Occurrence of 28- and 27-Carbon ecdysteroids and sterols in developing worker pupae of the leaf-cutting ant acromyrmex octospinosus (reich) (hymenoptera,formicidae: Attini)

The major ecdysteroids in large worker pupae of the leaf-cutting ant Acromyrmex octospinosus were characterized at the peak ecdysteroid concentration by using high-performance liquid chromatography, enzyme immunoassay, and mass spectrometry. In decreasing amounts, they were determined to be makisterone A, an unidentified C₂₈ ecdysteroid bearing a molecular weight of 494, 20-hydroxyecdysone (ratio of 1 to 6 as compared to makisterone A), and putative but negligible ecdysone. The presence of both C₂₈ and C₂₇ ecdysteroids is discussed in relation to the content of 4-desmethylsterols determined by gas chromatography and mass spectrometry to be ergosta-5,7,24 (28)-trien-3β-ol, ergosterol, ergosta-5,7-dien-3β-ol and ergosta-7,24(28)-dien-3β-ol for the main sterols, and with a small amount of cholesterol.     

In-vivo behaviour of hypodermically implanted microfabricated glucose sensors

The in-vivo behaviour of microfabricated GOD (glucose oxidase)/H2O2 glucose sensor implanted subcutaneously in normal anaesthetized rats has been studied. The sensor consists of a planar, three-electrode microcell, an enzyme membrane (glucose oxidase and bovine serum albumin cross-linked with glutaraldehyde) and an outer diffusion limiting polyurethane membrane. The sensor behaviour during hyperglycaemic (13.8 mM and 11.2 mM), euglycaemic (7.8 mM) and hypoglycaemic (3.5 mM) plateau levels was determined. The values of the in-vivo sensitivity (0.64 +/- 0.05 nA/mM) and background current (1.25 +/- 0.4 nA) were determined using a two-point calibration method and then used to calculate apparent subcutaneous glucose concentrations. The results show the presence of a good correlation between all the plasma glucose levels (G) and the apparent subcutaneous tissue concentrations (G'), with G' = 0.997.G - 0.066, r = 0.9782.     

Screening of geriatric patients for thyroid dysfunction with thyrotropin-releasing-hormone test, sensitive thyrotropin and free thyroxine estimation

Hospitalized geriatric patients (N = 354) from an iodine-deficient area were screened with sensitive thyrotropin (TSH), free and total thyroxine (FT4, T4) and total triiodothyronine (T3) to determine the occurrence rate of clinical and subclinical thyroid dysfunction. The diagnostic value of the tests was compared to each other and to that of the thyrotropin-releasing-hormone test (TRH-test) in order to find the optimal first line screening test in geriatric patients. Clinical hyperthyroidism was found in 13, subclinical hyperthyroidism in 10, overt hypothyroidism in 6 and subclinical hypothyroidism in 8 cases. 20.6% of the patients were euthyroid but had subnormal TSH response to TRH, as a sign of possible thyroid autonomy. The low occurrence rate of clinical thyroid disorders (4.8%) does not justify the screening of geriatric patients in general, but the high probability of thyroid autonomy makes reasonable the investigation of every geriatric patient before iodine administration. Suppressed basal TSH and high FT4 were found to be both sensitive and specific in diagnosing clinical hyperthyroidism, but the predictive value was insufficient; elevated T4 and T3 are specific, but not sensitive. Basal TSH is sensitive, specific and has a good predictive value in diagnosing euthyroidism, whereas normal T4, FT4 or T3 are not specific enough for euthyroidism. Basal TSH is better as a first line test of thyroid function than FT4. A normal basal TSH confirms euthyroidism by itself. Other tests (TRH test, T4, FT4, T3) are necessary to elucidate the clinical importance of a subnormal or suppressed basal TSH.     

Spectral sensitivities of retinular cells measured in intact,living flies by an optical method

Summary The spectral sensitivity of the peripheral retinular cells R1–6 in nine species of intact flies was determined using non-invasive, optical measurements of the increase in reflectance that accompanies the pupillary response. Our technique is to chronically illuminate a localized region of the eye with a long wavelength beam, adjusted to bring pupillary scattering above threshold, then, after stabilization, to stimulate with monochromatic flashes. A criterion increase in scattering is achieved at each wavelength by adjusting flash intensity. Univariance of the pupillary response is demonstrated by Fig. 3.Action spectra measured with this optical method are essentially the same as the published spectral sensitivity functions measured with intracellular electrophysiological methods (Fig. 4 forCalliphora, Fig. 5 forDrosophila, Fig. 7 forEristalis, and Fig. 8 forMusca). This holds for both the long wavelength peak and the high sensitivity in the UV as was consistently found in all investigated fly species.Spectral sensitivity functions for R1–6 of hover flies (family Syrphidae) are quite different in different regions of the same eye. There can also be substantial differences between the two sexes of the same species. The ventral pole of the eye of femaleAllograpta (Fig. 10) contains receptors with a major peak at 450 nm, similar to those ofEristalis. However, the dorsal pole of the same eye contains receptors with a major peak at 495 nm, similar to those ofCalliphom. Both dorsal and ventral regions of the maleToxomerus eye, and the ventral region of the female eye, contain only the 450 nm type of R1-6 (see Fig. 12). However, the dorsal region of the female eye also contains another spectral type of receptor that is maximally sensitive at long wavelength. Eyes of both sexes ofAllograpta (Figs. 10 and 11) contain a mixture of spectral types of receptors R1-6.We thank Dr. Chris Maier of the Connecticut Agricultural Experiment Station, for determination of the Syrphidae. This work was supported by grants EY01140 and EY00785 from the National Eye Institute, U.S.P.H.S., (to GDB), by the Connecticut Lions Eye Research Foundation (to GDB), and by the Netherlands Organization for the Advancement of Pure Research (Z.W.O.), (to DGS).     

Causes and consequences of Robertsonian exchange

At least two types of Robertsonian exchange are now known in the acrocentric chromosomes of man. Both types involve breakage in the arms adjacent to the centromere. Evidence is presented for a third type of exchange, one involving breakage within the centromere itself, in the grasshopper Percassa rugifrons. In this species, which is regularly homozygous for a single fusion metacentric, the eighteen rod autosomes have small but pronounced granules at the centric end of the chromosome. When C-banded these granules show differential Giemsa staining and appear to represent centromeric chromomeres; these chromomeres are lacking in the metacentric fusion product. Equivalent fusions may have occurred in some mammal species too and possible examples of this are discussed in sheep and mice. The Percassa fusion has led to a modification in both the frequency and the distribution of chiasmata as judged by a comparison of these properties in the metacentric relative to the two next smallest rod equivalents. Comparable modifications are known to occur in other naturally occurring fusions but these changes are certainly not automatic consequences of fusion since they are not shown in at least some newly produced fusion mutants.     

The metabolism of steviol to 13-hydroxylated ent-Gibberellanes and ent-kauranes

Steviol(ent-13-hydroxykaur-16-en-19-oic acid) is rapidly metabolised by the mutant B1-41a of Gibberellafujikuroi. The initial product is the ent- 7-α-hydroxy derivative which is then further metabolised to gibberellins A₁, A₁₈, A₁₉, A₂₀, 13-hydroxy GA₁₂, the ent-6α, 7α, 13- and ent-6β, 7α, 13 (19,6-lactone)-trihydroxykaurenoic acids, and a seco-ring B diacid. This apparently low substrate specificity of the enzymes operative beyond the block in the mutant B1-41a provides a useful model for the biosynthetic pathways to 13-hydroxylated gibberellins of higher plants and a preparative route to these plant gibberellins.