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Biomedical subjects

R Mackintosh

Publications and source records attributed to R Mackintosh.

5 recordsLinked to original sources
PubMed1991

Heart rate variability as a measure of autonomic function during weight change in humans.

Changes in autonomic function were studied during experimentally induced weight changes in seven subjects. A spectral analysis of heart rate variability (HRV) was used to evaluate autonomic activity during weight change. With a 10% increase in body weight above the usual or starting weight, there was a decline in parasympathetic power accompanied by a rise in mean heart rate. Heart rate declined during weight reduction, but the power of HRV did not change significantly. Because heart rate power at the frequency of respiratory rate can be affected by respiratory rate, three additional subjects were tested at a constant respiratory rate. Weight increases in this group also led to a decline in the power of HRV at a frequency attributable to the parasympathetic nervous system. Such a parasympathetic effect of weight increase may be one mechanism for the arrhythmias and other cardiac alterations that accompany obesity.

Adult↗
PubMed1986

The role of radiation therapy in squamous cell carcinoma of the upper aerodigestive tract with positive surgical margins.

One hundred four patients with squamous cell carcinoma of the upper aerodigestive tract and with histologically positive surgical margins were evaluated for this historically controlled study to determine the efficacy of postoperative radiation therapy. Positive margins were defined as the presence of one or more of the following: carcinoma in situ, tumor within 0.5 cm from the surgical margins, microscopic disease, or dysplasia. Patients received either surgery alone (44 cases) or surgery plus postoperative radiation therapy (60 cases) and were followed for a minimum of 2 years. Treatment strategies, stage by stage, were similar for all patients. Surgery varied from simple excision in T1 to composite resection and/or laryngopharyngectomy with radical neck dissection in advanced cases. Radiation therapy was given postoperatively with doses ranging from 4,500 to 7,500 cGy. The overall 2-year survival rate with no evidence of disease (NED) was consistently higher in the surgery plus radiation therapy group. Furthermore, when the subgroup of patients who had dysplasia at the surgical margins was excluded from the analysis, the 2-year NED survival rate difference became statistically significant (p = 0.05). This outcome favored combined therapy (36 of 58 patients) over surgery alone (13 of 32 patients). This favorable result was obtained despite the high percentage of T3-T4 stages (79 vs. 21%) and clinically positive lymph nodes (83 vs. 17%) in patients who had received postoperative radiation therapy. The significance of dysplasia at the surgical margins and the impact of radiation therapy on the tumor and nodal control in this group of patients needs further clarification.

California↗
PubMed1986

Major salivary gland tumors: treatment results and prognostic factors.

A retrospective review of 133 patients with major salivary gland carcinomas treated between 1955 and 1981 is presented. The majority of cases (104) originated in the parotid gland. The most common histological type was mucoepidermoid carcinoma (39 cases). Tumor-free interval was longest for patients with acinic cell and mucoepidermoid carcinomas. In contrast, adenoid cystic carcinoma was poorly controlled, regardless of the form of treatment. Initial control of primary major salivary gland tumors was inversely related to the presence of disease at the surgical margins. In cases with microscopic or gross disease at the surgical margins, postoperative radiation therapy controlled the tumor locally in 18 of 26 patients (69%). Postoperative radiation therapy was generally used only in cases with high-grade histologies, advanced stages, or positive surgical margins. Of the patients treated with surgery alone, 53% achieved local control, as compared to 75% of the group which received postoperative radiation therapy. Although the difference was not statistically significant, we would have expected the combined therapy group to have a lower control rate due to more advanced disease. There was a low salvage rate (22%) and a high incidence of distant metastasis (60%) in recurrent cases. The data indicates that complete surgical resection results in the best local control, with or without adjuvant radiation. When the surgical margin is inadequate and re-excision not possible, adjuvant radiation therapy appears to have a role to optimize local control and survival.

Adolescent↗
PubMedDate not supplied

Nutritionally-induced changes in parasympathetic function.

It is possible to quantify the input of the parasympathetic nervous system to heart rate variability in man by the spectral analysis of heart rate variability. This is done by noninvasive, computerized electrocardiography over several minutes of observation. Earlier studies from this laboratory demonstrated that when body weight of obese or nonobese subjects is increased 10% or decreased below usual body weight, there are accompanying changes in autonomic function, as measured by alterations in heart rate variability. The clearest of these changes is an abrupt decline in parasympathetic function with increase in body weight, and an increase in parasympathetic activity as body weight declines, and when new, lower body weights are maintained. Recently, it has been possible to examine this phenomenon by a pharmacologic dissection of the autonomic input to heart rate variability. The separate input of each branch of the nervous system to cardiac variability, as well as the intrinsic heart rate, is measured by this approach. The subjects studied to date have been few, but there is confirmation of a major change in parasympathetic function with weight alteration whereas sympathetic changes are small.

Body Weight↗