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Biomedical subjects

R Hudson

Publications and source records attributed to R Hudson.

At least 55 records · Page 3Linked to original sources
PubMed1996

A study of long-term odor memory in squirrel monkeys (Saimiri sciureus).

Five squirrel monkeys (Saimiri sciureus) were trained to discriminate between pairs of odors, and their ability to recognize these as positive or negative was tested at intervals of up to 7 months. Retention was excellent up to 15 weeks and remained significantly above chance even after 30 weeks. Good performance at the shorter intervals was not due to rapid relearning, although at the longer intervals considerable savings were demonstrated by the animals' ability to reach criterion more rapidly than with novel odors. Thus, squirrel monkeys possess a robust memory for odors and show flat forgetting curves consistent with reports for human subjects.

Animals↗
PubMed1996

Separate associations between visceral and subcutaneous adipose tissue distribution, insulin and glucose levels in obese women.

OBJECTIVE: The primary purpose of this study was to determine the separate associations between visceral (VAT) and subcutaneous adipose tissue (SAT) distribution, skeletal muscle (SM), and plasma insulin and glucose levels, and. A second objective was to determine whether anthropometric methods could be used to identify those women who are at increased metabolic risk. RESEARCH DESIGN AND METHODS: Whole-body SAT, SM, and VAT volume were measured (in liters), using a multislice magnetic resonance imaging (MRI) protocol in 40 premenopausal obese women. Plasma insulin and glucose levels were measured after an overnight fast and in response to a 75-g oral glucose tolerance test (OGTT). RESULTS: With the exception of fasting glucose, VAT was positively correlated with all insulin and glucose variables (P < 0.01). This observation remained true whether VAT was derived from multiple MR images (i.e., VAT volume [in liters]) or from a single MR image (i.e., VAT area [in squared centimeters]). Furthermore, the segmentation of intraperitoneal adipose tissue (portally drained adipose tissue) from VAT did not improve the observed relationships. VAT remained a significant (P < 0.05) correlate of insulin and glucose area after adjusting for either SAT or abdominal SAT (ASAT). SAT, ASAT, and SM volume were not related to any metabolic variable. Waist circumference (WC) was the single strongest anthropometric correlate for fasting insulin and insulin area (P < 0.05). Because it has been reported that disturbances in insulin-glucose homeostasis are more likely associated with a WC value > 1 m, in subjects matched for total adiposity, we compared the glucose and insulin area values for those with a WC above (n = 17) and below (n = 15) this value. The group with a WC > 1 m had significantly higher values for both insulin and glucose areas (P < 0.05). CONCLUSIONS: The primary observation is that VAT is associated with plasma insulin and glucose variables independent of whole-body SAT, ASAT, and SM in obese women. In addition, the findings provide support for the utility of WC as an anthropometric tool that may be used to identify a subgroup of obese patients at increased metabolic risk.

Adipose Tissue↗
PubMed1996

Sensitivity associated with the identification of visceral adipose tissue levels using waist circumference in men and women: effects of weight loss.

OBJECTIVE: The first objective was to determine the associated sensitivity (true positives) and specificity (false positives) associated with the use of waist circumference (WC) to predict specific visceral adipose tissue (VAT) levels. Because WC is a strong correlate of VAT, and, a WC of 100 cm and a VAT area of 130 cm2 (L4-L5) have been suggested as thresholds for increased disturbances in insulin-glucose homeostasis and lipid metabolism, we assessed the sensitivity and specificity when using a WC of 100 cm to identify a VAT of 130 cm2 or greater. A second objective was to evaluate the effects of diet and exercise induced weight loss on VAT and WC to establish the utility of using WC to follow reductions in VAT. RESEARCH DESIGN AND METHODS: The sensitivity between WC and VAT was assessed using 50 male (BMI: 30.9 +/- 4.7, age: 41.0 +/- 11.2 y) and 49 female (BMI: 33.3 +/- 5.0, age: 36.9 +/- 7.4 y) subjects. The effects of weight loss on WC and VAT were evaluated in a subgroup of 20 male and 38 female subjects. VAT was measured by magnetic resonance imaging. RESULTS: The sensitivity associated with the prediction of a VAT of 130 cm2 or greater using a WC of 100 cm was high (83%), however, so too was the incidence of false positives (38%). Significant (p < 0.01) correlations were obtained between concurrent reductions in VAT and WC for both the male (r = 0.69) and female (r = 0.47) groups. For the two groups combined, regression analysis indicated that a 1 cm reduction in WC was associated with a 4% reduction in VAT mass (p < 0.01). CONCLUSIONS: The misclassification of individuals with VAT accumulation above 130 cm2 suggest that WC alone lacks the sensitivity required to identify specific VAT values. The diet and exercise induced reductions in visceral adiposity are positively related to corresponding reductions in WC for both genders is a positive result, and demonstrates the potential utility of using WC to follow changes in the AT depot that conveys the greatest health risk.

Adipose Tissue↗
PubMed1995

Parturition in the rabbit is compromised by daytime nursing: the role of oxytocin.

Rabbits nurse briefly only once each night and are frequently both pregnant and lactating. To investigate the influence of the daily timing of nursing on parturition, does (n = 10 per group) were remated after giving birth and were allowed to nurse under one of three schedules: group 1 every 24 h in the light, group 2 every 24 h in the dark, and group 3 at any time. Whereas does from groups 2 and 3 nursed and gave birth normally, does of group 1, forced to nurse out of phase with the normal schedule, showed disturbed nursing behavior and prolonged gestation followed by many stillbirths. In a second experiment, pregnant does (n = 10 per group) were treated daily either with oxytocin (OT) in the light (group 4), with OT in the dark (group 5), or with progesterone (P; group 6) or saline (group 7) in the light. All does gave birth normally except those of group 4, which responded similarly to group 1 does. These findings demonstrate that in the rabbit, parturition may be seriously compromised if does nurse out of phase with the normal schedule and suggest that a shift in the daily timing of OT release may underlie this.

Animals↗
PubMed1994

Learning of suckling odors by newborn rabbits declines with age and suckling experience.

After being nursed just once for 4-5 min by an artificially scented doe, newborn rabbits show the full pattern of nipple-search behavior when placed on a fur scented with the same odor as their mother. It was the aim of the present study to test whether such rapid learning is dependent on age. In Experiment 1 in which normally raised pups were nursed by a scented doe either on Days 1, 3 or 5, conditionability was found to decline markedly by postnatal Day 5. In Experiment 2 conditionability was maintained in pups deprived of suckling experience by bottle feeding from Days 1-4, but not in hand-raised pups allowed to search on a doe for 4 min daily without milk intake. Possible mechanisms underlying the decline in conditionability to suckling odors, as well as the potential functional significance of this early learning for immediate postnatal and later life are discussed.

Aging↗
PubMed1994

Effect of photoperiod and exogenous melatonin on correlates of estrus in the domestic rabbit.

It was the purpose of this study to test whether inhibition of estrus in the rabbit by short photoperiod could be simulated by subcutaneous implants of the pineal hormone melatonin. By measuring two non-invasive and readily quantifiable correlates of estrus, emission of the so-called nipple-search pheromone and scent-marking behavior (chinning), it was found that: 1. In intact does kept in stimulatory long photoperiod, melatonin suppressed chinning but had no effect on emission of nipple-search pheromone. 2. In intact, melatonin-treated does which were returned from inhibitory short day to stimulatory long day, chinning remained suppressed, whereas pheromone emission increased as for the vehicle-treated, control does. 3. In ovariectomized does, estradiol administration stimulated both pheromone emission and chinning whereas melatonin failed to suppress these effects. Thus, although the administration of melatonin had an inhibitory effect on chinning it failed to suppress emission of the nipple-search pheromone and therefore failed to fully simulate the effect of short photoperiod on these two correlates of estrus. Several explanations for this discrepancy are considered, including the possibility that melatonin is not the sole mediary of the photoperiodic response, and that at least in female rabbits, other pineal products may also play a significant role.

Animals↗
PubMed1994

Visceral adiposity, androgens, and plasma lipids in obese men.

The primary purpose of this study was to investigate the relationships between adipose tissue (AT) distribution, particularly visceral adipose tissue (VAT), circulating androgens, and plasma lipids in a group of 17 obese (body mass index [kg/m2], 31.8 +/- 3.8) android (waist to hip ratio [WHR], 1.01 +/- 0.05) men. AT distribution was measured by magnetic resonance imaging (MRI) using a multislice model in which 41 equidistant images were acquired from head to foot. Although the subjects were homogenous with respect to total adiposity, a sevenfold variation in VAT was observed. VAT and the visceral to subcutaneous ratio (VSR) were significantly correlated with triglyceride (TG) levels and the ratio of apolipoprotein (apo) B to low-density lipoprotein cholesterol ([LDL-C] P < .05). Neither proximal-thigh AT area nor lower-body subcutaneous adipose tissue (SAT) volume was significantly related to any lipid variable. However, the ratio of visceral AT area to thigh AT area (VTH) was positively correlated with TG (P < .05), and the ratio of VAT volume to lower-body SAT volume (VLBS) was positively correlated with TG, total cholesterol (TC), LDL-C (P < .05), and apo B (P = .057). Total testosterone (TT), free testosterone (FT), and sex hormone-binding globulin (SHBG) were not significantly related to any of the plasma lipid variables; however, the percentage of FT (%FT) was positively correlated with high-density lipoprotein cholesterol ([HDL-C]P < .01) and HDL-C/LDL-C (P < .05). TT, FT, %FT, and SHBG were not related to MRI-measured VAT. Age waa not related to either VAT or androgen levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1994

Assessing pain threshold in the rat: changes with estrus and time of day.

Pain threshold was determined in female rats using the tail flick test. Latency to respond depended on the locus of the tail heated, with the most distal sites resulting in the shortest response times (Experiment 1). Tail flick latency also varied according to the time of day, with shorter response times recorded around the middle of the dark phase than near its beginning or after its end. This was the case for intact, for ovariectomized, and for ovariectomized, estradiol-treated rats (Experiment 2). However, response times also varied across the estrous cycle, with significantly shorter latencies recorded during estrus and metestrus. Ovariectomy abolished these fluctuations, and whereas administration of estradiol increased response times, progesterone had little effect (Experiment 3). These results suggest that site of tail heating, time of day, and presence of ovarian hormones can influence tail flick latency independently, thus demonstrating the complexity of the mechanisms that may contribute to pain threshold even within the same paradigm.

Animals↗
PubMed1994

Circadian wheel running activity rhythms in two strains of domestic rabbit.

Results from experiments on two strains of domestic rabbit show that despite their hopping gait, circadian locomotor rhythms can be successfully measured using running wheels specially designed for large laboratory mammals. Three female rabbits of an English outbred strain were monitored in a 13:11 light:dark (LD) cycle and in constant light (LL), while 12 Dutch-Himalayan rabbits were monitored in a 14:10 LD cycle and constant dark (DD). Much stronger rhythms were observed in the latter strain, which under LD conditions showed individuals with patterns that varied from nocturnal (n = 5), diurnal (n = 4), crepuscular (n = 1), and predominantly arrhythmic (n = 2). In DD, 10 rabbits showed strong free-running rhythms, five with tau (tau) less than 24 h and five longer. The predominantly arrhythmic activity pattern in the remaining two made estimation of tau difficult. Differences in circadian patterns both under LD and DD were unrelated to sex. Results show that locomotor rhythms of the rabbit can be measured using the running wheel, the traditional apparatus of chronobiology. However, the experiments suggest also that the large-bodied breed of rabbits that tend towards obesity, such as the English outbred strain, are relatively inactive and that smaller, more active breeds such as the Dutch-Himalayan may be more suitable for studying circadian rhythmicity if the running wheel is employed.

Animals↗
PubMed1994

Transmission of food preference in the rabbit: the means of information transfer.

Rabbit pups raised by mothers fed different diets during pregnancy and lactation show a clear preference for the diet of their mother at weaning. By supplementing does' lab chow diet with aromatic juniper berries, the present study aimed to investigate the relative importance of 1) fecal pellets deposited by the mother in the nest, 2) prenatal experience in utero, and 3) contact with the mother during nursing in determining pups' later food preference. The three means of transmission were found to be equally effective. Thus, pups from normally fed does raised with fecal pellets from juniper-fed mothers, pups from juniper-fed mothers cross-fostered to normally fed does immediately after birth, and pups of normally fed mothers nursed by juniper-fed does all showed as strong a preference for juniper as pups raised by juniper-fed mothers exclusively. Such apparent redundancy may not only help insure that less aromatic substances or substances transmitted differentially by these routes are learned, but also that pups can acquire a preference for a variety of foods eaten by their mother at different times.

Animals↗
PubMed1994

Olfactory function in patients with hypogonadotropic hypogonadism: an all-or-none phenomenon?

Hypogonadotropic hypogonadism (HH) refers to an endocrine defect of hypothalamic origin resulting in gonadal hypoplasia and frequently associated with anosmia or severely impaired olfactory function (Kallmann's syndrome). This apparently results from a disruption in the migration of neurons from the olfactory placode to the bulb and hypothalamus early in development, and so provides a unique opportunity to investigate olfactory function in human subjects with congenitally incomplete peripheral systems. Olfactory performance in 37 HH patients and 37 age-matched controls was compared using a modified version of the Munich Olfaction Test. This test is based on the sniff-bottle method and includes tests of (i) odor quality discrimination, (ii) intensity discrimination, (iii) detection thresholds, and (iv) recognition, hedonic evaluation and identification ability. The patients could be divided into two distinct groups differing significantly on all four subtests and showing no overlap in performance: 20 anosmics, conforming to Kallmann's syndrome, and 17 apparent normosmics whose performance was slightly poorer, but not significantly different to that of the controls. The unexpected failure to find a continuum of olfactory dysfunction now raises the question whether HH with or without anosmia represents two syndromes with distinct etiologies, or rather reflects the ability of the olfactory system to function well despite morphological impairment.

Adult↗
PubMed1994

Prolactin stimulates emission of nipple pheromone in ovariectomized New Zealand white rabbits.

Using ovariectomized New Zealand white rabbits and the nipple-search behavior of pups as a bioassay, we evaluated the capacity of prolactin to stimulate the emission of an odor signal that allows newborn pups to locate the mother's nipples and suckle. Whereas emission of this so-called nipple pheromone was minimal in untreated, ovariectomized does, emission was stimulated by the administration of progesterone (1 mg/day) to estrogen-treated does (0.5 microgram estradiol benzoate/day) and decreased after withdrawal of progesterone despite continuous administration of estrogen. However, substituting ovine prolactin (1.5 mg/day) for progesterone, under continuous estrogen administration, resulted in an increase in pheromone emission to near-maximal levels. This stimulatory effect of prolactin was not progesterone-dependent since it also occurred in does pretreated with estrogen alone and, to a lesser extent, even in females without estrogen priming. From these and previous data, we propose that emission of nipple pheromone in the rabbit is induced during pregnancy by the combined action of estrogen and progesterone, and maintained during lactation by the dual action of estrogen and prolactin.

Animals↗
PubMed1993

Discriminating parts from the whole: determinants of odor mixture perception in squirrel monkeys, Saimiri sciureus.

In a task designed to simulate olfactory-guided foraging, the ability of squirrel monkeys to discriminate an artificial 12-component odorant from 3-, 6-, 9- or 11-component submixtures was investigated. A combination of factors was found to contribute to the animals' performance: 1. Discriminability generally decreased as the number of components in the submixture increased. 2. Submixtures did not contribute equally to mixture perception, and one component in particular (cineole) disproportionately influenced stimulus discriminability. 3. Interactive effects between submixtures resulted in marked deviations from the general pattern of discriminability. 4. Changes in the relative concentration of submixtures could also influence discriminability. 5. Finally, individual differences in responsiveness to particular stimuli were apparent. These findings demonstrate that the interaction between components in odor mixtures can be complex and that seemingly small changes in composition can strongly affect perception and thus potential signal function. It is therefore suggested that in future investigations of squirrel monkey semiochemistry, the method of systematically varying submixtures may be particularly useful in defining the contribution of components to a signal.

Adult↗
PubMed1993

Assessing olfactory performance in a New World primate, Saimiri sciureus.

Using a task designed to simulate olfactory-guided foraging behavior, this study demonstrates for the first time that olfactory performance can be reliably assessed in squirrel monkeys. Small flip-top vials were fixed in random order to the arms of a climbing frame and equipped with odorized strips signalling either that they contained a peanut food reward (S+) or that they did not (S-), and three adult female monkeys were allowed 1 min to harvest as many baited nuts from this tree as possible. Given five 1-min trials per day, animals took between 15 and 25 days to reach the criterion of 80% correct choices, could readily transfer to new S+ or S- stimuli, and could remember the task even after a 1-month break. The precision and consistency of the monkeys' performance in tests of discrimination ability and sensitivity demonstrate the suitability of this paradigm for assessing olfactory function, and a first test of human subjects using the same cups and odorants showed that it may also be used to directly compare olfactory performance in human and nonhuman primates.

Adult↗
PubMed1993

Olfactory imprinting.

The term imprinting is used to refer to biologically relevant learning during a sensitive period defined by a particular developmental stage or physiological state. Although olfactory imprinting may occur at any age, and some of the best-studied paradigms involve adult animals, recent reports of long-term memory for odorants experienced during prenatal life present a particular challenge to our understanding of olfactory learning. Firstly, it is possible that these paradigms represent a form of exposure learning based on mechanisms different to the more familiar associative paradigms. Secondly, given the substantial addition of neural elements occurring during the perinatal period, these paradigms raise the question as to how the olfactory system, and eventually the brain, is able to acquire and retain information under conditions of major neural growth and change.

Aging↗