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Biomedical subjects

J L Wood

Publications and source records attributed to J L Wood.

13 recordsLinked to original sources
PubMed1979

Transfer of persulfide sulfur from thiocystine to rhodanese.

THiocystine (bis-[2-amino-2-carboxyethyl]trisulfide) is a natural substrate for rhodanese (thiosulfate:cyanide sulfurtransferase, EC 2.8.1.1). Analogs of thiocystine were prepared by eliminating the carboxyl or amino group or by lengthening the carbon chain. Of these only homothiocystine (bis-[2-amino-2-carboxypropyl]trisulfide) had appreciable activity as a substrate. At pH 8.6, the optimum for rhodanese, transfer of sulfane sulfur to cyanide in the presence of rhodanese was nonspecific. Only the sulfane sulfur of 35S-labeled thiocystine was transferred to rhodanese. Thus, thiocystine and thiosulfate both produce a rhodanese persulfide as a stable intermediate in sulfur transfer.

Chemical Phenomena↗
PubMed1979

Photooxidation products of 7,12-dimethylbenz[a]anthracene.

The principal products of the photooxidation of 7,12-dimethylbenz[a]-anthracene (DMBA) in aqueous solutions by photooxidation induced by laboratory lighting have been characterized by high performance liquid chromatograms (HPLC), ultraviolet and mass spectrograms and by comparisons with authentic samples. The products identified were the 7,12-epidioxy-7,12-dihydro-7-12-dimethyl-, 7,12-dione, 7-hydroxymethyl-12-methyl-, 12-hydroxymethyl-7-methyl-, 7-formyl-12-methyl-, 12-formyl-7-methyl-, and 12-hydroxy-12-methyl-7-one derivatives of benz[a]-anthracene. The HPLC profile of products is similar to that obtained from oxidation of DMBA by 'one-electron' reagents, singlet oxygen, or liver microsomal metabolism. The first points of attack are the 7- and 12- positions. The mechanism of photooxidation appears to be generation of singlet oxygen by photodynamic effect of DMBA. None of the products is photosensitizing, however.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1978

Refinements in the short-circuit technique and its application to active potassium transport across the cecropia midgut.

1. The conventional, two-electrode method for measuring potential difference across an epithelium is subject to error due to potential gradients caused by current flow in the bathing medium. Mathematical analysis shows that the error in measuring short-circuit current is proportional to the resistivity of the bathing medium and to the separation of the two recording electrodes. It is particularly serious for the insect larval midgut, where the resistivity of the medium is high, and that of the tissue is low. 2. A system has been devised, which uses a third recording electrode to monitor directly the potential gradient in the bathing medium. By suitable electrical connexions, the gradient can be automatically compensated, leaving a residual error which depends on the thickness of the tissue, but not on the electrode separation. Because the thicknesses of most epithelia are smaller than the smallest practical electrode spacing, this error is smaller than that inherent in a two-electrode system. 3. Since voltage-gradients are automatically compensated, it is possible to obtain continuous readings of potential and current. A 'voltage-clamp' circuit is described, which allows the time-course of the short-circuit current to be studied. 4.The three-electrode system has been used to study the larval midgut of Hyalophora cecropia. The average results from five experiments were: initial potential difference (open-circuit): 98+/-11 mV (S.E.M.); short-circuit current at time 60 min: 498+/-160 microA cm=2; 'steady-state' resistance at 60 min: 150+/-26 omega cm2. The current is equivalent to a net potassium transport of 18.6 mu-equiv cm-2 h-1. 5. The electrical parameters of the midgut change rapidly with time. The potential difference decays with a half-time of about 158 min, the resistance increases with a half-time of about 16 min, and the short-circuit current decays as the sum of two exponential terms, with half-times of about 16 and 158 min respectively. In addition, potential and short-circuit current show transient responses to step changes. 6. The properties of the midgut are compared with those of other transporting epithelia, and their dependence on the degree of folding of the preparation is discussed. Their time-dependence is discussed in the context of changes in potassium content of the tissue, and the implications for measurements depending on the assumption of a steady state are outlined.

Animals↗
PubMed1976

A solitary calyx in a human kidney.

A solitary kidney containing a single calyx and probably a single papilla is described. The embryology of this entity and its similarity to the unipapillary kidney in other mammals are discussed.

Female↗
PubMed1976

Active transport of calcium across the isolated midgut of Hyalophora cecropia.

1. The net flux of 45Ca from lumen to blood side across the isolated and short-circuited Cecropia midgut was 1-9 +/- 0-2 muequiv. cm-2h-1 in 8 mM Ca and the flux ratio was as high as 56 to 1. 2. The calcium influx was depressed by anoxia; 73% after 30 min. 3. The kinetics of Ca transport were anomalous; the apparent Km varied with Ca concentration from less than 0-2 to greater than 5-6 mM Ca and the apparent Vmax varied from less than 1-3 to greater than 3-3 muequiv. cm-2h-1. 4. The calcium influx showed a delay before the tracer steady state was attained, indicating the existence in the transport route of a calcium pool equivalent to 5-7 muequiv/g. wet weight of midgut tissue. 5 High calcium (16 mM) depressed the short-circuit current and potassium transport from blood to lumen side across the midgut. 6. Calcium depressed magnesium transport, from lumen to blood side across the midgut, and magnesium depressed the calcium transport. 7. Ca transport by the midgut does not regulate the Ca level in the haemolymph in vivo; it merely aids the diffusion of calcium down its electrochemical gradient. However, Ca transport may assist the uptake of the nutrients from the midgut contents.

Animals↗
PubMed1976

Mechanical properties and density of bone in a case of severe endemic fluorosis.

Mechanical properties of 25 standardized specimens of compact bone from a 45-year-old man with extreme endemic fluorosis were compared with similar specimens of nonfluorotic bone. Data from dry and wet tested specimens were compared. Tensile strength, strain, energy absorbed to failure, and modulus of elasticity were reduced in fluorotic specimens while compressive strength, strain and energy were increased in both wet and dry specimens. Compressive properties exceeded tensile properties. Drying increased tensile and compressive strength and modulus but decreased tensile and compressive strength and energy absorbed. Dry specimens tended to follow Hooke's Law but wet specimens exhibited visco-elastic behavior. Wet fluorotic specimens had lower tensile properties but higher compressive properties and were more dense than fresh human compact bone.

Bone and Bones↗
PubMed1975

The inhibition of glyceradehyde-3-phosphate dehydrogenase by benz(a)anthracene and its derivatives after exposure to laboratory lighting.

Colloidal dispersions of polycyclic aromatic hydrocarbons were found to inhibit glyceraldehyde-3-phosphate dehydrogenase (GPDH) and lactic acid dehydrogenase (LDH) after a short exposure of the incubation medium to laboratory lighting. The activation effect was observed with substituted 7-methyl derivatives of 12-methylbenz(a)anthracene also. One minute exposure of 7-methoxymethyl-12-methylbenz(a)anthracene (MeO-DMBA) to light was sufficient to produce a measurable amount of GPDH inhibition. The rate of enzyme inhibition was related to the pH of the dispersion. A small but significant effect of light on the inhibition of the enzymes by K-region epoxides was seen. Protein binding of the epoxides was not well correlated with the inhibition. The light effect was oxygen-dependent and was related to the hydrocarbon concentration. The active form decayed over a period of more than 25 days. The necessity for protecting reactions involving hydrocarbons and their derivatives from light is emphasized.

Amino Acids↗
PubMed1975

Active transport of potassium by the Cecropia midgut; tracer kinetic theory and transport pool size.

1. Tracer influx kinetics have been analysed theoretically to determine the size of the transport pool with no assumptions regarding the transport pathway. 2. For a calculation of the size of the transport pool to be made, the following six conditions are required by the theory: tracer steady state attained, tissue steady state attained, Isc measures next flux, small magnitude and constant time-course of efflux, and correction for decay in pumping rate. 3. The size of the pool, SI, is given by the steady state influx, Finfinity, divided by the mixing-time constant, alpha. 4. Some experimental results are analysed by three different graphical methods, and it is shown that these three methods are equivalent. Specifically, alpha is equal to the reciprocal of the 75% mixing time, t75, divided by 1n 4 and is equal to the reciprocal of the lag time, X. 5. The tracer kinetic theory is applied to active potassium transport across the isolated short-circuited midgut: the transport meets the six conditions required by the theory. 6. The size of the transport pool of potassium in one midgut is calculated to be 80.5 muequiv./g wet weight under high-K steady-state conditions. A value as high as this suggests that the pool is intracellular.

Animals↗
PubMed1975

Active transport of magnesium across the isolated midgut of Hyalophora cecropia.

1. The 28Mg-measured net flux of magnesium from lumen-side to haemolymph-side of the isolated and short-circuited midgut was 1.97 +/- 0.28 mu-equiv cm(-2) /(-1) in 8 mM-Mg2+. 2. The magnesium-influx shows a delay before the tracer steady-state is attained, indicating the existence of a magnesium-transport pool equivalent to 6.7 mu-equiv/g wet weight of midgut tissue. 3. Magnesium depresses the short-circuit current produced the midgut but not the potassium transport, the depression being equal to the rate of magnesium transport. 4. Magnesium transport yields a linear Lineweaver-Burk plot with an apparent Km of 34 mM-Mg2+ and an apparent Vmax of 14.9 mu-equiv cm(-1) /(-1). 5. Magnesium is actively transported across the midgut and contributes to the regulation of the haemolymph magnesium concentration in vivo.

Animals↗
PubMed1975

Cation distributions across the larval and pupal midgut of the lepidopteran, Hyalophora cecropia, in vivo.

1. The levels of potassium, sodium, magnesium and calcium in leaves, midgut contents, midgut tissue, and blood were analysed in seven developmental stages between feeding, fourth-instar larvae and new pupae of the Cecropia silkworm. 2. Three dramatic changes in cation levels were found: the K level in the contents drops from 284 /+- 51 mEquiv./1 tissue water in the fifth-instar larva to 51 +/- 6 mEquiv./1 in the new pupa; the Mg level in the midgut tissue increases from 28 +/- 3 mEquiv./1 at the time of gut evacuation to 1093 +/- 104 mEquiv./1 in the new pupa; and the Ca level in the contents drops temporarily from 56 +/- 12 mEquiv./1 in the feeding fourth instar larva to 17 +/- 5 mEquiv./1 in the new fifth instar larva. The Na level was nerve higher than 2.8 +/- 0.5 mEquiv./1. 3. The relative levels of the four cations were different for each tissue studied, but each tissue maintained the same relative levels during the developmental stages studied. The sequences are: leaf, Ca greater than K GREATEr than Mg greater than Na; midgut contents, K greater than Ca greater than Mg greater than Na; midgut tissue, K GREATEr than Mg greater than Ca greater than Na; and blood, Mg greater than K greater than Ca greater than Na. 4. There were three large concentration gradients across the midgut; the K level in the midgut contents is approximately 10 times the level in blood; the Mg level in contents is one-half to one-sixth the level in blood; and the Ca level in contents is 3-4 times the level in blood. The K gradient and the Ca gradient are opposed and the Mg gradient is favoured by the electrical gradient across the larval midgut, the contents being 100 mV positive with respect to the blood. The K gradient and the electrical gradient are not present across the pupal midgut while the Mg gradient and the Ca gradient persist. 5. The K gradient is presumably maintained by the midgut K pump, the Mg gradient is aided by the midgut Mg pump, and the Ca gradient suggests that the midgut may possess a Ca pump.

Age Factors↗
PubMed1975

Inhibitors of dopamine-beta-hydroxylase in human plasma.

There are two types of endogenous inhibitors of DBH in human plasma. One is sensitive to copper, or N-ethyl-maleimide, and is dialyzable. The other is not sensitive to copper, maleimide, or dialysis. Both types can be counteracted by diluting the plasma, thus eliminating the need for inactivators during the assay of plasma.

Blood Chemical Analysis↗
PubMedDate not supplied

First trimester abortion by vacuum aspiration: interphysician variability.

This study compares the performances of four physicians using two types of plastic cannulae (flexible and rigid) for 1100 vacuum aspiration procedures. The criteria for assessing physician performance by cannula type were: (a) frequency of cannula obstructions, (b) amount of retained tissue obtained by sharp curettage after vacuum aspiration, (c) estimated blood loss during the procedure and (d) time required to perform the procedure. Data for each physician were compared and yielded significantly different results. The length of time required to use the cannula differed significantly among physicians; two of them had significantly shorter cannula times with the flexible instrument. The others had the lowest distributions of blood loss and the most difference between cannula usage. Consistent grouping over several variables suggests that differences in these criteria are more likely to be attributable to subtle distinctions in operator technique than to variations in equipment.

Abortion, Induced↗