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Biomedical subjects

C A Ryan

Publications and source records attributed to C A Ryan.

At least 109 records · Page 6Linked to original sources
PubMed1996

Sexual behaviors and risk factors for HIV infection among men who have sex with men in the Dominican Republic.

OBJECTIVE: To describe self-reported types of sexual identity of men who have sex with men (MSM) in the Dominican Republic, assess sociodemographics and behavioral characteristics, and measure the prevalence of HIV-1 and syphilis. DESIGN: Cross-sectional study of MSM recruited from a variety of community settings. METHODS: A total of 354 men agreed to participate after giving verbal informed consent. Information was obtained using a standardized questionnaire assessing demographics and AIDS-relevant information. Blood was obtained for HIV and syphilis testing. RESULTS: Five main sexual identity groups emerged: cross dressers, homosexuals, gigolos, bisexuals and heterosexuals. Receptive anal and oral intercourse were commonly reported by men self-identifying as cross dressers or homosexuals, whereas nearly all of the remaining three groups practiced only insertive intercourse. Sexual contact with women was also commonly reported; overall, consistent condom use was infrequent. HIV antibodies were detected in 11.0% and serologic evidence of syphilis was found in 7.3%. Factors independently associated with HIV infection included serologic evidence of syphilis, having visited at least one of four local brothels in 1975-1985, and having had receptive anal intercourse with four or more partners in the last 12 months. CONCLUSIONS: Syphilis, sexual practices and social context of sex (commercial sex), rather than sexual identity per se, were associated with HIV infection. The complex social networks of MSM in this setting, the tendency to practice either insertive or receptive sex, but not both, infrequent condom use, high rates of syphilis and the frequency of sex with women need to be taken into account for targeted HIV prevention programs to be successful.

Adolescent↗
PubMed1996

An octadecanoid pathway mutant (JL5) of tomato is compromised in signaling for defense against insect attack.

The activation of defense genes in tomato plants has been shown to be mediated by an octadecanoic acid-based signaling pathway in response to herbivore attack or other mechanical wounding. We report here that a tomato mutant (JL5) deficient in the activation of would-inducible defense genes is also compromised in resistance toward the lepidopteran predator Manduca sexta (tobacco hornworm). Thus we propose the name defenseless1 (def1) for the mutation in the JL5 line that mediates this altered defense response. In experiments designed to define the normal function of DEF1, we found that def1 plants are defective in defense gene signaling initiated by prosystemin overexpression in transgenic plants as well as by oligosaccharide (chitosan and polygalacturonide) and polypeptide (systemin) elicitors. Supplementation of plants through their cut stems with intermediates of the octadecanoid pathway indicates that def1 plants are affected in octadecanoid metabolism between the synthesis of hydroperoxylinolenic acid and 12-oxo-phytodienoic acid. Consistent with this defect, def1 plants are also compromised in their ability to accumulate jasmonic acid, the end product of the pathway, in response to wounding and the aforementioned elicitors. Taken together, these results show that octadecanoid metabolism plays an essential role in the transduction of upstream would signals to the activation of antiherbivore plant defenses.

Animals↗
PubMed1995

An international evaluation of the murine local lymph node assay and comparison of modified procedures.

The murine local lymph node assay is a predictive test for the identification of skin-sensitizing chemicals. The method has been the subject both of national inter-laboratory studies and of extensive comparisons with guinea pig tests. In the investigations reported here, the local lymph node assay has been evaluated further in the context of an international study comprising five independent laboratories. In addition, the influence of minor modifications to the standard assay procedure on the performance of the test has been examined. The modified procedures investigated were exposure of mice for 4 rather than 3 consecutive days, excision of lymph nodes 4 rather than 5 days after the initiation of exposure and the use of an alternative isotope. All five laboratories, irrespective of whether the standard or a modified protocol was used, were able to identify accurately, and with comparable sensitivity, potassium dichromate and 2,4-dinitrochlorobenzene as skin sensitizers. Using standard criteria, none of the laboratories recorded positive responses with methyl salicylate, a non-sensitizer. In the standard protocol, lymph nodes are pooled for each experimental group and the vigor of responses measured as a stimulation index relative to vehicle controls. A stimulation index of 3 or greater is considered to indicate skin-sensitizing potential. One further modification adopted by three of the laboratories was to analyze nodes from individual animals and, thereby, permit statistical evaluation. This allowed a direct comparison of statistical significance with the conventional stimulation index as criteria for a positive response. The data indicate that, while statistical evaluation may provide, in some instances, for small increases in sensitivity, this may be at the expense of some loss of selectivity. There are, however, insufficient data presently to draw firm conclusions regarding the relative value of statistical analysis. These studies demonstrate that the local lymph node assay is sufficiently robust to accommodate minor procedural and technical modifications without material changes in test performance.

Analysis of Variance↗
PubMed1995

Oligogalacturonides and chitosan activate plant defensive genes through the octadecanoid pathway.

Jasmonic acid, synthesized from linolenic acid (the octadecanoid pathway), has been proposed to be part of a signal transduction pathway that mediates the induction of defensive genes in plants in response to oligouronide and polypeptide signals generated by insect and pathogen attacks. We report here that the induction of proteinase inhibitor accumulation in tomato leaves by plant-derived oligogalacturonides and fungal-derived chitosan oligosaccharides is severely reduced by two inhibitors (salicylic acid and diethyldi-thiocarbamic acid) of the octadecanoid pathway, supporting a role for the pathway in signaling by oligosaccharides. Jasmonic acid levels in leaves of tomato plants increased several fold within 2 hr after supplying the polypeptide systemin, oligogalacturonides, or chitosan to the plants through their cut stems, as expected if they utilize the octadecanoid pathway. The time course of jasmonic acid accumulation in tomato leaves in response to wounding was consistent with its proposed role in signaling proteinase inhibitor mRNA and protein synthesis. The cumulative evidence supports a model for the activation of defensive genes in plants in response to insect and pathogen attacks in which various elicitors generated at the attack sites activate the octadecanoid pathway via different recognition events to induce the expression of defensive genes in local and distal tissues of the plants.

Journal Article↗
PubMed1995

Systemin activates synthesis of wound-inducible tomato leaf polyphenol oxidase via the octadecanoid defense signaling pathway.

Tomato plants overexpressing a prosystemin gene that encodes the precursor of a mobile wound signal called systemin have been shown previously to constitutively synthesize extraordinarily high levels of two defensive proteinase inhibitor proteins in leaves in the absence of wounding. We herein report that leaves of these transgenic plants possess enhanced levels of another defensive protein, polyphenol oxidase (PPO) at levels that are up to 70-fold higher than levels found in leaves of wild-type plants. Supplying young wild-type tomato plants with systemin through cut stems induced PPO activity in leaves, and wounding lower leaves of young tomato plants induced PPO activity in both wounded and unwounded leaves to levels equal to those induced by systemin. Exposing young tomato plants to methyl jasmonate vapor caused an increase in PPO activity equivalent to levels found in plants overexpressing the prosystemin gene. The data indicate that PPO and proteinase inhibitor genes are coactivated systemically by wounding via the octadecanoid signal transduction pathway and that systemin has a much broader role in signaling plant defensive genes than was previously known.

Acetates↗
PubMed1995

Characterization of two proteinase inhibitor (ATI) cDNAs from alfalfa leaves (Medicago sativa var. Vernema): the expression of ATI genes in response to wounding and soil microorganisms.

cDNAs encoding two Bowman-Birk proteinase inhibitors were isolated from the leaves of alfalfa (Medicago sativa). The cDNAs are derived from a small gene family (3 to 10 genes) encoding alfalfa trypsin inhibitors (ATIs). Each cDNA clone encoded a mature ATI that was part of a larger, putative preprotein. ATI mRNAs are continuously expressed in flower parts, but are mechanically wound-inducible in the stems and leaves. ATI mRNA is shown to be continuously present in roots of soil-grown plants, but its presence is primarily in response to microorganisms present in the soil. Additionally, while mechanical wounding of the alfalfa roots induced ATI mRNA synthesis both in the roots and in the leaves, microbial infection of the roots triggered ATI mRNA synthesis in the roots but not in the leaves. These results suggest that both local and systemic signalling pathways for proteinase inhibitor synthesis are present in alfalfa plants.

Amino Acid Sequence↗
PubMed1995

Radiological decompression of bowel gas and return of mediastinal shift in congenital diaphragmatic hernia: a signal for surgical repair?

The objective of this study was to document the pattern of bowel gas decompression and mediastinal shift in infants with congenital diaphragmatic hernia (CDH) before delayed surgical correction. The setting was the Neonatal Intensive Care Unit, Royal Alexandra Hospital, Edmonton. The design was a retrospective review of radiographs and charts of all infants with CDH between January 1990 and December 1993. Bowel gas in the upper and middle one third of the hemithorax was classified as grade III and grade II, respectively. Bowel gas in the lower one third of the hemithorax or absent bowel gas was classified as grade I. All the infants showed partial return of the contralateral shift in the mediastinum toward the midline when comparing the admission chest radiographs with the immediate preoperative films. Complete return of the mediastinum to normal (using the first postoperative radiograph as the gold standard) occurred in all but 1 of the 10 infants on extracorporeal membrane oxygenation (ECMO) (90%) and 7 of 13 (54%) of conventionally treated infants (P = .12). At the time of the first radiograph, a similar proportion of non-ECMO and ECMO infants (61% versus 70%, respectively) had either grade II or III bowel gas patterns. By 72 hours none of the non-ECMO-treated infants (who were paralyzed with muscle relaxants) had bowel gas in the middle and upper one third of the hemithorax. In contrast, 66% of infants on ECMO still had a grade II bowel gas pattern at 72 hours (P < .05), with 4 infants showing an actual increase in bowel gas after discontinuation of muscle relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Case-Control Studies↗
PubMed1995

Congenital diaphragmatic hernia: associated malformations--cystic adenomatoid malformation, extralobular sequestration, and laryngotracheoesophageal cleft: two case reports.

Two infants with unusual bronchopulmonary malformations associated with congenital diaphragmatic hernia (CDH) are presented. One infant had extralobular sequestration and cystic adenomatoid malformation of the lower lobe, in addition to a left-sided CDH. The second infant had a laryngotracheoesophageal cleft extending to the carina (type III) in addition to a left-sided CDH. These associated malformations can have major implications in terms of diagnosis, resuscitation, and surgical management of infants with CDH.

Abnormalities, Multiple↗
PubMed1995

Inhaled nitric oxide for premature infants after prolonged rupture of the membranes.

We evaluated the use of inhaled nitric oxide in eight premature infants (520 to 1440 gm, 24 to 31 weeks of gestation) who failed to respond to conventional management and who had prolonged rupture of the membranes and oligohydramnios. All infants had a significant improvement in oxygenation and a fall in mean airway pressure with inhaled nitric oxide. Further studies are required to determine the safety and efficacy of this form of therapy.

Administration, Inhalation↗
PubMed1995

Induction of wound response genes in tomato leaves by bestatin, an inhibitor of aminopeptidases.

Bestatin, an inhibitor of some aminopeptidases in plants and animals, is a powerful inducer of defense genes in tomato leaves; these genes are also induced by herbivore attacks, mechanical wounding, systemin, and methyl jasmonate. Unlike wounding and systemin, bestatin does not cause an increase in intracellular jasmonic acid concentrations, and inhibitors of the octadecanoid pathway do not inhibit induction by bestatin. Furthermore, defense genes were induced by bestatin in a mutant tomato line (JL-5) with a defect in the octadecanoid pathway. Bestatin therefore appears to be exerting its effects close to the level of transcriptional control of these genes, where it may be inhibiting a regulatory protease.

Aminopeptidases↗
PubMed1995

Antenatal corticosteroid therapy to prevent respiratory distress syndrome.

The recent National Institutes of Health Consensus Development Conference on ANS was strongly supportive of the use of ANS, even for 24 hours but, if possible, for 48 hours, in all fetuses between 24 and 34 weeks of gestation and at risk of preterm delivery regardless of race, gender, or the availability of surfactant replacement. For preterm rupture of membranes at less than 30 to 32 weeks, the use of ANS was also recommended in the absence of amnionitis, and patients eligible for tocolytic therapy were also deemed eligible for ANS. Thus the currently available literature indicates that pediatricians should encourage obstetricians to provide ANS in high-risk pregnancies, as outlined in the proposed National Institutes of Health guidelines. Even if a full 48-hour course of ANS cannot be achieved, ANS given less than 24 hours before delivery is associated with a decreased incidence of intraventricular hemorrhage and periventricular leukomalacia. In addition, we propose that investigators, reviewers, and editors ensure uniformly high maternal ANS exposure, consistent with the realities of clinical practice, when designing, evaluating, and publishing clinical trials with outcomes (e.g., RDS, intraventricular hemorrhage, periventricular leukomalacia, bronchopulmonary dysplasia, and death) that can be significantly affected by ANS. Otherwise, studies will continue to be performed on infants who, as fetuses, were deprived of treatment that may have prevented or ameliorated the disorder being assessed. Studies with an infrequent use of ANS may not be applicable or generalizable to an era when the use of ANS is an essential part of perinatal practice. Future trials should document both ANS use and the reasons for failure to achieve an acceptable level of such treatment.

Adrenal Cortex Hormones↗
PubMed1994

Identification of a 50-kDa systemin-binding protein in tomato plasma membranes having Kex2p-like properties.

A protein of 50-kDa (SBP50) was identified in plasma membranes of tomato leaves which resembles proteases of the family of Kex2p-like prohormone convertases. To our knowledge, proteases of this class have not been reported in plants previously. A biotinylated derivative of systemin, the 18-aa polypeptide inducer of proteinase inhibitors in tomato and potato leaves, was bound by SBP50 with high specificity. When a systemin derivative was labeled with biotin at residue 8 and with [35S]methionine at position 15, the biotin moiety but not the radioactive label was bound by SBP50. At least 4 aa from the C terminus that included [35S]methionine were missing, indicating that proteolytic cleavage had occurred. Whereas residues in systemin most important for binding SBP50 appear to be located in the N-terminal half of the molecule, amino acids crucial for proteinase inhibitor induction are located within the C terminus. The residues important for binding include a cleavage site for furin, a member of the family of Kex2p-like prohormone-processing enzymes. Processing of systemin at the predicted furin cleavage site was confirmed in vitro. An antiserum against a Kex2p-like protease from Drosophila inhibited binding of biotinylsystemin to SBP50 and recognized a protein of about 60 kDa in Western blot analyses of tomato plasma membrane proteins. The data suggest a possible role for a membrane bound, furin-like protease in the mechanism of defense gene signaling by systemin.

Amino Acid Sequence↗
PubMed1994

Overexpression of the prosystemin gene in transgenic tomato plants generates a systemic signal that constitutively induces proteinase inhibitor synthesis.

Tomato plants (Lycopersicon esculentum, var. Better Boy) were stably transformed with a gene consisting of the open reading frame of a prosystemin cDNA under the regulation of the cauliflower mosaic virus 35S promoter. The leaves of the transgenic plants constitutively produced proteinase inhibitor I and II proteins, which accumulated over time to levels exceeding 1 mg/g of dry leaf weight. This phenotype contrasts with that of untransformed plants, which produce proteinase inhibitor proteins in leaves only in response to wounding or chemical inducers. The transgenic plants were also stunted, although they appeared normal in all other respects. Grafting the upper half (scion) of an untransformed tomato plant onto the lower half (root stock) of a tomato plant expressing the prosystemin transgene resulted in the constitutive expression of proteinase inhibitor proteins in the leaves of both the transformed root stock and the untransformed scion, demonstrating that expression of the prosystemin transgene generates a mobile wound signal. These results show that systemic signal propagation in the transgenic plants does not require wounding, and they support the proposed role of systemin as the mobile wound signal.

Agrobacterium tumefaciens↗
PubMed1994

Extracorporeal membrane oxygenation in infants with congenital diaphragmatic hernia and cardiac malformations.

Since the introduction of neonatal extracorporeal membrane oxygenation (ECMO) in Canada, the authors have treated three infants with congenital diaphragmatic hernia (CDH) who had serious congenital cardiac anomalies (among 26 infants with CDH treated with ECMO). To determine the incidence of and outcome for infants with combined lesions who received ECMO, 19 years' data (April 1973 to October 1992) from the Extracorporeal Life Support Organization (ELSO) registry were reviewed. Seventeen infants with combined cardiac and diaphragmatic lesions were registered as receiving ECMO in the United States or Canada. Thus, the incidence of combined cardiac and diaphragmatic lesions was 2.5 per thousand neonates (17 of 6,295) receiving ECMO and 13 per thousand neonates (17 of 1,318) receiving ECMO for CDH. Five (29.4%) of the 17 infants survived. A congenital cardiac lesion may not be an absolute contraindication to ECMO in infants with CDH. Decisions to cannulate for ECMO should be based on the potential outcome of the underlying cardiac defect.

Canada↗