Biomedical subjects

J Baker

Publications and source records attributed to J Baker.

At least 253 records · Page 14Linked to original sources

PubMed1985

Clinical pharmacodynamics of theophylline.

The clinical pharmacodynamics of theophylline, which concerns the correlation between the serum theophylline concentration ([TH]) attained during therapy for asthma and improved pulmonary function or unwanted side effects, serves to link the pharmacokinetics of theophylline with the time course of clinical outcome. Although the minimum effective and maximum safe [TH]s have been known for some years, it was only recently shown that maximal improvement in pulmonary function lags behind rapidly changing [TH]s and that improved pulmonary function relates to increasing [TH]s within the therapeutic range. While much is known about the determinants of theophylline disposition in patients with asthma, enabling individualized pharmacokinetically based therapy, it is difficult to predict the clinical pharmacodynamic outcome. Investigation of the effects of age, cardiopulmonary disease, concurrent drugs, diet, circadian rhythms, and other patient features on theophylline clinical pharmacodynamics may provide a basis for prediction of individual patient responsiveness to theophylline and lead to further optimization of theophylline therapy in asthma.

Asthma↗

PubMed1985

Permanent pacing through a persistent left superior vena cava: an approach and report of dual-chambered lead placement.

The patient with a persistent left superior vena cava who requires permanent pacing presents difficulties if no right superior vena cava is present or if it is encountered unexpectedly at pacemaker implantation. A case is presented that illustrates potential problems and suggests a general approach to this situation. Successful transvenous universal pacemaker insertion through a persistent left superior vena cava is reported.

Adult↗

PubMed1985

Vital apicoectomy of the teeth: a 1-4 week histopathological study in Macaca mulatta.

Several studies have reported devitalization of teeth following surgical procedures in the area of the root apices. The purpose of this investigation was to observe the 1-4-week wound healing pattern in monkey dental tissues following intentional vital apicoectomy (IVA). Two adult Macaca mulatta were used in this study. All of the teeth were surgically transected within the apical one-third with a bur. The soft tissues were then closed. At death, a maxillary and a mandibular quadrant for 1, 2, 3 and 4 weeks following surgery were obtained after vascular perfusion. Each quadrant was demineralized in EDTA, processed, serially sectioned at 7 microns and alternately stained with hematoxylin and eosin, Preece's modified trichome, and McKay's bacterial stains. Examination of sequential IVA cuts showed an initial disruption of the pulpal neurovascular supply resulting in pulpal necrosis. The pulpal tissues underwent a process of replacement with PDL-like connective tissues and deposition of cementum on all cut dentin surfaces of the tooth roots as well as in some of the pulp chambers. No abscesses, external resorption or ankylosis were found.

Alveolar Process↗

PubMed1985

Spatial and temporal response properties of the vestibulocollic reflex in decerebrate cats.

Vestibulocollic reflex responses of several neck muscles in decerebrate cats were studied during angular rotations of the whole body in a large number of vertical and horizontal rotation planes, at frequencies from 0.07 to 1.6 Hz. Vestibulocollic responses were compared to eye muscle and forelimb muscle vestibular responses. Electromyographic activity was recorded by fine wires inserted in biventer cervicis, complexus, longus capitis, obliquus capitis inferior, occipitoscapularis, rectus capitis major, splenius, lateral rectus, and triceps brachii. At frequencies of approximately 0.5 Hz and above, neck muscle electromyographic response gains were sinusoidal functions of stimulus orientation within a set of vertical or horizontal planes, and a muscle's response phase remained constant across rotation planes, or reversed by 180 degrees. Response patterns at high frequencies were consistent with vestibulocollic reflex activation by semicircular canals through brain circuitry that modifies canal dynamics. At frequencies of approximately 0.5 Hz and above, the stimulus orientation in which a given neck muscle's response was maximal remained nearly constant across frequencies. Thus, we used responses to rotations at high frequencies to calculate axes of maximal response of each muscle in three-dimensional space. Lateral rectus, obliquus, and to a lesser extent, splenius and longus capitus were activated predominantly by horizontal rotations. Biventer was activated predominantly by pitch, triceps predominantly by roll, and complexus, occipitoscapularis, and rectus major significantly excited by rotations in all three coordinate planes. In some cases, at frequencies less than 0.5 Hz, neck muscle response phase varied depending on the vertical plane in which the cat was rotated, and the optimal response plane was poorly defined and varied with frequency. These responses indicated that, at some frequencies, neck muscle activity can result from summation of inputs with differing spatial orientation and dynamics (spatial-temporal convergence). Differences between responses to vertical and horizontal rotations suggested that low-frequency spatial-temporal convergence behavior of the vestibulocollic reflex during vertical rotations was due to convergent semicircular canal and otolith receptor inputs.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1985

Carboplatin: a very active new cisplatin analog in the treatment of small cell lung cancer.

Carboplatin, a cisplatin analog without significant clinical nephrotoxicity, has been evaluated in the treatment of 56 patients with small cell lung carcinoma at a dose of 300-400 mg/m2 iv monthly in a phase II study. Twenty-three patients (41%) achieved a response, including five (9%) complete remissions. Of 30 previously untreated patients, 18 (60%) achieved a response, including three (10%) complete remissions. Median response duration was 4.5 months (range, 2-9). No nephrotoxicity was seen and hydration was not required. Nausea or vomiting occurred in only 24 patients (43%) and was rarely severe. Myelosuppression was dose-limiting: 20 patients (36%) developed leukopenia and eight (14%) developed thrombocytopenia, but leukopenic infections occurred in only three patients. Carboplatin is a very active new agent in the treatment of small cell lung cancer, with less toxicity and better tolerance than cisplatin. It merits further investigation in combination chemotherapy and against non-small cell lung cancer.

Adult↗

PubMed1984

Optimal response planes and canal convergence in secondary neurons in vestibular nuclei of alert cats.

Responses to natural stimulation were studied in electrically identified secondary vestibular neurons of awake cats. A class of neurons was identified whose response dynamics and responses to rotations in several vertical and horizontal planes indicated that they received semicircular canal input. Each canal neuron had clearly defined planes of maximal and null sensitivity to rotation. The orientation of these planes indicated that 44% of the neurons received input from one pair of canals, 40% from two, and 16% from all 3 canal pairs. Many cells also had oculomotor-related discharges and/or responded weakly to neck rotation.

Animals↗

PubMed1984

Spatial and temporal response properties of secondary neurons that receive convergent input in vestibular nuclei of alert cats.

Responses to rotation in many vertical and horizontal planes were studied in electrically identified secondary vestibular neurons of alert cats. This report concerns secondary neurons that gave responses which could not be explained as due to a summation of semicircular canal inputs. These cells responded to sinusoidal rotation of the cat in any vertical plane, and response phase depended on the plane of rotation. The responses were modeled as the result of summation of two inputs that differed in their spatial orientations and dynamics. Response dynamics and a comparison of responses to vertical and horizontal rotations showed that some cells were sensitive to rotation with respect to gravity. Their responses both to gravity and horizontal rotations argue that these secondary neurons received convergent otolith and canal inputs. Some cells also had oculomotor related discharges and/or responded weakly to neck rotation.

Animals↗

PubMed1984

Breast conservation in the treatment of early breast cancer. A 20-year follow-up.

Two hundred sixty-three patients with unilateral primary breast cancer, treated by local excision of the primary tumor and radical radiation therapy between 1954 and 1969, were followed up for a minimum of 10 years and a maximum of 20 years. The treatment plan delivered 4500 rad in fractions of orthovoltage irradiation to five fields: tangential breast fields, axilla with posterior axillary field, parasternal and supraclavicular, with a subsequent boost of 1000 rad to the primary tumor site, axilla, and supraclavicular fossa. Patients were clinically staged using the TNM (UICC) system; 115 patients had tumors less than 2 cm in diameter and a clinically negative axilla (T1N0N1a), 96 had tumors 2 to 5 cm in diameter with a clinically negative axilla (T2N0N1a), and 52 had tumors less than 5 cm in diameter and clinical axillary lymph node metastases (T1T2N1b). The actuarial relapse-free survival of patients with T1N0N1a tumors was 72% at 5 years, 59% at 10 years, and 47% at both 15 and 20 years. The relapse-free survival of patients with T2N0N1a tumors was not statistically different (P greater than 0.05). A significantly worse survival was observed in patients with clinical axillary lymph node metastases (T1T2N1b), with a survival of 37% at 5 years, 29% at 10 years, 23% at 15 years, and 22% at 20 years, when compared with patients with clinically negative lymph nodes (P less than 0.01). Locoregional relapse occurred in 22%, at 10 years, of those patients with T1 or T2N0N1a tumors and 52% of the patients with T1T2N1b tumors. The pattern of locoregional relapses indicated that approximately 50% occur at least 5 years after treatment; this contrasts with the pattern of early locoregional relapse after mastectomy. The commonest sites of relapse were in the breast in 19% and axilla in 6% of patients with T1 or T2N0N1a tumors. There was no attenuation of the radiation dose administered at the site of a subsequent relapse. Surgery for radiation failure produced a 42% crude relapse-free survival at 5 years after salvage mastectomy in those patients originally treated for T1 or T1N0N1a tumors. The results of this study suggest that a significant proportion of patients relapse locally over a prolonged period after breast conservation. The evolution of new radiation techniques may provide better locoregional control and early salvage surgery may result in improved long-term survival.

Adult↗

PubMed1984

An application of multiattribute utility theory to the planning of emergency medical services.

This research considers the problem of relating Emergency Medical Services (EMS) to patient outcome. The hypothesis is that response time alone may be misleading as an EMS performance criterion. This research uses methods for approximating multiattribute utility functions to consider both response time and on-the-scene care. The final result is an optimization problem where the response time and desired personnel requirements are decision variables. These are important inputs in the planning for Emergency Medical Services.

Emergency Medical Services↗

PubMed1984

Effect of exercise on repolarisation abnormalities in patients with asymptomatic QT prolongation.

Patients with congenital QT prolongation have an increased incidence of ventricular arrhythmias and sudden death. Altered sympathetic tone has been suggested as an important contributing factor in this syndrome. Although some patients with an increased QT interval and arrhythmias have an abnormal QT response during exercise, the effect of exercise has not been reported in patients with acquired QT prolongation without clinical manifestations. The purpose of this study was to determine the pattern of QT change with exercise in patients with QT prolongation without exercise-induced arrhythmias in order to: 1) determine the most frequent response in this group; 2) observe the effect of posture on QT changes; and 3) compare the rate of QT change with a control group. Treadmill exercise testing was performed in 10 patients (mean age 52.1 +/- 8.0 years) with a QTc greater than 0.44 s; the results were compared with 14 patients with a normal QTc (mean age 45.8 +/- 12.1 years). Patients with an increased QT interval at rest experienced a significant reduction in QT interval during exercise (0.315 +/- 0.030 s vs 0.394 +/- 0.046 s standing at rest; P less than 0.01), as cycle length was decreased from 0.732 +/- 0.175 s to 0.489 +/- 0.062 s. Patients in the control group had a similar change in QT interval (0.297 +/- 0.015 s vs 0.359 +/- 0.029 s standing at rest (P less than 0.01), with a comparable change in cycle length 0.733 +/- 0.097 s vs 0.511 +/- 0.059 s.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1984

Quality of life in treated head and neck cancer patients: a preliminary report.

A psychological study of 48 elderly men after treatment for buccopharyngeal cancers was carried out to see whether treatment type (surgery alone, irradiation alone or salvage surgery after failed radiotherapy) was associated with differences in quality of life. Eight measures were used, covering functional disability, appearance, pain, depression, psychological well being and life satisfaction. Functional disability was lower and performance status high in those treated by irradiation alone. There was greater dissatisfaction with appearance in patients treated by surgery. Levels of depression were high in all groups. There were no significant differences between treatment groups however for depression, present pain, psychological well being or life satisfaction.

Affect↗

PubMed1984

Experimental infection of mares with Haemophilus equigenitalis.

Inoculation of Haemophilus equigenitalis into the uterus of 7 mares caused a disease clinically indistinguishable from contagious equine metritis. The duration of clinical signs varied from 4 to 11 days. The causative organism persisted for a relatively short time (2 to 10 weeks) in 5 mares, but in 2 others it established a carrier status and persisted until they were killed 6 and 10 months after infection. H. equigenitalis was recovered from the vestibule of the vagina and from a combined swab of the clitoral fossa and sinuses throughout the course of the infection. In some mares there were extended periods (2 weeks) when it could not be reisolated. All mares experienced a transitory serological response to infection. The complement fixation test was generally negative 12 weeks after infection whereas antibodies detected by the passive haemagglutination test and serum agglutination test were more persistent. In some animals the PHT and SAT titres increased during the breeding season following infection. The serological response did not appear to be related to the duration of infection.

Animals↗

PubMed1984

Incidence of lung cancer by cell type: a population-based study in New Hampshire and Vermont.

Identified were 1,906 cases of confirmed lung cancer that occurred among all residents of New Hampshire and Vermont over a 4-year period. Medical records, pathologists' reports, and, when possible, pathology slides were obtained and reviewed to assign cases to a specific histologic diagnosis. The diagnosis made by the original pathologist was generally confirmed upon review, except for the large cell undifferentiated cell type which appeared to be an unreliable classification. Among men at all ages incidence rates for squamous cell cancer far exceeded those for adenocarcinoma and small cell undifferentiated carcinoma, and the three age-incidence curves showed a similar pattern, rising until the eighth decade of life and then declining. Among women these three major cell types occurred about equally often, but the age-incidence curves differed in shape with adenocarcinoma reaching a peak incidence at an earlier age.

Adenocarcinoma↗

PubMed1984