A fluorescence depolarization study of the orientational distribution of crossbridges in muscle fibres

A fluorescence depolarization study of the orientational distribution of crossbridges in dye-labelled muscle fibres is presented. The characterization of this distribution is important since the rotation of crossbridges is a key element in the theory of muscle contraction. In this study we exploited the advantages of angle-resolved experiments to characterize the principal features of the orientational distribution of the crossbridges in the muscle fibre. The directions of the transition dipole moments in the frame of the dye and the orientation and motion of the dye relative to the crossbridge determined previously were explicitly incorporated into the analysis of the experimental data. This afforded the unequivocal determination of all the second and fourth rank order parameters. Moreover, this additional information provided discrimination between different models for the orientational behaviour of the crossbridges. Our results indicate that no change of orientation takes place upon a transition from rigor to relaxation. The experiments, however, do no rule out a conformational change of the myosin S 1 during the transition. Correspondence to: Y. K. Levine     

The Evolutionary Origin and Homologues of the Supracochlear Lamina: a Contribution to our Knowledge of Mammalian Ancestry

In cetaceans, each otic capsule is bound anteriorly to the remainder of the endocranium by an aliform structure called the supracochlear lamina. This lamina has been established here as the homologue of the sphenocochlear commissure of other mammals. Most researchers believe that these two structures arose within mammals. However, a comparative study involving data from both extant and extinct craniates suggests that the supracochlear lamina and the sphenocochlear commissure have a long premammalian history. The conclusion is that the lower of the two pharyngeal segments at the upper end of the mandibular branchial arch first became incorporated in the endocranium, constituting the cartilago trabecularis in the embryos of jawed craniates. The distal, or posterior, extremity of the trabecular cartilage projected outwardly to form the basitrabecular process. This process, which when ossified is called the processus basipterygoideus, functioned as a jaw support. Later, one more jaw support, termed the basivincular, evolved immediately in front of the basipterygoid process. Both these supports for the upper jaw existed in the piscine forerunners of the tetrapods. Subsequently, in the lineages leading to mammals, the basivincular jaw support became the processus alaris to which is attached an upper jaw endoskeletal remnant, called the ala temporalis. The basipterygoid jaw support, however, vanished as a consequence of the evolution of an exoskeletal joint system for the jaws of mammals. Yet the basipterygoid process persisted and as the sphenocochlear commissure or the supracochlear lamina assumed the new function of supporting the cochlear part of the auditory capsule.     

Efficient generation of chimaeric mice using embryonic stem cells after long-term culture in the presence of ciliary neurotrophic factor

The aim of our study was to evaluate whether ciliary neurotrophic factor (CNTF) can substitute for leukaemia inhibitory factor (LIF) in maintaining pluripotential embryonic stem (ES) cells in culture. Two subclones of D3 ES cells were used to assess cell proliferation and differentiation in the presence of CNTF, LIF or Buffalo rat liver (BRL) cell-conditioned medium, or in the absence of exogenous differentiation inhibiting factors. ES cells maintained in medium supplemented with CNTF for up to four weeks were injected into blastocysts to investigate theirin vivo pluripotency in terms of chimaera formation. CNTF inhibited ES cell differentiation in a dose-dependent manner. The most effective concentration was 10 ng CNTF per ml of medium. The effects of CNTF on ES cell differentiation and proliferation were comparable to those of LIF at the same concentration. BRL cell-conditioned medium was less effective at preventing ES cell differentiation but induced their proliferation very markedly. Both ES cell clones efficiently formed chimaeras after long-term culture with CNTF as the only differentiation inhibiting agent. The ability of these ES cells to colonize the germ-line is the ultimate proof that CNTF can preserve the pluripotency of ES cells.     

Insulin-like growth factor I enhances the formation of type I collagen in hydrocortisone-treated human osteoblasts

We have studied the effect of insulin-like growth factor I (IGF-I) on the formation of osteocalcin and type I collagen in isolated human osteoblasts. IGF-I at and above 0.1 nM stimulated the formation of type I collagen as measured by the type I procollagen carboxyterminal peptide (PICP), in human osteoblasts, incubated for 72 hrs in serumfree conditions. The secretion of osteocalcin was not affected by IGF-I while 1,25(OH)₂ vitamin D₃ significantly enhanced the formation of osteocalcin. When human osteoblast-like cells were incubated with hydrocortisone (1 M), a significant decrease in the release of both PICP and osteocalcin was seen. Addition of IGF-I to human osteoblasts also treated with hydrocortisone normalized the PICP-formation but did not affect the suppressed osteocalcin-formation. These data indicate that IGF-I reverses selective effects of hydrocortisone on bone.     

Determination of cisplatin and cis-diammineaquachloroplatinum(II) ion by liquid chromatography using post-column derivatization with diethyldithiocarbamate

A post-column derivatization method has been developed for the determination of cisplatin and its monohydrated form. Cisplatin was isolated on a strong anion-exchange column, while a strong cation-exchange column was used for the monohydrated complex. Diethyldithiocarbamate was used as reagent and the influence of temperature, pH and methanol content on the yield of derivative was investigated. The reaction was quantitative using a packed-bed reactor with a surrounding temperature of 115°C and a mobile phase consisting of 0.125 M succinic acid—sodium hydroxide buffer pH 5.2 and methanol (2:3, v/v). The resulting complex, Pt(DDTC)₂, was monitored photometrically at 344 nm. The precision of the determination was 11.5% (C.V.) at an injected amount of 20 ng (n = 12) for monoaqua and 8.0% (C.V.) at 9 ng (n = 10) for cisplatin. The method was used to evaluate the plasma concentration of cisplatin and its monohydrated form in a patient.     

Klassifikation der Prachtfinken, Spermestidae, auf Grund der Rachenzeichnungen ihrer Nestlinge

Ohne ZusammenfassungMotto: Mitunter gerät der Taxonom in ein Dilemma, worin ihm keine Nomenklatur-Regel zu Hilfe kommt.E. Stresemann, Vierteljahrsschr. Naturf. Ges. Zürich, Jahrg. 104, 1959, S. 213.     

Nature and metabolism of a thymus cyst studied by histochemistry and autoradiography

Summary A thymus cyst was discovered in connection with autoradiographical studies on sulphur metabolism of the rat. The coincidence must be considered unique and has motivated amplifying histochemical investigations.The cyst-content showed a strong positive PAS-reaction and after toluidine blue -metachromasia, which along with the incorporation of S³⁵ makes the presence of acid mucopolysaccharides likely. A strong blackening was noticed on the autoradiogram over the greater part of the cyst. This infers that the content has been metabolized here, in contradistinction to the centre with inactive colloid.     

Attempts to Determine the Roles of Visual and Olfactory Inputs in Initial Orientation and Homing of Pigeons over Familiar Terrain

The role of familiar visual landmarks in pigeon homing is still unsettled. If they are involved, they must be thought to be utilized in parallel with olfactory signals. In order to recognize the effectiveness of either one of the input channels separately, vision and olfaction, it is therefore necessary to interfere with both of them. Pigeons were temporarily deprived of image vision by spectacles made of translucent white paper, producing a condition called V^- as compared with the largely unimpaired condition V⁺. Access to olfactory signals was temporarily prohibited by charcoal filters before release and nasal anaesthesia upon release, resulting in condition O^- versus unimpaired smelling of natural air in O⁺. Prior to the test releases, all the participating pigeons had been made familiar with the two or four test sites (and with other sites in the area) by training flights. According to decreasing levels of initial homeward orientation and homing performance, the four combinations of treatments are to be arranged in the following order: V⁺O⁺, V⁺O^-, V^-O⁺, V^-O^-. In the last type, no trace of initial homeward orientation remained, indicating that at least one of the two input channels need be functional to enable home-related orientation. Over well known terrain, either alone seems to be more or less sufficient. The results are indicative but not definitely conclusive. Effects of visual impairment on behavioural activities in general cannot clearly be separated from orientation-specific effects. Therefore, and because many pigeons refuse to fly in V^- condition or fail to provide useful data, we stopped applying this method.     

Psychological complications after stillbirth--influence of memories and immediate management: population based study.

OBJECTIVE--To identify factors that may predict long term psychological complications among women who have had a stillborn child. DESIGN--Nationwide population based study using epidemiological methods. SUBJECTS--380 subjects and 379 controls who had had a stillborn or non-deformed live child in Sweden in 1991. RESULTS--Information was provided by 636 (84%) women. The ratio (95% confidence interval) of proportions of women with symptoms related to anxiety above the 90th centile for women who had had a stillborn child compared with those who had not was 2.1 (1.2 to 3.9). An interval of 25 hours or more from the diagnosis of death in utero to the start of delivery gave a ratio of 4.8 (1.5 to 15.9). The ratio was 2.3 (1.1 to 5.3) for not seeing the child as long as the mother had wished and 3.1 (1.6 to 6.0) for no possession of a token of remembrance. CONCLUSION--It is advisable to induce the delivery as soon as feasible after the diagnosis of death in utero. A calm environment for the woman to spend as much time as she wants with her stillborn child is beneficial, and tokens of remembrance should be collected.