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Thyroid cancer is very rare during pregnancy, but a thyroid nodule is more likely to be cancerous if discovered during pregnancy (43 p. cent versus 15 p. cent). The diagnosis is more difficult. Tests using radioactive substances are contraindicated during pregnancy. Ultrasonography does not permit to specify the nature of the nodule and aspiration biopsy with cytological examination becomes the examination of choice. One should not hesitate to operate on these nodules, during pregnancy, if the diagnosis is made. It is difficult to assert that the prognosis is aggravated by pregnancy since there are so few cases, but several authors report a few cases with an abnormally fast progression during pregnancy. Forms which are properly treated and occurred before the age of 40, are not a contraindication to subsequent pregnancies, if they are not anaplastic or metastatic forms. However, a reasonable delay of the surgery is advised in order to stabilize the hormonal treatment and the calcium-phosphorus balance.

Kinetic studies of pyridoxal 5'-phosphate binding to glutamate dehydrogenase (EC 1.4.1.3) has provided evidence for two specific binding sites, chemically identified as Lys 126 and Lys 333. Use of protecting ligands permitted the selective modification of only one of these lysines, and showed that (1) Lys 333 modification results in depolymerisation of the enzyme into active hexamers; (2) Lys 126-modified enzyme was 92% inactivated. The residual activity was desensitized to GTP. The inactivation process was cooperative, maximum inactivation occurring as soon as half of the Lys 126 were modified.

The movement of the 2 flagella of Oxyrrhis marina was examined with respect to their individual waveforms and the swimming behavior of the organism. The longitudinal flagella propagated helicoidal waves whose amplitude decreased toward the tip of th flagellum. Their beat frequencies were 50-60 Hz. The transverse flagella beat helicoidally within a furrow. Sudden changes in the direction of the cell trajectories were generated by transient arrests of the longitudinal flagellum beat, which were accompanied by a switch from the backward orientation to a forward one. This sweeping motion generated the rotation of the cell body. Ca2+ ions highly stimulated the frequencies of this arrest response, which compared to the "walking-stick" behavior of sea urchin spermatozoa. Isolated flagella were ATA-reactivated after detergent treatment. They exhibited 2 types of motion within the same experimental conditions. A progressive helicoidal motion was generated upon longitudinal flagellum reactivation, whereas a rolling motion with little progression characterized transverse flagellum reactivation. The differences in motile behavior reflect regulations of flagellar movement which were not destroyed by the isolation procedure and may be indicative of regulation by accessory structures.

Sperm flagella like somatic cilia consist of an axoneme of 9 + 2 microtubules. Several projections protrude form the A subfiber of each microtubule doublets: the 2 rows of Dynein arms, the Radial Spokes and the Nexin Links. All the axonemal components constitute the flagellar motor. The energy necessary to generate microtubule sliding, responsible of the flagellar beat, is provided by Mg2+-ATP hydrolysis by Dynein ATPase. The Dynein ATPase is a group microtubule A called Dynein arms. Mg2+-ATP binding and hydrolysis generate transient cross-bridges that cause the microtubule doublets walk one upon another. The transformation of sliding to bending is produced by the Radial Spokes which eventually go through a cycle of transient attachment to the central sheath. The flagellar movement is controlled by intra-flagellar factors mostly Ca2+, responsible for the symmetry of the beat and the arrest of flagellar motility. Further, cAMP increase is associated in certain conditions with the initiation or increase of sperm motility. Extrinsic factors seem to play a major role in the control of sperm motility, such as proteins that coat the sperm membrane or factors associated with the egg, like the peptide "speract", extracted from sea urchin egg, which stimulates sperm respiration rate and increases cAMP and cGMP concentrations.

Spermatozoa from siphonophores have been shown to be attracted towards an extracellular structure, the cupule, which covers the predetermined site of fertilization of the egg. Observations on sperm behaviour during the chemotactic response show that spermatozoa describe trajectories of large diameter (700-1000 micron) while far from the cupule, and of smaller diameter (200 micron) in the cupule area. The transition between the two types of swimming occurs progressively when spermatozoa cross a 3 mm wide area around the cupule. After a few minutes 99% of the spermatozoa keep swimming around the attractant source, following circular paths 150-200 micron in diameter. In the absence of the attractant, comparable modifications of sperm trajectories are observed in the presence of the ionophore A23187 and high calcium concentrations. In the presence of 10(-2) M calcium ions, A23187-treated spermatozoa describe trajectories 200 micron in diameter, which increase up to 800 micron at lower calcium concentrations (10(-6) M). In the absence of calcium ions, spermatozoa swim across the cupule area without modification of their trajectories and no sperm accumulation can be detected. This requirement of the chemotactic response for calcium ions is observed either with fresh cupules stuck on the eggs, with cupules separated from the eggs, or with cupule extracts. Moreover, a soluble component fractionated from the cupule induces, when diluted in sea water, a reduction in the size of the sperm trajectories and this also requires calcium ions. The present data show that the chemotactic response of siphonophore sperm, which requires millimolar concentrations of calcium ions, occurs through a non-transient induction of increased asymmetry of the flagellar waveform. It is proposed that the natural attractant operates to produce an increase in the intraaxonemal calcium concentration.

Xenopus spermatozoa have a characteristic corkscrew-shaped head and a flagellum with a conventional "9 + 2" structure (Bernardini et al.: J Ultrastruct Md Struct Res: 94:188-194. They are motile in water and media of low osmolarities, but not in media of osmolarities higher than 200 mosm/liter, regardless of the ionic composition. External calcium and pH are not involved in the inhibition of sperm movement at high osmolarities. The duration of sperm motion was less than 10 min, and both flagellar beat frequencies and sperm velocities declined progressively. However, in demembranated and reactivated tails, flagellar beating was sustained for longer times. Flagella propagated three-dimensional waves that induced a spinning motion of the whole spermatozoon. This pattern of movement is not dependent on the shape of the sperm head, since isolated, reactivated flagella exhibited three-dimensional waves.