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Biomedical subjects

C Baxter

Publications and source records attributed to C Baxter.

At least 37 records · Page 2Linked to original sources
PubMed1991

Effects of surfactant-associated protein SP-B synthetic analogs on the structure and surface activity of model membrane bilayers.

The effect of several synthetic peptides based on the sequence of human pulmonary surfactant-associated protein B (SPB) on the molecular packing of model membrane lipids (7:1 dipalmitoyl phosphatidylcholine (DPPC)/dipalmitoyl phosphatidylglycerol (DPPG)) was studied using fluorescence anisotropy. This information was then correlated with complementary biophysical data obtained on both a modified Wilhelmy-Langmuir balance and a pulsating bubble surfactometer. The SP-B peptides examined in these studies are synthetic human SP-B Phe1-Ser78 (SP-B 1-78, full-length sequence), synthetic human SP-B Phe1-Thr60 (SP-B 1-60), synthetic human SP-B Phe1-Ala20 (SP-B 1-20), synthetic human SP-B Ala20-Thr60 (SP-B 20-60), synthetic human SP-B Leu27-Ser78 (SP-B 27-78), synthetic human SP-B Leu40-Thr60 (SP-B 40-60) and synthetic human SP-B Tyr53-Ser78 (SP-B 53-78). trans-parinaric acid was utilized to detect changes in ordering of lipids within the interior upon incorporation of synthetic SP-B peptide, whereas 1-hexadecanoyl-2-[N-(7-nitro-2-benzoxa-1,3-diazol-4-yl)-a min ohexanoyl] phosphatidylcholine (6-NBD-PC) and 1-acyl-2-[N-(7-nitro-2-benzoxa-1,3-diazol-4-yl)aminohexanoyl ] phosphatidylglycerol (6-NBD-PG) were utilized to determine alterations in lipid order at the surface of the model membrane bilayer. With the exception of SP-B 40-60, which corresponds to the most hydrophobic segment of the full-length SP-B, none of the other peptide significantly perturbed the interior bilayer as determined by fluorescence anisotropy of trans-parinaric acid. Incorporation of any of the peptides with the exception of SP-B 40-60, resulted in an increase in anisotropy of NBD-PC. The most significant enhancements resulted from the addition of SP-B 1-78, SP-B 1-20, SP-B 27-78 or SP-B 53-78. The magnitude of anisotropy increase with these peptides is similar to that observed with an equivalent molar ratio of native SP-B isolated from a bovine source. These observations suggest that these four synthetic peptides have the structural and compositional characteristics required for surface ordering of the membrane bilayer in a manner similar to that observed with native SP-B, thereby facilitating the surfactant-like properties of phospholipid mixtures.

Fluorescence Polarization↗
PubMed1989

Investigating stigma as stress in social interactions of parents.

A new approach to the study of stigma was introduced and applied in an exploratory study designed to investigate the parental experience of stigma within the theoretical framework of the stress process. Interviews were conducted with 131 mothers and fathers of mentally retarded children in three age cohorts. Parent-perceived stress attributed to social attitudes was measured on a 5-point, Likert-type scale. Three deviating characteristics of the child were identified as 'stressors'. 'Noticeability' of the child's speech and behaviour, and also behaviour management problems were found to be significantly associated with parental stress. No association was found between 'noticeability' of the child's appearance and parental stress. Distressing reactions of others, such as staring, displaying discomfort, inappropriately ignoring and drawing attention to the child were also identified as stressors. Multiple regression analysis showed that these two sets of variables accounted for 57% of the variance in explaining parental stress. The concept of stigma as stress was assessed as offering a promising direction for further research.

Adolescent↗
PubMed1989

Brucellosis in an inuit child, probably related to caribou meat consumption.

A 9-year-old Inuit boy with brucellosis is presented. The most likely source of his infection was contaminated caribou meat. Brucella suis is enzootic in Canadian caribou herds and this case indicates that natives of the Arctic are a risk group for acquiring brucellosis through the ingestion of raw caribou meat.

Animals↗
PubMed1989

ELISA HIV testing and viral culture in the screening of corneal tissue for transplant from medical examiner cases.

The spread of AIDS and its association with a retrovirus, commonly called T-lymphotropic virus type III (HIV) has produced great concern among those involved in transplantation about the possibility for transmission of this disease through tissue and organ transplant. Isolation of the virus from conjunctiva and tears further heightened this concern for corneal transplants. This review of medical examiner (ME) cases, a population in which high numbers of transplant corneas are retrieved, has revealed positive serologic tests for HIV in serum from 5 cases in 205 screens. These represent potential donors based on other standard medical criteria available at the time of collection. This tissue was also submitted for viral culture, and virus was recovered from the corneal tissue in McCarey-Kaufman (MK) media. These findings and case reviews are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Race and child abuse.

Very little is known about the relationship between race and child abuse. Skills in prevention, detection and family support have not increased at the same pace as for the majority population. This article looks at some of the factors associated with child abuse in black and ethnic minority communities and suggests how health professionals can improve their skills in working with this section of our population.

Adolescent↗
PubMed1988

Racial inequalities in health: a challenge to the British National Health Service.

The existence of racial inequalities in health in the United Kingdom is examined using both indirect and direct data. The evidence strongly supports the view that the health experience of black and other ethnic minority groups is worse than that of the indigenous white population. Ways of improving this situation are outlined; they indicate the need for a coordinated Health service response incorporating planning, training, and equal opportunities in both service provision and employment practices.

Black People↗
PubMed1986

Renal tubular transport of cyclosporine A (CSA) and associated changes in renal function.

In an effort to understand the mechanisms of nephrotoxicity of cyclosporine A (CSA), this study has been undertaken to evaluate the CSA clearance by the kidney and its tubular transport, with simultaneous studies on the multiple renal functional parameters. New Zealand white rabbits weighing approximately 2.5 kg were used in the study. Rabbits were infused with 14C labelled inulin to determine GFR. Blood pressure was monitored throughout the study via ear artery cannula. The rabbits were catheterized by the bladder and remained conscious throughout the entire study. When an infusional steady state was achieved, three clearance periods of 15 minutes were undertaken, followed then by a bolus of 10 mg/kg CSA, followed by an infusion of 1 mg/kg. A further three clearance periods were undertaken, studying the clearance of CSA at the same time as the GFR. Additional studies were made of plasma renin activity, aldosterone, 6-keto-PGF1 alpha, urinary sodium excretion and urinary potassium excretion rate. CSA was determined in whole blood and urine by HPLC. The results indicate that CSA, as determined by HPLC, has a whole blood renal clearance of 0.029 +/- 0.011 ml/min/kg body weight. Glomerular filtration rate showed no difference in animals pretreated with an infusion of mannitol when comparing pre- and post-CSA administration. Without mannitol, there was a significant decrease in the GFR following administration of CSA. CSA administration was accompanied by a rise in plasma renin activity in animals treated with mannitol and without mannitol. The rate of 6-keto-PGF1 alpha excretion without pretreatment with mannitol showed a significant rise following CSA administration.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Influence of cyclosporine A (CSA) on intrarenal control of GFR.

In the acute clinical situation, CSA produces reversible renal impairment. Studies by Morris et al. [1982] and others indicate that this is rapidly reversible when the drug is ceased. A series of studies have been performed in rats with the aim of examining changes in GFR, together with changes in the intrarenal renin-angiotensin system and renal release of prostaglandins. Rats were treated for 3-7 days with CSA and at the end of the experiment kidneys were removed and renal cortical slices prepared. There was increased renin secretion from the CSA-treated rats, compared to controls, and the response was dose-dependent. There was an increase in renal cortical renin content paralleling the renin release. Determinations of plasma renin in these animals also indicated a rise in plasma renin activity associated with time. In animals not pretreated with CSA, the renal cortical slices incubated with CSA demonstrated a stimulation of renin release. A further group of rats pretreated with 100 mg/kg/day of CSA for 3-7 days showed no change in renal slice release of 6-keto-PGF1 alpha, thromboxane B2, PGE2 and PGF2 alpha. This data indicates that the renal renin-angiotensin system is activated by CSA and produces a dissociation of the linkage between renal slice prostaglandin release and the renin angiotensin system. This would indicate that CSA affects the intrarenal control of GFR. However, the exact site of the modulation remains to be determined.

Animals↗
PubMed1983

Influence of time of day on all-out swimming.

The effect of time of day on all-out swim performances was examined. Fourteen subjects performed maximal front crawl swim tests on separate days over 100 m. and 400 m. at 5 different times of day between 06.30 h. and 22.00 h. Performance showed a significant linear trend with time of day in close though not exact association with the circadian rhythm in oral temperature: a goodness of fit test confirmed that the values predicted from linear trend analysis coincided with the measured values (p less than 0.05). The steady improvement throughout the day was 3.5% for 100 m. and 2.5% for 400 m. swims. Trunk flexibility displayed a time of day variation with a trough in the morning and a peak in the afternoon. No significant rhythm was observed in ankle and shoulder flexibility, grip strength or peak expiratory flow rate (p greater than 0.05). It was concluded that maximal swimming trials are best scheduled for the evening and worst in the early morning. Specific fitness factors cannot clearly account for the higher exercise capability in the evening which is strongly related to the circadian curve in body temperature.

Adolescent↗
PubMed1983

Influence of time of day on reactions to cycling at a fixed high intensity.

The circadian cycle in all-out competitive performance may be due to changes in motivational drive to tolerate strenuous exercise rather than to rhythms in maximal physiological functions. This experiment explored the hypothesis that a fixed relative loading of high intensity aerobic effort could be sustained for longer in the evening compared with the morning. Eight females cycled to exhaustion at 95% VO2 max at 06.30 h. and at 22.00 h. after a 5 min, moderate load of 40% VO2 max. Oral temperature was 0.4 degrees C higher at 22.00 h. compared with the earlier time. Perceived exertion showed no significant effect of time of day at either work load but exercise tolerance time, total work done and peak lactate production were significantly greater at 22.00 h. (p = 0.05). Perceived exertion at the high load was significantly related to endurance time (r = -0.77) and to the rating at the low work level (r = 0.75). Peak lactate was not significantly correlated with the time to exhaustion (p less than 0.05). It was concluded that superior exercise performance in the evening may be attributed to a greater tolerance for high intensity exercise which is closely associated with the acrophase in body temperature.

Adult↗
PubMed1979

Effect of age on angiotensin II receptors from rat brain.

1. Angiotensin II receptor binding was studied in specific regions of rat brain at different ages from birth to 14 weeks. 2. The number of specific angiotensin II receptors increased in all regions during the first 2 weeks of life and then decreased to adult levels. Peak numbers of receptors were up to 10 times the adult numbers. 3. The midbrain and thalamus-hypothalamus had maximum numbers of angiotensin II receptors at 2 weeks of age, whereas the rest of the brain regions had maximum number at 1 week. 4. Saralasin-infusion experiments suggested that circulating angiotensin-related peptides could reach brain angiotensin II receptors in 2 week old rats, but not in 6 week old rats. 5. It is postulated that the centrally mediated actions of circulating angiotensin II may be particularly important in the newborn.

Aging↗