SURGICAL TREATMENT OF CONVERGENT STRABISMUS

In convergent strabismus, glasses, visual training and exercises are often helpful, but operation is usually needed in addition to produce a functional or cosmetic cure.Babies who are born cross-eyed should be examined early and nonsurgical treatment started so that proper visual appreciation will be developed in both eyes.Children in whom strabismus develops some time after birth (usually between 18 months and six years of age) should be examined with atropine, glasses prescribed when indicated and full medical treatment instituted. If those measures fail, operation should be done on one or both eyes, the operation depending on the magnitude of the deviation.     

THE MANAGEMENT OF STRABISMUS

The original causes of strabismus and the complications that develop from efforts by a child to adjust to the condition may present a complex diagnostic and therapeutic problem. The complications of suppression, amblyopia, contractures and anomalous visual habits may become more difficult to correct than the cause of the strabismus. The longer the duration of strabismus, the more complex the problem, the more difficult the treatment, and the less the probability of functional cure. Treatment should be started early. Correction may be brought about by the use of glasses, eye patches and orthoptic training, or by operation. If anatomic abnormality prevents bringing the eyes into line by conservative means, operation should be carried out after the best results possible by these means have been achieved. Surgical treatment, too, where it is indicated, should be done early, in order that normal binocular cooperation can develop before abnormal visual habits can become established.     

ELECTROMYOGRAPHY IN STRABISMUS

Electromyography of the human extraocular muscles is a new research tool designed to elucidate many problems in ocular physiology. Although at present it affords little clinical help in the diagnosis and treatment of strabismus, it may in time be of value in neuro-ophthalmologic disease.     

SYNTHESIS OF PEPTIDE-OLIGONUCLEOTIDE PHOSPHOROTHIOATE CONJUGATES BY CONVERGENT OR STEPWISE SOLID-PHASE STRATEGIES

A convergent strategy was employed to link eight 10–27-mer peptides to oligonucleotide phosphorothioates, resulting in twenty-six various conjugates. A stepwise synthesis strategy for the preparation of peptide-oligonucleotide phosphorothioate conjugates, employing Fmoc peptide chemistry, was developed and applied to the synthesis of four conjugates. Three of these conjugates contained either a 10 or 16-mer peptide, incorporating either 2 or 3 arginine residues, respectively.     

CONVERGENT EVOLUTION IN INVERTEBRATES

Resemblance between animal taxa may be due to convergence rather than to recent common ancestry. Constraints on biological materials and adaptation to particular habits or habitats will produce widespread convergence. How may we distinguish the two causes of resemblance? The relationship between convergence and taxonomy is discussed, demonstrating that the choice of taxonomic method will itself determine the extent to which convergence is perceived. In particular, cladistic analysis based on parsimony will tend to minimise and thus conceal convergence: neither the resulting cladogram nor a consistency index derived from it can be used to assess the prevalence of convergence. With any taxonomic system, there can be no substitute for evaluation of the morphological characters used. Complementary use of molecular characters shows promise: we wait further understanding of constraints in genetic evolution and of the possibilities of convergence at this level also. These general principles are illustrated with a range of examples from within and between invertebrate phyla: the phylogeny of Cnidaria and Platyhelminthes cannot be traced with certainty, but where the fossil record allows clear rooting, as for the echinoderms and in particular the echinoids, combination of morphological and molecular methods has made much progress. Sub-groups within a phylum, for example opisthobranch molluscs and the dipteran Phoridae, may show an uncontested phylogeny, and here studies have precisely identified convergence and shown that it may be the commoner cause of resemblance. Adaptation to exacting environments shown by terrestial and freshwater nemertines may also result in a predominance of convergent resemblance. Traditional grouping of phyla breaks down on re-examination of supposedly key characters, such as segmentation, body cavities, germ layers and symmetry, each of which must have had multiple origins: nor are developmental stages (especially not larvae) a reliable guide to relationships. Demarcation of phyla may be difficult, as with arthropods, and location of phyla is even more difficult, due to their early and rapid radiation. Over-simplified definition of characters has bedevilled invertebrate classification and the use of molecular data has not yet resolved the major controversies. The question ‘How common is convergence?’ remains unanswered and may be unanswerable. Our examples indicate that even the minimum detectable levels of convergence are often high, and we conclude that at all levels convergence has been greatly underestimated.     

壳斗科次生木质部水分输导分子间连接通道结构的研究

壳斗科次生木质部水分运输聚合体及其连接通道结构,根据水分运输方向可分纵向和横向两大系统。水分纵向运输通道有导管分子间的穿孔,导管分子侧壁间的管间纹孔,导管分子与无穿孔管状分子间的侧壁纹孔,无穿孔管状分子与无穿孔管状分子间的侧壁纹孔。