No description available.

No description available.

Polyphenoloxidases (EC 1.10.3.1) (PPO) were extracted from the skin layer between the muscle and exoskeleton, of lobster (Homarus americanus) by the successive steps of (NH$ sb4) sb2$SO$ sb4$ fractionation, ion-exchange chromatography and isoelectric focusing. The lobster 'PPO-fraction' recovered by the 40-80% (NH$ sb4) sb2$SO$ sb4$ fractionation step was found to exist in the inactive precursor form which required trypsin for activation and was inhibited by polyvinyl pyrrolidone (PVP). A comparative study of the lobster 'PPO-fraction' and the commercial tyrosinase from mushroom (EC 1.14.18.1) indicated that the two enzymes were similar with respect to substrate specificity, response to pH and selected inhibitors (cysteine, EDTA and PABA). However, both enzymes differed from one another in terms of their thermal and pH stabilities. Their catalytic efficiencies indicated that tyrosinase was better suited to catalyze oxidation of DOPA than lobster 'PPO-fraction'. Also, the activity of both enzymes were enhanced by copper. / Further purification of the 'PPO-fraction' by ion-exchange chromatography and preparative isoelectric focusing with a Rotofor unit yielded three isozymes designated PPO 1, PPO 11 and PPO 111. These isozymes had pI values of 3.89, 4.26 and 4.54 and molecular weights of 32,180, 35,480 and 39,300 respectively. The isozymes were similar with respect to their pH and temperature activity profiles but differed from one another (especially PPO 1 versus PPOs 11 and 111) in terms of their pH and thermal stabilities. They also exhibited varying degrees of differences in their catalytic efficiencies. All three isozymes were inhibited by PABA, EDTA and cysteine, with PABA being a competitive inhibitor, and EDTA or cysteine a noncompetitive inhibitor. Lower concentrations of ascorbate and mercaptoethanol had no effect on the isozymes. The free amino acid analysis suggested that melanosis might originate from the skin of the lobster.

Alpine melanism, a tendency to become darker with increased elevation and latitude, occurs in many species of butterflies. In Parnassius phoebus (Papilionidae) it has been assumed that alpine melanism is the result of adaptation to colder environments at higher elevations and latitudes, owing to the ability of darker wings to transfer more solar energy to the body as heat. I examined five independently variable components of wing melanism for agreement with this hypothesis, as well as the subsidiary hypothesis that size is inversely correlated to melanism because it also affects thermoregulation. Basal patch blackness (proportion of scales which are black) in both sexes is well correlated with elevation, latitude, and air temperature during the flight season. In males, increased basal patch blackness is advantageous because it increases the proportion of total time spent in flight looking for mates, but is locally disadvantageous because it increases the probability of dispersal. Basal patch width is only poorly correlated with elevation, latitude, and air temperature during the flight season in males, and not correlated in females. Increased patch width also results in increased flight activity, but does not affect dispersal. Basal wing transparency has little correlation with elevation, and no effect on activity, although it does slightly affect body temperature. Within individual mountains, distal wing blackness and transparency are correlated with elevation, but show no correlation when many mountains are considered together. Distal wing characters have no effect on flight activity or dispersal. Size is well correlated with elevation and latitude, but is less well correlated with air temperature. Smaller males disappear from the population more rapidly than large males, apparently through increased mortality because small males do not disperse more rapidly. Females disperse more than males, with larger females dispersing more than smaller females. Variation in basal patch blackness may have a similar adaptive significance in both sexes, but all the other melanism characters appear to have a different significance for each sex. I develop a new hypothesis for the mechanism of the effect of wing color on thermoregulation in dorsal basking butterflies. I suggest that most transfer of solar radiation to the body by the wings occurs while in flight, rather than while dorsal basking on a substrate. This hypothesis is used to explain the observation that the minimum levels of air temperature and solar radiation at which flight can occur does not depend on wing color in Parnassius phoebus, in contrast to phenotype dependent flight thresholds in lateral basking Colias. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Melanosis vesicae (or bladder melanosis) is a rare, benign condition referring to the presence of dark pigmented melanin deposits usually within the bladder mucosa. The clinical presentation can be mistaken for primary or metastatic melanoma of the bladder, and thus a histologic assessment is useful for ruling out a malignant diagnosis. All documented cases of melanosis vesicae have presented with urinary symptoms, including hematuria, symptoms of cystitis, incontinence and obstruction. This is a case report presenting a 57-year-old female with complaints of incomplete bladder emptying who met criteria for urinary retention. She underwent in-office cystoscopy and was found to have suspected melanosis vesicae. The diagnosis was later confirmed on pathology following a bladder biopsy. The next phase in care for this patient is planned sacral neuromodulation for treatment of urinary retention. Previous case reports of bladder melanosis have suggested an association with melanin deposition and inflammatory mechanisms and have not demonstrated malignant transformation during follow up. This is, to our knowledge, the first report of documented bladder melanosis in conjunction with urinary retention. Further studies are required to understand the etiology, clinical significance, and clinical correlation of melanosis vesicae with urinary dysfunction.

Thesis (M.Sc.(Physiological Chemistry)--University of the Witwatersrand, Faculty of Science, 1954.

Thesis (M.D.) -- University of Texas Southwestern Medical Center at Dallas, 2007. / Vita. Bibliography: pp. 18-19.

Black spot development or "melanosis" is a common defect in fresh shrimp which results in product being devalued and rejected by consumers. Currently, sulfiting agents are used to control melanosis in shrimp. However, with increasing regulatory and consumer concerns about the safety of sulphites as a method of melanosis control, the shrimp processing industry is actively seeking alternative methods to control melanosis on, and extend the shelf life of, fresh shrimp. One method which has the potential to fulfill both objectives is glucose oxidase (GOX)/glucose dipping solutions in conjunction with Modified Atmosphere Packaging (MAP). / Preliminary studies have shown that black spot development can be controlled for 14 days at 4$ sp circ$C in white shrimp (Pandalus occidentalis) and pink shrimp (Pandalus borealis) using GOX/glucose or GOX/glucose/ascorbic acid in conjunction with gas packaging (60% CO$ sb2$: 40% N$ sb2$). This dipping/packaging treatment also improves the physical, chemical and microbiological changes in white shrimp compared to samples dipped only in water and air packaged. This study has shown that the combined use of two or more "barriers" can be used to extend the shelf life of, and control melanosis on, fresh shrimp. This novel process of "dipping" shrimp in GOX/glucose solutions in conjunction with MAP will have a significant effect in the area of shrimp hygiene and will have the potential to minimize shrimp spoilage incurred through melanosis.

Many insect populations become darker at high elevations and high latitudes. Despite absence of empirical evidence, it is commonly believed that melanism allows more efficient basking by insects in sunlight, thereby raising body temperature and increasing activity. Variation in melanism within a single population of alpine Colias sulphur butterflies (Lepidoptera:Pieridae) allowed determination of the advantage, in cold environments, for this characteristic. Alternative hypotheses relating the effect of melanism to fecundity, predation, diel activity, and seasonal survivorship were tested by field and laboratory observation and experiment. At low temperature, melanistic females are more fecund. A balancing advantage for light coloured females does not exist at high temperatures. Dark individuals suffer lower predation rates at high altitude than do light individuals; the opposite is not true at low elevation. Duration of diel activity is markedly extended for darker butterflies under cool conditions, but only slightly for light individuals during warm sunny periods. Melanistic individuals are able to prolong the duration of activity for feeding, mate location, oviposition and escape from predation under cold conditions. This appears to the prime benefit for melanism in this population. This is the first demonstration, in a natural population, of the benefit of alpine melanism in insects. / Science, Faculty of / Zoology, Department of / Graduate