cytosol'.

Adenosine Triphosphate↗
PubMed1986

The renal washout parameter as an indicator of transplant rejection.

The accumulation of intravascular fibrin thrombosis in both acute and chronic renal rejection leads to a delay in the transit of perfusion. This study examines the renal washout parameter as an indicator of transit time. By mathematical simulation of renal time-activity curves various factors which can influence this parameter are investigated, a simple analysis is proposed and clinical results are correlated with biopsy findings. A washout parameter greater than 28 s is found to be consistent with histologically diagnosed rejection over a range of bolus qualities.

Graft Rejection↗
PubMed1986

The effect of exogenous progestins on endogenous progesterone secretion in pregnant mares.

Twenty-four pregnant, light horse mares were used in a study to determine if an exogenous progestin or progesterone would alter serum concentrations of progesterone. On day 40 of gestation, mares were randomly assigned to one of three administration groups: 1) 250 mg of progesterone in oil every other day, 2) 22 mg of Altrenogest (Regumate, American Hoechst, Somerville, NJ 08876) orally every day, or 3) 10 ml of neobee oil (control) orally every day. The treatment period was from day 40 to 105. Pregnancy status was monitored on days 40, 60, 80, 100 and 105 and a single jugular blood sample was obtained daily from days 40 to 46, 69 to 75 and 99 to 105. Serum concentrations of progesterone were determined by radioimmunoassay. Concentrations of progesterone were similar (P>0.05) among groups at each sampling period. Overall concentrations of progesterone increased (P<0.001) from days 40 to 46. Injection of 250 mg of progesterone in oil failed (P>0.05) to maintain concentrations of progesterone in serum above baseline for 24 hr. Thus higher doses and/or more frequent injections would be needed in order to increase concentrations of progesterone above those seen in untreated controls. In summary, Altrenogest was found to be a nonstressful, convenient method of administering progestins to pregnant mares without altering their endogenous secretion of progesterone.

Journal Article↗
PubMed1986

Emergency screening for ethylene glycol in serum.

We have exploited the "interference" of ethylene glycol in the Du Pont aca triglyceride method to develop a convenient and rapid screening method for detecting ethylene glycol in serum. Pretreatment of patient's serum with lipase, glycerol kinase, and other cofactors usually added for triglyceride analysis removes triglycerides and glycerol, but not ethylene glycol, from the sample. The aca triglyceride method may then be used to estimate the ethylene glycol concentration in serum.

Emergencies↗
PubMed1986

Graphical comparisons of interferences in clinical chemistry instrumentation.

Instrument- and analyte-specific interferences can be produced by adding known concentrations of potentially interfering substances to serum from healthy volunteers. Analytical results are expressed as a percentage of the original (unaffected) result. Graphical displays of the transformed data document the conditions under which erroneous results would be probable for specimens containing the additive. If several analytical systems are available, one can make an informed choice of which to use for a particular analysis by comparing the appropriate graphical information. Comparisons of such displays of data from newer systems being considered for purchase may facilitate decisions regarding laboratory instrumentation.

Bilirubin↗
PubMed1984

Effects of carbohydrates on membrane stability at low water activities.

The relative effectiveness of a variety of carbohydrates in preserving the structural and functional integrity of membranes at low water activities was studied, using Ca-transporting microsomes from muscle as a model membrane. The order of effectiveness (greatest to lowest) was: trehalose, lactose, maltose, cellobiose, sucrose, glucose, fructose, sorbitol, raffinose, myo-inositol, glycerol. At the highest concentrations of the most effective sugars tested, microsomes were obtained upon rehydration that were similar structurally and functionally to fresh membranes. The least effective carbohydrates, alcohol sugars, all appear to be fusogenic. A structural explanation for relative effectiveness of the sugars was sought, but no clear relationship was found, except that effectiveness does not appear to be related to the number of position of hydroxyl groups available for hydrogen bonding.

Animals↗
PubMed1983

Preservation of structural and functional activity in lyophilized sarcoplasmic reticulum.

Ca-transporting microsomes isolated from abdominal muscle of lobster were lyophilized in the presence and absence of trehalose. The dry membranes appeared with freeze fracture to collapse into cup-shaped structures embedded in a matrix of trehalose when lyophilized in the presence of trehalose. Upon rehydration, the dry membranes yielded vesicles that were morphologically indistinguishable from freshly prepared ones. These rehydrated vesicles also showed ATPase activity and Ca transport only slightly different from those activities in freshly prepared vesicles. The concentration of trehalose required to achieve this degree of stabilization is about 0.3 g trehalose/g membrane. When the membranes were dried at lower trehalose concentrations extensive fusion occurred between vesicles, along with lateral phase separations of membrane proteins and lipids. The rehydrated vesicles showed poor Ca uptake and coupling between ATPase activity and Ca uptake. The membranes may also be stabilized in the dry state by lyophilizing them in sucrose, but about three times as much sucrose is required as trehalose.

Animals↗
PubMed1981

Evaluation of image processing and presentation methods in thallium-201 myocardial scintigraphy.

Using a phantom to simulate the LAO 45 degrees thallium-201 myocardial image with a transmural infarct of variable detectability, thirteen methods of computer image processing are evaluated for a group of eight observers using receiver operating characteristics (ROC curves). Initial results using electrostatic hardcopy images clearly demonstrate that images with three applications of a nine point smoothing routine and 30% background subtraction, displayed with three cycles of the grey scale, produce significantly more accurate interpretation (P less than 0.001) than the raw data, or any of the other methods used. This method provides an overall increase in the diagnostic sensitivity for the group and does not introduce a false positive bias. Grey scale cycling provides effective contrast enhancement as does a colour scale presentation. Comparing images as processed above with similarly smoothed images presented with a fifteen colour level scale on a TV monitor, the diagnostic sensitivities are not significantly different and this method provides the optimum image evaluation in this study.

Computers↗
PubMed1981

Characterization of a spectrophotometric assay for angiotensin converting enzyme.

Although serum angiotensin converting enzyme (EC 3.4.15.1) activity has generally been shown to be increased in patients with sarcoidosis, considerable variation in the diagnostic usefulness of this test has been reported. We investigated the possibility that this variation may be the result of inhibition of the widely used spectrophotometric assay by various substances. We also prospectively examined the predictive value of measurements of this enzyme in serum from 100 patients being evaluated for sarcoidosis. The following did not significantly affect the results: storage at 4 or 25 degrees C for one week, hemoglobin, lipoproteins, or corticosteroid medications. Bilirubin, at concentrations of 20 mg/L of serum or move, significantly inhibited the assay. Sera with increased activity showed nonlinear reaction rates during the usual 60-min reaction interval, This was corrected by shortening the reaction time to 30 min. We found a predictive value of 88% when the serum angiotensin converting enzyme test was applied to the diagnosis of active sarcoidosis.

Acetylcholinesterase↗
PubMed1980

A film badge dosimeter for UVA radiation.

An inexpensive film badge technique, using a commercially available plastic film, and requiring minimal processing to determine UVA exposure is described. It has been found useful in determining the body dose distribution in apparatus used for the photochemotherapy of psoriasis.

Film Dosimetry↗
PubMed1980

Automated electrooculography--a microprocessor application example.

An Intel 8080 microprocessor is used to control the running, and also analyse the results of a clinical test, the electrooculogram. The processor provides a moving stimulus using a strip of thirty-two light emitting diodes. From electrodes attached medial and lateral to the eyes, the sinusoidal signals generated by the stimulated lateral eye movements are monitored, digitised by the processor and the peak values stored for subsequent analysis. Results are plotted both numerically and graphically each minute of the test on a standard teletype. Throughout the test, systems faults are recognised and appropriate error messages produced. The test is automatically terminated and results calculated when sufficient data has been collected. The development of this system and the advantages of a microprocessor in this application are discussed.

Computers↗
PubMed1979

The fibrous structure of bone determined by x-ray diffraction.

The fibrous structure of both primary and secondary type cortical bone is determined. The three dimensional fibrous orientation is expressed quantitatively by pole figures of the (002) diffraction. Whilst both types of bone exhibit one major axis of fibrous orientation which is aligned on average with the long axis of the femur, primary type bone exhibits a planar orientation which is consistent with a fibrous spread within the laminations but not from one lamination to the next. Secondary type bone exhibits a degree of preferred orientation with rotational symmetry about the main fibre axis.

Aged↗
PubMed1979

The optimum illuminance level for clinical electro-oculography.

The variation of Arden Index with the level of illuminance used for the light adaptation phase in electro-oculographic examination is investigated. A level of 300 Lux is suggested as producing maximum response and minimum patient discomfort. Situations where greater levels of illuminance are specifically required are discussed.

Adult↗
PubMed1978

The morphology of bone mineral crystals.

Electron microscopical observations of the size and shape of bone mineral crystallites have not been in complete agreement with X-ray diffraction findings. The two prevalent viewpoints consider bone mineral crystals to be either rod, or plate like in habit. There appears to be agreement that the smallest dimension of the crystals is about 5 nm, but there is discrepancy in the reported c-axial lengths. The method of dark field imaging is used to obtain a quantitative measurement of the c-axial length distribution in rabbit, ox and human bone: mean c-axial lengths 32.6 nm, 36.2 nm and 32.4 nm, respectively, show no significant difference at the 5% level to the mean c-axial length measured by X-ray line broadening. Both bright and dark field images strongly suggest that bone mineral has a plate like form. Reasons for past discrepancies are discussed.

Animals↗
PubMed1971

Allotypically related sequences in the Fd fragment of rabbit immunoglobulin heavy chains.

The sequence has been completed of the N-terminal 94 residues of the variable section of the Fd fragment of heavy chains from rabbit immunoglobulin G (IgG) of allotype As1. Most of the sequence of the same section from IgG of allotype Aa3 is also reported. These results, in conjunction with a substantial sequence of the variable region of allotype Aa2 reported elsewhere (Fleischman, 1971), show the presence of 16 positions (including six consecutive positions) in which the residue present correlates with the allotype. No allotype-related sequence variation has been found in the constant section of the Fd fragment. This evidence supports the view that two genes code for the heavy chain and it can be used as evidence in favour of somatic mutation as the origin of the variability in the sequence of the N-terminal section. The evolutionary origin of the ;a' locus allotypes of rabbit immunoglobulins remains obscure.

Amino Acid Sequence↗