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Biomedical subjects

M Young

Publications and source records attributed to M Young.

At least 163 records · Page 9Linked to original sources
PubMed1995

Adrenal steroids and cardiac fibrosis.

Uninephrectomized rats maintained on 0.9% NaCl as drinking fluid and infused for 8 weeks with aldosterone 0.75 micrograms/h via subcutaneous osmotic minipumps respond with hypertension, cardiac hypertrophy, and both interstitial and perivascular cardiac fibrosis. Similar animals injected with desoxycorticosterone (20 mg/week), or the glucocorticoid antagonist RU 486 (2 mg/day) show interstitial cardiac fibrosis to a lesser degree than animals injected with aldosterone, and show perivascular fibrosis to a greater degree. These findings suggest that glucocorticoid antagonist activity may play a role in exacerbating perivascular collagen deposition in response to chronic mineralocorticoid and salt imbalance.

Aldosterone↗
PubMed1995

Measurement and modeling of depth cue combination: in defense of weak fusion.

Various visual cues provide information about depth and shape in a scene. When several of these cues are simultaneously available in a single location in the scene, the visual system attempts to combine them. In this paper, we discuss three key issues relevant to the experimental analysis of depth cue combination in human vision: cue promotion, dynamic weighting of cues, and robustness of cue combination. We review recent psychophysical studies of human depth cue combination in light of these issues. We organize the discussion and review as the development of a model of the depth cue combination process termed modified weak fusion (MWF). We relate the MWF framework to Bayesian theories of cue combination. We argue that the MWF model is consistent with previous experimental results and is a parsimonious summary of these results. While the MWF model is motivated by normative considerations, it is primarily intended to guide experimental analysis of depth cue combination in human vision. We describe experimental methods, analogous to perturbation analysis, that permit us to analyze depth cue combination in novel ways. In particular these methods allow us to investigate the key issues we have raised. We summarize recent experimental tests of the MWF framework that use these methods.

Bayes Theorem↗
PubMed1995

A visual inspection protocol for measuring characteristics of used syringes.

This article reports on the use of a Visual Inspection Protocol (VIP) to measure observable characteristics of syringes deposited at the San Francisco needle exchange program. Syringes received by the program were evaluated by several inspectors using the VIP, and interrater reliability was assessed for each item. In Study I, syringes bearing individual markings made by the user (n = 568) were more likely to be capped at the point end and plunger end, and more often were new in appearance when compared with unmarked syringes (n = 2,820). In Study II, syringes with a short street life (n = 250) were more often new in appearance and were less likely to contain blood than syringes with a long street life (n = 246). Syringes having individual markings also show signs of more careful use, and marking syringes may represent an ad hoc HIV prevention strategy for some injection drug users.

HIV Infections↗
PubMed1995

TLC of p-nitroanilines and their analogues with cyclodextrins in the mobile phase.

The addition of alpha-, beta-, gamma-, and hydroxypropyl-beta-cyclodextrins to aqueous mobile phases can be used to enhance the migration of p-nitroanilines and their analogues on thin-layer chromatography. Urea, which is used to solubilize the cyclodextrins in aqueous solutions, is also found to increase the migration of these compounds. The equilibrium binding constants for the solute-cyclodextrin complexes formed in the mobile phase are determined. The results obtained using either silica gel or polyamide plates are similar.

Aniline Compounds↗
PubMed1995

The expression of antisense and ribozyme genes targeting citrus exocortis viroid in transgenic plants.

Four ribozyme and antisense genes targeting citrus exocortis viroid (CEVd) positive- and negative-strand RNA molecules were constructed and used to transform the tomato Lycopersicon lycopersicum cv. UC82B. The tomato is a readily transformable plant and will support replication of CEVd following mechanical inoculation. The ribozyme genes contained three hammerhead catalytic motifs with long hybridizing arms and synthetic RNA transcripts were shown to cleave the target CEVd RNA molecule in vitro. Homozygous transgenic plants were produced from independent transformants expressing either ribozymes or antisense constructs. Inoculation of transgenic seedlings expressing antisense constructs targeting the negative-strand CEVd RNA molecule with CEVd resulted in a moderate reduction in the accumulation of CEVd RNA. In contrast, similarly inoculated transgenic plants expressing constructs targeting the positive-strand CEVd RNA molecule resulted in an increase in the rate of CEVd RNA accumulation. Addition of the ribozyme motifs to the antisense genes did not enhance their efficiency in the suppression of viroid replication and a moderation or elimination of the observed antisense effects was seen in plants expressing the corresponding catalytic RNA-encoding genes.

Citrus↗
PubMed1995

Molecular genetics and the initiation of solventogenesis in Clostridium beijerinckii (formerly Clostridium acetobutylicum) NCIMB 8052.

A physical map of the Clostridium beijerinckii (formerly Clostridium acetobutylicum) NCIMB 8052 chromosome has been constructed, encompassing about 90 rare restriction sites. The 14 rrn operons together with about 40 genes have been assigned positions on the map. Genetic analysis and gene transfer have been developed in this organism to enable in vivo analysis of the roles of cloned genes using marker replacement technology. Experiments using the available genetic tools have shown that spo0A plays a cardinal role in controlling several aspects of the transition from exponential growth to stationary phase in C. beijerinckii. These include initiation of sporulation, accumulation of the storage polysaccharide, granulose, and production of acetone and butanol. Several C. beijerinckii and C. acetobutylicum genes concerned with fermentative metabolism, whose expression is modulated at the onset of solventogenesis, contain sequence motifs resembling 0A boxes in their 5' regulatory regions. This invites the speculation that they are under the direct control of Spo0A, and additional data are now required to test this prediction.

Base Sequence↗
PubMed1995

Physical map of the Clostridium beijerinckii (formerly Clostridium acetobutylicum) NCIMB 8052 chromosome.

A combined physical and genetic map of the single, circular, 6.7-Mbp chromosome of the NCIMB 8052 strain of Clostridium beijerinckii (formerly Clostridium acetobutylicum) has been constructed by using a combination of cloned DNA fragments as hybridization probes and a bank of strains harboring insertions of the conjugative transposon Tn1545. The positions of 81 restriction endonuclease cleavage sites and 32 genes have been determined. Eight genes concerned with solventogenic fermentation are found at three different locations. The chromosome contains at least 13 rrn operons, 11 of which have been located on the map. Their transcriptional orientation diverges from the presumed location of the replication origin.

Chromosome Mapping↗
PubMed1995

Hypogammaglobulinaemia secondary to reflux oesophagitis.

A 7 year old girl referred for investigation of hypogammaglobulinaemia had hypoalbuminaemia and severe necrotising oesophagitis on oesophagogastroduodenoscopy. Nissen fundoplication resolved all clinical and laboratory abnormalities, but she remains under surveillance because of histological findings of Barrett's oesophagus. Erosive reflux oesophagitis can present with minimal localising symptoms, and hypogammaglobulinaemia and hypoalbuminaemia, presumably from protein loss.

Agammaglobulinemia↗
PubMed1995

Determinants of cardiac fibrosis in experimental hypermineralocorticoid states.

Uninephrectomized rats maintained on 1.0% NaCl to drink and infused with aldosterone (0.75 microgram/h) for 8 wk have previously been shown to develop hypertension, cardiac hypertrophy, and cardiac fibrosis. In the present study we have shown that K+ supplementation (1.0% NaCl plus 0.4% KCl drinking solution) alters neither the interstitial nor the perivascular fibrotic response to mineralocorticoid treatment. Second, rats receiving 0.75 microgram/h 9 alpha-fluorocortisol, a mineralocorticoid and glucocorticoid agonist, respond with hypertension and cardiac fibrosis without cardiac hypertrophy. Finally, intracerebroventricular infusion of the mineralocorticoid receptor antagonist RU-28318 blocks blood pressure elevation, but not cardiac hypertrophy or fibrosis, when aldosterone is coinfused peripherally. We conclude that the myocardial fibrosis observed in response to chronic mineralocorticoid elevation and salt loading is a humorally mediated event independent of hypokalemia, hypertension, and cardiac hypertrophy. It remains to be determined whether the fibrosis observed in the presence of excess salt represents a direct (e.g., cardiac) effect of mineralocorticoid hormones or one mediated via a primary action on classical epithelial aldosterone target tissues (e.g., kidney).

Adrenalectomy↗
PubMed1995

Morbidity and mortality of infants born before arrival at the hospital.

Recently, a number of infants have been born at home, in an ambulance, car, etc., before arrival at the District of Columbia General Hospital. Many of these infants had poor outcome. To evaluate the prevalence and outcome of these infants, we reviewed medical records of all infants born before arrival at the hospital (out-born infants) and compared them with in-hospital deliveries from July 1988 to June 1992. Data were analyzed using Fisher's Exact Test and chi-square test. There were 151 (1.8%) out-born infants and 8,169 (98.2%) in-born infants during this 4-year period. Infants in both groups were predominantly black (85%). The following were significant differences (P < 0.001) between out-born and in-hospital deliveries, respectively: illicit drug exposure 35% vs 21%; low-birth-weight (< 2,500 g) infants 39% vs 16%; intensive care unit admissions 29% vs 15%; and neonatal deaths per 1,000 live births 80 vs 7. We conclude that there is a twofold increase in the morbidity (required intensive care) and an 11-fold increase in the mortality among out-born infants compared with infants delivered in-hospital. Even though out-born infants were < 2% of the total deliveries, they accounted for 17% of total neonatal mortality.

Black People↗
PubMed1995

The effects of Dynavision rehabilitation on behind-the-wheel driving ability and selected psychomotor abilities of persons after stroke.

OBJECTIVE: Many conventional rehabilitation exercises, such as pencil-and-paper and computer tasks, may not train perceptual and motor skills as applied to a complex, multiskill activity such as driving. The present study examined the usefulness of the Dynavision apparatus for driving-related rehabilitation. The Dynavision was designed to train visual scanning, peripheral visual awareness, visual attention, and visual-motor reaction time across a broad, active visual field. METHOD: Ten persons with a cerebrovascular accident participated in the study. All had failed behind-the-wheel driving assessments. Subjects participated in a 6-week Dynavision training program using exercises designed to impose various motor, perceptual, and cognitive demands. RESULTS: Dynavision training resulted in significantly improved behind-the-wheel driving assessments as compared to expected outcomes. Comparisons between pretests, posttests, and follow-up tests on a number of Dynavision, response, and reaction time variables showed significant improvements and maintenance effects. Dynavision performance, and, to a lesser extent, choice visual reaction and response times, were found to differentiate between persons assessed as safe and unsafe to drive, and between older and younger drivers. Subject self-reports suggested that a variety of training-related improvements had occurred in everyday functioning. CONCLUSION: Dynavision training shows some rehabilitative promise for improving driving and basic psychomotor skills. Future research on the benefits and limitations of this apparatus should use finer laboratory skill measures and more comprehensive tests of driving and daily functioning to assess more thoroughly skill improvements in persons after stroke.

Aged↗
PubMed1995

Postneonatal screening for congenital syphilis.

The incidence of congenital syphilis has recently reached epidemic proportions. With the resurgence of this important clinical entity, currently recommended screening procedures may be inadequate. We describe three cases that highlight the limitations of these screening procedures. All these infants had associated maternal risk factors for congenital syphilis, such as poor prenatal care and illicit drug use. All the infants and mothers were seronegative for syphilis at the time of birth but the infants became seropositive at 2 months of age. These cases support the need to reexamine current screening policies. In addition to prenatal and at-delivery screenings for congenital syphilis, it may be appropriate to screen infants born to high-risk mothers at 4 to 8 weeks of age.

District of Columbia↗