Showing papers by "University of Florida published in 1988"

Self-Organization, Transformity, and Information

Abstract: Ecosystems and other self-organizing systems develop system designs and mathematics that reinforce energy use, characteristically with alternate pulsing of production and consumption, increasingly recognized as the new paradigm. Insights from the energetics of ecological food chains suggest the need to redefine work, distinguishing kinds of energy with a new quantity, the transformity (energy of one type required per unit of another). Transformities may be used as an energy-scaling factor for the hierarchies of the universe including information. Solar transformities in the biosphere, expressed as solar emjoules per joule, range from one for solar insolation to trillions for categories of shared information. Resource contributions multiplied by their transformities provide a scientifically based value system for human service, environmental mitigation, foreign trade equity, public policy alternatives, and economic vitality.

Forward integration into distribution: An empirical test of transaction cost analysis

Abstract: The issue of forward vertical integration has attracted a good deal of attention from researchers in several disciplines, including economics, marketing, and law. Many explanations have been offered for this phenomenon, including technological interrelationships involving economies of scale and scope (Chandler), uncertainty and risk considerations (Arrow, 1969), information externalities (Green), and strategic purposes. Blair and Kaserman (1983) offer an extensive survey of the extant literature in this area. Of particular note, however, is the recent rise in prominence of the transaction costs analysis (TCA) of vertical integration. This approach consists of a blend of institutional economics, organizational theory, and contract law, and has been developed primarily by Oliver Williamson (1979, 1985). He views vertical integration as a response to the inability of arms-length market relationships to govern exchange efficiently under particular circumstances. The level of specialized assets' required to support the exchange, the uncertainty2 surrounding the exchange, and the frequency3 of exchange are

Ion-exchanged glass waveguides: a review

Abstract: Passive glass waveguides made by ion-exchange technique are potential candidates for integrated optics (IO) applications. The authors review the advantages in the technology as applied to fabrication of useful single-mode structures. Progress in process, fabrication, modeling, and waveguide performance using different monovalent cation systems and glass compositions is described with emphasis on fiber-compatible single-mode structures prepared from molten baths. It is shown how a systematic study allows a correlation between the process parameters and the waveguide characteristics so desirable in assuring reproducible characteristics of the devices. >

Site of G protein binding to rhodopsin mapped with synthetic peptides from the alpha subunit

Abstract: The interaction between receptors and guanine nucleotide binding (G) proteins leads to G protein activation and subsequent regulation of effector enzymes. The molecular basis of receptor-G protein interaction has been examined by using the ability of the G protein from rods (transducin) to cause a conformational change in rhodopsin as an assay. Synthetic peptides corresponding to two regions near the carboxyl terminus of the G protein alpha subunit, Glu311-Val328 and Ile340-Phe350, compete with G protein for interaction with rhodopsin. Amino acid substitution studies show that Cys321 is required for this effect. Ile340-Phe350 and a modified peptide, acetyl-Glu311-Lys329-amide, mimic G protein effects on rhodopsin conformation, showing that these peptides bind to and stabilize the activated conformation of rhodopsin.

Temporal relationship between bone loss and increased bone turnover in ovariectomized rats

Abstract: To characterize osteopenic changes in ovariectomized (OVX) rats as a function of time, female Sprague Dawley rats (240 g body weight, 90 days old) were subjected to bilateral ovariectomy or sham surgery and killed at various times from 14–180 days postovariectomy. The proximal tibial metaphysis was processed undecalcified for quantitative bone histomorphometry. Osteopenia and increased indices of bone resorption and formation were detected in OVX rats as early as 14 days. Longitudinal bone growth was also significantly increased by ovariectomy at 14 days, but returned to control levels at all later times. In OVX rats, osteopenia became progressively more pronounced with time up to 100 days postovariectomy, after which trabecular bone volume appeared to stabilize at the markedly reduced level of 5%. Changes in osteoclast surface, osteoblast surface, and fluoro-chrome-based indices of bone formation in OVX rats followed a similar time course. The maximal increase in these parameters occurred during the first several months postovariectomy followed by a gradual decline toward control levels. Our results indicate that the initial rapid phase of bone loss in OVX rats is coincident with the maximal increase in bone turnover. At later times postovariectomy, bone loss and bone turnover both subside. These findings emphasize the close temporal association between the development of osteopenia and increased bone turnover in OVX rats.

Adeno-associated virus general transduction vectors: analysis of proviral structures.

Abstract: We used two kinds of adeno-associated virus (AAV) vectors to transduce the neomycin resistance gene into human cells. The first of these (dl52-91) retains the AAV rep genes; the second (dl3-94) retains only the AAV terminal repeats and the AAV polyadenylation signal (428 base pairs). Both vectors could be packaged into AAV virions and produced proviral structures that were essentially the same. Thus, the AAV sequences that are required in cis for packaging (pac), integration (int), rescue (res), and replication (ori) of viral DNA are located within a 284-base-pair sequence that includes the terminal repeat. Most of the G418r cell lines (73%) contained proviruses which could be rescued (Res+) when the cells were superinfected with the appropriate helper viruses. Some produced high yields of viral DNA; other rescued at a 50-fold lower level. Most of the lines that were Res+ (79%) contained a tandem repeat of the AAV genome (2 to 20 copies) which was integrated randomly with respect to cellular DNA. Junctions between two consecutive AAV copies in a tandem array contained either one or two copies of the AAV terminal palindrome. Junctions between AAV and cellular sequences occurred predominantly at or within the AAV terminal repeat, but in some cases at internal AAV sequences. Two lines were seen that contained free episomal copies of AAV DNA. Res+ clones contained deleted proviruses or tandem repeats of a deleted genome. Occasionally, flanking cellular DNA was also amplified. There was no superinfection inhibition of AAV DNA integration. Our results suggest that AAV sequences are amplified by DNA replication either before or after integration and that the mechanism of replication is different from the one used during AAV lytic infections. In addition, we have described a new AAV general transduction vector, dl3-94, which provides the maximum amount of room for insertion of foreign DNA and integrates at a high frequency (80%).

ODP Leg 107 in the Tyrrhenian Sea: Insights into passive margin and back-arc basin evolution

Abstract: Leg 107 of the Ocean Drilling Program drilled a west-northwest-east-southeast transect of seven sites across the Tyrrhenian Sea, the youngest of the sub-basins of the Mediterranean Sea. Sites 654, 653, 652, and 656 document the rifting and subsidence of the Sardinia passive continental margin. On the upper margin (Site 654), we cored a classic transgressive sequence: subaerial conglomerates, overlain by oyster-bearing sands, overlain by marine marl. Comparison between the recovered lithologies and seismic reflection profiles suggests that the synrift sediments on the upper margin are Tortonian (late Miocene) to Messinian (latest Miocene) in age, whereas synrift sediments on the lower margin are Messinian to Pliocene in age. During the Messinian desiccation of the Mediterranean, Sites 654 and 653, now on the upper Sardinian margin, apparently occupied a basinal setting, where they received nannoplankton-bearing clays interbedded with laminated gypsum. Sites 656 and 652, now on the lower Sardinia margin, were apparently higher standing during the desiccation event; their Messinian facies are subaerial and lacustrine, respectively. We infer from these lines of evidence that tilting and subsidence occurred more than a million years earlier on the upper margin than on the lower margin. Such diachroneity can be interpreted in terms of migration of the zone of maximum extension above a "rolling-back" subduction zone, or in terms of extension of continental crust, by shear along a deep "detachment fault." Sites 655, 651, and 650 were drilled into two small basalt-floored basins of the central and eastern Tyrrhenian. Emplacement of basaltic crust in the central Tyrrhenian (Vavilov Basin) apparently began more than a million years before, emplacement of basaltic crust in the eastern Tyrrhenian (Marsili Basin). This observation is compatible with previous suggestions that the Tyrrhenian has grown southeastward in response to "rollback" of the down-going slab that currently dips northwestward under the toe of Italy. At the easternmost site, high vesicularity of the basalt and benthic foram assemblages in the oldest sediments imply that the basalt erupted in water shallower than 2,500 m. It has apparently subsequently subsided to its present depth of >4,100 m below sea level nearly three times as fast as normal subsidence of crust formed at a mid-ocean ridge.

Churches-as political communities

Abstract: Most studies of contextual influences on political attitudes and behavior have treated geographical areas as the operative social environment. As early research on social influence processes noted, the conditions that promote consensus among inhabitants of a common environment are likely to be present in formal organizations that encourage face-to-face interaction. Churches possess many of the characteristics that should maximize behavioral contagion and are thus fertile ground for the dissemination of common political outlooks. This expectation is tested by assessing the link between theological and political conservatism in 21 Protestant congregations. The theological climate in the churches is found to contribute strongly to the members' political conservatism over and above the personal commitment of respondents to traditional Christian values and a variety of social and attitudinal variables. As churches constitute the single most widespread form of voluntary organizational affiliation in the United States, their potential political impact appears to be considerable.

Terrorist bombings. Lessons learned from Belfast to Beirut.

Abstract: Experience in the management of mass casualties following a disaster is relatively sparse. The terrorist bombing serves as a timely and effective model for the analysis of patterns of injury and mortality and the determination of the factors influencing casualty survival in the wake of certain forms of disaster. For this purpose, a review of the published experience with terrorist bombings was carried out, providing a study population of 3357 casualties from 220 incidents worldwide. There were 2934 immediate survivors of these incidents (87%), of whom 881 (30%) were hospitalized. Forty deaths ultimately occurred among these survivors (1.4%), 39 of whom were among those hospitalized (4.4%). Injury severity was determined from available data for 1339 surviving casualties, 251 of whom were critically injured (18.7%). Of this population evaluable for injury severity, there were 31 late deaths, all of which occurred among those critically injured, accounting for an overall "critical mortality" rate of 12.4%. Overall triage efficiency was characterized by a mean overtriage rate (noncritically injured among those hospitalized or evacuated) of 59%, and a mean undertriage rate (critically injured among those not hospitalized or evacuated) of .05%. Multiple linear regression analysis of all major bombing incidents demonstrated a direct linear relationship between overtriage and critical mortality (r2 = .845), and an inversely proportional relationship between triage discrimination and critical mortality (r2 = 0.855). Although head injuries predominated in both immediate (71%) and late (52%) fatalities, injury to the abdomen carried the highest specific mortality rate (19%) of any single body system injury among immediate survivors. These data clearly document the importance of accurate triage as a survival determinant for critically injured casualties of these disasters. Furthermore, the data suggest that explosive force, time interval from injury to treatment, and anatomic site of injury are all factors that correlated with the ultimate outcome of terrorist bombing victims. Critical analysis of past disasters should allow for sufficient preparation so as to minimize casualty mortality in the future.

Neuroendocrine (Merkel cell) carcinoma of the skin. Its natural history, diagnosis, and treatment.

Abstract: Over 400 cases of neuroendocrine (Merkel cell) carcinoma of the skin (NCS) have been reported. This tumor continues to pose problems in diagnosis and effective treatment for physicians unfamiliar with its biological characteristics. Reported here are five additional cases of NCS and the literature for this rare neoplasm is comprehensively reviewed. An early and accurate diagnosis is made possible by combining clinical presentation with results of histologic study, immunoperoxidase staining for neuron-specific enolase (NSE), epithelial membrane antigen (EMA), cytokeratins, and electron microscopy. NCS is an aggressive tumor. Depending on the length of follow-up, up to 40% of tumors locally recur, 55% develop regional nodal metastases, and 36% undergo distant metastasis. Survival is sex, but not age, dependent, with an overall 2-year survival rate of 72% (males 58% vs. females 79%). No standard procedure for initial and/or follow-up treatment for NCS exists. The authors recommend that NCS be treated, whenever possible, using the same rationale as applied for the treatment of squamous cell carcinoma of the skin.

Estrogen Treatment Prevents Osteopenia and Depresses Bone Turnover in Ovariectomized Rats

Abstract: Female Sprague-Dawley rats were subjected to bilateral ovariectomy (OVX) or sham surgery (control). Groups of ovariectomized (OVX) and control rats were injected daily with low, medium, or high doses of 17β-estradiol (10, 25, or 50 μg/kg BW, respectively). An additional group of OVX and control rats was injected daily with vehicle alone. All rats were killed 35 days after OVX, and their proximal tibiae were processed undecalcified for quantitative bone histomorphometry. Trabecular bone volume was markedly reduced in vehicletreated OVX rats relative to that in control rats (12.1% vs. 26.7%). This bone loss was associated with a 2-fold increase in osteoclast surface and a 4-fold increase in osteoblast surface. The bone formation rate, studied with fluorochrome labeling, was also significantly elevated in vehicle-treated OVX rats (0.111 vs. 0.026 μ3/μm2.day). contrast, treatment of OVX rats with the three doses of estradiol resulted in normalization of tibial trabecular bone volume and a decline in histom...

Complications inherent in scaling the basal rate of metabolism in mammals

Abstract: The scaling of the basal rate of metabolism in mammals is reexamined. Both the power and level of the scaling function are sensitive to various factors that interact with body mass and rate of metabolism, including the precision of temperature regulation, food habits, and activity level. This sensitivity implies that the rate of metabolism is a highly plastic character in the course of evolution. Consequently, the singular effect of mass on the rate of metabolism is most effectively analyzed in ecologically and physiologically uniform sets of species, rather than in taxonomically defined groups, which often are ecologically and physiologically diverse. Otherwise, all fitted curves for mammals integrate a variety of competing factors, thereby reflecting the species used and denying unique analytic significance to the power in scaling relations. Kleiber's eutherian curve may represent a relatively uniform set of data because all the species included were domesticated and because selection for high rates of ...

Unified presentation of 1/f noise in electron devices: fundamental 1/f noise sources

Abstract: 1/f noise in semiconductors, semiconductor devices, and collision-free devices (like vacuum tubes) is presented from a unified point of view, using an extended version of the F.N. Hooge equation (Physica, vol. 83b, p.9, 1976), which is generalized to all collision-dominated systems involving mobility, diffusion, and cross-section fluctuations. It also applies to collision-free processes involving vacuum tubes, Schottky barrier diodes operating in the thermionic mode, and in devices such as p-i-n diodes in which collision processes are not the determining factor. A generalized schematic is given for expressing the noise spectrum S/sub 1/(f) in the external circuit in terms of distributed noise sources of the nonuniform devices in terms of alpha /sub H/, so the latter can be determined from the former. It is then found that the Hooge parameter. alpha /sub H/ introduced by this equation can be used as a general measure of the noisiness of a system or device. Several cases in which the noise does not obey the quantum 1/f noise theory are discussed. Measurements on many different devices are examined, and an attempt is made to correlate measured values of the Hooge parameter with the values calculated from P.H. Handel's quantum theory of 1/f noise (1975, 1980). >

Evaluation of Selectable Markers for Obtaining Stable Transformants in the Gramineae

Abstract: Cell suspension cultures of Triticum monococcum, Panicum maximum, Saccharum officinarum, Pennisetum americanum, and a double cross trispecific hybrid between Pennisetum americanum, P. purpureum, and P. squamulatum were tested for resistance to kanamycin, hygromycin, and methotrexate for use in transformation studies. All cultures showed high natural levels of resistance to kanamycin, in excess of 800 milligrams per liter, and variable levels of resistance to hygromycin. Methotrexate was a potent growth inhibitor at low concentrations with all species. Kanamycin and hygromycin were growth inhibitory only if added early (within 5 days after protoplast isolation and culture). Protoplasts of T. monococcum, P. maximum, S. officinarum, and the tri-specific hybrid were electroporated with plasmid DNA containing hygromycin (pMON410), kanamycin (pMON273), or methotrexate (pMON806) resistance genes. Resistant colonies were obtained at low frequencies (1 × 10−5 to 2 × 10−6) when selected under conditions which were growth inhibitory to protoplasts electroporated without DNA. Southern blot hybridization confirmed stable integration of plasmid DNA into T. monococcum using hygromycin vectors and P. maximum using the methotrexate vector with 1 to 10 copies integrated per haploid genome.

Edge Effects and Conservation of Biotic Diversity

Abstract: For three-quarters of a century the edge or zone of transition between different ecological associations has intrigued ecologists. The high diversity of plants and animals associated with edges and ecotones quickly became known as the edge effect principle, which is widely referred to as a fundamental concept of ecology (e.g., Wiens 1976). For the 55 years since enunciation as a game management principle, wildlife biologists have considered that "the potential density of game of low radius requiring two or more types is, within ordinary limits, proportional to the sum of the type peripheries" (Leopold 1933:132). Standard habitat management guides include the prescription to "create as much 'edge' as possible because wildlife is a product of the places where two habitats meet" (Yoakum & Dasmann 1971). But increasing emphasis on plant and nongame wildlife conservation during the last two decades has revealed many characteristics of edges and ecotones that are now considered undesirable. The term "ecotone" derives from the Greek root tonus, referring to tension. As originally coined, "ecotone" referred to the zone of tension between ecological communities. As it turns out, the term was a harbinger of tension that now exists between scientific communities. Debate about whether land managers should or should not continue to prescribe the creation of edges in the name of wildlife conservation now simmers in the wildlife profession and several land management agencies. This subject was the topic of a special session at the 1987 annual meeting of the Society for Conservation Biology. This introduction and three of the five papers presented in that session provided the historical and much of the contemporary basis for evaluating such land management decisions. As originally formulated, "The line that connects the points of accumulated or abrupt change ... is a stress line or ecotone" (Clements 1907:297). This as well as other early formulations clearly alluded to a onedimensional concept, and ornithologists such as Kendeigh (1944) and Johnston (1947) went so far as to conclude that bird densities should be reported as pairs per 100 acres for forest interior species, but pairs per mile of edge for edge species. Numerous indices aimed at assessing habitat interspersion and/or landscape diversity-for example, the shoreline index-are based on this one-dimensional aspect of edge (Welch 1948; Baxter & Wolfe 1972; Scheurholtz 1974; Patten 1974; Fried 1975; Ghiselin 1977; Taylor 1977; Thomas, Maser, & Rodiek 1979; Asherin, Short, & Roelle 1979; Hays, Summers, & Seite 1981). But confusion surrounding the nature of edges and ecotones emerged shortly after the concept was coined. Shelford (1913) clearly referred to a two-dimensional phenomenon when he stated "The forest margin, as we have seen, possesses in addition to the characteristic species . .. . " and Deventer (1936) treated swamp edge, forest edge, and fence row as though they were discrete habitat types. Johnston (1947) concluded her classic study by stating "The forest edge is considered to be a distinct community because it is inhabited by a characteristic set of species...." Beecher's (1942) analysis nearly foretold the current forest management quandary when he observed that forest margins only function as edge habitat when their extent is greater than some "minimum threshold acreage." Richard Yahner has published extensively on the topic of edge effects as they pertain to various groups of wildlife and his paper presented here reviews these various issues as they are understood by practicing wildlife ecologists and managers. Swynnerton was perhaps the first to be confronted with intrinsic contradictions of managing for edge ef-

Nonspecific factors involved in attachment of entomopathogenic deuteromycetes to host insect cuticle.

Abstract: The attachment of the conidia of the insect-pathogenic fungi Nomuraea rileyi, Beauveria bassiana , and Metarrhizium anisopliae to insect cuticle was mediated by strong binding forces. The attachment was passive and nonspecific in that the conidia adhered readily to both host and nonhost cuticle preparations. The hydrophobicity of the conidial wall and the insect epicuticle appeared to mediate the adhesion process. Detergents, solvents, and high-molecular-weight proteins known to neutralize hydrophobicity reduced conidial binding when added to conidium-cuticle preparations. However, these chemicals did not remove the hydrophobic components from the epicuticle or from conidial preparations. The outer surface of the conidium consists of a resilient layer of well-organized fascicles of rodlets. Intact rodlets extracted from B. bassiana conidia bound to insect cuticle and exhibited the hydrophobicity expressed by intact conidia. Both electrostatic charges and various hemagglutinin activities were also present on the conidial surface. However, competitive-inhibition studies indicated that these forces played little, if any, role in the adhesion process. Images

Attitudes and Farmer Conservation Behavior

Abstract: Conservation behavior is influenced by the attitudes of farmers and by context variables, like income and farm terrain. Important attitudes were selected by using the theory that fundamental value ranks or weights affect attitudes and that only certain values are important to the conservation decision. An extension of the tobit estimation approach, handling both censored observations of the dependent variable and measurement error for the nonlimit observations, was used. Conservation behavior models can be improved with a merger of concepts and approaches from social psychology and economics.

Inducing rules for expert system development: an example using default and bankruptcy data

Abstract: With rapidly growing interest in the development of knowledge-based computer consulting systems for various problem domains, the difficulties associated with knowledge acquisition have special importance. This paper reports on the results of experiments designed to assess the effectiveness of an inductive algorithm in discovering predictive knowledge structures in financial data. The quality of the results are evaluated by comparing them to results generated by discriminant analysis, individual judgments, and group judgments. A partial intersection of predictive attributes occurs. More importantly, for all cases tested, the inductively produced knowledge structures perform better than the competing models.

Tissue-specific regulation of zinc metabolism and metallothionein genes by interleukin 1.

Abstract: Interleukin 1 (IL 1) production is stimulated by infection, cellular injury, and inflammation. This cytokine directs a wide spectrum of host responses. Human interleukin 1 alpha (IL 1 alpha) was used to examine the time course of effects on zinc metabolism as part of the acute phase response. IL 1 produced a transient depression in the serum zinc concentration and increased serum ceruloplasmin. Metallothionein levels were increased in liver 14-fold after IL 1. Increased expression of metallothionein-1 and -2 genes following IL 1 were observed in liver, bone marrow, and thymus. Pulse-labeling experiments with i.v.-administered 65Zn showed that IL 1 drastically altered zinc distribution kinetics among tissues. More 65Zn was taken up (and/or retained) by the liver, bone marrow, and thymus 6 h after IL 1, whereas correspondingly less 65Zn was found in bone, skin, and intestine. Uptake by other tissues was not affected by IL 1. Chromatography of cytosol from tissues with increased 65Zn uptake suggests the IL 1-induced redistribution may be driven by enhanced metallothionein synthesis. Collectively, the results show that IL 1 regulates zinc metabolism and may direct its preferential, tissue-specific distribution via elevated metallothionein-1 and -2 gene expression.

Immunosuppression with azathioprine and prednisone in recent-onset insulin-dependent diabetes mellitus.

Abstract: We randomly assigned 46 patients (mean age, 11.7 years; range, 4.5 to 32.8) with newly diagnosed insulin-dependent diabetes mellitus within two weeks of beginning insulin to receive either corticosteroids for 10 weeks plus daily azathioprine for one year or no immunosuppressive therapy. Half the 20 immunosuppressed patients completing the one-year trial had satisfactory metabolic outcomes (hemoglobin A1c less than 6.8 percent; stimulated peak C peptide greater than 0.5 nmol per liter; insulin dose less than 0.4 U per kilogram of body weight per day) as compared with only 15 percent of the controls. Three of 20 immunosuppressed patients, but no controls, were insulin independent at one year. Two of these continue to receive azathioprine without insulin after more than 27 months of follow-up. The response to immunosuppression correlated with older age, better initial metabolic status, and lymphopenia (less than 1800 lymphocytes per cubic millimeter) resulting from immunosuppression. The side effects of azathioprine included vomiting in one patient and mild hair loss in several others. Prednisone use resulted in a transient cushingoid appearance, weight gain, and hyperglycemia. The growth rate remained normal in all patients. We conclude that early immunosuppression with short-term use of corticosteroids plus daily azathioprine can improve metabolic control in some patients with insulin-dependent diabetes mellitus, but results from this unblinded study are preliminary and require further confirmation and long-term follow-up.

Translocation of RNA-coated gold particles through the nuclear pores of oocytes.

Abstract: In the present study, various sized gold particles coated with tRNA, 5S RNA, or poly(A) were used to localize and characterize the pathways for RNA translocation to the cytoplasm. RNA-coated gold particles were microinjected into the nucleus of Xenopus oocytes. The cells were fixed after 15, 60 min, or 6 h, and the particle distribution was later observed by electron microscopy. Similar results were obtained with all classes of RNA used. After nuclear injection, particles ranging from 20-230 A in diameter were observed within central channels of the nuclear pores and in the cytoplasm immediately adjacent to the pores. Particles of this size would not be expected to diffuse through the pores, suggesting that some form of mediated transport occurred. In addition, it was found that the translocation process is saturable. At least 97% of the pores analyzed appeared to be involved in the translocation process. Gold coated with nonphysiological polynucleotides (poly[I] or poly[dA]) were also translocated. When nuclei were injected with either BSA-, ovalbumin-, polyglutamic acid-, or PVP-coated gold, the particles were essentially excluded from the pores. These results indicate that the accumulation of RNA-gold within the pores and adjacent cytoplasm was not due to non-specific effects. We conclude that the translocation sites for gold particles coated with different classes of RNA are located in the centers of the nuclear pores and that particles at least 230 A in diameter can cross the envelope. Tracer particles injected into the cytoplasm were observed within the nuclear pores in areas near the site of injection. However, only a small percentage of the particles actually entered the nucleus. It was also determined, by performing double injection experiments, that individual pores are bifunctional, that is, capable of transporting both proteins and RNA.

Star chromatic number

Abstract: A generalization of the chromatic number of a graph is introduced such that the colors are integers modulo n, and the colors on adjacent vertices are required to be as far apart as possible.

The effects of variations in the number and sequence of targeting signals on nuclear uptake.

Abstract: To determine if the number of targeting signals affects the transport of proteins into the nucleus, Xenopus oocytes were injected with colloidal gold particles, ranging in diameter from 20 to 280 A, that were coated with BSA cross-linked with synthetic peptides containing the SV-40 large T-antigen nuclear transport signal. Three BSA conjugate preparations were used; they had an average of 5, 8, and 11 signals per molecule of carrier protein. In addition, large T-antigen, which contains one signal per monomer, was used as a coating agent. The cells were fixed at various times after injection and subsequently analyzed by electron microscopy. Gold particles coated with proteins containing the SV-40 signal entered the nucleus through central channels located within the nuclear pores. Analysis of the intracellular distribution and size of the tracers that entered the nucleus indicated that the number of signals per molecule affect both the relative uptake of particles and the functional size of the channels available for translocation. In control experiments, gold particles coated with BSA or BSA conjugated with inactive peptides similar to the SV-40 transport signal were virtually excluded from the nucleus. Gold particles coated with nucleoplasmin, an endogenous karyophilic protein that contains five targeting signals per molecule, was transported through the nuclear pores more effectively than any of the BSA-peptide conjugates. Based on a correlation between the peri-envelope density of gold particles and their relative uptake, it is suggested that the differences in the activity of the two targeting signals is related to their binding affinity for envelope receptors. It was also determined, by performing coinjection experiments, that individual pores are capable of recognizing and transporting proteins that contain different nuclear targeting signals.

The meningioma controversy: postoperative radiation therapy.

Abstract: Total surgical excision is the main goal of therapy for intracranial meningiomas. The controversy today involves the efficacy of postoperative radiation therapy. To evaluate this question, 132 patients with benign intracranial meningiomas, treated between October 1964 and April 1985, were evaluated. All patients had a minimum 2-year follow-up. The actuarial local control rates at 10 years for the three treatment groups were as follows: subtotal excision alone, 18%; subtotal excision plus postoperative radiation therapy, 82%; and total excision alone, 77%. The actuarial determinate survival rates at 10 years were 49%, 81%, and 93%, respectively. Postoperative radiation therapy was also effective for patients treated at the time of the first recurrence, with an actuarial local control rate at 10 years after salvage treatment of 30% for patients treated with surgery alone and 89% for patients receiving postoperative radiation therapy at the time of salvage. This analysis suggests that radiation therapy has a significant role in the treatment of subtotally excised and recurrent intracranial meningiomas.