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Biomedical subjects

D Monson

Publications and source records attributed to D Monson.

10 recordsLinked to original sources
PubMed2006

Patterns of growth and body condition in sea otters from the Aleutian archipelago before and after the recent population decline.

1. Growth models for body mass and length were fitted to data collected from 1842 sea otters Enhydra lutris shot or live-captured throughout south-west Alaska between 1967 and 2004. Growth curves were constructed for each of two main year groups: 1967-71 when the population was at or near carrying capacity and 1992-97 when the population was in steep decline. Analyses of data collected from animals caught during 2004, when the population density was very low, were precluded by a small sample size and consequently only examined incidentally to the main growth curves. 2. Growth curves demonstrated a significant increase in body mass and body length at age in the 1990s. Asymptotic values of body mass were 12-18% higher in the 1990s than in the 1960s/70s, and asymptotic values for body length were 10-11% higher between the same periods. Data collected in 2004 suggest a continued increase in body size, with nearly all data points for mass and length falling significantly above the 1990s growth curves. 3. In addition to larger asymptotic values for mass and length, the rate of growth towards asymptotic values was more rapid in the 1990s than in the 1960s/70s: sea otters reached 95% of asymptotic body mass and body length 1-2 years earlier in the 1990s. 4. Body condition (as measured by the log mass/log length ratio) was significantly greater in males than in females. There was also an increasing trend from the 1960s/70s through 2004 despite much year-to-year variation. 5. Population age structures differed significantly between the 1960s/70s and the 1990s with the latter distribution skewed toward younger age classes (indicating an altered lx function) suggesting almost complete relaxation of age-dependent mortality patterns (i.e. those typical of food-limited populations). 6. This study spanned a period of time over which the population status of sea otters in the Aleutian archipelago declined precipitously from levels at or near equilibrium densities at some islands in the 1960s/70s to < 5% of estimated carrying capacity by the late 1990s. The results of this study indicate an improved overall health of sea otters over the period of decline and suggest that limited nutritional resources were not the cause of the observed reduced population abundance. Our findings are consistent with the hypothesis that the decline was caused by increased killer whale predation.

Aging↗
PubMed2002

Epithelioid sarcoma: clinical, MR imaging and pathologic findings.

OBJECTIVE: To report and describe the MR imaging features of eight new cases of this rare soft tissue sarcoma and correlate them with the clinical and histologic findings. DESIGN AND PATIENTS. Retrospective analysis was carried out for the MR imaging characteristics and histologic findings of eight patients with pathologically proven epithelioid sarcoma and the literature was reviewed. Findings were correlated in each case with the patient's clinical presentation and eventual outcome. RESULTS: The patients, whose primary tumors ranged from 2.5 cm to 19 cm in maximum dimension, were 1 to 90 years of age. Tumors involved the extremities ( n=5), the scalp ( n=2) and the paraspinal muscles ( n=1). Five tumors presented as well-defined, frequently painful, deeply situated masses and three as subcutaneous nodules or cutaneous ulcers with no palpable mass. Four patients had associated regional lymphadenopathy and one had distant metastases at diagnosis. MR imaging showed tumor infiltration of adjacent tissues in seven patients. Signal characteristics reflected varying degrees of cellularity, and the presence of necrosis, hemorrhage, fibrosis, hyalinization and inflammation. Bone marrow involvement was demonstrated in one patient. Clinical outcomes were generally poor. CONCLUSIONS: Epithelioid sarcoma is an aggressive soft tissue sarcoma with a varied clinical presentation, growth pattern, MR signal characteristics and histologic picture. The tumor favors the distal extremities and is commonly infiltrative and accompanied by enlarged regional lymph nodes. This neoplasm may present as an intramuscular mass but should also be suspected in patients with ulcerating cutaneous nodules with or without regional lymphadenopathy.

Adult↗
PubMed1994

A comparison of the prognoses for deep and subcutaneous sarcomas of the extremities.

We evaluated 172 patients who had a soft-tissue sarcoma of the extremity in order to determine whether the prognosis for a subcutaneous sarcoma was better than that for a deep sarcoma. At a median of thirty-six months after the biopsy or definitive operation at our hospital, six of the fifty-two patients who had had a subcutaneous sarcoma had died and one had had a local recurrence; in contrast, forty of the 120 patients who had had a deep sarcoma had died and eight had had a local recurrence. Twenty-five (48 percent) of the subcutaneous sarcomas were malignant fibrous histiocytomas, and thirty-eight (73 percent) were small (five centimeters or less in the largest dimension). The three-year estimates of disease-free survival were 85 percent for the patients who had a subcutaneous sarcoma and 54 per cent for those who had a deep sarcoma (p = 0.002). Although the survival estimates remained significantly different when the groups were matched for histological diagnosis and for intracompartmental location (p = 0.0001 and 0.0006, respectively), they were not significantly different when the groups were matched for the size of the tumor (p = 0.42). A Cox proportional-hazards model confirmed that a tumor size of more than five centimeters and the histological grade are the most significant prognostic factors (p = 0.0007 and p = 0.004, respectively): a tumor size of more than five centimeters was associated with a relative risk of 3.5 (95 per cent confidence interval, 1.7 to 7.3), and a higher histological grade was associated with a relative risk of 4.0 (95 per cent confidence interval, 1.6 to 10.3). Subcutaneous location, when considered separately, was not a significant prognostic factor (p = 0.45). The data indicate that a tumor size of more than five centimeters is a more important prognostic indicator than histological diagnosis, depth, or intracompartmental location.

Adolescent↗
PubMed1988

Soft tissue tumors of the foot and ankle.

Seven patients with malignant soft tissue tumors of the foot and ankle were retrospectively reviewed. Emphasis was placed on the value of various diagnostic modalities used preoperatively for staging and the adequacy of treatment rendered using current tumor surgery principles. The malignant tumors included synovial cell sarcoma (four), clear cell sarcoma (one), fibrosarcoma (one), and melanoma (one). Surgical management of the malignant lesions included intracapsular excision, marginal excision, wide excision, and radical amputation. Preoperative diagnostic and staging studies that were found to be helpful include ultrasonography, xeroradiography, triple-phase bone scan, and CT and magnetic resonance imaging (MRI) scans. Surgical guidelines include the use of longitudinal skin incisions to obtain excisional biopsies of smaller lesions, keeping the tourniquet inflated until either a benign diagnosis is made or until the definitive procedure is performed. Wide excision or partial foot versus radical amputation may be required depending on the size, location, and extent of malignant soft tissue sarcomas.

Adolescent↗
PubMed1983

Abrogation of second-set rejection with cyclosporine.

Cyclosporine was evaluated for its ability to delay or prevent accelerated rejection in a model of the second-set immune response. Lewis rats sensitized by LBN skin grafts or subcutaneous heart fragments experienced accelerated rejection of heterotopic, vascularized LBN hearts with a mean survival time (MST) of approximately 5 days versus MST of 9.5 days for primary grafts. A short course of cyclosporine (10 mg/kg/day for 10 days) significantly prolonged graft survival in presensitized hosts to approximately 12 days (P less than 0.01) as compared with the nontreated controls. Adjunctive splenectomy failed to further extend graft survival; MSTs were 12.0 and 5.7 days with and without cyclosporine, respectively. A comparable abrogation of second-set rejection was also achieved with a short course of antithymocyte serum (MST of 10.6 days). Rejection promptly ensued in all of the above groups shortly after cessation of immunosuppression. In contrast, a maintenance regimen of cyclosporine, given in a tapering dose, markedly extended graft survival to from 77 to 100+ days. Again, however, rejection eventually occurred following withdrawal of the cyclosporine. These data suggest that cyclosporine can indeed effectively prolong allograft survival in presensitized hosts.

Animals↗
PubMed1983

Coronary revascularization in septuagenarians.

Despite a 15 year experience with the aorta-coronary bypass operation, indications for its use remain unsettled, especially in the elderly. Between January, 1974, and June, 1980, 2,667 patients underwent coronary artery revascularization with an overall mortality of 3.8% (101/2,667). During the last 12 months the mortality has decreased to 1%. There were 2,562 patients below the age of 70, with a mortality of 3.5% (90/2,562), in contrast to 105 patients over the age of 70, with a mortality of 10.5% (11/105) (p = 0.002). In patients less than 70 years of age there was a significant difference between the mortality of men, 3.12% (67/2,146), and that of women, 5.53% (23/416) (p = 0.015). This disparity of operative risk was far more pronounced in patients over 70 years of age: men 6% (5/84) and women 28.6% (6/21) (p = 0.002). The overall operative mortality of women, 6.6% (29/437), was significantly different from the overall mortality of men, 3.2% (72/2,230) (p = 0.001). An in depth analysis of past medical history, risk factors, and catheterization data is presented in those patients over the age of 70. The average number of vessels bypassed was 2.40: men 2.47 and women 2.09 (p = NS). The ages varied from 70 to 81 years with a mean of 72.5. Smoking (p = 0.012) and diabetes (p = 0.0078) were significant risk factors for coronary disease. Smoking (p = 0.032) and abnormal pulmonary artery pressures (p = 0.0429) were significant variables affecting mortality. A 97.1% follow-up was obtained up to 78 months. Coronary artery revascularization can be performed in men below the age of 70 with acceptable mortality, but there is a twofold increase above the age of 70. Women can undergo revascularization below the age of 70 with a significantly higher risk than males. Those above the age of 70 are at severe risk and should undergo revascularization only after careful selection.

Age Factors↗
PubMed1980

Descending aortic aneurysmectomy without adjuncts to avoid ischemia.

Encouraged by reports on the safety of simple aortic cross-clamping for resection of descending aortic aneurysm, we began utilizing this technique more liberally in 1976. This study was undertaken to examine the results of operation in 36 patients, equally divided into two distinct groups. In Group 1, either extracorporeal circulation or indwelling temporary shunts were employed during the period of aortic occlusion. In Group 2, simple aortic cross-clamping was utilized to manage the lesion. No adjuncts were used to avoid ischemia in the latter group. The only 2 early deaths and two instances of paraplegia occurred in Group 1. In general, there were fewer complications in Group 2, with approximately two-thirds of the patients experiencing an uneventful postoperative course. These differences are considered important since the two groups were similar in respect to the extent and nature of the lesions and other factors contributing to operative risk.

Adolescent↗