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Biomedical subjects

G W Bates

Publications and source records attributed to G W Bates.

At least 73 records · Page 4Linked to original sources
PubMed1983

Fusion of plant protoplasts by electric fields.

The electrical fusion technique of Zimmermann and Scheurich (1981 Planta 151: 26-32) has been used to fuse mesophyll protoplasts of Avena, Zea, Vigna, Petunia, and Amaranthus. Electrical fusion proves to be a simple, effective, and general fusion technique that can be controlled to form either dikaryons or large multinucleate fusion bodies. In addition, we show that Vigna mesophyll protoplasts that are subjected to the electrical fields used in this technique are viable in culture. The construction of the fusion chambers, necessary electrical equipment, and the fusion protocol are described in sufficient detail for reproduction of the technique.

Journal Article↗
PubMed1982

The exchange of Fe3+ between acetohydroxamic acid and transferrin. Spectrophotometric evidence for a mixed ligand complex.

Transferrin, the serum iron transport protein, provides an excellent model for studying biological metal ion exchange reactions. A curious problem is that while a mixed ligand species of chelate-Fe3+-protein is anticipated from theoretical considerations and supported by kinetic results, no clear spectrophotometric evidence for such an intermediate has heretofore been obtained. In this study of the exchange of Fe3+ between acetohydroxamic acid and transferrin such evidence has been found. The reaction of Fe2+-acetohydroxamic acid with apotransferrin-CO3(2-) is distinctly biphasic when examined by stopped flow spectrophotometry. The first phase is complete within approximately 4 s and results in the formation of a transient species with a distinct spectral maximum at 432 nm. The second phase requires approximately 2 min and results in the formation of Fe3+-transferrin-CO3(2-). We suggest that the transient species is a mixed ligand complex. The reaction rate-concentration relationship for the formation of the intermediate is linear for Fe3+-acetohydroxamic acid and hyperbolic for apotransferrin-CO3(2-). This suggests a rate-limiting labilization of Fe3+-(acetohydroxamic acid)3 preceding attack by the apotransferrin-CO3(2-). The reverse reaction, the removal of Fe3+ from the Fe3+-transferrin-CO3(2-) by acetohydroxamic acid, does not provide spectral evidence for the intermediate. The velocity-concentration relationship shows a hyperbolic dependence on acetohydroxamic acid concentration and a linear dependence of Fe3+-transferrin-CO3(2-), suggesting a rate-limiting labilization of the Fe3+ of Fe3+-transferrin-CO3(2-) resulting from a conformational change.

Carbonates↗
PubMed1982

Effects of obesity on sex steroid metabolism.

In a study designed to compare plasma androgens in obese, anovulatory women with non-obese, ovulatory women, we found a statistically significant increase in plasma androstenedione and testosterone in obese, anovulatory women. Plasma androstenedione was 252 +/- 18 ng/dl (mean +/- SEM) in the obese women compared with 173 +/- 9 ng/dl in the non-obese ovulatory women (p less than 0.001). Plasma testosterone was 66 +/- 5.7 ng/dl (mean +/- SEM) in the obese women compared with 41 +/- 3.0 ng/dl in the non-obese ovulatory women (p less than 0.001). Androstenedione and testosterone are the substrates for estrone and estradiol-17 beta production. Menstrual disorders associated with obesity are largely due to estrogen excess. From the findings of this study we suggest that androgen excess in obesity results in subsequent tonic estrogen production and estrogen excess.

Androstenedione↗
PubMed1982

Elevated cerebrospinal fluid prolactin concentration in women with pseudotumor cerebri.

When comparing cerebrospinal fluid (CSF) prolactin concentration in women having pseudotumor cerebri with men and women having other neurologic disorders, we found a significant increase in CSF prolactin in those subjects with pseudotumor cerebri. This finding suggest an active role for prolactin in CSF production and an etiologic role for prolactin in pseudotumor cerebri.

Adult↗
PubMed1982

Reproductive failure in women who practice weight control.

Forty-seven women (29 with unexplained infertility and 18 with menstrual dysfunction) practiced weight control by caloric restriction in order to maintain a fashionable body habitus. All of these women were below ideal body weight (IBW) when compared with Metropolitan Life Insurance Company tables for height and weight. When 36 of these women followed a dietary regimen designed to increase their weight to predicted IBW, 19 of 26 infertile women (73%) conceived spontaneously; 9 of 10 women (90%) with secondary amenorrhea resumed menstruation. Eleven women (23%) would not accept their practice of weight control as the cause of reproductive failure and did not participate in the study. Differences in the serum gonadotropin luteinizing hormone:follicle-stimulating hormone (LH:FSH) ratio were found to be significantly related to differences in the percentage of IBW. The practice of weight control may be a cause of unexplained infertility and menstrual disorders in otherwise healthy women.

Adolescent↗
PubMed1982

Effect of body weight reduction on plasma androgens in obese, infertile women.

Although a variety of disorders are associated with polycystic ovarian disease (PCOD), obesity, hirsutism, and menstrual dysfunction are the most frequent manifestations. We investigated the possibility that obesity per se may give rise to androgen excess through alterations in estrogen metabolism and, consequently, through alterations in gonadotropin secretion. Eighteen obese, infertile women with PCOD were compared with 20 control women. Plasma androstenedione (A) was 252 +/- 18 ng/dl (mean +/- standard error of the mean [SEM]) in the obese women compared with 173 +/- 9 ng/dl in the controls (P less than 0.001); plasma testosterone (T) was 66 +/- 5.7 ng/dl, compared with 41 +/- 3 ng/dl (P less than 0.001). Thirteen of the obese women lost greater than 15% of their body weight by dietary restriction; ten of these women (77%) conceived spontaneously. In seven of the ten women who conceived, we remeasured plasma androgens following weight reduction but prior to conception. A decreased from 295 +/- 19 ng/dl to 179 +/- 5 ng/dl; T decreased from 75 +/- 8 ng/dl to 39 +/- 5 ng/dl (P less than 0.001). We conclude that obesity may play a role in the genesis of PCOD.

Androgens↗
PubMed1981

The formation of Fe3+-transferrin-CO3(2-) via the binding and oxidation of Fe2+.

This paper examines the reaction pathway in which Fe2+ is bound by apotransferrin and subsequently oxidized by O2 to yield Fe3+-transferrin-CO3(2-). The time course of the reaction follows a curved first order function suggesting somewhat different reactivities of the two transferrin binding sites. The initial velocity of the oxidation reaction follows saturation kinetics with regard to apotransferrin, Fe2+, and NaHCO3. We suggest an equilibrium between these components and Fe2+-transferrin-CO3(2-). The initial velocity is a linear function of O2 concentration. This is consistent with the rate-limiting step of the overall reaction being the oxidation of the Fe2+-transferrin-CO3(2-). A second order rate constant of approximately 4 X 10(3) M-1 s-1 was estimated for the oxidation of Fe2+-transferrin-CO3(2-) by O2. Oxidation by H2O2 is about 30 times faster. The reaction velocity increases with increasing pH between pH 6.0 and 7.5 Fe3+-transferrin-anion complexes are formed by the binding and oxidation of Fe2+ iun the presence of O2 and synergistic anions. The anion is found to have a strong effect on the reaction rate and provides additional evidence for the proposed reaction route. The presence of chelating agents also strongly affects the rate of Fe3+-transferrin-CO3(2-) formation. EDTA and N-(2-hydroxyethyl)ethylenediaminetriacetic acid severely depress the rate, while other chelating reagents have a moderately inhibiting effect. Thioglycolate is found to enhance the reaction by a factor of 9. The formation of a quaternary complex consisting of thioglycolate-Fe2+-transferrin-CO3(2-) is suggested. The results are correlated with an earlier study on the reductive release of iron from transferrin (Kojima, N., and Bates, G. W. (1979) J. Biol. Chem. 254, 8847-8854).

Carbonates↗
PubMed1981

The effect of chemical agents, beverages, and spinach on the in vitro solubilization of iron from cooked pinto beans.

The solubilization of iron from cooked pinto beans was examined using an improved in vitro methodology. The iron content of the beans was found to exist in three populations: 1) that which is spontaneously soluble upon incubation; 2) that which can be mobilized by chelating or reducing agents; and 3) that which is more firmly bound to the insoluble bean residue. These fractions constitute approximately 25, 45, and 30%, respectively, of the bean iron content when using consecutive 30-min incubations at pH 2 and 6. Ascorbic acid is maximally effective in iron mobilization under acidic conditions and acts via iron reduction. Citric acid is maximally effective near pH 6. The combination of ascorbic acid and citric acid leads to the solubilization of 70% of the iron content of the beans. Orange juice also leads to maximal soluble iron, predominantly in the Fe2+ state. Tea severely decreases iron solubility in the system. Only 3% of the iron content of spinach is solubilized by 10 mM ascorbic acid. Whole spinach suspension and the insoluble spinach residue are able to remove iron from solution that was previously solubilized from beans.

Beverages↗
PubMed1981

pH-Dependent Interactions between Pea Cell Wall Polymers Possibly Involved in Wall Deposition and Growth.

In an effort to detect a pH-dependent release of polymers such as xyloglucans, thought to be involved in auxin-induced cell wall expansion during growth, radioactively labeled cell walls from pea stem tissue were incubated at different pH values, and changes in water-soluble, ethanol- or trichloroacetic acid-insoluble components were determined. This revealed the occurrence, at neutral pH, of a time- and pH-dependent binding of soluble pectin, in the walls, to a heat-labile, presumably protein, wall component, yielding a trichloroacetic acid-insoluble pectin-protein complex. This reaction, which can also be observed between polymers in water extracts of cell walls, is inhibited at low pH and by Ca(2+), and appears to be of a physical, possibly lectin-like, nature. Progressive binding of pectin or of the pectin-protein complex to the insoluble wall structure is also observed. These reactions may be involved in wall assembly during its deposition, and may participate in, or be analogous to pH-dependent physical interactions that participate in, wall extension during cell growth.

Journal Article↗