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B J Taylor

Publications and source records attributed to B J Taylor.

At least 37 records · Page 2Linked to original sources
PubMed2001

Molecular genetic dissection of the sex-specific and vital functions of the Drosophila melanogaster sex determination gene fruitless.

A multibranched hierarchy of regulatory genes controls all aspects of somatic sexual development in Drosophila melanogaster. One branch of this hierarchy is headed by the fruitless (fru) gene and functions in the central nervous system, where it is necessary for male courtship behavior as well as the differentiation of a male-specific abdominal structure, the muscle of Lawrence (MOL). A preliminary investigation of several of the mutations described here showed that the fru gene also has a sex-nonspecific vital function. The fru gene produces a complex set of transcripts through the use of four promoters and alternative splicing. Only the primary transcripts produced from the most distal (P1) promoter are sex-specifically spliced under direction of the sex-determination hierarchy. We have analyzed eight new fru mutations, created by X-ray mutagenesis and P-element excision, to try to gain insight into the relationship of specific transcript classes to specific fru functions. Males that lack the P1-derived fru transcripts show a complete absence of sexual behavior, but no other defects besides the loss of the MOL. Both males and females that have reduced levels of transcripts from the P3 promoter develop into adults but frequently die after failing to eclose. Analysis of the morphology and behavior of adult escapers showed that P3-encoded functions are required for the proper differentiation and eversion of imaginal discs. Furthermore, the reduction in the size of the neuromuscular junctions on abdominal muscles in these animals suggests that one of fru's sex-nonspecific functions involves general aspects of neuronal differentiation. In mutants that lack all fru transcripts as well as a small number of adjacent genes, animals die at an early pupal stage, indicating that fru's function is required only during late development. Thus, fru functions both in the sex-determination regulatory hierarchy to control male sexual behavior through sex-specific transcripts and sex-nonspecifically to control the development of imaginal discs and motorneuronal synapses during adult development through sex-nonspecific transcript classes.

Alleles↗
PubMed2001

Ventilatory responses to rebreathing in infants exposed to maternal smoking.

UNLABELLED: This study assessed the effect of maternal smoking during pregnancy on ventilatory and waking responses of infants to a respiratory challenge. This challenge mimicked the time-course and concentration of gases that an infant would experience rebreathing face-down into soft bedding. Control (C; n = 97) and smokers' infants (SM; n = 96) were studied at ages I and 3 mo. Asphyxial gas (hypercapnia/hypoxia) was delivered to the supine sleeping baby via a hood by slowly altering the inspired air: CO2 maximum 5% and O2 minimum 13.5%. Respiratory pattern was recorded by inductive plethysmography as the sum of ribcage and abdominal movements. The change in ventilation with inspired CO2 was measured over 5-6 min of the test. The slope of a linear curve fit relating inspired CO2 to the logarithm of ventilation was taken as a quantitative measure of ventilatory asphyxial sensitivity (VAS). Protective responses were graded from 1: no waking and an estimated arterial carbon dioxide tension (PaCO2) > or = 60 mmHg (least protective), to 4: fully awake (most protective). The results showed VAS was higher in SM infants than controls: +0.03 (p = 0.04). The oxygen saturation (SaO2) of SM infants fell -0.4% (p = 0.02) more than SaO2 of controls despite a greater tidal volume increase: +13.0% (p = 0.04). Overall protective responses were the same between groups, but grade 1, although rare, was found in 7 SM infants and only 4 control infants; this difference was not significant. CONCLUSION: The study did not confirm the postulate that infants of mothers who smoked during pregnancy have a reduced ventilatory response or raised waking thresholds.

Female↗
PubMed2000

Enrichment and localization of ganglioside G(D3) and caveolin-1 in shed tumor cell membrane vesicles.

Tumor cell ganglioside shedding has been implicated in the process of tumor formation. Previously, we identified three forms of tumor ganglioside shedding: micelles, monomers and membrane vesicles. Here, we have explored the membrane vesicle form of ganglioside shedding, using a newly identified human ovarian carcinoma cell line, CABA I. These cells synthesize and express a spectrum of gangliosides, including the disialoganglioside, G(D3). Immunostaining using the monoclonal antibody R24 confirmed G(D3) expression and its presence in the plasma membrane of these cells. Cellular gangliosides were detected in the culture supernatant by HPTLC autoradiography, confirming an active shedding rate of 3% of cellular gangliosides/24 h. CABA I cell membranes also express caveolin-1, a characteristic protein marker for caveolae, which was detected by flow cytometric analysis and by Western blotting in both the cell membranes and the isolated membrane vesicles. To further define the expression of G(D3) and caveolin-1, we used immunogold electron microscopy. This revealed localization of G(D3) in small clusters in the plasma membrane as well as enrichment and localization of ganglioside G(D3) and caveolin-1 in shed membrane vesicles, with 58-78% of vesicles carrying both G(D3) and caveolin-1. Together, these results suggest that membrane vesicle shedding originates in plasma membrane domains enriched in gangliosides and caveolin-1.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed2000

Spatial, temporal, and sexually dimorphic expression patterns of the fruitless gene in the Drosophila central nervous system.

The fruitless (fru) gene of Drosophila produces both sex-specifically and non-sex-specifically spliced transcripts. Male-specific fru products are believed to regulate male courtship. To further an understanding of this gene's behavioral role, we examined the central nervous system (CNS) for temporal, spatial, and sexually dimorphic expression patterns of sex-specific fru products by in situ hybridization and immunohistochemistry. For the latter, antibodies were designed to detect only male-specific forms of the protein (FRU(M)) or amino acid sequences that are in common among all translated products (FRU(COM)). Sex-specific mRNAs and male-specific proteins were first observed in mature larvae and peaked in their apparent abundances during the first half of the pupal period. At later stages and in adults, faint mRNA signals were seen in only a few neural clusters; in contrast, relatively strong FRU(M) signals persisted into adulthood. Twenty neuronal groups composed of 1700 fru-expressing neurons were identified in the midpupal CNS. These groups overlap most of the neural sites known to be involved in male courtship. Anti-FRU(COM) led to widespread labeling of neural and nonneural tissues in both sexes, but in the female CNS, only in developing ganglia in a pattern different from that of the male's FRU(M) cells. Expression of sex-specific fru mRNAs in the CNS of males analyzed from the earliest pupal stages indicated that sex-specific alternative splicing is not the exclusive mechanism regulating expression of fruitless transcripts.

Animals↗
PubMed2000

Vasoconstriction following spontaneous sighs and head-up tilts in infants sleeping prone and supine.

The cutaneous vasoconstrictor responses following a 60 degrees head-up tilt and a spontaneous sigh were measured in 36 infants at 1 and 3 months age to investigate the effects of age, sleep state and sleep position on these responses. The vasoconstrictor response was determined by a measure of cutaneous blood flow using a laser Doppler flowmeter. The mean reduction in blood flow (vasoconstriction) was 52% following the tilt, and 33% following the sigh. Prone positioning 1-month-old infants as compared to supine, reduced the degree of vasoconstriction following the tilt (P=0.027) and sigh (P=0.026). The supine to prone reduction was: tilt, -11% in quiet sleep (QS) (from 55.1 to 49.1% vasoconstriction) and -18% in active sleep (AS) (from 52.0 to 42.9%) and; sigh, -26% in QS (35-26%), and -15% in AS (31-26%). The degree of vasoconstriction following the sigh was significantly greater in 3- compared to 1-month-old infants (+26%, P=0.040). The mean response to the tilt in the older age group was 12% greater but this did not reach significance (P=0.069). Sleep state did not affect the degree of vasoconstriction but influenced transmission of the response so that latency to minimal vasoconstriction was 1 s shorter in AS than QS. This study provides data on two simple measures of sympathetic activity during sleep that have not previously been described in any detail in infant studies, and add more evidence that autonomic activity is reduced in the prone position compared to supine during sleep.

Female↗
PubMed2000

Modeling prevention program effects on growth in substance use: analysis of five years of data from the Adolescent Alcohol Prevention Trial.

The efficacy of prevention programs is typically determined through analysis of covariance. To date, a growth curve modeling approach is not used extensively in program evaluation. However, for longitudinal data there are several advantages to using this approach as compared to methods comparing means at two time points in a piecemeal fashion. In this study, latent growth curve models were used to evaluate the effect of a program on the average level of drug use, rate of change (growth) of drug use, and acceleration or deceleration in the rate of change of drug use. The study relied on data from the Adolescent Alcohol Prevention Trial, a randomized longitudinal drug use prevention program. The program consists of drug use information, resistance skills training, and normative education components. Data regarding cigarette and alcohol use were collected over a 5-year period, grade 7 to grade 11. Students receiving the normative education program had significantly lower average levels of reported cigarette and alcohol use, lower rates of growth for reported cigarette and alcohol use, and less deceleration of reported levels of cigarette and alcohol use as compared with the control group. Growth curve analysis is a powerful and effective tool with which to model change and program efficacy.

Adolescent↗
PubMed2000

Aberrant splicing and altered spatial expression patterns in fruitless mutants of Drosophila melanogaster.

The fruitless (fru) gene functions in Drosophila males to establish the potential for male sexual behaviors. fru encodes a complex set of sex-specific and sex-nonspecific mRNAs through the use of multiple promoters and alternative pre-mRNA processing. The male-specific transcripts produced from the distal (P1) fru promoter are believed to be responsible for its role in specifying sexual behavior and are only expressed in a small fraction of central nervous system (CNS) cells. To understand the molecular etiology of fruitless mutant phenotypes, we compared wild-type and mutant transcription patterns. These experiments revealed that the fru(2), fru(3), fru(4), and fru(sat) mutations, which are due to P-element inserts, alter the pattern of sex-specific and sex-nonspecific fru RNAs. These changes arise in part from the P-element insertions containing splice acceptor sites that create alternative processing pathways. In situ hybridization revealed no alterations in the locations of cells expressing the P1-fru-promoter-derived transcripts in fru(2), fru(3), fru(4), and fru(sat) pharate adults. For the fru(1) mutant (which is due to an inversion breakpoint near the P1 promoter), Northern analyses revealed no significant changes in fru transcript patterns. However, in situ hybridization revealed anomalies in the level and distribution of P1-derived transcripts: in fru(1) males, fewer P1-expressing neurons are found in regions of the dorsal lateral protocerebrum and abdominal ganglion compared to wild-type males. In other regions of the CNS, expression of these transcripts appears normal in fru(1) males. The loss of fruitless expression in these regions likely accounts for the striking courtship abnormalities exhibited by fru(1) males. Thus, we suggest that the mutant phenotypes in fru(2), fru(3), fru(4), and fru(sat) animals are due to a failure to appropriately splice P1 transcripts, whereas the mutant phenotype of fru(1) animals is due to the reduction or absence of P1 transcripts within specific regions of the CNS.

Amino Acid Sequence↗
PubMed2000

Ventilatory sensitivity to mild asphyxia: prone versus supine sleep position.

AIMS: To compare the effects of prone and supine sleep position on the main physiological responses to mild asphyxia: increase in ventilation and arousal. METHODS: Ventilatory and arousal responses to mild asphyxia (hypercapnia/hypoxia) were measured in 53 healthy infants at newborn and 3 months of age, during quiet sleep (QS) and active sleep (AS), and in supine and prone sleep positions. The asphyxial test mimicked face down rebreathing by slowly altering the inspired air: CO(2), maximum 5% and O(2), minimum 13.5%. The change in ventilation with inspired CO(2) was measured over 5-6 minutes of the test. The slope of a linear curve fit relating inspired CO(2) to the logarithm of ventilation was taken as a quantitative measure of ventilatory asphyxial sensitivity (VAS). Sleep state and arousal were determined by behavioural criteria. RESULTS: At 3 months of age, prone positioning in AS lowered VAS (0.184 prone v 0.269 supine, p = 0.050). At newborn age, sleep position had no effect on VAS. Infants aged 3 months were twice as likely to arouse to the test than newborns (p = 0.013). Placing infants prone as opposed to supine increased the chances of arousal 1.57-fold (p = 0.035). CONCLUSION: Our findings show 3 month old babies sleeping prone compared to supine have poorer ventilatory responses to mild asphyxia, particularly in AS, but the increased prevalence of arousal is a protective factor.

Arousal↗
PubMed2000

The effect of cold stimulation to the face on the metabolic rate of the febrile piglet.

Sudden infant death syndrome has been associated with winter climates, infection, and overwrapping of babies. The hypothesis has been tested in this laboratory that two different causes of increased metabolic rate, high core temperature (via the van't Hoff or 'Q10' effect) and face-cooling, might synergistically induce hyperthermia. This proved not to be the case. We now report on a 'febrile' state adding Salmonella abortus equi pyrogens. The combination of face-cooling and pyrogen administration to 14 already hot piglets produced an increase in oxygen consumption of 47% in 6 of the animals (19% overall). Face-cooling alone caused a 6.5% fall in oxygen consumption, and injection of pyrogens alone had no effect on oxygen consumption. We conclude that there may be a danger of life-threatening hyperthermia in the combination of a cold face and febrile state.

Animals↗
PubMed2000

Factors affecting heart rate variability and heart rate responses to tilting in infants aged 1 and 3 months.

Heart rate variability (HRV) and heart rate (HR) responses following a 60 degree head-up tilt were measured in 60 infants at 1 and 3 mo of age to investigate the effects on these of age, sleep state, sleep position, and mother's smoking status. HRV was determined from Poincaré plots of 500 sequential RR intervals to measure overall variability derived from the SDRR of this plot, and instantaneous variability derived from the SDdeltaRR. HR responses to the tilt were measured as changes in RR interval length from rest to immediately following the tilt and again once a stable pattern was reached. SDRR and SDdeltaRR increased 20 and 40%, respectively, with age (p < 0.0001), SDRR was higher in active sleep (AS) than quiet sleep (QS, +72%, p < 0.0001) but both measures of variability (SDRR and SDdeltaRR) were lower in the prone position compared with supine (-18%, p < 0.0001). However, several findings were dependent on the basal RR interval, thus the age effect disappeared once RR interval was taken into account, sleep state remained an important factor and the lower variability when prone now became a difference of -3% (p = 0.034). The tilt generally provoked a reflex tachycardia followed by a bradycardia and settling to a stable HR level below, at, or above baseline within 30 s. The more unusual responses were no HR change, sustained tachycardia or sustained bradycardia (15% of total). These were more likely to occur in younger infants (p = 0.008) and in AS (p < 0.0001). No changes were seen in any of the cardiac indices related to maternal smoking status. The findings confirm several reports indicating that prone sleeping damps some physiologic responses. The data emphasize the need to consider basal heart rate, and sleep position as well as sleep state in autonomic function testing during infant sleep.

Female↗
PubMed1999

Water fluoridation and the sudden infant death syndrome.

AIMS: To determine whether exposure to fluoridated water supplies prenatally or postnatally at the time of death increases the risk of sudden infant death syndrome (SIDS). METHODS: A nationwide, case-control study, with infant's water fluoridation status determined from census area unit information for mother's usual address at the time of the infant's birth, infant's usual address at the time of death / nominated sleep and address where infant died / was at nominated sleep. SIDS risk associated with fluoride exposure postnatally was assessed according to method of infant feeding (breast or reconstituted formula), for the two days prior to infant's death / nominated sleep. RESULTS: Infants exposed to fluoridated water supplies during pregnancy were not at increased risk for SIDS, adjusted odds ratio (OR) 1.19 (95% confidence interval (CI) 0.82, 1.74). For breast-fed infants at the time of death / nominated sleep, fluoridated water exposure was not associated with an increased risk for SIDS, adjusted OR 1.09 (95% CI 0.66, 1.79). Similarly, 'fluoridated' formula feeding, when compared with 'unfluoridated' formula feeding, showed no increased risk of SIDS, adjusted OR 1.25 (95% CI 0.73, 2.13). There was no evidence of an interaction between fluoridation and infant feeding for the last two days (chi2 = 0.171, df = 1, p = 0.68). CONCLUSION: Exposure to a fluoridated water supply prenatally or postnatally at the time of death did not affect the relative risk for SIDS.

Analysis of Variance↗
PubMed1999

International child care practices study: methods and study population.

The study set out to document child care practices in as many different countries and cultures as possible with the aim of providing baseline child care data and stimulating new hypotheses to explain persisting differences in sudden infant death syndrome (SIDS) rates between countries. The protocol, piloted in four countries in 1992, was distributed to 80 potential centres in 1995. Data from 19 centres were received. This paper describes the demographic characteristics of the data from the different centres. Comparison showed significant differences for a number of variables including mean age of completion of the study, response rate, mean gestation, mean birth weight, method of delivery and incidence of admission to neonatal intensive care units. High caesarean section rates identified in the Chinese samples (44 and 40%) were unexpected and have important public health implications. This finding warrants further study but may be related to China's one child policy. We consider that international comparison of child care practice is possible using standardised data collection methods that also allow some individual variation according to local circumstances. However, in view of the heterogeneity of the samples, it will be important to avoid over-interpreting differences identified and to view any differences within the qualitative context of each individual sample. Provided there is acknowledgement of limitations, such ecological studies have potential to produce useful information especially for hypothesis generation.

Birth Weight↗
PubMed1999

Use of duvets and the risk of sudden infant death syndrome.

BACKGROUND: The use of duvets in infancy is not recommended in the UK and Australia because of a reported association with sudden infant death syndrome (SIDS). AIMS: To examine the association between the use of duvets and the risk of SIDS. METHODS: A nationwide case control study (393 cases, 1592 controls). The use of duvets was assessed by interview with the parent or guardian. RESULTS: The use of duvets was associated with an increased risk of SIDS (odds ratio (OR) = 1.65; 95% confidence interval (CI), 1.31 to 2.08); however, after adjustment for potential confounders there was no increased risk of SIDS (OR = 1.04; 95% CI, 0.77 to 1.38). Furthermore, subgroup analysis did not identify any group in which the use of duvets was associated with an increased risk of SIDS. CONCLUSIONS: This study does not support the recommendation to avoid duvets.

Bedding and Linens↗
PubMed1998

Pharmacokinetics and pharmacodynamics of ranitidine in neonates treated with extracorporeal membrane oxygenation.

The pharmacokinetics and pharmacodynamics of ranitidine were studied in 13 term neonates with stable renal and hepatic function who were treated with extracorporeal membrane oxygenation (ECMO). Ranitidine was initially administered as a single 2 mg/kg dose over 10 minutes and intragastric pH was monitored to determine response. Within 90 minutes after administration of ranitidine, intragastric pH for all of the patients whose initial reading was < or = 4 had increased to > 5. Intragastric pH remained > 4 for a minimum of 15 hours. Mean +/- 1 standard deviation elimination half-life was 6.61 +/- 2.75 hours, and 41.5 +/- 22.2% of the single dose was eliminated in urine within 24 hours. Total plasma clearance of ranitidine correlated well with estimated glomerular filtration rate. Twenty-four hours after the initial dose, a continuous infusion of ranitidine (2 mg/kg/24 hr) was started and continued for 72 hours or until ECMO was discontinued. Eleven patients completed 48 hours of continuous infusion and seven completed all 72 hours. Plasma clearance and elimination half-life were determined from steady-state plasma ranitidine concentrations 24, 48, and 72 hours after the start of the infusion. There were no significant differences in clearance between these intervals. These data suggest that for term neonates with stable renal and hepatic function, ranitidine does not need to be administered more frequently than every 12 hours. A continuous infusion of 2 mg/kg/24 hours maintained intragastric pH above 4 in more than 90% of our patients, and in our opinion is the preferred method for delivering ranitidine to term neonates undergoing ECMO who require H2 antagonists. Response to therapy should be monitored by repeated measurement of gastric pH and the dose should be adjusted accordingly.

Extracorporeal Membrane Oxygenation↗
PubMed1998

Sheepskin bedding and the sudden infant death syndrome. New Zealand Cot Death Study Group.

We carried out a nationwide case-control study, comparing 393 case patients with sudden infant death syndrome (SIDS) with 1592 control subjects, in order to examine sheepskin bedding as a risk factor. Sheepskin use was similar for case patients and control subjects (both, 42%; adjusted odds ratio [OR] = 1.28; 95% CI = 0.92, 1.79). Sheepskin use among the control subjects was associated with socioeconomic advantage. The relative risk for SIDS with sheepskin use was significantly increased in the infants placed prone to sleep (adjusted OR = 1.70; 95% CI = 1.08, 2.67), but not for infants placed in the supine or lateral position (adjusted OR = 0.82; 95% CI = 0.45, 1.48). An interaction between sheepskin use and bed sharing was also found. Sheepskin use was associated with a decreased risk of SIDS among infants sharing beds (adjusted OR = 0.61; 95% CI = 0.38, 0.99), but an increased risk among infants not bed sharing (adjusted OR = 2.25; 95% CI = 1.32, 3.86). We conclude that if an infant needs to be placed prone to sleep for medical reasons, a sheepskin should not be used as underbedding. However, for infants placed supine to sleep, sheepskins are not associated with an increased risk of SIDS.

Animals↗
PubMed1998

Responses to an increasing asphyxia in infants: effects of age and sleep state.

Infants aged 0-6 months were assessed for respiratory and arousal responses to mild asphyxia during sleep. Ventilatory sensitivity was assessed from the relationship between inspired carbon dioxide (FICO2) and ventilation. Arousal and ventilatory sensitivity were significantly related. Respiratory response increased with age and was greater in quiet sleep than in REM sleep. Arousal occurred more frequently in REM sleep (55/102) than quiet sleep (38/165, P < 0.05) and more frequently at the newborn age (54/117) than at 6 months (13/58, P < 0.05). Arousal in quiet sleep occurred in babies with high ventilatory sensitivities (mean ventilatory asphyxial sensitivity (VAS) 0.476 +/- 0.288) and in REM sleep was more associated with low ventilatory sensitivities (mean VAS 0.194 +/- 0.334, P <0.05). We conclude infants respond to mild asphyxia during sleep with an increase in ventilation, an arousal or both. The exact response is dependent on age and sleep state.

Arousal↗