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Biomedical subjects

R Thayer

Publications and source records attributed to R Thayer.

17 recordsLinked to original sources
PubMed2001

The incidence of hematuria in middle distance track running.

The purpose of this study was to establish if middle distance track athletes experience hematuria during their competitive season interval workouts and, if so, what type of workout based on intensity and distance was most associated with hematuria. During a 4-week observational period, athletes (n = 10) underwent reagent strip urinalysis before and after their twice weekly interval sessions. Positive samples for hematuria were analyzed microscopically to accurately determine red blood cell (RBC) loss. Seventy-one individual interval workouts were observed, of which 32 cases of hematuria were reported. Nine cases of hematuria exhibited >100 RBC per High Power Field (Hpf). Furthermore, 90% of the athletes experienced post-workout hematuria at least once. The highest incidence of hematuria was observed after workouts run at 110% of VO(2peak) over short (600-1,500 m) to moderate (1,501-3,000 m) distances. All post-exercise cases of hematuria resolved within 2 hr of recovery.

Adult↗
PubMed2000

A decade of aerobic endurance training: histological evidence for fibre type transformation.

BACKGROUND: Researchers employing a variety of training methods have demonstrated a fast-to-slow fibre transformation in animal skeletal muscle. The observation as to whether this occurs in exercise trained humans is limited and equivocal. METHODS EXPERIMENTAL DESIGN: to examine this issue, skeletal muscle from seven subjects who had participated in a decade or more of high intensity aerobic training (DT) and six nontrained (NT) subjects was obtained by muscle biopsy from the vastus lateralis muscle (VL) and subjected to a modified myofibrillar ATPase technique to identify muscle fibre types. Muscle tissue was histochemically treated by exposure to an alkaline preincubation (pH 9.9), an acid preincubation (pH 4.3 or 4.6) and the formate-KCI preincubation buffer (pH 4.54), previously employed in animal studies. RESULTS: The formate-KCl preincubation medium identified all major fibre types at a single pH in human subjects. The percentage of type I fibres in DT was 70.9% vs 37.7% in NT (p<0.01), while the type IIa fibres in DT (25.3%) was much lower (p<0.01) than NT (51.8%). Surprisingly, type IIa fibres in the DT group displayed lesser oxidative staining intensity (p<0.01) than type IIa fibres from the NT group. Mean cross-sectional area of type I fibres for DT (6233.9+/-1421.7 microm2) was greater (p<0.05) than either type I (5746.8+/-1135.2 microm2) or II (5693.5+/-1214.6 microm2) from NT. CONCLUSIONS: The results revealed that endurance training may promote a transition from type II to type I muscle fibre types and occurs at the expense of the type II fibre population.

Adenosine Triphosphatases↗
PubMed2000

Comparison of fructose and glucose ingestion before and during endurance cycling to exhaustion.

BACKGROUND: Pre-exercise and exercise ingestion of fructose and glucose during cycling exercise were compared. METHODS EXPERIMENTAL DESIGN: Seventeen trained subjects ingested a placebo prior to and during a cycling test to exhaustion at 75% VO2max (control group = CG). One week later, subjects were matched on exercise time to exhaustion (ETE) and assigned to a fructose group (FG) or a glucose group (GG). Subjects then performed a second cycling test to exhaustion, ingesting fructose or glucose doses. For all groups (CG, FG and GG), blood was drawn before and at timed intervals during exercise to determine glucose, lactate and free fatty acid (FFA) levels. RESULTS: The ETE for CG was less than either FG (p<0.02) or GG (p<0.001) but FG and GG were similar. FG and GG did not show any differences in blood lactate or blood FFA during the ETE. However, CG FFA levels were higher than those of FG (p<0.02) prior to exercise. CONCLUSIONS: This study demonstrated that fructose and glucose are of equal value in prolonging ETE in endurance cycling Ingesting fructose before and during exercise apparently provided a more constant supply of glucose to be available to the working muscles. The more stable blood glucose levels with fructose ingestion may be beneficial in reducing perceived exhaustion, and thereby allowing for an enhancement in exercise performance.

Adult↗
PubMed1999

Cardiovascular responses to facial cooling are age and fitness dependent.

PURPOSE: Aging of the cardiovascular system may be altered by differences in physical fitness. We investigated the cardiovascular responses to brief periods of facial cooling (5 degrees C) in 20 healthy men differing in age and aerobic fitness (VO2max). METHODS: Facial cooling was administered at rest in the supine position during 60-s quiet breathing to 6 fit young (FY; VO2max = 75.8 +/- 18 mL x kg(-1) x min(-1); 29 +/- 7 yr), 6 sedentary young (SY; VO2max = 36.0 +/- 2.2 mL x kg(-1) x min(-1); 27 +/- 3 yr), 6 fit old (FO; VO2max = 56.1 +/- 4.0 mL x kg(-1) x min(-1); 54 +/- 5 yr), and 6 sedentary old (SO; VO2max = 29.6 +/- 5.0 mL x kg(-1) x min(-1); 62 +/- 2 yr) volunteers. The following were measured before and after facial cooling: heart rate (HR), mean arterial blood pressure (MAP), pressure-rate product (PRP), and M-mode echocardiographically determined left ventricular internal dimensions, peak circumferential shortening (peak V(CF)), and ejection fraction (EF). RESULTS: Facial cooling produced a statistically significant bradycardia in all groups except for the SO whereas MAP was increased in the young groups but unchanged in the older groups. Pressure-rate product was significantly reduced in the FY, unchanged in the SY and FO, and significantly increased in the SO group. None of the groups showed a change in left ventricular dimensions, whereas only the SO group showed an increase in peak V(CF) (P < 0.05). CONCLUSIONS: These data suggest that endurance training and fitness level do not significantly alter cardiovascular responses to facial cooling in young men or physically fit older men. However, in older subjects, a sedentary lifestyle appears to be associated with an absent facial cooling reflex bradycardia, an increased PRP, and contractility (peak V(CF)).

Adult↗
PubMed1998

The effect of exercise intensity on hematuria in healthy male runners.

The purpose of this study were: (1) to establish the prevalence of exercise-induced hematuria in a group of otherwise healthy male runners (n = 70), and (2) to investigate the role of exercise intensity in those runners who exhibited exercise-related hematuria (n = 10) by evaluating the effect of running and cycling at high and low intensities. The identified and recruited subjects participated in four different exercise protocols: (1) a 60-min treadmill run (RUN) at 90% of anaerobic threshold (Th(ae)), (2) a 60-min leg cycle ergometer ride (BIKE) at 90% of Th(ae), (3) a 3x400-m sprint (SPRINT), each followed by 4 min of rest or light walking, and (4) 3x60-Wingate leg cycle ergometry tests, each followed by 4 min of rest or light cycling. The study employed a 3x4 (time by protocol) within-subjects design and dependent variables were measured before exercise, 4 min after, and 1 h after exercise, and included measurements of hematuria, proteinuria, urinary pH, serum haptoglobin concentration, serum creatine phosphokinase activity, plasma lactate concentration, and hemoglobin. The 400-m sprint at maximal effort significantly increased both hematuria and proteinuria (P<0.01). Post-exercise hematuria for the SPRINT protocol was significantly different than that for the BIKE (P<0.01) and RUN (P<0.01) protocols. Due to the significant increase in hematuria and proteinuria following the SPRINT protocol, it was concluded that exercise-related changes in renal function were associated with weight-bearing exercise intensity rather than non-weight-bearing exercise duration.

Adolescent↗
PubMed1994

Comparison of effects of two interval-training programmes on lactate and ventilatory thresholds.

Twenty-one women subjects were matched in terms of their Vo2max and assigned to one of two groups: (1) training at 30 s; or (2) 2 min with a 1:1 work: relief ratio (1:1 WR) before participating in a 7-week training programme which began at an intensity of 85% Vo2max and increased 5% every two weeks (90% and 95% Vo2max). The subjects trained to exhaustion four times per week. Maximal oxygen consumption (Vo2max), lactate threshold (Tlac) and ventilatory threshold (Tvent) were determined before and after the training programme. After training, there were significant increases (P < 0.05) in Vo2max (5% and 6%), Tlac (19.4% and 22.4%), and Tvent (19.5% and 18.5%). There were no significant group differences on any dependent measure but this research adds support to previous training studies in that a strong correlation (P < 0.05) between Tlac and Tvent is maintained from before to after the test. It was concluded that both formats of high intensity aerobic interval-training produce similar changes in Vo2max, Tlac and Tvent and that these changes appear to be independent of the length of the work interval.

Adult↗
PubMed1990

Acute and chronic responses of skeletal muscle to endurance and sprint exercise. A review.

Skeletal muscle adapts to the stress of endurance and sprint exercise and training. There are 2 main types of skeletal muscle fibre--slow twitch (ST) and fast twitch (FTa, FTb, FTc). Exercise may produce transitions between FT and ST fibres. Sprint training has decreased the proportion of ST fibres and significantly increased the proportion of FTa fibres, while endurance training may convert FTb to FTa fibres, and increase the proportion of ST fibres (i.e. FTb----FTa----FTc----ST). However, the high proportion of ST fibres documented for elite endurance athletes may be simply the result of natural selection. ST fibres function predominantly during submaximal exercise, whereas FT fibres are recruited as exercise intensity approaches VO2max and/or glycogen stores are depleted. Long distance runners have greater ST and FT fibre areas than untrained controls. However, doubt remains as to whether the ST or FT fibre area is greatest in endurance athletes. Increases in FT fibre area seem to occur during the first 2 months of training whereas ST fibre areas appear to increase after 2 to 6 months of training. Sprint training leads to the preferential use of FT fibres and male, but not female sprinters have larger FT fibres than untrained controls. Mitochondrial proteins and oxidative enzymes, as opposed to VO2max, are important determinants of the duration of endurance exercise. Endurance training increases intramuscular glycogen stores in both FT and ST fibres and produces a 'glycogen-sparing' effect which is characterised by an increased free fatty acid (FFA) metabolism. The activity of glycogen synthase is also increased by endurance training. Sprint training increases glycogen concentrations similarly in all fibre types, reduces the rate of glycogen utilisation at submaximal workloads and allows supramaximal workloads to be maintained for longer periods of time. During endurance exercise the pattern of glycogen depletion varies between muscle fibre types and between muscle groups. Glycogen stores in ST fibres are utilised initially, followed by stores in FTa then FTb fibres. Sprint activities are associated with a much greater rate of glycogen depletion. However, it is unlikely that glycogen depletion causes fatigue during sprinting. Sprint work is associated with a preferential depletion of glycogen from FTb then FTa and ST fibres. Endurance training appears to increase triglyceride stores adjacent to mitochondria and ST fibres have greater triglyceride stores than FT fibres. Endurance exercise is associated with a preferential use of triglycerides from ST fibres and endogenous triglycerides may account for over 50% of the total lipid oxidised during exercise.(ABSTRACT TRUNCATED AT 400 WORDS)

Humans↗
PubMed1989

Biological and molecular characterization of human immunodeficiency virus (HIV-1BR) from the brain of a patient with progressive dementia.

HIV-1BR was isolated from the autopsied brain tissue of a 57-year-old man who died of progressive dementing illness. This virus was shown to be HIV-1 by hybridization to HIV-specific DNA probes. The expression of viral proteins as tested by radioimmunoprecipitation assay revealed the presence of HIV-1-specific proteins. HIV-1BR replicated in cultures of CD4+ T-lymphoid cells and induced cytopathic effects in these cells. HIV-1BR also replicated in monocytoid cell lines. The genetic nature of this isolate was determined by molecular cloning and sequencing of the 3'-half of the genome. DNA sequence information established that HIV-1BR is a unique HIV-1 isolate. A stretch of approximately 30 bases in the nef gene of HIV-1BR was found duplicated when compared with the other sequenced HIV-1 genomes. The functional significance of this duplication remains to be determined.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Identification of a common nucleotide sequence in the 3'-untranslated region of mRNA molecules specifying inflammatory mediators.

Recently, cDNA sequences have been reported for both human and murine tumor necrosis factor (TNF; cachectin). The coding region of the TNF genes is highly conserved between man and mouse; 80% homology is apparent at the amino acid level. We now observe that a 33-nucleotide sequence, comprised entirely of A and T residues and located in the 3'-untranslated region, is conserved in toto in the murine and human TNF mRNAs. Since the 3'-untranslated region is normally not conserved, we reasoned that this sequence might play a regulatory role. We identified a consensus sequence (TTATTTAT) present in the 3'-untranslated region of both human and mouse TNF mRNAs, as well as the mRNAs encoding human lymphotoxin, human colony stimulating factor, human and mouse interleukin 1, human and rat fibronectin, and most of the sequenced human and mouse interferons. All of these mRNAs, except the lymphotoxin mRNA, lack homology to the TNF mRNAs in the coding region. The consensus sequence is uncommon among mammalian mRNAs in general, but it appears with a frequency greater than chance alone would dictate, suggesting that it may serve a specific regulatory function among the mRNAs in which it is found. It is particularly prevalent among mRNAs encoding proteins related to the inflammatory response.

Amino Acid Sequence↗
PubMed1985

Preovulatory concentrations of progesterone and estradiol in plasma and their relationships with eggshell quality in the laying hen.

Laying hens were divided into high and low shell quality groups on the basis of egg specific gravity during the 5th, 7th, and 9th months of egg production. Concentrations of progesterone and estradiol-17 beta in the plasma were determined by radioimmunoassay in blood samples taken by cardiac puncture from hens at either 18, 21, or 24 hr postoviposition. Egg production and egg weight were not significantly different between shell quality groups; however, hens in the low shell quality group were heavier (P less than .05), had longer clutches (P less than .05), and lower egg specific gravity (P less than .0001) than hens in the high shell quality group. Egg production and clutch size declined (P less than .01) in both groups with increased age. Plasma estradiol and progesterone concentrations were not different between shell quality groups or among periods of production, though progesterone and estradiol concentrations were greater (P less than .005) at 21 hr postoviposition than at 18 or 24 hr. The correlation coefficient between plasma concentrations of estradiol and progesterone was significant. There was no significant association between the plasma concentrations of these hormones and egg shell quality. These data suggest that concentrations of estradiol and progesterone in plasma, during the 6 hr before ovulation, are not highly related to shell quality in the laying hen.

Animals↗
PubMed1979

Affirmative action: what's really fair?

The concept of affirmative action has been the subject of much controversy in the past. Opponents of the concept believe that it provides preferential treatment for minorities and females based upon factors of race and sex that are both unconstitutional and illegal. Proponents believe the concept is needed to make up for past abuses. In this article, the author attempts to illustrate how an objective affirmative action program can enhance a hospital's personnel development system.

Chicago↗