Search PubMed⌕ Search

Biomedical subjects

R Hudson

Publications and source records attributed to R Hudson.

At least 73 records · Page 4Linked to original sources
PubMed1993

Black spots on the scalps of schoolchildren. A recurrent condition in the windy west.

During the past 10 years, epidemics of black spots on the scalps of schoolchildren have caused considerable concern in at least 4 communities in the Rocky Mountain states. We describe the clinical presentation of "black spots" in a group of Wyoming elementary school students and the epidemiologic investigation that revealed the cause. Our study included a questionnaire survey of students' parents, examination of students at the affected school and at two other schools, observation of playground activity patterns, and laboratory analysis of specimens taken from affected children and from the school environment. The black material in the scalp spots was chemically identical to flakes of black material found on the playground and tar from the school roof. We concluded that the spots were caused by flakes of windblown tar from the school roof. Previous outbreaks of black spots may have had a similar cause.

Air Pollutants↗
PubMed1991

Rapid odor conditioning in newborn rabbits: amnesic effect of hypothermia.

Rabbit pups are completely dependent on a maternal pheromone for the release of suckling behavior. However, if the mother is perfumed prior to nursing, pups will learn to respond to the novel odor with the characteristic nipple-search behavior in just one 3-4 min nursing episode. In a first investigation of the processes underlying this recently developed learning paradigm, time-dependent effects of hypothermia on retention of the task could be demonstrated. Thus pups whose whole body was cooled to a mouth temperature of 7 degrees C immediately after conditioning (n = 10) and tested 24 h later for 3 min on a perfumed fur did not differ significantly in their search response from naive, untreated controls (n = 10). In contrast, pups cooled 4 h after conditioning (n = 10) demonstrated clear retention of the learned response and searched as vigorously as conditioned but uncooled animals (n = 10). As pups of all groups demonstrated normal nipple-search behavior when tested on a lactating doe, the deficits associated with immediate cooling appear to have been specific to the learning task and time of treatment.

Animals↗
PubMed1991

The use of bacteriophage MS2 as a model system to evaluate virucidal hand disinfectants.

A model system which would closely reflect the resistance of poliovirus but could be easily performed in any microbiology laboratory would offer considerable advantages for rapidly screening hand decontamination products. The use of the bacteriophage MS2 as a simple model for virucidal testing has been evaluated. In suspension tests the sensitivity of MS2 to alcohols, organic acids and alkalis generally reflected that observed in studies using poliovirus. MS2 could be applied and recovered from the hands of volunteers with high efficiency. Furthermore MS2 proved to be a suitable replacement for Escherichia coli in a standard hand-decontamination test.

Acids↗
PubMed1990

Sensitivity of female rabbits to changes in photoperiod as measured by pheromone emission.

Newborn rabbits are completely dependent on a pheromone on the mother's belly for the release of nipple-search behaviour and suckling. Using the stereotyped behavioural response of the pups as a bioassay it could be shown that: 1. In non-breeding does pheromone emission is stimulated by experimental long day and suppressed by experimental short day conditions within 1 to 2 weeks of reversing the light regime. 2. Under constant long day conditions pheromone emission, readiness to mate, conception rate and litter size remain high with no evidence of endogenous seasonal rhythmicity. 3. Experimental changes in daylength of just 1 or 2 h in either direction are sufficient to induce marked alterations in the level of pheromone emission, number of successful matings and average litter size within 2 to 3 weeks. Pheromone emission would thus seem to provide a sensitive test of photoperiodic responsiveness in non-breeding female rabbits, and a convenient, non-invasive indicator of their reproductive state.

Animals↗
PubMed1990

Effects of reversible nare occlusion on the development of the olfactory epithelium in the rabbit nasal septum.

To investigate environmental influences on the development of the olfactory epithelium, semi-thin sections were taken from the nasal septum of newborn and 30-day-old rabbits; the epithelial thickness and the number of olfactory knobs, supporting cells, dark basal cells, and receptor cells were compared. During normal development, a marked increase in epithelial thickness was found, largely because of an increase in the number of receptor cells. Whereas unilateral nare occlusion on day 1 resulted in 10% fewer receptor cells and 25% fewer knobs on the deprived side by day 30, nare occlusion either up to or after day 5 had little effect, and even temporary reopening from days 6-7 was sufficient to stimulate receptor-cell development on the occluded side. Although in these latter cases, a slight deprivation effect of 6% was still found in the number of receptor-cell nuclei, there was no longer a significant difference in the number of knobs between the open and closed sides. Thus, whereas exposure to the environment during the first days of life appears to be sufficient to stimulate sustained growth, the deprived epithelium may retain the capacity to respond to such cues beyond this time. However, as nare occlusion also had an effect on the respiratory epithelium and nasal lymphatic tissue, the nature of the cues stimulating receptor-cell development, whether olfactory or non-olfactory, is not yet clear.

Afferent Pathways↗
PubMed1990

A morphometric comparison of the olfactory epithelium of newborn and weanling rabbits.

As part of a study of the development of olfactory function in the rabbit, a morphometric analysis of the olfactory epithelium in newborn and 30-day-old animals was carried out. Surface area, thickness and cell densities of the olfactory epithelium were compared in hematoxylin-eosin stained serial sections through the nasal cavities of 4 newborn and 3 weanling rabbits. While the basic structure of the olfactory cavity changed little with age, a large quantitative development in the epithelium was observed. The pattern of growth appeared uniform and resulted in a 3-fold increase in total surface area from about 1 cm2 per side in the newborn to about 3 cm2 in the weanling, and an increase in thickness from approximately 65 microns to about 90 microns. The increase in thickness was due mainly to a disproportionate, 5-fold increase in the number of olfactory neurons. This resulted in a total of about 32 million cells per side by day 30, and represented an increase in the ratio of neurons to basal cells of 7:1 to 10:1, and neurons to supporting cells of 2:1 to 4:1. While such an increase in the number of primary neurons presumably improves the animal's perceptual abilities, it nevertheless raises the question as to how perceptual constancy can be maintained during a period of such rapid neural change.

Animals↗
PubMed1990

Pulmonary oedema in two parturients with hypertrophic obstructive cardiomyopathy (HOCM).

Two patients with hypertrophic obstructive cardiomyopathy (HOCM) presented for delivery. The first had a repeat Caesarean section with general anaesthesia and the second gave birth vaginally with epidural analgesia. Both patients developed pulmonary oedema in the peripartum period. These cases highlight the delicate fluid requirements of the pregnant patient with HOCM. The fluid management of the parturient is discussed with particular emphasis on the pathophysiology of HOCM. The indications for invasive monitoring are presented.

Adult↗
PubMed1990

Chin marking behavior, sexual receptivity, and pheromone emission in steroid-treated, ovariectomized rabbits.

The effect of daily injections of estradiol benzoate (1 or 10 micrograms) and of progesterone (10 mg) on chin marking activity, sexual receptivity, and emission of nipple-search pheromone in ovariectomized rabbits was investigated. Both estradiol treatments resulted in a significant increase in all three measures over baseline and control group levels within 1-3 days, and withdrawal in a return to pretreatment levels within 2 weeks (Experiment I). In contrast, the administration of progesterone to such estradiol-primed does resulted in an almost immediate suppression of chin marking and lordosis, but in marked enhancement of pheromone emission and aggressive behavior (Experiment II). However, progesterone given alone to nonprimed does had no effect on any of these measure (Experiment III). The response profiles resulting from these treatments correspond well to patterns reported for intact does during estrus (= estradiol alone), pregnancy (= estradiol plus progesterone), and at parturition (= progesterone withdrawal).

Animals↗
PubMed1990

A behavioral bioassay for analysis of rabbit nipple-search pheromone.

To suckle, newborn rabbits are completely dependent on a pheromone present on the doe's ventrum and also apparently contained in the milk. Pups presented in a standardized test with 30 microliters of fresh rabbit milk on a glass rod reacted with vigorous search-like movements in 93%, and with grasping of the rod in 70% of trials, but did not respond to control presentations of other odorants. The pups were found to be most reactive 1-3 hours before the once daily nursing, and although they rapidly habituated to repeated testing, a break of 30 minutes was sufficient for the recovery of responsiveness. Even milk diluted by as much as 1:10(4) elicited significantly more responses than control substances. However, when left at room temperature it lost this behavior-releasing quality within about 20 minutes, but retained it for several months when stored at -40 degrees C. Rabbit milk thus appears to represent a ready source of nipple-search pheromone, and the behavioral response of pups to be reliable enough to serve as a bioassay for further pheromonal analysis.

Aging↗
PubMed1990

Rapid cryopreservation of sheep embryos by direct transfer into liquid nitrogen vapour at -180 degrees C.

The in vitro survival of control and rapidly cryopreserved sheep embryos was examined as a function of the duration of exposure to a vitrification medium (25% glycerol + 25% propylene glycol). Embryos in late morula to late blastocyst stages were permeated by a mixture of 10% glycerol + 20% propylene glycol for 10 min at 18-23 degrees C and then exposed to the vitrification medium for 0.5, 1, 2 or 4 min at 18-23 or 4-12 degrees C. The cryoprotectants were removed without cryopreservation (control embryos) or after rapid cryopreservation by direct transfer into liquid nitrogen vapour at -180 degrees C. The duration of exposure to the vitrification medium at 18-23 degrees C affected the in vitro survival rate of control embryos (P = 0.06) but had no effect on the survival of rapidly cryopreserved embryos. However, at 4-12 degrees C the duration of exposure affected the survival of cryopreserved embryos (0.5 min: 64%, 18/28; 1-4 min: 43%, 34/80; P = 0.074). Overall, the in vitro survival rate of control and cryopreserved embryos increased with advancing development from late morulae (36%) to late blastocysts (70%). The in vivo survival of embryos that had been exposed to the vitrification medium for 0.5 min at 4-12 degrees C and then vitrified was tested. The rate of development to term was 11% (4/35) for late morulae or early blastocysts and 32% (6/19; P greater than 0.1) for blastocysts to hatching blastocysts. These results showed that sheep embryos can be successfully cryopreserved by a simple, rapid procedure.

Animals↗
PubMed1990

Selective expression of factors preventing cholinergic dedifferentiation.

Chicken retina neurons from 8-9-day-old embryos developed prominent cholinergic properties after several days in stationary dispersed cell (monolayer) culture. These cells accumulated [3H]choline by a high-affinity, hemicholinium-sensitive transport system, converted [3H]choline to [3H]-acetylcholine [( 3H]ACh), released [3H]ACh in response to depolarization stimuli, and developed choline acetyltransferase (ChAT) activity to levels comparable to those of the intact retina. The cholinergic state, however, was not permanent. After 7 days in culture, the capacity for [3H]ACh release decreased drastically and continued to diminish with longer culture periods. Loss of this capacity seemed not to be due to loss of cholinergic neurons, because high-affinity choline uptake was unchanged. However, a substantial decrease of ChAT activity was observed as a function of culture age, and probably accounted for the low level of ACh synthesis in long-lasting cultures. The loss of ChAT activity could be prevented in at least two different ways: (a) Maintaining the neurons in rotary (aggregate) rather than stationary culture completely blocked the loss of enzyme activity and gave a developmental profile identical to the known "in situ" pattern of differentiation; and (b) Conditioned medium from aggregate cultures significantly reduced the drop in ChAT activity of neurons maintained in stationary, dispersed cell cultures. Activity that stabilized cholinergic differentiation was nondialyzable, heat-sensitive, and not mimicked by functional nerve growth factor. Production of activity by aggregates was developmentally regulated; medium obtained from aggregates after 3 days in culture had no effect on cholinergic differentiation, whereas medium obtained from aggregates between 6 and 10 days in culture produced a fivefold increase of ChAT in monolayers.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1987

Regional autonomy in the peripheral processing of odor signals in newborn rabbits.

In newborn rabbits, small and apparently arbitrary regions of the olfactory bulb and associated epithelium appear capable of a high degree of odor processing. After medial or lateral removal of up to 80% of the olfactory bulbs, including the accessory bulb, newborn pups were still able to respond appropriately to the pheromone-governing suckling behavior (Expt. I), could rapidly learn to associate a novel, artificial odor with suckling (Expt. II), and continued to respond appropriately to artificial odors learned prior to lesioning (Expt. III). These findings suggest that the perception and recognition of such suckling signals does not depend on the integration of information from the entire bulb or epithelium, and question the extent to which patterns of 2-deoxyglucose uptake in the bulb reflect the neural coding for specific odors. However, as the tasks set here only required detection of odor signals and not true odor discrimination, it may still be that the full bulbar pattern of activation is necessary for higher-order processing, such as distinguishing between odors and attributing different meanings to them.

Animals↗
PubMed1986

Pheromonal release of suckling in rabbits does not depend on the vomeronasal organ.

Newborn rabbits are completely dependent on a pheromone present on the mother's belly for the release of the highly stereotyped nipple-search behavior and for nipple attachment. Surgical removal of the vomeronasal organ had no effect on pups' ability to respond to the pheromone when tested on a lactating female, nor on their ability to obtain milk in the normal nursing situation. Lesioned pups could also learn to associate the odor of citral with nipple-search behavior when nursed by a citral-scented doe. In contrast, irrigating the nasal mucosa with ZnSO4 completely eliminated responsiveness both to the pheromone and to the conditioned odor of citral. This is of particular interest given the important role attributed to the accessory olfactory system in pheromonal perception. However, it might be necessary to distinguish between pheromones associated with suckling and therefore peculiar to mammals, and other pheromones.

Animals↗