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R Hudson

Publications and source records attributed to R Hudson.

At least 19 recordsLinked to original sources
PubMed2001

Diversity and development of circadian rhythms in the European rabbit.

Three main concerns underlie this review: 1) The need to draw together the widely dispersed information available on the circadian biology of the rabbit. Although the rabbit is a classic laboratory mammal, this extensive body of information is often overlooked by chronobiologists, and despite several advantages of this species. In terms of its general biology the rabbit is the best studied laboratory mammal in the wild, it demonstrates a wide variety of robust circadian functions, and being a lagomorph, it provides a useful comparison with more commonly studied rodent species. 2) The need to more fully exploit a developmental approach to understanding circadian function, and the particular suitability of the rabbit for this. Female rabbits only visit their altricial young for a few minutes once every 24 h to nurse, and survival of the young depends on the tight circadian-controlled synchronization in behavior and physiology of the two parties. Patterns of circadian rhythmicity in neonatal pups associated with nursing do not form a smooth continuum into weaning and adult life, and may reflect the action of separate mechanisms operating in their own right. 3) Using information from the first two points, to emphasize the diversity and complexity of circadian rhythms underlying behavioral and physiological functions in adult and developing mammals. Information accruing on circadian functions in the rabbit makes it increasingly difficult to account for these in terms of one or two regulatory mechanisms or "oscillators." Thus, it is argued that in addition to the reductionist, molecular approaches currently dominating much of chronobiology, the study of circadian systems as emergent characteristics of whole organisms operating in complex environments merits special attention.

Animals↗
PubMed2001

Judgement of odor intensity is influenced by subjects' knowledge of the odor source.

Odor perception, including intensity, is affected by knowledge of odor source. For 76 subjects tested with 24 everyday odorants, ratings of intensity, pleasantness and familiarity were enhanced when subjects either could identify the odor source themselves or were provided with the name by the experimenter. Ratings were highest when subjects judged that the names provided matched their own perception, suggesting an interaction between individuals' cognitive representation of odors and their immediate perceptual experience.

Adult↗
PubMed2001

Caffeine ingestion decreases glucose disposal during a hyperinsulinemic-euglycemic clamp in sedentary humans.

The purpose of this investigation was to examine the effect of caffeine (an adenosine receptor antagonist) on whole-body insulin-mediated glucose disposal in resting humans. We hypothesized that glucose disposal would be lower after the administration of caffeine compared with placebo. Healthy, lean, sedentary (n = 9) men underwent two trial sessions, one after caffeine administration (5 mg/kg body wt) and one after placebo administration (dextrose) in a double-blind randomized design. Glucose disposal was assessed using a hyperinsulinemic-euglycemic clamp. Before the clamp, there were no differences in circulating levels of methylxanthines, catecholamines, or glucose. Euglycemia was maintained throughout the clamp with no difference in plasma glucose concentrations between trials. The insulin concentrations were also similar in the caffeine and placebo trials. After caffeine administration, glucose disposal was 6.38 +/- 0.76 mg/kg body wt compared with 8.42 +/- 0.63 mg/kg body wt after the placebo trial. This represents a significant (P < 0.05) decrease (24%) in glucose disposal after caffeine ingestion. In addition, carbohydrate storage was 35% lower (P < 0.05) in the caffeine trial than in the placebo trial. Furthermore, even when the difference in glucose disposal was normalized between the trials, there was a 23% difference in the amount of carbohydrate stored after caffeine administration compared with placebo administration. Caffeine ingestion also resulted in higher plasma epinephrine levels than placebo ingestion (P < 0.05). These data support our hypothesis that caffeine ingestion decreases glucose disposal and suggests that adenosine plays a role in regulating glucose disposal in resting humans.

Administration, Oral↗
PubMed2000

Morphology of developing olfactory axons in the olfactory bulb of the rabbit (Oryctolagus cuniculus): a Golgi study.

Transient expression of axon collaterals plays an important role in enabling neurons to find appropriate targets during development. In the olfactory bulb, the numbers of both sensory neurons and their targets, the glomeruli, increase markedly during the postnatal period. In the present study, the morphology of developing olfactory axons in the olfactory bulb of 1-21-day-old rabbits was analyzed using stereological methods and the rapid Golgi technique. The findings demonstrated a change in axon morphology from the olfactory nerve layer to the glomeruli suggestive of a sequence in axon development. In the olfactory nerve layer, axons typically had knob-like growth cones and a few collateral branches. Close to glomeruli, axons increased in thickness, formed rather complex and irregular growth cones, and typically gave off many collaterals. Within glomeruli, the axons formed terminal branches and boutons. Extraglomerular branches were apparently removed once axons had entered a glomerulus, insofar as these branches often displayed morphological signs of degeneration. In contrast, collateral branches ending in the same glomerulus remained, indicating that formation of collaterals may assist olfactory axons in locating glomerular targets.

Animals↗
PubMed2000

Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men. A randomized, controlled trial.

BACKGROUND: The independent effects of diet- or exercise-induced weight loss on the reduction of obesity and related comorbid conditions are not known. The effects of exercise without weight loss on fat distribution and other risk factors are also unclear. OBJECTIVE: To determine the effects of equivalent diet- or exercise-induced weight loss and exercise without weight loss on subcutaneous fat, visceral fat skeletal muscle mass, and insulin sensitivity in obese men. DESIGN: Randomized, controlled trial. SETTING: University research center. PARTICIPANTS: 52 obese men (mean body mass index [+/-SD], 31.3 +/- 2.0 kg/m2) with a mean waist circumference of 110.1 +/- 5.8 cm. INTERVENTION: Participants were randomly assigned to one of four study groups (diet-induced weight loss, exercise-induced weight loss, exercise without weight loss, and control) and were observed for 3 months. MEASUREMENTS: Change in total, subcutaneous, and visceral fat; skeletal muscle mass; cardiovascular fitness; glucose tolerance and insulin sensitivity. RESULTS: Body weight decreased by 7.5 kg (8%) in both weight loss groups and did not change in the exercise without weight loss and control groups. Compared with controls, cardiovascular fitness (peak oxygen uptake) in the exercise groups improved by approximately 16% (P < 0.01). Although total fat decreased in both weight loss groups (P < 0.001), the average reduction was 1.3 kg (95% CI, 0.3 to 2.3 kg) greater in the exercise-induced weight loss group than in the diet-induced weight loss group (P = 0.03). Similar reductions in abdominal subcutaneous, visceral, and visceral fat-to-subcutaneous fat ratios were observed in the weight loss groups (P < 0.001). Abdominal and visceral fat also decreased in the exercise without weight loss group (P = 0.001). Plasma glucose and insulin values (fasting and oral glucose challenge) did not change in the treatment groups compared with controls (P = 0.10 for all comparisons). Average improvement in glucose disposal was similar in the diet-induced weight loss group (5.6 mg/kg skeletal muscle per minute) and in the exercise-induced weight loss group (7.2 mg/kg skeletal muscle per minute) (P > 0.2). However, these values were significantly greater than those in the control and exercise without weight loss groups (P < 0.001). CONCLUSIONS: Weight loss induced by increased daily physical activity without caloric restriction substantially reduces obesity (particularly abdominal obesity) and insulin resistance in men. Exercise without weight loss reduces abdominal fat and prevents further weight gain.

Abdomen↗
PubMed2000

Reference-based pricing.

Explore the source record for details and available documents.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2000

Metabolic correlates of the circadian pattern of suckling-associated arousal in young rabbits.

Young rabbits (Oryctolagus cuniculus) are only nursed for 3-5 min every 24 h. They show a circadian increase in activity in anticipation of this, which is entrained by suckling. Our aim was to determine whether serum and liver metabolites show diurnal fluctuations which could act to regulate this circadian pattern. Stomach weight, liver glycogen and serum metabolites were measured every 3 h in 7- to 8-day-old pups when normally nursed (up to 24 h after suckling) and fasted (up to 48 h after suckling). The results suggest: 1. Energy balance between feeds was maintained by a cascade in the use of fuels, first glucose from the milk, then glycogen stores and gluconeogenesis from circulating products of proteins and triglycerides, and finally, in late-fasted animals, the mobilization of free fatty acids. 2. The empty stomach and depletion of glycogen 23-24 h after the last feed could act to trigger anticipatory arousal in normally nursed pups, and the release of free fatty acids 45 48 h after the last feed could trigger this in fasted pups. 3. Unmasking of rhythmicity by fasting in serum levels of glucose and proteins suggests their regulation by endogenous oscillators, which may also be the case for the mobilization of free fatty acids.

Animals↗
PubMed2000

Plasma leptin in moderately obese men: independent effects of weight loss and aerobic exercise.

The independent effects of weight loss and exercise on plasma leptin and total (AT), subcutaneous (SAT), and visceral (VAT) adipose tissue were investigated in 52 obese men. Subjects were randomly assigned to four 12-wk protocols: 1) control (C, n = 8), 2) diet-induced weight loss (DWL, n = 14), 3) exercise-induced weight loss (EWL, n = 14), and 4) exercise with weight maintenance (EWS, n = 16). Plasma leptin was unchanged in C (from 7.8 +/- 1.3 to 7.7 +/- 1.0 ng/ml). Equivalent weight loss (7.5 kg) decreased leptin significantly but similarly (DWL, from 8.5 +/- 1.0 to 4.8 +/- 0.6 ng/ml; EWL, from 10.1 +/- 1.0 to 5.0 +/- 0.6 ng/ml). Exercise in the absence of weight loss did not alter leptin levels (from 10.1 +/- 1. 3 to 9.2 +/- 1.2 ng/ml). Changes in leptin correlated with changes in AT and SAT (both P < 0.05) but not in VAT. We conclude that reduction in adipose tissue after weight loss results in a collateral decrease in circulating leptin, and exercise, independent of its effects on weight loss, has no profound influence on leptin secretion.

Adipose Tissue↗
PubMed1999

Fragile X premutation is a significant risk factor for premature ovarian failure: the International Collaborative POF in Fragile X study--preliminary data.

The preliminary results of an international collaborative study examining premature menopause in fragile X carriers are presented. A total of 760 women from fragile X families was surveyed about their fragile X carrier status and their menstrual and reproductive histories. Among the subjects, 395 carried a premutation, 128 carried a full mutation, and 237 were noncarriers. Sixty-three (16%) of the premutation carriers had experienced menopause prior to the age of 40 compared with none of the full mutation carriers and one (0.4%) of the controls. Based on these preliminary data, there is a significant association between fragile X premutation carrier status and premature menopause.

Adolescent↗
PubMed1999

The flavor of life: perinatal development of odor and taste preferences.

Despite the importance of chemosensation in the regulation of ingestive behavior, we still know surprisingly little about the development of the olfactory, trigeminal and gustatory systems. All three, however, are functional to some degree prenatally, and by birth infants are able to respond to a wide range of odors and can clearly distinguish between the tastes of sweet, sour and bitter. Based on findings from our work in the rabbit, we report that learning of odors associated with the mother's diet can occur very early in development, even prenatally, that it can have a long-term influence on later food choice, and may even lead to enhanced, stimulus-specific sensitivity of the basic sensory apparatus. Whether comparable phenomena exist in human infants is not known, although our recent findings that nationalities differ in judgements of the pleasantness of food odors depending on whether these are recognized as representing familiar, culture-typical foods, suggests that it might. A cross-cultural study is currently in progress examining the influence of culture-specific childhood eating experiences on adult preferences for food-associated odors.

Adult↗
PubMed1999

From molecule to mind: the role of experience in shaping olfactory function.

The olfactory system is faced with a particular problem--the high dimensionality and inherent unpredictability of the chemical world. Most natural odorants encountered in everyday life are complex mixtures of many different volatiles. This means that from the outset the olfactory system has to contend with a great and often unpredictable diversity of molecules, making it difficult for stable primary features of the chemical world to be mapped onto the sensory surface. One solution to such unpredictability is provided by learning. Learning confers flexibility, enabling individuals of a given species to acquire and make use of the most appropriate information in a particular environment. Two examples of this are presented: learning of maternal odors in neonatal rabbits, including evidence that the sensory surface itself may be influenced by environmental conditions so as to enhance sensitivity to molecules of particular ecological relevance, and cross-cultural human studies suggesting that experience with everyday odors influences not only the way these are evaluated, but also their perceived intensity. It is concluded that an adequate understanding of odor coding and olfactory function will not be possible without taking such experience-dependent factors into account.

Animals↗
PubMed1999

Temporal and behavioral patterning of parturition in rabbits and rats.

Although the rabbit (Oryctolagus cuniculus) continues to play an important role in the study of parturitional processes, a detailed behavioral description of birth in this species, necessary for accurately assessing the effects of experimental manipulation, is lacking. It is the aim of this report to provide such a description and to compare it with corresponding behavior in the better-studied rat. Ten pregnant chinchilla-breed rabbits and 10 pregnant Wistar rats were placed in glass-bottomed observation cages 2 days before term, and their behavior recorded on closed-circuit video, viewing the animals from below. All aspects of parturition were accomplished much faster in rabbits than rats; latency to birth of first pup, rate of delivery, duration of vaginal retention, time spent by mothers eating placentas, and in licking and nursing pups. In contrast to rat pups, rabbits were usually born separated from the placenta and already free from membranes. They were much more active, and well able to cast off any remaining membranes, suckle, and survive, whether directly attended to by the mother or not. We conclude that the tight temporal organization of events in the rabbit provides an unusually sensitive assay for investigating mechanisms underlying mammalian parturition.

Animals↗
PubMed1999

Expression of c-fos in the main olfactory bulb of neonatal rabbits in response to garlic as a novel and conditioned odour.

Expression of c-Fos was examined in the olfactory bulbs of 3-day-old rabbits after they had been presented with the odour of garlic as a novel stimulus, as a learned odour, or during conditioning, and this expression compared with baseline levels in non-stimulated controls. Exposure to garlic odour resulted in substantial and widespread increases in c-Fos expression in the olfactory bulbs of all animals. However, although conditioned pups showed a specific behavioural response to the learned garlic odour, neither the amount nor pattern of c-Fos expression differed compared to pups exposed to garlic as a novel odour. The odour-induced expression of c-Fos was not well localised, although there was a significant increase in the number of granule cells expressing c-Fos in the ventrolateral region of the bulb. These results support previous reports that the response to odours in the olfactory bulb of new-born animals is not as spatially distinct as that in adults. Nevertheless, the immature olfactory system of these young animals is clearly capable of very specific odour learning.

Analysis of Variance↗
PubMed1999

Perception of everyday odors--correlation between intensity, familiarity and strength of hedonic judgement.

In this study, 40 Japanese, 44 German and 39 Mexican women were presented with 18 everyday odorants. They were asked to rate them for intensity on a six-point scale from not detectable to very strong, for pleasantness on an 11-point scale from -5, to neutral at 0, to +5, and for familiarity on a six-point scale from completely unknown to extremely familiar. Consistent positive correlations were found between paired rating scores for the three measures, and although they were not particularly strong (r(s) range, 0.19-0.60), for most odorants all three correlations were significant. Similar results were obtained whether the data were analyzed on an individual or a national basis. Most notable were the consistent positive correlations between perceived intensity and ratings of familiarity and hedonic strength. It is suggested that the perceived intensity of the odorants depended not only on stimulus concentration but probably also on experience-dependent factors.

Adult↗