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Biomedical subjects

M Walton

Publications and source records attributed to M Walton.

At least 19 recordsLinked to original sources
PubMed1992

Helicobacter pylori eradication with doxycycline-metronidazole-bismuth subcitrate triple therapy.

Triple therapy containing tetracycline HCl is currently among the most efficient combination therapies for eradication of Helicobacter pylori. Substitution of doxycycline for tetracycline HCl offers advantages of less frequent dosing and extrarenal excretion. In this study patients with duodenal ulcer or non-ulcer dyspepsia positive for H. pylori were randomized to either doxycycline or tetracycline HCl triple therapy in conjunction with bismuth subcitrate and metronidazole. Of the 34 patients taking doxycycline, only 22 (65%) achieved H. pylori eradication at the 4-week rebiopsy, compared with 36 of 39 (92%) taking tetracycline HCl (p = 0.004). We conclude that doxycycline-containing triple therapy is less effective for H. pylori eradication and offers no clinical advantage over tetracycline HCl-containing triple therapy.

Adult↗
PubMed1991

Strength retention of chromic gut and synthetic absorbable sutures in a nonhealing synovial wound.

The rate at which absorbable sutures lose their mechanical strength in a slow healing wound is clinically important, particularly because the factors inhibiting normal healing are not always apparent at the time of closure. Sutures of chromic catgut and two monofilament absorbable synthetic suture materials (polydioxanone and polyglyconate) were used to close a synovial incision in the knees of sheep. A corticosteroid was applied around the wound resulting in minimal tissue healing when the sutures were retrieved up to six weeks later. The failure load and maximum tensile strength of the retrieved sutures were measured. The mechanical degradation of the materials followed a pattern similar to that in normally healing wounds except that the early fragmentation of chromic gut and polydioxanone occurred far less frequently and neither weakened further after three weeks. Polyglyconate was significantly the strongest material up to three weeks but thereafter continued to weaken. The strength of absorbable sutures was retained longer than in a healing lesion probably because of the absence of the phagocytic cells of an inflammatory tissue.

Animals↗
PubMed1990

Cure of duodenal ulcer after eradication of Helicobacter pylori.

Eighty-two patients, whose duodenal ulcers were recurrent or resistant to H2-receptor antagonist therapy, were entered in a treatment protocol of ranitidine followed by a four-week "triple therapy" course to eradicate Helicobacter pylori (HP) infection. The triple therapy consisted of colloidal bismuth subcitrate, tetracycline and metronidazole. Duodenal ulcer healed in all 78 patients available for endoscopy and H. pylori infection was shown to be eliminated in 75 patients (96%) at rebiopsy four weeks after cessation of therapy. In these 75 remaining patients the relapse rates for H. pylori infection and duodenal ulcer were studied endoscopically, yearly and at any recurrence of symptoms. At Year 1, 71 of 73 patients remained free of H. pylori infection (HP-negative) and duodenal ulcer. The corresponding figures subsequently were: Year 2, 57/57; Year 3, 34/34; Year 4, 15/15. No duodenal ulcers recurred in HP-negative patients who were followed for up to four years. Two patients of the original cohort of 75 HP-negative patients were HP-positive with endoscopic duodenitis at 12 months, and one at 36 months, but all were without reulceration. Distorted duodenal caps gradually returned to near-normal appearance in 80% of patients by two years. From this four-year follow-up study we conclude that duodenal ulcer disease will not recur provided the patient remains free of H. pylori.

Adult↗
PubMed1989

Strength retention of chromic gut and monofilament synthetic absorbable suture materials in joint tissues.

The rate at which absorbable sutures lose their mechanical strength in vivo is particularly important in orthopedic applications where high physical loads, often increased by early mobilization, severely test the strength of sutures. The failure load and maximum tensile strength of chromic catgut and two monofilament absorbable synthetic suture materials (polydioxanone and polytrimethylene carbonate) were measured up to six weeks after implantation in sheep as: (1) a suture securing a synovial incision and (2) coils located either within the synovial cavity of the knee or intramuscularly. Although all synovial wounds healed satisfactorily, the performances of the different materials varied. The strength of chromic gut was largely lost within a week and fragmentation occurred at Week 4. The synthetic materials lost their strength relatively slowly. Polytrimethylene carbonate degraded in a linear manner, remaining intact but with little strength by Week 6. Polydioxanone, though losing strength at a slower rate, tended to fragment early, which may be of clinical importance in situations of delayed wound healing.

Animals↗
PubMed1988

The aerobic cost of saltatory locomotion in the fowler's toad (Bufo woodhousei fowleri).

Studies of kangaroos suggest that hopping provides energy savings during locomotion at high speeds, although studies of small mammals suggest that hopping is no more economical than running. To obtain comparative data on anurans, we exercised Fowler's toads (Bufo woodhousei fowleri, 25.8 g) on treadmills at speeds ranging from 0.09 to 0.63 km h-1 while measuring oxygen consumption (VO2), endurance or hop kinematics. The toads walked at slow speeds and hopped at fast speeds. Steady-state VO2 (VO2,ss) increased linearly with speed to a maximum (VO2, max) of 1.17 ml O2 g-1 h-1 at 0.27 km h-1 and was nine times the average pre-exercise VO2. The maximum rate of oxygen consumption during treadmill exercise was comparable to VO2,max previously reported for less natural exercise regimes. At speeds greater than or equal to 0.27 km h-1, VO2,ss was independent of speed. At speeds less than or equal to 0.36 km h-1, toads moved for over 1h, but endurance decreased sharply at higher speeds. Hop rate, hop length, hop height and angle of take-off increased with speed. Hopping in B.w. fowleri was not less costly than running in other animals of similar body size and was inefficient at converting metabolic to mechanical energy. The present study suggests that hopping in toads, as in small mammals, is not economical during sustained locomotion and is most important during short bursts of high-intensity activity.

Animals↗
PubMed1988

Fibroblastic healing of grade II ligament injuries. Histological and mechanical studies in the sheep.

A method is described which produces an isolated Grade II injury in the medial collateral ligament of the sheep's knee. The untreated injury was followed in 32 animals for up to six weeks. Histology revealed progressive healing of the lesions by a cellular response mediated by fibrocytes rather than by the classically described inflammatory response. Mechanical testing showed that the tensile strength of the ligament was initially reduced to 13% of normal but that strength and compliance were regained after six weeks.

Animals↗
PubMed1983

Reactions of thigh tissues of sheep to blunt trauma.

Severe damage to the deep musculature of the thigh was caused by standardized crushing injuries applied to muscle overlying the femora of anesthetized sheep. The injuries caused an acute inflammatory response, with the formation of granulation tissue and, later, extensive scarring. Periosteal bone formed in all cases, in some instances resulting in a spike of bone that protruded into the overlying soft tissue. Heterotopic bone formed in 16.6% of the legs of sheep within three weeks to three months after trauma by intramembranous ossification within scar tissue replacing muscle tissue.

Animals↗
PubMed1979

Patella displacement and osteoarthrosis of the knee joint in mice.

Surgical stabilisation of the normally medially--subluxing patella of STR/ORT male mice, prevented the normal development of osteoarthrosis in the medial compartment of the femoro-tibial joint. Surgically produced medial dislocation of the patella in non-arthrosis-prone male CBA/ORT mice often gave rise to osteoarthrosis of the medial condyles. This, with further evidence from previous studies, strongly indicates that the high incidence of degenerative joint disease in male STR/ORT mice occurs because of a tendency of the patella to dislocate medially due to some unknown cause.

Animals↗
PubMed1979

The relation of Vmax to INa, GNa, and h infinity in a model of the cardiac Purkinje fiber.

The inward sodium current in cardiac muscle is difficult to study by voltage clamp methods, so various indirect experimental measures have been used to obtain insight into its characteristics. These methods depend on the relationship between maximal upstroke velocity of the action potential (Vmax) and the sodium current (INa), usually defined in terms of the Hodgkin-Huxley model. These relationships were explored using an adaptation of this model to cardiac Purkinje fibers. In general Vmax corresponded to INa, and it could be used to determine the relationship of membrane potential to GNa, and h infinity. The results, however, depended on the method of stimulation of the action potential, and an optimal stimulation method was determined. A commonly used experimental technique called "membrane responsiveness" was shown to distort seriously the properties of steady-state gating inactivation that is supposed to measure. Estimation of the changes in maximal sodium conductance, such as those produced by tetrodotoxin (TTX), would be accurately measured. Some experimental results have indicated a voltage-dependent effect of TTX. Characteristics of the measures of TTX effect under those conditions were illustrated. In summary, calculations with a model of the cardiac Purkinje fiber action potential provide insight into the accuracy of certain experimental methods using maximal upstroke velocity as a measure of INa, and cast doubt on other experimental methods, such as membrane responsiveness.

Action Potentials↗
PubMed1979

Obesity as an aetiological factor in the development of osteoarthrosis.

A quantitative survey was carried out on the subcutaneous and abdominal adipose tissue of two inbred strains of mouse; STR/ORT is a strain in which the knee joints of the males have a very high incidence of osteoarthrosis, whereas the incidence of the disease in the females is much lower; the CBA/ORT mice represent a normal laboratory strain which rarely suffers from osteoarthrosis. In terms of the weight of readily removable subcutaneous and abdominal adipose tissue, the male STR/ORT mice were slightly leaner than the male CBA/ORT mice, the female STR/ORT mice were obese when compared with their CBA/ORT counterparts. Thus, in these mice, there was no positive correlation between obesity and osteoarthrosis. This evidence confirms previous mouse studies and is contrary to the commonly held view that in humans obesity predisposes to osteoarthrosis.

Adipose Tissue↗
PubMed1979

Bone thickening in osteoarthrosis. Observations of an osteoarthrosis-prone strain of mouse.

Estimations were made of the amount of bone (histologically) and the rate of bone formation (85Sr incorporation) in the epiphyses of the knees of osteoarthrosis-prone (STR/ORT) and normal (CBA/ORT) mice. Though the bone was significantly thicker in the STR/ORT mice, this was not the cause of the articular degeneration. Bone sclerosis and cartilage breakdown were chronologically very closely related with perhaps the cartilage changes occurring initially. In male STR/ORT mice bone formation was depressed in the cancellous bone of the epiphyses as, unlike the normal mice, it was at the same level as the compact bone of the femoral shaft. As there was no elevation of the osteoblastic activity in knee joints with developing osteoarthrosis, it would appear that bone sclerosis associated with the disease was due to decreased osteoclasis.

Animals↗
PubMed1978

A spontaneous ankle deformity in an inbred strain of mouse.

A spontaneous subluxation and subsequent dislocation of the bones of the ankle has been described in the males of an inbred strain of mouse (STR/ORT). It consisted of a gradual elevation of the calcaneum which eventually came to lie along the distal end of the tibia after 6--8 mth. The astragalus rotated forward. Articulations with the navicular and tarsal bones were severely disrupted with the accompanying development of peri-articular calcifications and ossifications. With one exception the arthropathy only occurred in male mice. Of the male members of the colony over the age of 3 mth, 26.7 per cent. had at least one ankle affected. Possible aetiological factors are discussed.

Animals↗
PubMed1977

Degenerative joint disease in the mouse knee; radiological and morphological observations.

Gross anatomical and radioligical techniques have been used to investigate the form and incidence of degenerative joint disease in the knee joint of an inbred strain of mouse (STR/ORT). The disease was seen radiographically as a thickening of the subchondral bone in the medial tibial and femoral condyles predominantly in the males. In fresh and macerated joints only advanced lesions could be seen with light microscopy and these appeared as concave (tibial) or flattened (femoral) erosions with hard shiny eburnated surfaces. Medial patella dislocation was a common feature of the arthrotic joints and there was associated widespread periarticular heterotopic calcification. These growths started as peripheral exostoses from the patella and as small loci of mineralisation within the synovial tissue but later enlarged into plaques of calcified tissue. Ossific centres within the menisci were present in all knees but became greatly enlarged in the osteoarthrotic joints. Calcification of the collateral ligaments occurred in non-arthrotic joints, especially laterally, but progressed to thick ossification in the medial ligament of arthrotic knees. Eventually all these enlarging sites of calcification and ossification began to fuse together, thus limiting the degree of movement of the joint. There was a statistically significant positive relationship between the severe arthropathy and (a) marked patella dislocation and (b) the presence of calcification in the medial collateral ligament.

Aging↗