Popliteal-based filleted lower leg musculocutaneous free-flap coverage of a hemipelvectomy defect.

A 33-year-old man suffered from locally recurrent malignant fibrous histiocytoma of his left thigh unresponsive to previous excision, radiation therapy, chemotherapy, and hyperthermic treatment. He underwent radical hemipelvectomy for cure. Because of extensive tumor involvement, a free flap consisting of his distal left leg based on the popliteal artery was utilized to close the defect. Both the tibia and fibula were removed from their periosteal sheaths, and the foot was excised from the flap. The popliteal artery and vein were anastomosed to the iliac vessels. The flap survived, and the patient was discharged home after physical rehabilitation. We suggest that uninvolved portions of the distal leg may be utilized as a free flap to successfully close hemipelvectomy defects in selected patients when conventional pedicle flaps are unavailable.     

Metabolic cost of walking: equation and model

Twenty years of published experience with the Workman-Armstrong equation for predicting walking VO2 is reviewed. The equation is reexpressed in currently accepted terminology, and it is shown that the equation serves well as a basic model of normal walking. Employing this model to analyze VO2/step leads to the elaboration of a three-compartment model of the metabolic cost of walking. This three-compartment model provides a rational estimate of the fraction of walking's metabolic cost that powers the actual walking movement. Doubt is expressed that "comfortable speed of walking" is definable in energy terms. It is suggested that the requirements of maintaining balance while walking may determine both the comfortable speed of walking and the curvilinearity of the relationship between ground-speed and freely chosen step frequency of walking.     

Nucleoprotein hybridization: a method for isolating specific genes as high molecular weight chromatin

We describe a new technique designed to isolate specific eukaryotic genes as native oligonucleosome fragments. The isolation method consists of hybridization of single-stranded termini of chromatin restriction fragments to complementary mercurated DNA probes, followed by isolation of the hybrids by sulfhydryl-Sepharose chromatography. SV40 minichromosomes were used to test the effectiveness of the technique. About 80% of KpnI- or BamHI-restricted and lambda exonuclease treated SV40 minichromosomes hybridized to an appropriate DNA probe after a 12-h hybridization reaction under mild conditions (0.1 M aqueous salt, 37 degrees C, pH 8). When the restricted minichromosomes were mixed with a 15-fold excess of "background" chromatin from sea urchin embryos, nucleoprotein hybridization was able to reisolate the SV40 chromatin to 88% purity with a 63% yield. This represented a 115-fold enrichment of specific genes as chromatin. Results of electron microscopy and polyacrylamide gel electrophoresis indicate that the hybridized SV40 chromatin has not lost the major chromosomal proteins characteristic of SV40 nor acquired significant amounts of protein due to exchange with background chromatin. Our experimental results show that it is currently possible to isolate repeated genes from higher eukaryotes for structural and biochemical study of the proteins involved with gene regulation.     

A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera

Levels of mitochondrial DNA (mtDNA) sequence divergence between species within each of several avian (Anas, Aythya, Dendroica, Melospiza, and Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were compared. An analysis of digestion profiles generated by 13-18 restriction endonucleases indicates little overlap in magnitude of mtDNA divergence for the avian versus nonavian taxa examined. In 55 interspecific comparisons among the avian congeners, the fraction of identical fragment lengths (F) ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these translate into estimates of nucleotide sequence divergence (p) ranging from 0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater than 0.070. The small mtDNA distances among avian congeners are associated with protein-electrophoretic distances (D values) less than approximately 0.2, while the mtDNA distances among assayed fish and amphibian congeners are associated with D values usually greater than 0.4. Since the conservative pattern of protein differentiation previously reported for many avian versus nonavian taxa now appears to be paralleled by a conservative pattern of mtDNA divergence, it seems increasingly likely that many avian species have shared more recent common ancestors than have their nonavian taxonomic counterparts. However, estimates of avian divergence times derived from mtDNA- and protein-calibrated clocks cannot readily be reconciled with some published dates based on limited fossil remains. If the earlier paleontological interpretations are valid, then protein and mtDNA evolution must be somewhat decelerated in birds. The empirical and conceptual issues raised by these findings are highly analogous to those in the long-standing debate about rates of molecular evolution and times of separation of ancestral hominids from African apes.      

Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes

Statistical methods for computing the standard errors of the branching points of an evolutionary tree are developed. These methods are for the unweighted pair-group method-determined (UPGMA) trees reconstructed from molecular data such as amino acid sequences, nucleotide sequences, restriction-sites data, and electrophoretic distances. They were applied to data for the human, chimpanzee, gorilla, orangutan, and gibbon species. Among the four different sets of data used, DNA sequences for an 895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979) gave the least reliable one. The DNA sequence data suggested that the chimpanzee is the closest and that the gorilla is the next closest to the human species. The orangutan and gibbon are more distantly related to man than is the gorilla. This topology of the tree is in agreement with that for the tree obtained from chromosomal studies and DNA-hybridization experiments. However, the difference between the branching point for the human and the chimpanzee species and that for the gorilla species and the human-chimpanzee group is not statistically significant. In addition to this analysis, various factors that affect the accuracy of an estimated tree are discussed.      

Temporal and ontogenetic aspects of protein induction in foliage of the tomato, Lycopersicon esculentum

Damage to foliage of the tomato, Lycopersicon esculentum, causes the induction of proteinase inhibitors and of the oxidative enzymes polyphenol oxidase, peroxidase, and lipoxygenase. The time courses of induction of these proteins by feeding of two caterpillar species (Manduca sexta and Helicoverpa zea) were studied in a series of experiments. In another series of experiments, the effects of plant age on the inducibility of these proteins were studied. In the time course experiments, induction of proteinase inhibitors and oxidative enzymes in the damaged leaflet was rapid, with higher protein activities evident in damaged leaflets within 12–24 h of damage, depending on the enzyme and the species of insect used to damage the plant. Systemic induction of proteinase inhibitors was also rapid, but systemic induction of polyphenol oxidase was delayed relative to systemic induction of proteinase inhibitors, possibly because high constitutive polyphenol oxidase activities obscured expression of systemic induction at earlier time points. Lipoxygenase and peroxidase were not induced systemically. Induction of all proteins persisted for at least 21 days. In the phenology experiments, inducibility of all proteins decreased in magnitude and was less consistent as plants aged. The results of these experiments exemplify the numerous constraints on induction in tomato plants. Knowledge of these physiological constraints is important to an understanding of the ecological role and causal basis of induced resistance.