RESUMEN

The purpose of this study was to assess morphological differences between stunted and non-stunted white perch Morone americana and green sunfish Lepomis cyanellus. Few female M. americana were captured; thus, morphological differences between adult males and juveniles were assessed for M. americana. Similarly, few immature (juvenile) L. cyanellus were captured for the stunted morphotype; thus, male and female morphological differences were assessed for L. cyanellus. Features of the head tended to be relatively larger in stunted fish of both species, whereas the mid-body tended to be relatively larger in non-stunted M. americana, but not in non-stunted L. cyanellus. Adult and juvenile morphology overlapped considerably in non-stunted M. americana, but there was a clear distinction between adult and juvenile morphology of stunted M. americana. There was little sexual dimorphism in shape in stunted L. cyanellus, whereas sexual dimorphism was evident in non-stunted L. cyanellus. It appears that selective forces imposed by predation and food limitation may contribute to morphological diversification between stunted and non-stunted fishes.

Asunto(s)

RESUMEN

The bacterium Erwinia chrysanthemi is a model plant pathogen, responsible for causing cell death in plant tissue. Cell-wall depolymerizing enzymes and avirulence proteins essential for parasitism by this bacterium utilize dedicated type II and type III secretion systems, respectively. Although E. chrysanthemi is not recognized as a mammalian pathogen, we have observed that the bacterium can adhere to, cause an oxidative stress response in and kill cultured human adenocarcinoma cells. These bacteria express a surface protein that bears immunological identity to intimin, a protein required for full virulence of enterohemorrhagic and enteropathogenic Escherichia coli. A type III secretion mutant of E. chrysanthemi was observed to have a significantly lower capability of causing death than the wild-type strain in parallel cultures of human colon adenocarcinoma cells. These observations suggest that E. chrysanthemi has the potential to parasitize mammalian hosts as well as plants.

Asunto(s)

RESUMEN

The concept of an intrinsic "biological age" or "physiological age" is very important in comparative ecological and evolutionary studies, but its implementation has been problematic. Although many authors have discussed the importance of intrinsic measures of age over the past 75 years, only Reiss (1989 ) has proposed an operational definition in terms of cumulative metabolism; however, Reiss' measure cannot be easily applied to assessing the age of individual organisms. Measurement of the level of accumulation of fluorescent age pigments (particularly lipofuscins) in post-mitotic tissues, which seems to occur at a rate proportional to cumulative metabolism, in principle provides a mechanism for estimating the biological age of individual organisms. This study has shown that brain-tissue FAP levels vary in direct proportion to chronological age and body size within four species of poeciliid fishes, and has documented interspecific differences in rate of accumulation of fluorescent age pigments, differences that seem to be a function of the degrees of relatedness. Rather than proposing that FAP level by itself be used as a measure of biological age, however, I propose that it be used in conjunction with other estimates, such as chronological age and body size, to derive a composite "age factor."

Asunto(s)

RESUMEN

A morphological study of postlarval stages of the blacklegged tick, Ixodes scapularis Say, was conducted to examine congruence between northern (formerly I. dammini Spielman, Clifford, Piesman & Corwin) and southern morphotypes. The character set totaled 17 for females, 25 for males, and 28 for nymphs. Populations from 6 geographic areas, F1 progeny from reciprocal crosses between I. scapularis from Massachusetts and Georgia, and I. pacificus Cooley & Kohls from California were measured. Characters, except cornua length in nymphs, were positively correlated with PC1, indicating it was a general-size eigenvector. Characters used previously by others to distinguish northern and southern forms had a highly positive allometric relationship to general size. In canonical variate analysis (CVA) of nymphs, canonical score 1 (CAN1) discriminated I. pacificus from all other groups, canonical score 2 (CAN2) discriminated the remaining groups in a pattern that correlated with latitude, and canonical score 3 (CAN3) separated the western (Minnesota and Missouri) from the eastern groups. Size-free CVA indicated that north-south discrimination was size dependent, but that variation between Missouri and all other groups was not size related. Mahalanobis distances between groups within stages were significant with the exception of the 2 groups of female progeny of reciprocal crosses (Massachusetts x Georgia). Analysis of variance and Student-Newman-Keuls tests revealed that each geographic population differed from all other groups in at least 1 nymphal character. Nymphs from northern areas (Minnesota, Massachusetts, Maryland) differed from those from southern areas (Missouri, North Carolina, Georgia) in characters associated with the basis capitulum (longer intercornua and interauricular distances, basis capituli, and hypostome internal files, larger auriculae, but shorter cornua). Western populations (Minnesota, Missouri) differed from eastern populations in idiosomal characters (broader scutum, larger coxae III and IV). Frequency polygons of characters with the greatest differences indicated that data are continuous and geographic variation is overlapping. Thus, the data support the previous contention of conspecificity of I. scapularis and I. dammini. I. scapularis appears to be a polytypic species with a widespread geographic distribution exhibiting north-south and east-west morphological clines in eastern North America.

Asunto(s)

RESUMEN

OBJECTIVE: To evaluate the effects of aminophylline (Am) in children hospitalized with asthma. METHODS: Prospective, randomized, double-blind, placebo-controlled trial. Subjects were children between the ages of 5 and 18 years admitted for asthma exacerbation to either a tertiary care children's hospital or an inner-city general hospital in New York. Exclusion criteria were admission to the intensive care unit, initial theophylline level > 5 micrograms/dL, or the presence of other systemic disorders. All patients received nebulized albuterol therapy and intravenous glucocorticosteroids in standardized doses. Thirty-one patients were randomized to receive either an Am bolus followed by continuous Am infusion or placebo (P) bolus and infusion. The outcome variables were: duration of hospitalization, percent of predicted peak expiratory flow rates recorded at 12-hour intervals, number of albuterol treatments required, and adverse effects. RESULTS: There were no significant differences at study entry in age, sex, race, number of previous hospital admissions, prior medications used, clinical symptom scores, or initial peak flow rates for the two groups. For 26 patients who completed this study, 15 patients in the P group were hospitalized for a mean duration of 2.33 +/- 1.3 days, whereas 11 patients in the Am group required 2.58 +/- 1.5 days. There were no significant differences between the two groups for hospital days, peak flow rates at any time interval, or amount of albuterol therapy required (P > .2). In the Am group, 6 of the 14 patients who entered the study experienced significant adverse effects consisting of nausea, emesis, headache, abdominal pain, and palpitations. Only 1 of 17 patients in the P group had an adverse effect (P < .05). CONCLUSIONS: There is no benefit and considerable risk of adverse effects associated with the use of Am in hospitalized asthmatic children.

Asunto(s)

RESUMEN

In this paper, the ideas and concepts of expert systems were combined with the principles of fitness to demonstrate how an expert system could be designed to prescribe exercise routines for corporate employees. Since the examples and the rules of fitness used herein were just a small fraction of what could be used in building such a system, it would be possible to spend years developing a huge system that employs thousands of rules. However, as the supply of skilled labor continues to fall short of corporations' needs, more effort will be brought to bear on maintaining fitness in the work force. Such expert systems may be a reality in the not-too-distant future.

Asunto(s)

RESUMEN

Metamorphic vertebrate species are of particular interest in ecological and evolutionary studies because the decoupling of larval and adult growth patterns potentially allows adaptive diversifications of the separate stages. Larval and adult growth might be much more constrained if allometric patterns were constant throughout ontogeny. To better understand how differential growth patterns might contribute to tadpole diversification, we have analyzed growth allometries in relation to interspecific morphometric differences in Gastrophryne carolinensis, Acris gryllus, and Hyla gratiosa. Growth patterns in all species are significantly allometric and moderately concordant, despite many differences in detail. The species can be completely discriminated in even the smallest post-hatching tadpoles. However, the differences that distinguish the species do not seem to be a function of differential growth patterns at the tadpole stage. Rather, morphological differences ostensibly originate during embryonic development and are well established by the time the tadpoles become free-swimming.

Asunto(s)

RESUMEN

Archaeopteryx is almost universally considered a primitive bird. Debate persists, however, about the taxonomic assignment of the six skeletal fossils. Allometric scaling of osteological data shows that all specimens are consistent with a single growth series. The absence of certain bone fusions suggests that no specimen is full-grown. Allometric patterns, as compared to growth gradients of other dinosaurs, extant ectotherms, and extant endotherms, suggest that Archaeopteryx was likely a homeothermic endotherm with rapid growth and precocial abilities for running and flying. Multivariate allometric models offer a significant potential for interpreting ontogenetic patterns and phylogenetic trends in the fossil record.

Asunto(s)

Asunto(s)