History of total nasal reconstruction with particular emphasis on the folded forehead flap technique

The history of plastic surgery is identified throughout the centuries with the history of rhinoplasty. The Indian Koomas first and later the Italian surgeons found valid solutions to the problems caused by partial loss of the nasal pyramid. However, the idea of rebuilding, with a single forehead flap, the tip and columella and providing at the same time a lining of skin for the newly formed nose goes back to the middle of the nineteenth century. The Italian Natale Petrali (1842) and the Germans Johann Friedrich Dieffenbach (1845) and Ernst Blasius (1848) contend for precedence in carrying out this important procedure still used today, which, barring postoperative contracture, represented a great advance in successful total rhinoplasty.     

Physiological effects of an allozyme polymorphism: Glutamate-pyruvate transaminase and response to hyperosmotic stress in the copepod Tigriopus californicus

In order to regulate cell volume during hyperosmotic stress, the intertidal copepod Tigriopus californicus, like other aquatic crustaceans, rapidly accumulates high levels of intracellular alanine, proline, and glycine. Glutamate-pyruvate transaminase (GPT; EC 2.6.1.2), which catalyzes the final step of alanine synthesis, is genetically polymorphic in T. californicus populations at Santa Cruz, California. Spectrophotometric studies of homogenates derived from a homozygous isofemale line of each of the two common GPT alleles indicated that the GPT^F allozyme has a significantly higher specific activity than the GPT^S allozyme. Under conditions of hyperosmotic stress, individual adult copepods of GPT^F and GPT^F/S genotypes accumulated alanine, but not glycine or proline, more rapidly than GPT^S homozygotes. When young larvae were subjected to the same hyperosmotic conditions, GPT^S larvae suffered a significantly higher mortality than GPT^F or GPT^F/S larvae. These results suggest that the biochemical differences among GPT allozymes result in specific physiological variation among GPT genotypes and that this physiological variation is manifested in differential genotypic survivorships under some naturally occurring environmental conditions.This work was supported in part by a grant from the Lerner Fund for Marine Research of the American Museum of Natural History, an NIH Training Grant in Integrative Biology, and NIH Grants GM 28016 and GM 10452.     

Analysis of normal somite development

We describe how the first 6 somite pairs form, using the third somites as examples. This history is based upon time-lapse movies of carbon-marked embryos and histological studies by light and electron microscopy of embryos fixed in situ with glutaraldehyde and osmium tetroxide. At head-process stage a continuous sheet of mesoblast occupies the regions of the future third somites. Mesoblast cells attach either to hypoblast or to overlying neural plate which is already a simple pseudostratified columnar epithelium. Prospective somite cells are those attached to the neuroepithelium, and they extend laterally exactly as far as the neural plate does. By head-fold stage, regression of the node down the midline is shearing the sheet of mesoblast into right and left halves. Somite cells hang from the bottom of the neural plate. As the neural plate condenses toward the midline, attached somite cells are compacted. When the somite segments, somite cells are tightly apposed to one another, and, in addition to junctions binding their basal ends, new junctions appear between their apical ends. This leads to reorganization into the typical somite rosette configuration. Spaces filled with extracellular materials form around the whole somite.     

Development of neuronal locus specificity in Xenopus retinal ganglion cells after surgical eye transection after fusion of whole eyes

A developmental program is established in the stage 28–32 optic cup of Xenopus embryos, which specifies the permanent AP and DV reference axes for positional information in the retina, and thereby determines the pattern of spatial deployment of ganglion cell locus specificities subserving assembly of retinotopically organized connections in the tectum. This developmental program has previously proved unmodifiable in intact eye primordia submitted to a variety of rotation, transplantation, and tissue culture conditions. Here we report that the program can be modified by surgical transection of stage 32 eye primordia (with subsequent fusion of the disconnected halves to reconstitute a whole eye) and by fusion of whole stage 38 eyes, although most of the transected eyes did develop normal visuotectal projections. The remaining vertically transected eyes, and all eyes formed when a left and right stage 38 eye fused along apposed temporal edges, developed “double-nasal compound” projections to the tectum: the nasal and temporal halves of the adult retina each projected to the entire tectum, and each tectal locus was driven from two stimulus positions symmetrically disposed about the vertical meridian. The remaining horizontally transected eyes, and all eyes formed when a left and right stage 38 eye fused along apposed dorsal edges, developed “double-ventral compound” projections to the tectum: the dorsal and ventral halves of the adult retina each projected to the entire tectum, and each tectal locus was driven from two stimulus positions symmetrically disposed about the horizontal meridian. The results are considered in terms of (1) the kinds of cellular processes that could mediate the observed modifications in the original developmental program; (2) the nature and stability of the program; and (3) the general suitability of eye fragment-fusion experiments for analysis of the assembly of retinotectal connections.     

Genetic Analysis of the Glutamate Permease in Escherichia coli K-12

The glutamate permeation system in Escherichia coli K-12 consists of three genes: gltC, gltS, and gltR. The genes gltC and gltS are very closely linked, and are located between the pyrE and tna loci, in the following order: tna, gltC, gltS, pyrE; gltR is located near the metA gene. The three glt genes constitute a regulatory system in which gltR is the regulator gene responsible for the formation of repressor, gltS is the structural gene of the glutamate permease, and gltC is most probably the operator locus. The synthesis of glutamate permease is partially repressed in wild-type K-12 strains, resulting in the inability of these strains to utilize glutamate as the sole source of carbon. Derepression due to mutation at the gltC locus enables growth on glutamate as a carbon source both at 30 C and at 42 C. Temperature-sensitive gltR mutants capable of utilizing glutamate for growth at 42 C but not at 30 C were found to be derepressed for glutamate permease when grown at 42 C and partially repressed (wild-type phenotype) upon growth at 30 C. These mutants produce an altered thermolabile repressor which can be inactivated by mild heat treatment (10 min at 44 C) in the absence of growth.