Showing papers by "Tulane University published in 1995"

Passage of Cytokines across the Blood-Brain Barrier

Abstract: One mechanism by which blood-borne cytokines might affect the function of the central nervous system (CNS) is by crossing the blood-brain barrier (BBB) for direct interaction with CNS tissue. Saturabl

Natural photolysis by ultraviolet irradiance of recalcitrant dissolved organic matter to simple substrates for rapidbacterial metabolism

Abstract: Whole leachate and humic and fulvic acid fractions of dissolved organic matter (DOM) released from senescent littoral aquatic plants were exposed to varying spectra of ultraviolet radiation as well as natural UV of sunlight over different periods of time. Examination of the DOM by solid-state 13C nuclear magnetic resonance and pyrolytic gas chromatography-mass spectrometry before and after photolysis revealed only subtle changes to the bulk DOM. However, the DOM exposed to natural UV radiation showed immediate stimulation of and sustained bacterial growth. Chemical analyses by high performance liquid chromatography (HPLC) of the small organic fractions generated by photolysis of humic substances showed marked, pro- ’ gressively increasing release of numerous small fatty acids, particularly acetic, formic, citric, pyruvic, and levulinic, among others. Use of radiolabeled humic substances demonstrated that these small compounds photolyzed from the humic substances were readily metabolized by the bacteria.

Age discrimination in simulated employment contexts: An integrative analysis.

Abstract: In the area of age discrimination in simulated employment settings, the present study meta-analytically tested 4 primary hypotheses derived from the social psychological stereotyping literature, referred to as the in-group bias, job information, salience, and job stereotype hypotheses. In general, the results supported the in-group bias, job information, and salience hypotheses, in that younger raters tended to give less favorable ratings to older workers when they were not provided with job-relevant information about the workers and when they concurrently rated old and young workers. Future research, including the initiation of research on economic-based age stereotypes, as well as practice directions related to valuing age diversity in organizationa l stakeholder groups are discussed. With the imminent aging of the labor force (cf. Forteza & Prieto, 1994; Warr, 1994), attitudes and beliefs about the aging work population are of critical importance to the quality of work life. Although older workers are sometimes perceived as being slower, less creative, less flexible, more resistant to change, disinterested in training, and prone to illness and accidents (Doering, Rhodes, & Schuster, 1983; Rhodes, 1983; Stagner, 1985), these beliefs often are inconsistent with the research literature. A number of empirical studies and research reviews (cf. Avolio, Waldman, & McDaniel, 1990; Forteza & Prieto, 1994; Mayrand, 1992; McEvoy & Cascio, 1989; Smith, 1990; Waldman & Avolio, 1986; Warr, 1994) have indicated that there is often a positive or no statistically significant association between a worker's age and many aspects of job performance. Despite this expanding body of knowledge, age discrimination with respect to employment decisions continues, as evidenced by the thousands of complaints filed each year under the Age Discrimina

Effect of recombinant human osteogenic protein-1 on healing of segmental defects in non-human primates.

Abstract: The effect of recombinant human osteogenic protein-1 on the healing of segmental bone defects was studied in twenty-eight African green monkeys (Cercopithecus aethiops). A 2.0-centimeter osteoperiosteal defect was created in the middle of the ulnar shaft in fourteen animals and in the diaphysis of the tibia in the other fourteen. The ulnar defect was filled with an implant consisting of 1000 micrograms of recombinant human osteogenic protein-1 in 400 milligrams of bovine bone-collagen carrier in six animals, with collagen carrier alone in two animals, and with autogenous cancellous bone graft from the contralateral tibia and femur in six animals. The tibial defect was filled with 250, 500 (two tibiae), 1000, or 2000 micrograms of recombinant human osteogenic protein-1 in 400 milligrams of collagen carrier in five animals, with collagen carrier alone in one animal, and with autogenous cancellous bone graft in six animals; in the two remaining animals (controls), the tibial defect was left unfilled. The tibial defects were stabilized with an intramedullary Steinmann pin. All animals were killed at twenty weeks postoperatively. Healing of the defects was evaluated with biweekly radiographs, with histological examination, and with mechanical testing. Radiographically, all of the defects that had been treated with recombinant human osteogenic protein-1 exhibited new-bone formation, but they differed in the degree of healing and remodeling. Five of the six ulnae treated with recombinant human osteogenic protein-1 and four of the five tibiae treated with this substance exhibited complete healing at six to eight weeks, with bridging of the defect by new bone first observed at four weeks. The two unhealed defects both exhibited new-bone formation but incomplete union, which precluded mechanical testing. No defect that had been filled with collagen carrier or that had been left unfilled exhibited any signs of healing or major new-bone formation. None of the six ulnae that had been filled with autogenous bone graft exhibited complete healing, compared with five of the six tibiae that had been so treated. Histological evaluation of the defects treated with recombinant human osteogenic protein-1 revealed the formation of new cortices with areas of woven and lamellar bone and normal-appearing marrow elements at twenty weeks postoperatively. The tibial defects that had been treated with autogenous bone graft had a similar appearance. All control ulnar and tibial defects and all ulnar defects that had been treated with autogenous bone graft had fibrous union with little new-bone formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of Oxidative Stress and Antioxidants in Male Infertility

Abstract: Oxygen toxicity is an inherent challenge to aerobic life, including spermatozoa, the cells responsible for propagation of the species. How this toxicity affects the spermatozoan in its interactions with the ovum is still unknown. An increase in oxidative damage to sperm membranes, proteins, and DNA is associated with alterations in signal transduction mechanisms that affect fertility. Recent evidence suggests that spermatozoa and oocytes possess an inherent but limited capacity to generate ROS to aid in the fertilization process. Though a variety of defense mechanisms encompassing antioxidant enzymes (SOD, catalase, and GSH peroxidase and reductase), vitamins (E, C, and carotenoids), and biomolecules (GSH and ubiquinol) are available, a balance of the benefits and risks from ROS and antioxidants appears to be necessary for the survival and functioning of spermatozoa. An assay system for the evaluation of OSS needs to be developed. Such an assay will assist the clinician in the assessment of fertility status of both male and female partners. The determination of this OSS value will also theoretically identify the subgroups of responders and nonresponders to any putative antioxidant therapy. Though the therapeutic use of antioxidants appears attractive, clinicians need to be aware of exaggerated claims of antioxidant benefits by various commercial supplements for fertility purposes until proper multicenter clinical trial have been completed.

Sliding mode observers. Tutorial

Abstract: Discusses the problem of designing observers for state estimation using sliding modes. The theory and design principles are presented for linear and nonlinear systems. For linear systems the observers are developed using a block-observable form which is similar to a lower triangular matrix form. Compared with known approaches such observers have better robustness properties. In the case of nonlinear systems an equivalent control concept makes it possible to develop finite-time observers for a wide class of systems.

Escaping the symmetry dilemma through a pair-density interpretation of spin-density functional theory

Abstract: In the standard interpretation of spin-density functional theory, a self-consistent Kohn-Sham calculation within the local spin density (LSD) or generalized gradient approximation (GGA) leads to a prediction of the total energy E, total electron density n(r)=${\mathit{n}}_{\mathrm{\ensuremath{\uparrow}}}$(r)+${\mathit{n}}_{\mathrm{\ensuremath{\downarrow}}}$(r), and spin magnetization density m(r)=${\mathit{n}}_{\mathrm{\ensuremath{\uparrow}}}$(r)-${\mathit{n}}_{\mathrm{\ensuremath{\downarrow}}}$(r). This interpretation encounters a serious ``symmetry dilemma'' for ${\mathrm{H}}_{2}$, ${\mathrm{Cr}}_{2}$, and many other molecules. Without changing LSD or GGA calculational methods and results, we escape this dilemma through an alternative interpretation in which the third physical prediction is not m(r) but the on-top electron pair density P(r,r), a quantity more directly related to the total energy in the absence of an external magnetic field. This alternative interpretation is also relevant to antiferromagnetic solids. We argue that the nonlocal exchange-correlation energy functional, which must be approximated, is most nearly local in the alternative spin-density functional theory presented here, less so in the standard theory, and far less so in total-density functional theory. Thus, in LSD or GGA, predictions of spin magnetization densities and moments are not so robust as predictions of total density and energy. The alternative theory helps to explain the surprising accuracy of LSD and GGA energies, and suggests that the correct solution of the Kohn-Sham equations in LSD or GGA is the fully self-consistent broken-symmetry single determinant of lowest total energy.

A Randomized Trial Comparing Fluconazole with Clotrimazole Troches for the Prevention of Fungal Infections in Patients with Advanced Human Immunodeficiency Virus Infection

Abstract: Background Cryptococcal meningitis and other serious fungal infections are common complications in patients infected with the human immunodeficiency virus (HIV). Fluconazole is effective for long-term suppression of many fungal infections, but its effectiveness as primary prophylaxis had not been adequately evaluated. Methods We conducted a prospective, randomized trial that compared fluconazole (200 mg per day) with clotrimazole troches (10 mg taken five times daily) in patients who were also participating in a randomized trial of primary prophylaxis for Pneumocystis carinii pneumonia. Results After a median follow-up of 35 months, invasive fungal infections had developed in 4.1 percent of the patients in the fluconazole group (9 of 217) and in 10.9 percent of those in the clotrimazole group (23 of 211; relative hazard, as adjusted for the CD4+ count, 3.3; 95 percent confidence interval, 1.5 to 7.6). Of the 32 invasive fungal infections, 17 were cryptococcosis (2 in the fluconazole group and 15 in the cl...

Successful Succession in Family Business

Abstract: Successful succession of CEOs is a crucial goal for family firms: without the next generations leadership and direct management, the firm cannot survive as a family firm, let alone maintain its character. When owner-managers retire, more than two-thirds of family firms cease or pass to new owners; less than one-third are continued by the next generation (Beckhard and Dyer, 1983; Emshwiller, 1989; Lansberg, 1988). If the owners of the firm want it to remain under family ownership and direction, then succession becomes a crucial strategic issue. For roughly nine out of ten U.S. businesses that are familyowned and run (a higher proportion in the rest of the free world), continuity is an issue. For family firms, successful succession begins many years before an offspring takes over as CEO. It is the lengthiest strategic process for family firms. It is a time when the old must help the young with educational and operational challenges, for potential successors must learn to take advantage of their families' values and special competencies as well as to develop their own expertise. The succession process in family firms involves numerous participants. The behavior and expectations of the CEO parent and employed offspring are affected by other family members, other executives in the firm, suppliers, bankers, and customers (Figure 1). For the succession process to unfold smoothly, key participants must come to feel comfortable with one another. This article presents a framework integrating the factors affectingsuccession and focuses on those factors that can be controlled by core players.1 Keyplayers must also deal effectivelywith uncontrollable environmental factors that influence the firm, but they should 110t pretend to manage them.i Our framework can be used as a checklist to help parents and offspring assess their succession process and identify major conflicts. Use it to indicate directions for positive change.

Effect of Body Size, Ponderosity, and Blood Pressure on Left Ventricular Growth in Children and Young Adults in the Bogalusa Heart Study

Abstract: Background The measurement of left ventricular mass (LVM) is important because individuals with increased LVM are at increased risk for cardiovascular diseases, including myocardial infarction and congestive heart failure. There are limited longitudinal data on the acquisition of LVM in children and young adults and the relative importance of sex, growth, excess body weight, and blood pressure (BP) on change in LVM. Methods and Results The study cohort consisted of a cross section of 160 healthy children and young adults 9 to 22 years of age at first exam in the biracial community of Bogalusa, La. All had stable BP levels recorded over a 2- to 3-year period. Repeated examinations were performed 4 to 5 years apart. At each exam, 6 BPs were obtained with a mercury sphygmomanometer by trained examiners. The mean of the observations was used, with the fourth Korotkoff phase serving as the measure of diastolic BP. Anthropometric data, including height (HT), weight (WT), and triceps skin fold thickness (TSF), w...

Digit tip regeneration correlates with regions of Msx1 (Hox 7) expression in fetal and newborn mice

Abstract: We report that during mouse fetal development transcripts of Msx1 and Msx2 become progressively restricted to cells that will form more distal digit structures; the Msx2 expression domain is always more distal than Msx1. At birth both Msx1 and Msx2 are expressed in cells of the nail bed and hair follicle. We have found that the regenerative ability of mouse digit tips is restricted to levels in which the amputation plane is within the region of Msx1, but not Msx2, expression in early fetal digits and to levels where both Msx1 and Msx2 are expressed in late fetal and neonatal digits. Fetal digit tip regeneration is rapid and completed by birth, whereas neonatal digit tip regeneration requires 4 weeks and is sometimes imperfect. In both fetal and neonatal digits, we find that both Msx1 and Msx2 are expressed during regeneration, but not during wound healing associated with proximal amputations where no regenerative response is observed. These data support the hypothesis that the expression of Msx genes are important for digit cells to initiate and participate in a regenerative response.

Children's Activity Levels and Lesson Context During Third-Grade Physical Education

Abstract: Little is known about children's activity levels during physical education classes and how they relate to the national health objectives for the year 2000 (U.S. Public Health Service, 1991). We systematically observed students' physical activity and associated variables in 293 third-grade physical education lessons in 95 schools in 4 Child and Adolescent Trial for Cardio-vascular Health (CATCH) centers in California, Louisiana, Minnesota, and Texas. The influence of independent variables was assessed simultaneously by analysis of variance. Significant differences among study centers were evidenced for both physical activity and lesson context variables. Additionally, there were differences among variables for lesson location and teacher specialty, but not for teacher gender. Boys were more active than girls, but only during free play opportunities. The findings have widespread implications for educators responsible for developing and implementing health-related physical education programs, as wel...

Identification and characterization of three Encephalitozoon cuniculi strains

Abstract: Microsporidia are increasingly recognized as causing opportunistic infections in immunocompromised individuals. Encephalitozoon cuniculi is probably the most studied mammalian microsporidian that infects insects and mammals, including man. In this study, 8 E. cuniculi isolates were compared and were found to fall into 3 strains. Strain type I includes the rabbit type isolate, as well as isolates from an additional rabbit, a dwarf rabbit, and a mouse. Strain type II includes 2 murine isolates and strain type III includes 2 isolates obtained from domestic dogs. By SDS-PAGE, the 3 strains differ primarily in the molecular weight range of 54-59 kDa where strain type I displays an apparent broad singlet at 57 kDa, strain type II displays an apparent doublet at 54 and 58 kDa, and strain type III displays an apparent broad band at 59 kDa. Antigenic differences were detected in the molecular weight regions of 54-58 kDa as well as 28-40 kDa by Western blot immunodetection using murine antisera raised against E. cuniculi, Encephalitozoon hellem, and the Encephalitozoon-like Septata intestinalis. Polymerase chain reaction (PCR) products containing only small subunit rDNA sequences from the different E. cuniculi isolates formed homoduplexes whereas PCR products containing intergenic rRNA gene sequences formed heteroduplexes in mobility shift analyses. Fok I digestion of the PCR products containing the intergenic rRNA gene region resulted in unique restriction fragment length polymorphism patterns, and DNA sequencing demonstrated that in the intergenic spacer region, the sequence 5'-GTTT-3' was repeated 3 times in strain type I, twice in strain type II, and 4 times in strain type III. This study indicates that there exist at least 3 E. cuniculi strains which may become important in the epidemiology of human E. cuniculi infections. Furthermore, as additional E. cuniculi isolates are characterized, these strains will be named or reclassified once the criteria for taxonomy and phylogenetic tree construction for microsporidia become better defined.

Health effects of experiences of sexual violence for women with abusive partners

Abstract: We assessed the incidence of sexual violence, physical violence, physical health symptoms, gynecological symptoms, and risk behaviors for contracting an STD or HIV infection in women who had used a shelter for women with abusive partners. In addition, we investigated the relationships between sexual violence and the frequency of physical health symptoms, including specific gynecological symptoms. Results indicated that one fourth of the women interviewed had experienced sexual violence and nearly two thirds of the women had experienced physical violence in the past 6 months. The incidence of physical health symptoms, gynecological symptoms, and risk behaviors for exposure to STDs and HIV infection are presented. The correlations among sexual violence, physical violence, and experiences of physical health symptoms are also reported. This study is particularly valuable because previous research has not documented the relationship between sexual violence and physical health symptoms.

Simulated Urban Climate Response to Modifications in Surface Albedo and Vegetative Cover

Abstract: Three-dimensional meteorological simulations have been conducted to investigate the potential impact of urban surface characteristic modifications on local climate. Results for a base case simulation for the Los Angeles basin are compared to results from cases in which urban albedo or vegetative cover are increased. The methodology for determining the distribution and magnitude of these simulated surface modifications is presented. Increasing albedo over downtown Los Angeles by 0.14 and over the entire basin by an average of 0.08 decreased peak summertime temperatures by as much as 1.5°C. This level of albedo augmentation also lowered boundary layer heights by more than 50 m and reduced the magnitude and penetration of the sea breeze. A second simulation, in which vegetative cover was increased, showed qualitatively similar impacts. The results from these simulations indicate a potential to reduce urban energy demand and atmospheric pollution by 5%–10% through application of reasonable surface mo...

Increased expression of Aspergillus parasiticus aflR, encoding a sequence-specific DNA-binding protein, relieves nitrate inhibition of aflatoxin biosynthesis.

Abstract: The aflR gene from Aspergillus parasiticus and Aspergillus flavus may be involved in the regulation of aflatoxin biosynthesis. The aflR gene product, AFLR, possesses a GAL4-type binuclear zinc finger DNA-binding domain. A transformant, SU1-N3 (pHSP), containing an additional copy of aflR, showed increased transcription of aflR and the aflatoxin pathway structural genes, nor-1, ver-1, and omt-1, when cells were grown in nitrate medium, which normally suppresses aflatoxin production. Electrophoretic mobility shift assays showed that the recombinant protein containing the DNA-binding domain, AFLR1, bound specifically to the palindromic sequence, TTAGGCCTAA, 120 bp upstream of the AFLR translation start site. Expression of aflR thus appears to be autoregulated. Increased expression of aflatoxin biosynthetic genes in the transformant might result from an elevated basal level of AFLR, allowing it to overcome nitrate inhibition and to bind to the aflR promotor region, thereby initiating aflatoxin biosynthesis. Results further suggest that aflR is involved in the regulation of multiple parts of the aflatoxin biosynthetic pathway.

Small Subunit Ribosomal DNA Phylogeny of Various Microsporidia with Emphasis on AIDS Related Forms

Abstract: Phylogenetic analysis of the small subunit ribosomal DNA of a broad range of representative microsporidia including five species from humans (Enterocytozoon bieneusi, Nosema corneum, Septata intestinalis, Encephalitozoon hellem and Encephalitozoon cuniculi), reveals that human microsporidia are polyphyletic in origin. Septata intestinalis and E. hellem are very similar to the mammalian parasite E. cuniculi. Based on the results of our phylogenetic analysis, we suggest that S. intestinalis be designated Encephalitozoon intestinalis. Furthermore, analysis of our data indicates that N. corneum is much more closely related to the insect parasite Endoreticulatus schubergi than it is to other Nosema species. This finding is supported by recent studies which have shown a similarity between E. schubergi and N. corneum based on the origin and development of the parasitophorous vacuole. Thus these opportunistic microsporidian parasites can originate from hosts closely or distantly related to humans. Finally, the phylogeny based on small subunit ribosomal DNA sequences is highly inconsistent with traditional classifications based on morphological characters. Many ofthe important morphological characters (diplokaryon, sporophorous vesicle, and meiosis) appear to have multiple origins.

Aberrant p53 Expression Predicts Clinical Resistance to Cisplatin-based Chemotherapy in Locally Advanced Non-Small Cell Lung Cancer

Abstract: The development of cisplatin-based induction chemotherapy followed by surgical resection or radiation has improved the poor prognosis of stage III non-small cell lung cancer (NSCLC). In vitro studies indicate that p53 can modulate cisplatin-induced cytotoxicity, but the molecular genetic features determining response or resistance to cisplatin in vivo must be defined. For this reason, tumor specimens from 52 patients with stage IIIA NSCLC entered in a prospective clinical trial of cisplatin-based induction chemotherapy followed by surgical resection were examined for p53 expression by immunohistochemical staining before and after induction chemotherapy. p53 expression was correlated with clinical and pathological response using Fisher's exact test. No correlation was established between p53 expression and clinical response because 47 of the 52 patients studied had a major response. However, a significant association was observed between aberrant p53 expression and resistance to chemotherapy as assessed by pathological response. Only 3 of the 20 patients whose tumors exhibited a high level (+ + to + + + +) of p53 staining experienced a major (+ + + to + + + +) pathological response to chemotherapy. Only 7 of 52 cases examined before and after chemotherapy treatment exhibited a change in the level of p53 expression after cisplatin-based chemotherapy. These results indicate that cisplatin alters p53 expression infrequently and suggest a direct link between aberrant p53 expression and resistance to cisplatin-based chemotherapy in NSCLC.