Thyroid function after subtotal thyroidectomy for hyperthyroidism.

Among 76 patients who had had a subtotal thyroidectomy for hyperthyroidism from one to seven years previously recurrent hyperthyroidism was found in three and hypothyroidism in 13. The remaining 60 subjects were clinically euthyroid but a raised level of serum thyroid-stimulating hormone (TSH; greater than 5-0 mu U/ml) was found in 39. Analysis of the data showed that their serum thyroxine was significantly lower than in the subjects with a normal TSH. The serum triiodothyronine (T-3) was similar in both groups. It is concluded that subjects with a raised TSH remain clinically euthyroid by maintaining a normal serum T-3 concentration. There was no evidence of any long-term progressive deterioration of thyroid function after subtotal thyroidectomy.     

Circular dichroism and spin-label studies of carp hemoglobin

Circular dichroism (c.d.) spectra were obtained for deoxy, oxy, carboxy, nitrosyl, aquomet and azidomet derivatives of carp hemoglobin. The spectra of the hemolysate and its two major components are virtually identical. Binding of diatomic ligands induces large changes in the 287 nm ellipticity. In the case of oxygen binding this change appears to be proportional to the free energy of co-operation. The changes of L-band ellipticity and Soret rotational strength with ligation reflect tertiary structural alterations and bear no relationship to quaternary transitions. The c.d. results indicate that carp deoxyhemoglobin has very similar tertiary and quaternary structures between pH 6·4 and 8·0, whereas the oxyhemoglobin undergoes continuous conformational adjustment in response to pH changes. The effect of inositol hexaphosphate on c.d. spectra is much smaller than it is on the functional properties. Electron paramagnetic resonance spectra of iodoacetamide nitroxide label are sensitive to ligation, the label is probably attached to Cys142β.     

Pollen stigma interactions in Brassica oleracea

Summary Recent studies on the mechanism of self-incompatibility in Brassica indicate the location, nature and mode of action of the molecules involved. Characteristics of the pollen surface and the stigma surface are described in detail, together with new information pertaining to the recognition molecules located therein. A sequence of events is outlined leading from pollination, through adhesion, hydration, germination, and tube growth to acceptance and ultimate compatibility. The characteristics of rejection of incompatible grains are described for each stage of the pollen-stigma interaction. It is proposed that recognition of proteins from the coating of self-pollen by the molecules in the pellicle results in the formation of a biologically-active complex which inhibits water supply to the incompatible grain, and that all other manifestations of incompatibility are a consequence of this initial response.     

The activity of liver alcohol dehydrogenase with nicotinamide–adenine dinucleotide phosphate as coenzyme

1. The separation of nucleotide impurities from commercial NADP preparations by chromatography is described. All the preparations studied contained 0·1–0·2% of NAD. 2. The activity of pure crystalline liver alcohol dehydrogenase with NADP as coenzyme has been confirmed. Initial-rate data are reported for the reaction at pH 6·0 and 7·0 with ethanol and acetaldehyde as substrates. With NADP and NADPH₂ of high purity, the maximal specific rates were similar to those obtained with NAD and NADH₂, but the Michaelis constants for the former coenzymes were much greater than those for the latter. 3. The oxidation of ethanol by NADP is greatly inhibited by NADH₂, and this accounts for low values of certain initial-rate parameters obtained with commercial NADP preparations containing NAD. The kinetics of the inhibition are consistent with competitive inhibition in a compulsory-order mechanism. 4. Initial-rate data with NAD and NADPH₂ do not conform to the requirements of the mechanism proposed by Theorell & Chance (1951), in contrast with results previously obtained with NAD and NADH₂. The possibility that the deviations are due to competing nucleotide impurity in the oxidized coenzyme cannot be excluded. The data show that the enzyme reacts more slowly with, and has a smaller affinity for, NADP and NADPH₂ than NAD and NADH₂. 5. Phosphate behaves as a competitive inhibitor towards NADP.     

Taxonomy of agamic complexes in plants: A role for metapopulation thinking

The argument is made that species should be comparable with respect to the numbers of genotypes they include, regardless of whether their reproduction is exclusively sexual or not. Specifically, this means recognizing species at a level comparable to that of the section or series, as these are used in genera likeCrataegus L. orTaraxacum Weber ex F.H.Wigg. Anticipated advantages of this approach for the taxonomy of agamic complexes include the following: (1) a common basis for communication between taxonomists and population biologists, hence (2) the opportunity to find possible explanations for patterns of variation in theoretical models of population behavior. In addition, (3) revising the hierarchical level at which species are recognized will make it easier to avoid describing species that are paraphyletic, i.e. that include some but not all related genotypes sharing a common ancestor. As an example, revising the hierarchical level at which species are recognized makes it possible to see many agamic complexes as being made up of metapopulations of genotypes that arise and go extinct as habitats become available and then disappear for whatever reason (succession, disturbance, etc.) and at whatever scale (local, regional, continental).     

Order out of chaos in the nucleus

A report on the 'Nuclear architecture and control of gene expression' minisymposium at the first meeting of the European Life Scientists Organisation (ELSO), Geneva, Switzerland, September 2-6, 2000.     

Unilateral incompatibility within the brassicaceae: further evidence for the involvement of the self-incompatibility (S)-locus

Unilateral pollen-pistil incompatibility within the Brassicaceae has been re-examined in a series of interspecific and intergeneric crosses using 13 self-compatible (SC, Sc) species and 12 self-incompatible (SI) species from ten tribes. SC x SC crosses were usually compatible, SI x SC crosses showed unilateral incompatibility, while SI x SI crosses were often incompatible or unilaterally incompatible. Unilateral incompatibility (UI) is shown to be overcome by bud pollination or treating stigmas with cycloheximide — features in common with self-incompatibility. Treating stigmas with pronase prevents pollen tubes from penetrating the stigma in normally compatible intra-and interspecific pollinations. The results presented show that the presence of an incompatibility system is important in predicting the outcome of interspecific and intergeneric crosses and, combined with the physiological similarities between UI and SI, would suggest an involvement of the S-locus in UI.     

QUANTITATIVE COMPARISON OF FLORAL DEVELOPMENT IN VERONICA CHAMAEDRYS AND VERONICASTRUM VIRGINICUM (SCROPHULARIACEAE)

Development in Veronica and Veronicastrum was studied to elucidate the growth patterns responsible for differences between their mature flowers. Nineteen floral dimensions were measured on buds from initiation to anthesis, and representative stages were recorded with the scanning electron microscope. Bivariate plots indicate the heterochronic changes responsible for the derived flower form of Veronica. The growth patterns of the gynoecium and androecium were little changed. The calyx of Veronica showed slower size increase at the early stages, but continued to grow after that of Veronicastrum had stopped. The most striking change occurred in the corolla lobes of Veronica, where growth was retarded until the beginning of style formation, but afterward was accelerated relative to that of Veronicastrum. The corolla tube of Veronica remained short due to a later onset of growth and slower enlargement later in development. Multigroup principal components analysis (M-PCA) was used to summarize the measurements. The distribution of points along M-PC 1 describes size increase during floral development. Along M-PC 2 the trajectories of the two taxa diverge after the beginning of style growth, while along M-PC 3 they differ from the earliest stages on, corroborating differences observed with the scanning electron microscope. M-PCA can thus be used to portray differences in patterns of floral development, facilitating simultaneous quantitative comparisons of two or more taxa.