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Biomedical subjects

L C Jones

Publications and source records attributed to L C Jones.

At least 73 records · Page 4Linked to original sources
PubMed1990

Sex differences in voluntary locomotor activity of food-restricted and ad libitum-fed rats. Implications for the maintenance of a body weight set-point.

1. Male and female Wistar-strain rats were studied under either ad libitum or 23-hour food restriction conditions both with and without access to a running wheel. 2. Daily measures were taken of body weight, food consumption and wheel revolutions. 3. It was observed that food restriction was associated with decreased food consumption and body weight but increased wheel revolutions. 4. Irrespective of feeding regime, females exhibited higher running rates than males.

Animals↗
PubMed1990

Frequency of illness in mother-infant dyads.

The purpose of this study was to identify the frequency and types of illnesses experienced by mothers and their infants who were in the second half of the first year of life, the actions taken concerning these illnesses, the number of days the mother was hospitalized or in bed because of illness, and the subjective health status of both as rated by the mothers. During home visits mothers (N = 182) completed the Health Status Interview. They were asked about infant and maternal illness in the previous month and the actions taken in response to them. The number and types of illnesses reported indicate that mothers of full-term infants who were healthy at birth must deal with a number of minor illnesses in themselves and in their infants. The possible relationship of maternal illness to stress is discussed and suggestions are given for interventions by health professionals.

Adult↗
PubMed1989

Chronic ingestion of ethanol increases stimulation-induced voluntary activity in the rat.

Acute exposure of an animal to ethanol has a biphasic effect on activity; at low doses incurring stimulation of locomotor activity whilst at higher doses eliciting a depression in activity level. The present study reports the effect of short-term (10 days) exposure to ethanol on running wheel activity in female Wistar rats. Ethanol treatment (3 g/100 ml in drinking water) increased significantly the rate of accumulation of total distance run but not the daily rate of running when compared to control animals. This increase was attributable to an increased rate of running stimulated by daily feeding and handling by the experimenter.

Alcoholism↗
PubMed1988

Experimental determination of forces transmitted through the patello-femoral joint.

Tensions in the quadriceps tendon and infrapatellar ligament were measured as a function of flexion angle in eight cadaver knees using a load cell of a materials tester to determine the quadriceps force and a spring balance to quantify the patellar tendon force. The ratio between the tensions in the quadriceps tendon and the patellar tendon (FQ/FP) ranged from 1.55 at 70 degrees of flexion to 0.86 at 10 degrees of flexion. The patello-femoral joint reaction (PFJR) force for extension against resistance was maximal at 60 degrees. No change in the quadriceps force required to extend the knee occurred with changes of the Q-angle of +/- 5 degrees. This study demonstrates that FQ does not equal FP as several authors have reported (Bandi, 1972; Barry, 1979; Ficat and Hungerford, 1977; Hungerford and Barry, 1979; Reilly and Martens, 1972; Smidt, 1973). Furthermore, the difference in FQ and FP influences both the magnitude and direction of PFJR. Studies that assess the influence of surgical procedures which alter the patello-femoral joint or the extensor mechanism must take these differences into account.

Biomechanical Phenomena↗
PubMed1988

Effect of alcohol content on beer consumption by rats.

Three brands of beer of varying alcohol content were presented to separate groups of male rats. The consumption data indicated, firstly, an inverse relationship between acceptability of the beer and its alcohol content. The data also indicated that the acceptability of full-strength beer could be augmented by prior exposure to low-alcohol and alcohol-free beer. The results are discussed with reference to orosensory- and inebriation-based models of alcohol consumption.

Alcohol Drinking↗
PubMed1988

Clinical experience with a triradiate exposure of the hip for difficult total hip arthroplasty.

A triradiate exposure of the hip was developed to facilitate the performance of certain difficult primary and revision total hip arthroplasties. Using this triradiate skin and fascial incision, complete anterior and posterior exposure of the hip capsule can be performed with relative ease. Between October 1980 and January 1985, this exposure was used 50 times in selected cases, including 9 of 320 (3%) primary total hip arthroplasties. All of these cases involved obesity, acetabular protrusion, and/or fragile femoral bone, conditions that would have made safe, adequate exposure without trochanteric osteotomy considerably more difficult through a routine anterolateral or posterior approach. Over this period, the majority of revision hip arthroplasties were performed using triradiate exposure; trochanteric osteotomy was routinely performed in these revision cases. Excellent wound healing was observed in every case, despite unfavorable factors such as advanced age, prednisone therapy, and the presence of prior incisional scars. The triradiate incision offers safe, controlled, and improved exposure in selected primary and revision total hip arthroplasties. It has become nearly the routine incision for the senior author for revision cases.

Aged↗
PubMed1988

Ligament-tendon fixation: analysis of a new stitch and comparison with standard techniques.

A newly devised locking loop tendon-ligament suture was evaluated for its clinical application. The suture is relatively simple to use and is particularly suited to flat structures such as the medial collateral ligament, joint capsule, and patellar tendon. It affects tension and resistance to pull out without exerting major purse stringing or bunching. In a laboratory setting, this suture technique has been compared to fixation by individual sutures and several varieties of staple fixation. Simple suture fixation was quite weak, measuring 100 newtons (N). Staple fixation is not only weaker than the ligament suture, but is more highly dependent on bone quality and is generally more variable. When employed with strong suture material, a doubled ligament suture was found to be nearly twice as strong (392 N) as staple fixation into bone (208 N) and demonstrated a mean pullout strength close to the forces observed on human anterior cruciate ligaments. In combination with a well placed ligament staple into good quality bone, fixation was further enhanced (482 N) and statistically significantly improved (P greater than .05).

Animals↗
PubMed1988

The rationale of cementless revision of cemented arthroplasty failures.

Patients with failed cemented total hip replacements develop minor to massive bone loss. In nearly all cases, the quality of the endosteal surface has been converted to a sclerotic tube. Because of the bone loss and the change in character of the remaining bone stock with which to form an interface with polymethylmethacrylate (PMMA), the microinterlock necessary for long-term interface stability cannot be achieved. Moreover, the first failure leads to the production of cement particles that incite a histiocytic osteolytic response. The difficulty in achieving interfacial stability in the revision setting is borne out in the published clinical results of cemented revision total hip arthroplasties showing failure rates ranging from 17% to 60.3%. Porous-surfaced prostheses have been introduced to permit biologic fixation as an alternative to cement fixation of each implant component. The good midterm clinical results and the lack of catastrophic bone loss when failure does occur have given impetus to the application of this technology to the revision situation. The preliminary clinical experience with cementless revision arthroplasty has yielded favorable results. The authors have fully developed the rationale against the use of PMMA in revision total hip replacements and for the cementless approach with porous-surfaced metal prostheses and bone grafts. The latter appear as a viable approach to a growing clinical problem.

Adult↗
PubMed1987

Signal processing technique to extract neuronal activity from noise.

A method of extracting extracellularly recorded action potentials from background electronic noise is described. Segments of traces containing stimulus-induced activity are Fourier transformed and the increase in the total power density over that of control noise segments is used as a measure of stimulus-induced neuronal activity. We show first, with observations from the amphibian visual system and mammalian auditory system, that our technique yields similar quantitative information to that obtained from the conventional spike counting method when the recording arrangement is optimal. Moreover, the size and centre of a visual receptive field can be determined even when the evoked action potentials are buried in the background noise. To investigate the potential of this technique further, we have used it to study the auditory responses in the amphibian midbrain. The power spectral density, we demonstrate here, is proportional to the stimulus intensity over a wide range, and varies systematically with stimulus frequency and the direction of sound source. Other possible applications of this technique, together with the theoretical basis for it, are discussed.

Action Potentials↗
PubMed1987

Cement disease.

Does "cement disease" exist? The bony environment surrounding a loosened cemented prosthesis is an abnormal pathologic condition which, if left unattended, will progress to a total failure of the joint including an inhibition of function and immobilizing pain. That biomaterial properties of the cement used for fixation also contribute to the pathologic state separates this disease from other modes of loosening. This leads inevitably to the conclusion that "cement disease" does exist. Methyl methacrylate has revolutionized the treatment of severe joint dysfunction. There can be no doubt that improving surgical technique, cement handling, and the cement itself will continue to improve the results and reduce the incidence of failure due to loosening. Cement is undoubtedly satisfactory for elderly patients with low activity levels and relatively short life expectancies. However, because of the inherent biologic and biomechanical properties of methyl methacrylate, it is unlikely that it can be rendered satisfactory in the long run for the young, the active, or the overweight patient, for whom alternatives are currently being sought. In such cases, the elimination of "cement disease" can only occur with the elimination of cement. Alternatives include the search for other grouting materials and the development of prostheses with satisfactory surfaces for either press-fit or biologic ingrowth.

Age Factors↗
PubMed1987

The effect of sympathectomy on blood flow in bone. Regional distribution and effect over time.

Considerable interest has developed in the role of the autonomic nervous system and its effect on blood flow in bone. Theories pertaining to the long-term physiological effect of sympathectomy on blood flow in bone have been controversial. This study employed the radioactive tracer-microsphere technique to investigate the influence of sympathectomy on regional blood flow in bone over time in dogs. Blood flow was measured in fifteen adult dogs, weighing eighteen to twenty kilograms, at one hour, one day, and one, two, three, four, and six weeks after a transperitoneal sympathectomy from the first to the sixth lumbar level. Absolute control flow values were consistent with those that have been reported previously and had lower standard errors. Blood flow in bone in the femoral regions increased by 24.0 to 41.0 per cent. Greater elevations, of 37.0 to 59.0 per cent, were noted in the tibial sections. The largest increases (58.0 to 67.0 per cent) were seen in the metatarsals and proximal phalanges. All elevated values for blood flow returned to control values by six weeks. The data support the hypothesis that surgical sympathectomy exerts a significant yet transient effect on blood flow in bone. Furthermore, the greater increase distally is the first physiological evidence to support previous anatomical work that concluded that the major site of sympathetic tone lies distally in the lower extremity of the dog.

Animals↗