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Biomedical subjects

J F Carroll

Publications and source records attributed to J F Carroll.

At least 55 records · Page 3Linked to original sources
PubMed1995

Hormonal responses in elders experiencing pre-syncopal symptoms during head-up tilt before and after exercise training.

BACKGROUND: Hormonal responses of elderly individuals experiencing pre-syncopal symptoms during head-up tilt testing (HUT) were compared with responses of nonsymptomatic subjects both before (T1) and after (T2) 6 months of endurance training. METHODS: Based on responses to HUT at T1, 35 men and women (ages 61-79 years) were placed into symptomatic and nonsymptomatic groups for analysis. Symptomatic subjects (n = 5) experienced lightheadedness, nausea, sweating, or syncope during T1 HUT but completed 15 minutes of HUT at T2. Training consisted of treadmill walking or stairclimbing 3 x/wk, 30-45 min/day, at 75-85% of maximal heart rate reserve. Adrenocorticotropic hormone (ACTH), vasopressin, aldosterone, norepinephrine, epinephrine, hemoglobin, and hematocrit were measured during supine rest prior to HUT, and either at the end of the 15-minute HUT or at symptom onset. Plasma volume (PV) was measured at supine rest; tilt-induced changes in PV were calculated from changes in hemoglobin and hematocrit. RESULTS: During T1 HUT, symptomatic subjects had greater increases in vasopressin and a greater rate of PV loss (p < .05). Increases in ACTH and aldosterone were greater in symptomatic subjects at T1 and T2, while increases in norepinephrine were greater at T2 (p < .05). Reductions in tilt-induced vasopressin concentration and a decreased rate of PV loss were seen at T2 in symptomatic subjects. CONCLUSIONS: T1 results from symptomatic subjects are consistent with greater stimulation of volume-sensitive receptors induced by a greater rate of fall in PV. Exercise training resulted in increased tilt tolerance for symptomatic subjects associated with reductions in vasopressin concentration and rate of PV loss during tilt.

Aged↗
PubMed1995

Evidence for kairomonal influence on selection of host-ambushing sites by adult Ixodes scapularis (Acari: Ixodidae).

Unfed adult blacklegged ticks Ixodes scapularis Say, were tested under laboratory conditions for behavioral responses to substances rubbed from external glands on legs of white-tailed deer, Odocoileus virginianus (Zimmermann). In replicated trials, significantly more female ticks became stationary on portions of vertical glass tubing rubbed with the tarsal gland substances of both bucks and does than on nontreated tubing. This behavior, apparently an arrestant response, was infrequent among males. White-tailed deer urinate upon their tarsal glands, and doe urine also produced an arrestant response among female ticks. Metatarsal gland secretions of bucks elicited no arrestant response in either male or female I. scapularis, but doe metatarsal gland secretions elicited low-level positive responses from both sexes. A low-level arrestant response also was exhibited by females to secretions from the interdigital glands of bucks. In a second bioassay, three times as many females came to rest on the terminal ends of vertical glass rods whose bases were treated with secretions from buck interdigital glands than on rods with nontreated bases. This suggests that interdigital gland secretion influences blacklegged tick climbing behavior. Substances produced by or associated with the leg glands of O. virginianus may therefore serve as kairomones for host-seeking adult I. scapularis; interdigital gland secretions on soil or leaf litter may signal active deer trails, and tarsal gland substances may denote portions of vegetation contacted previously by white-tailed deer. In nature, use of these chemical cues by host-seeking adult I. scapularis may increase the probability of acquiring a suitable host.

Animals↗
PubMed1995

Effect of 6 months of exercise training on cardiovascular responses to head-up tilt in the elderly.

The purpose of this investigation was to evaluate the effect of 6 months of exercise training on cardiovascular responses to 70 degrees head-up tilt (HUT) in the elderly. Forty-four elderly men and women (ages 60-82 years) were assigned to endurance training alone (n = 18), endurance training in combination with selected resistance exercises (n = 17), or to a non-exercising control group (n = 9). Head-up tilt testing at the start (T1) and end (T2) of 26 weeks of training consisted of 30 min of supine rest, 15 min of 70 degrees HUT, and 15 min of supine recovery. Endurance training consisted of uphill treadmill walking or stair climbing exercise 3 times per week, 30-45 min/day, at 75-85% of maximal heart rate reserve. In addition, the endurance/resistance group completed one set of 8-15 repetitions of biceps curl (BC), triceps extension (TE), and leg press, 3 times per week. After 26 weeks, increases in VO2max averaged 16.2% and 12.3% for endurance and endurance/resistance groups, respectively. In addition, the endurance/resistance group increased BC and TE strength by 25.3% and 26.1%, respectively. Results from the HUT test indicated that only the endurance group increased supine resting stroke volume (SV) and cardiac output (Q) from T1 to T2; however, SV and Q during HUT were not augmented as a result of training. Training did not affect heart rate, blood pressure, or peripheral resistance responses at rest or during HUT in any of the groups. These results suggest that 6 months of endurance training, alone or in combination with selected resistance exercises, is not detrimental to blood pressure controlling mechanisms to head-up tilt in the elderly.

Aged↗
PubMed1995

Hemodynamic alterations in hypertensive obese rabbits.

There is little information on changes in overall and regional hemodynamics in obesity-associated hypertension. Therefore, the purpose of this study was to determine alterations in overall and regional blood flows and resistances in adipose and nonadipose tissues in a new model of obesity-associated hypertension in rabbits. Sixteen female New Zealand White rabbits were fed either a maintenance or high-fat diet; after 8 to 12 weeks cardiac output and regional blood flows were measured with the use of radioactive microspheres. Obese rabbits (5.22 +/- 0.14 versus 3.66 +/- 0.04 kg) had higher blood pressure (113 +/- 3 versus 95 +/- 1 mm Hg), cardiac output (812 +/- 59 versus 593 +/- 47 mL/min), and heart rate (269 +/- 12 versus 219 +/- 9 beats per minute) and lower overall peripheral resistance (0.14 +/- 0.01 versus 0.17 +/- 0.01 mm Hg/[mL/min]) than lean rabbits. Compared with lean controls, obese rabbits had higher weights of the ventricles, kidneys, liver, ovaries, adrenals, diaphragm, and spleen. Absolute blood flows were greater in the ventricles, kidneys, lungs, and ovaries, but differences were minimized when flows were normalized for organ weight. Adipose tissue flow per gram weight was significantly lower and resistance higher in obese rabbits. However, calculated total adipose tissue flow was higher in obese rabbits (86 versus 45 mL/min). Absolute resistances were lower in the left ventricle, kidneys, and large intestine, but when resistances were indexed for organ weight, kidney resistance tended to be higher in obese rabbits. These results indicate that even short periods of obesity-associated hypertension result in marked overall and regional hemodynamic changes.

Adipose Tissue↗
PubMed1995

Body fat and muscle thickness distributions in untrained young females.

Brightness-mode (B-mode) ultrasound was used to measure fat and muscle thicknesses on 44 untrained females (age = 18-29 yr, body density = 1.050 +/- 0.009 (SD)g.ml-1, %fat = 21.5 +/- 4.1%) at eight sites (triceps, biceps, forearm, subscapular, abdomen, quadriceps, hamstrings, and posterior calf). The correlation coefficients between fat and muscle thickness were not significant at any measurement site except for the triceps (r = -0.32, P < 0.05). Intercorrelation analyses among the eight sites were significant (P < 0.05) in almost all cases for fat thickness, while mainly between adjoining sites for muscle thickness. However, both tissues had a low degree of generality in thickness among sites. Fat thickness at all measurement sites was significantly correlated with body density except for the posterior calf; the best correlation was found with the quadriceps (r = -0.73). On the other hand, for muscle thickness, only the forearm and triceps were significantly correlated with body density. These results show 1) the extent of muscled and fat thicknesses are independent each of other within the same region, 2) fat and muscle thicknesses have a high degree of specificity in site distribution, and 3) fat thickness measurements determined from B-mode ultrasound may be of significant value assessing total body composition.

Adipose Tissue↗
PubMed1995

Effect of training on blood volume and plasma hormone concentrations in the elderly.

The purpose of this investigation was to determine the effects of 6 months of endurance training on resting plasma (PV) and blood volume (BV), and resting hormone and electrolyte concentrations in the elderly. Thirty-eight elderly men and women (ages 60-82 yr) were assigned to endurance exercise training (N = 29) or to control (N = 9) groups. Resting plasma levels of adrenocorticotropic hormone, vasopressin, aldosterone, norepinephrine, epinephrine, sodium, potassium, and protein were measured at the start (T1) and end (T2) of 26 wk of training. PV measurement was performed using the Evan's blue dye technique. Endurance training consisted of uphill treadmill walking or stairclimbing exercise 3 times.wk-1, 30-45 min.d-1, at 75-84% of maximal heart rate reserve. The exercise group increased VO2max by 11.2% (P < or = 0.05) and increased resting PV and BV by 11.2% and 12.7% (P < or = 0.05), respectively. Hormone and electrolyte levels in the exercise group remained unchanged; all variables were unchanged in the control group. These results are similar to findings in younger individuals. Because plasma hormone concentrations were maintained despite a chronically elevated BV, endurance training in healthy, elderly subjects may be associated with a resetting of volume receptors.

Adrenocorticotropic Hormone↗
PubMed1994

Host-seeking of blacklegged tick (Acari: Ixodidae) nymphs and adults at the woods-pasture interface.

To clarify the risk of pastured livestock for exposure to Ixodes scapularis Say (Acari: Ixodidae), we estimated the host-seeking activity of nymph and adult blacklegged ticks at the woods-pasture interface on horse farms in Maryland. Parallel linear transects of 100 m length and 1 m width were sampled repeatedly in pastures and adjacent woodland locations during periods of nymph (early summer) and adult (fall and spring) host-seeking activity. Data collected over two successive years indicated that adults were most abundant in ecotonal vegetation at the wood's edge, median values of 6.4 and 2.2 ticks per 100 m2 sample during fall and 1.2 and 0.5 ticks per 100 m2 sample for spring periods. Nymphs were most abundant in the shallow woods location, median values of 4.2 and 35 ticks per 100 m2 sample, followed by the deep woods and wood's edge locations. Host-seeking nymph and adult black-legged ticks also were collected repeatedly in pasture vegetation, median values ranging from 0.2-0.8 ticks per 100 m2 sample, with a progressive decrease in abundance from the fenceline into pasture. Adults and nymphs both were uncommon more than 5 m into pastures, where only two adults and one nymph were captured in 84 (fall and spring) and 24 (summer) 100-m2 samples, respectively. Levels of adult and nymph host-seeking in pasture vegetation were spatially correlated with tick abundance in adjacent woodlands when ticks were numerous; this condition presumably reflects a spillover of ticks from the woodlands-based population. These findings expand knowledge of black-legged tick host-seeking behavior and establish a basis for the exposure of pastured livestock to nymphs and adults.

Aging↗
PubMed1994

Exercise, age, and skeletal muscle function.

Skeletal muscle strength, muscle mass, and psychomotor performance decline with age. These declines are associated with reduced functional capacity and an increased risk of musculoskeletal injury and dependent care. Resistance exercise training is generally safe and effective for improving muscle strength and increasing muscle mass in the elderly. The magnitude of improvement depends on the intensity of training and the initial level of fitness. Because many elderly persons have low levels of muscular strength, they show a greater than average potential for relative improvement. Whether an exercise program can enhance psychomotor performance in the elderly is equivocal. Participating in a well-rounded program of physical activity throughout life may be the best approach to attenuating the decline in skeletal muscle function associated with aging.

Aged↗
PubMed1992

Incidence of injury during moderate- and high-intensity walking training in the elderly.

To evaluate the effect of 26 weeks of moderate- and high-intensity walking training on injury rates in the elderly, 68 healthy volunteers (31 men, 37 women) were assigned to moderate intensity (MOD, n = 26) or high-intensity (HI, n = 24) training, or to a control (CONT, n = 18) group. To achieve prescribed training intensity, many subjects walked uphill on a treadmill. Seven of 50 subjects who trained (14%) suffered a training-related orthopedic injury; one subject was injured during treadmill testing. Four training injuries (lower leg and foot) occurred during weeks 1-13; three training injuries (leg and groin) occurred during weeks 14-26. Six of the injuries were to women. Because only one training injury occurred during uphill treadmill walking, injuries appeared related to fast walking and not exercise intensity. The higher incidence of injury in females is consistent with our earlier work, indicating the importance of further research to determine the underlying cause.

Aged↗
PubMed1992

Simple in-vitro feeding system for northern fowl mites (Acari: Macronyssidae).

The use of Parafilm membranes for in-vitro feeding of northern fowl mites, Ornithonyssus sylviarum (Canestrini & Fanzago), is described. A membrane stretched in two perpendicular directions, folded, heat-sealed, inflated, and twisted at the ends to form a sphere allowed a high percentage (greater than 80%) of surviving adult female mites to feed on whole chicken blood. A high percentage (7 of 10) of protonymphs also fed through the membrane. Mites were able to feed from the same sac for 3 d and oviposited on the sac. This technology has potential applications for use in rearing O. sylviarum and other hematophagous arthropods, and for physiological experimentation.

Animals↗
PubMed1992

Tick sweep: modification of the tick drag-flag method for sampling nymphs of the deer tick (Acari: Ixodidae).

We describe a version of the standard tick drag-flag modified for use in close-growing and tangled vegetation, as well as under ornamental shrubbery and fallen branches. Two major features of the sweep are: (1) it allows the user to remain upright with the flag parallel to the ground, thus sampling effectively beneath low and fallen branches and around shrubs, as well as capturing host-seeking ticks in advance of the operator; and (2) the use of a flannel rubberized-laminate fabric (crib sheet) for the flag that is snag-proof and highly durable in dense and thorny vegetation. In simultaneous 100-m samples, the sweep was as effective as the 1-m standard tick drag for capturing nymphs of the deer tick, Ixodes dammini Spielman, Clifford, Piesman & Corwin, where understory vegetation was sparse, but was twice as effective in dense vegetation, capturing significantly more I. dammini nymphs. The sweep also captured nymphs of the American dog tick, Dermacentor variabilis (Say); rabbit tick, Haemaphysalis leporispalustris (Packard); and lone star tick, Amblyomma americanum (L.).

Animals↗
PubMed1992

Rehabilitation and life-style modification in the elderly.

The projected growth of the elderly population in the United States in the coming years underlines the importance of assuring that the quality of life for older persons is maintained. Because CHD is prevalent in this population, measures for preventing disease as well as for optimizing the abilities of those with disease will assume greater significance. Exercise training is a key component in achieving and maintaining optimal capacities in the elderly cardiac and noncardiac populations. These groups can safely undergo exercise training with proper screening and program design. Modifications in the components of the exercise prescription (i.e., frequency, intensity, duration, and activity mode) must be individualized according to the abilities, needs, and goals of each person. Risk factors for CHD still prevail in the elderly, although the predictive value of some risk factors may change with age. For this reason, efforts to control risk factors in older individuals should still be effective in reducing risk from CHD. Dietary modification, weight control, blood pressure control, smoking cessation, and endurance exercise training are several of the interventions used in concert to control risk for CHD.

Aged↗
PubMed1991

Injuries and adherence to walk/jog and resistance training programs in the elderly.

To evaluate the effects of 26 wk of aerobic and resistance training on the incidence of injury and program adherence in 70- to 79-yr-old men and women, 57 healthy volunteers (25 males, 32 females) were randomly assigned to a walk/jog (W/J, N = 21), strength (STREN, N = 23), or control (CONT, N = 13) group. Walk/jog training was for 30-45 min, 3 d.wk-1 with intensity equal to 40-70% heart rate max reserve (HRmax reserve) during the first 13 wk, and 75-85% HRmax reserve for weeks 14-26. STREN training consisted of one set (10-12 repetitions) each of 10 variable resistance exercises performed to volitional fatigue. Forty-nine of the original participants completed the training program. Walk/jog training increased VO2max from 22.5 to 27.1 ml.kg-1.min-1 (P less than or equal to 0.05) while STREN and CONT showed no change. STREN improved significantly in chest press and leg extension strength (P less than or equal to 0.05) while W/J and CONT showed no change. Adherence to training was 20/23 (87%) and 17/21 (81%) in STREN and W/J, respectively. One repetition maximum (1-RM) strength testing resulted in 11 injuries in the 57 subjects (19.3%) while STREN training resulted in only two injuries in 23 subjects (8.7%). Walk training during weeks 1-13 resulted in one injury in 21 subjects (4.8%). Eight of 14 subjects (57%) who began jogging intervals at week 14 incurred an injury: two of eight (25%) of the men and all of the women (6 of 6). All W/J training injuries were to the lower extremity.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

White-footed mice: tick burdens and role in the epizootiology of Potomac horse fever in Maryland.

One hundred ten white-footed mice (Peromyscus leucopus) were captured on horse farms in south-central Maryland, examined for ticks, and tested for specific antibodies to Ehrlichia risticii, the causative agent of Potomac horse fever. Peromyscus leucopus were consistently infested with immature American dog ticks (Dermacentor variabilis), with monthly prevalences as high as 80%. Sera from all 97 P. leucopus tested for antibodies to E. risticii were negative. This indicates that P. leucopus is not a reservoir of E. risticii, and suggests that immature D. variabilis do not acquire E. risticii in feeding upon white-footed mice.

Animals↗
PubMed1986

Treating multiple substance abuse clients.

The traditional separation of alcohol-dependent from drug-dependent persons no longer accords with contemporary patterns of substance abuse, especially for people below the age of 40. In ever-increasing numbers, the pattern of abuse is one of multiple substance abuse (MSA). Overwhelmingly, MSA involves the sequential or concurrent abuse of alcohol and one or more other drugs. Treatment centers need to be cognizant of this development, especially in taking accurate substance abuse histories and providing effective inpatient and aftercare services. A generic perspective of etiology, defenses, and treatment is provided, as well as a discussion of three varieties of combined treatment (conscious, overt; conscious, covert; and unconscious). Specific treatment interventions are suggested, as well as strategies for staffing and staff training. Finally, the need to provide a suitable therapeutic and living environment for the heterogeneity of clients likely to present with MSA is stressed.

Alcohol Drinking↗