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Notes: Abstract We determined intraocular pressure (IOP) in 55 premature infants (122 determinations) with stage V retinopathy of prematurity (ROP) by applanation and indentation tonometry corrected for scleral rigidity and found a modest correlation of r=0.52 between readings. Chronologic age and the scleral rigidity coefficient were the most significant factors affecting the closeness in readings. Our findings suggest that the applanation method of obtaining IOP values is preferable in infants with ROP because this method is less affected by technical error and the variable nature of premature infant sclera. Frequent examination may be necessary to detect an early IOP increase, especially in infants who have had successful retinal reattachment through vitreoretinal techniques.

Notes: Abstract Several relations between the structure of stable recurrent states and the statistics of avalanches in a one-dimensional sandpile automaton are derived and numerically verified. In particular, it is shown that the average avalanche size is determined by the second rather than the first moment of the distribution of trough distances. The two moments scale differently with system size, which implies multiscaling for the distribution. Moreover, the scaling of edge events (avalanches which fall off the pile) is shown to differ from that of bulk events (avalanches which remain on the pile).

Notes: An Unusual Pair of Bis(phosphido)-Bridged Diiron Carbonyl Complexes: [Fe2(CO)n{μ-P(tBu)2}(μ-PCy2)] (n = 5 and 6)Treatment of Na[Fe2(CO)6(μ-CO){μ-P(tBu)2}] with Cy2PCl gives [Fe2(CO)6{μ-P(tBu)2}(μ-PCy2)] (1) which loses CO on heating in toluene to afford [Fe2(CO)5{μ-P(tBu)2}(μ-PCy2)] (2). Complexes 1 and 2 have been characterized spectroscopically and by X-ray analyses. The central Fe2P2 unit in 1 is exactly planar whereas in 2 it is somewhat folded.

Notes: Alle Ausgleiche „brauchen Zeit, und alle verlaufen um so langsamer, je weiter der Ausgleich bereits fortgeschritten ist. Hierdurch kommt es, daß die Welt mit Gebilden erfüllt ist, die vom Standpunkt der Gleichgewichtslehre sozusagen keine Existenzberechtigung haben, und daher ihre Existenz nur auf Zeit geniessen“.…„Wir werden bald sehen, daß die stationären Erscheinungen in bestimmtem Sinne die Formen des Lebens sind, und daß alle Organismen sich als Gebilde auffassen lassen, deren verhältnismässige Beständigkeit auf der Ausbildung stationärer, durch Selbstregulierung entstehender Zustände beruht“.Diese Zitate entstammen keinem modernen Lehrbuch der Thermodynamik irreversibler Prozesse und der Selbstorganisation, sondern sie sind 90 Jahre alt und wurden von Wilhelm Ostwald in seinen „Vorlesungen über Naturphilosophie“ formuliert. Die auffallend große zeitliche Lücke zwischen den Ideen und Ansätzen Wilhelm Ostwalds und den heute anerkannten Paradigmen mag an Ostwalds Emeritierung und dem Ausbruch des ersten Weltkrieges gelegen haben, aber auch an innerwissenschaftlichen Gründen, wie etwa dem Mangel an mathematischen Methoden zur Beschreibung komplexer und nichtlinearer Systeme, die erst Jahrzehnte nach der Jahrhundertwende entwickelt wurden. Sich mit Ostwalds Arbeiten auf diesem Gebiet zu beschäftigen, ist heute sicher nicht allein von historischem Interesse, sondern vermag darüber hinaus Denkanstöße zu geben und das Verständnis aktueller Fragen für die dort Tätigen zu vertiefen.

Notes: Cells derived from an epithelial-mesenchymal transformation within the atrioventricular canal and outflow tract are involved in the partitioning of the early embryonic heart into a four-chambered organ. This transformation process has been shown to proceed from an inductive interaction between the myocardium and competent, target endothelial cells within these regions of the heart. Interestingly, immunohistochemistry revealed the presence of fibronectinpositive particulates within the matrix of mesenchyme-forming regions (Mjaatvedt et al., 1987). This particulate matrix is extractable by EDTA and can elicit the epithelial-mesenchymal transformation in culture (Mjaatvedt and Markwald, 1989). Analysis of EDTA extracts of embryonic heart tissue revealed the presence of fibronectin and about 40 unidentified proteins, 6 of which appeared to be enriched in the biologically active 100,000g pellet fraction (Mjaatvedt and Markwald, 1989). Based on these and other data we have proposed that the particulate matrix is composed of a multicomponent complex of fibronectin and one or more of the low-molecular-weight proteins in this pellet. The purpose of the present study was to begin a biochemical characterization of the nonfibronectin proteins thought to be present in the matrix particulates. Given that many matrix constituents are glycoproteins, lectins were used to initially characterize the particulate constituents. Of the lectins tested, soybean agglutinin (SBA) was found to be specific only for matrix particulates. Histochemical analyses showed that SBA and antibodies against fibronectin colocalized regionally and temporally to the same matrix particulates in embryonic heart tissue. SBA-agarose affinity chromatography resulted in the isolation of two major (56 and 69 kDa) and six minor (28, 46, 50, 53, 126, 220 kDa) proteins from EDTA extractable heart matrix. Temporal lectin histochemical studies indicate that SBA-positive particulates are present in the matrix prior to mesenchyme formation, but are absent shortly after the transformation event. These observations support our hypothesis that one or more of these SBA-positive glycoproteins participate in the endothelial-mesenchymal transformation of cardiac endothelium.

Notes: Recent in situ hybridization studies have correlated expression of potential regulatory genes with pattern formation in limb bud mesoderm (Tabin: Cell 66:199-217, 1991); however, the mechanism(s) controlling their expression in mesoderm and their relevance to the establishment of a limb morphogenetic pattern remain unknown. One likely candidate for regulating patterning events in limb mesoderm is the apical ectodermal ridge, as its removal in ovo results in a graded truncation of limb skeletal elements in the proximal-distal axis dependent upon the time of excision (Rowe and Fallon: J Embryol Exp Morph 68:1-7, 1982). In the present study, we investigate whether the hypothetical imprint of ridge ectoderm is retained in cultured mesoderm. Specifically, we sought to determine if a subpopulation of limb mesoderm that forms in collagen gel culture (Markwald et al: Anat Rec 226:91-107, 1990), retains any expression of “limbness” in the absence of limb ectoderm as characterized by the formation of a predictable number and distribution of limb-like chondrogenic elements in comparison to the temporal and spatial relationships of the in situ proximal, hindlimb skeletal structures. Accordingly, explants of undissociated mesoderm from stage 18-22 chicken leg buds were cultured without ectoderm on collagen gel lattices and the central subpopulation of mesoderm was examined morphologically. We show that this central subset of mesoderm will form chondrogenic cells which were not expressed uniformly throughout the subset, but rather distinct nodules or elements of cartilage were elaborated. Moreover, the number of elements expressed by the central subset increased with the age of the mesoderm at the time of explantation; spatially and temporally, the sequence of elements that formed always proceeded from the proximal, anterior margin of the subset to its distal, posterior border. The shapes of the initial elements (designated I and II) resembled the forms of in situ proximal skeletal structures (girdle and femur-like), whereas more distal elements (III-V) were often fused and without structural similarity to in situ skeletal structures. When cultures were established from the posterior mesoderm of stage 19/20 or 21 mesoblasts, the frequency of element I formation was reduced approximately one-half, whereas formation of more distal elements was unaffected. Conversely, element formation from the central subset established from isolated anterior mesoderm was virtually identical to intact mesoblasts, indicating a capacity to regulate for the loss of mesoderm as occurs in situ (Hampé: Archs Anat Microsc Morph Exp 48:345-378, 1959).We interpret these findings to mean that limb mesoderm which forms the central subset is not merely competent to express in the absence of continuous ectodermal co-culture, a chondrogenic phenotype, but also retains intrinsic, limblike morphogenetic potential to form, regulate, and, to a variable extent, shape a reproducibly specific number of cartilage elements. Because the number of chondrogenic elements that formed in culture appeared stage-specific, a role for the apical ridge in specifying chondrogenic elements prior to its removal is supported. Indeed, our temporal findings correlate closely with the predictable truncation of leg skeletal structures following removal of the apical ridge in ovo, indicating that the endogenous ectodermal influence upon limb mesodermal morphogenesis can be assayed in vitro without the requirement of their continuous co-culture. © 1992 Wiley-Liss, Inc.

Notes: The following studies have been undertaken to compare and correlate the effects of 12-0-tetradecanoylphorbol acetate (TPA), basic fibroblast growth factor (bFGF), cholera toxin (CT), and isobutyl methylxanthine (IBMX) on neonatal human melanocyte (NHM) proliferation, tyrosinase activity, and cyclic adenosine monophosphate (cAMP) concentration. NHM proliferated at a maximal rate in medium containing 8 nM TPA, 200 ng/ml CT, and 10-4 M IBMX. TPA alone did not result in optimal melanocyte proliferation, and, as previously shown, its mitogenic effect was greatly enhanced by the addition of CT and IBMX individually or concomitantly. Human recombinant (hr) bFGF could replace TPA in the NHM growth medium. Maximal proliferation was achieved using 3 ng/ml hrbFGF, 20 ng/ml CT, and 10-4 M IBMX. The mitogenic effect of 1.2 ng/ml hrbFGF was potentiated in the concomitant but not individual presence of CT and IBMX. TPA alone in the absence of CT and IBMX caused a dose-dependent stimulation of tyrosinase activity. Maximal tyrosinase activity was obtained in the presence of 0.8 nM TPA, 20 ng/ml CT, and 10-4 M IBMX. Unlike TPA, hrbFGF alone resulted in inhibition of tyrosinase activity. In the presence of hrbFGF, tyrosinase activity was potentiated by CT and IBMX, but not by CT alone. Neither TPA nor hrbFGF alone could increase intracellular cAMP levels. The effects of CT and IBMX on intracellular cAMP concentration were enhanced to a greater extent by TPA than by hrbFGF. Under our experimental conditions, in the presence of hrbFGF, CT but not IBMX resulted in a dose-dependent increase in cAMP concentration. Further studies on NHM will be aimed at determining the exact role of protein kinase C (PKC) in regulating proliferation and melanogenesis and the mechanism(s) activated by hrbFGF.