Biomedical subjects

M Dunham

Publications and source records attributed to M Dunham.

8 recordsLinked to original sources

PubMed2001

The development of functional response units: the role of demarcating stimuli.

An experiment with rats examined the roles of demarcating stimuli and differential reinforcement probability on the development of functional response units. It examined the development of units in a probabilistic, free-operant situation in which the presence of demarcating stimuli was manipulated. In all conditions, behavior became organized into two-response sequences framed by changes in local reinforcement probability. A tone demarcating the beginning and end of contingent response sequences facilitated the development of functional response units, as in chunking, but the same units developed slowly in the absence of the tone. Complex functional response units developed even though reinforcement contigencies remained constant. These findings demonstrate that models of operant learning must include a mechanism for changing the response unit as a function of reinforcement history. Markov models may seem to be a natural technique for modeling response sequences because of their ability to predict individual responses as a function of reinforcement history; however, no class of Markov chain can incorporate changing response units in their predictions.

Animals↗

PubMed1996

Prevalence and sources of patients' unmet expectations for care.

BACKGROUND: Patients' expectations and the role they play in medical care are increasingly considered to be important, but the factors that influence these expectations have not been well studied. OBJECTIVE: To examine the factors that influence patients' expectations for care in office practice. DESIGN: Qualitative inquiry nested within a large clinical survey. SETTING: Three general internal medicine practices in one mid-sized city in northern California. PATIENTS: 688 patients visiting their internists' offices were surveyed (response rate, 86%); 88 patients who reported one or more omissions of care on a post-visit questionnaire and were available for a telephone interview 1 to 7 days after the visit were included in the qualitative inquiry. MEASUREMENTS: Proportion of surveyed patients who reported one or more omissions of care, and qualitative analysis of the sources of patients' expectations, as determined from the telephone interviews. Interviews focused on the sources of expectations and perceptions of omission. Using an iterative process and working by consensus, investigators developed coding categories on a randomly selected 50% of the transcripts. The other 50% of the sample was used for validation. RESULTS: The 125 patients who had unmet expectations perceived omissions that were related to physician preparation for the visit (23%), history taking (26%), physical examination (30%), diagnostic testing (28%), prescription of medication (19%), referral to specialists (26%), and physician-patient communication (15%). Unmet expectations were shaped by patients' current somatic symptoms (intensity of symptoms, functional impairment, duration of symptoms, and perceived seriousness of symptoms) (74%); perceived vulnerability to illness (related to age, family history, personal lifestyle, or previously diagnosed conditions) (50%); past experiences (personal or familial) with similar illnesses (42%); and knowledge acquired from physicians, friends, family, or the media (54%). CONCLUSIONS: Patients' expectations for care are derived from multiple sources; their complexity should discourage simple schemes for "demand management." Nevertheless, the results of this study may help physicians to take a more empathetic stance toward their patients' requests and to devise more successful strategies for clinical negotiation.

Adult↗

PubMed1992

An unsuspected alkaline battery foreign body presenting as malignant otitis externa.

We describe a case of an unsuspected button battery foreign body in the ear canal causing symptoms that mimic malignant otitis externa in a previously healthy 13 year old. Button batteries in the ear canal may cause extensive liquefactive necrosis of the surrounding tissue by leaking an alkaline electrolyte solution. Suspicion of a foreign body should be maintained in any child presenting with a complicated otitis externa. Prompt evaluation and removal of button batteries are necessary to prevent tissue destruction.

Adolescent↗

PubMed1990

Le Fort fractures without mobility.

The Le Fort fracture without maxillary mobility constitutes 9 percent of maxillary fractures observed over a 3-year period. A high Le Fort (level II or III) injury exists as a one- or two-piece incomplete fracture. The degree of fracture is insufficient to permit mobility of the maxillary alveolus. Frequently, an obvious unilateral zygomatic fracture is present. Physical findings consist of bilateral eyelid ecchymosis and malocclusion. The occlusal disturbance may consist of either crossbite, open bite, maxillary rotation, or lack of proper dental intercuspation. On CT scan, fractures are best demonstrated in the posterior and medial maxillary walls at the Le Fort I level; they are most obvious unilaterally with contralateral fractures that may be subtle. Bilateral maxillary sinus fluid is consistently present on CT. Treatment usually consists of observation and traction elastics but may require mobilization of the fragments followed by open reduction and rigid fixation.

Humans↗

PubMed1990

Toward CT-based facial fracture treatment.

Facial fractures have formerly been classified solely by anatomic location. CT scans now identify the exact fracture pattern in a specific area. Fracture patterns are classified as low, middle, or high energy, defined solely by the pattern of segmentation and displacement in the CT scan. Exposure and fixation relate directly to the fracture pattern for each anatomic area of the face, including frontal bone, frontal sinus, zygoma, nose, nasoethmoidal-orbital region, midface, and mandible. Fractures with little comminution and displacement were accompanied by subtle symptoms and required simple treatment; middle-energy injuries were treated by standard surgical approaches and rigid fixation. Highly comminuted fractures were accompanied by dramatic instability and marked alterations in facial architecture; only multiple surgical approaches to fully visualize the "buttress" system provided alignment and fixation. Classification of facial fractures by (1) anatomic location and (2) pattern of comminution and displacement define refined guidelines for exposure and fixation.

Facial Bones↗

PubMed1986

Chronic syndrome of inappropriate antidiuretic hormone secretion and hypertension in a patient with olfactory neuroblastoma. Evidence of ectopic production of arginine vasopressin by the tumor.

A 28-year-old man with the chronic syndrome of Inappropriate antidiuretic hormone secretion and hypertension was found to have an olfactory neuroblastoma. We demonstrated evidence of elevated circulating arginine vasopressin levels, significantly elevated arginine vasopressin and vasopressin neurophysin levels in the tumor extract, and immunohistochemical staining for arginine vasopressin and vasopressin neurophysin in the tumor cells. The patient's clinical syndrome, including hypertension, resolved following subtotal removal of the tumor and radiation therapy. This study identified olfactory neuroblastoma as a definite cause of ectopic arginine vasopressin secretion causing the syndrome of inappropriate antidiuretic hormone secretion.

Adult↗

PubMed1984

Composite nasal septal cartilage graft for reconstruction after extended frontolateral hemilaryngectomy.

With the advent of extended partial laryngectomy for T2 and selected T3 true vocal cord carcinomas, the head and neck surgeon has had to deal not only with the rehabilitation of voice, but with the problem of laryngeal stenosis with obstruction of laryngeal airflow. To manage this difficult problem, it is necessary to restore the cartilagenous superstructure to prevent collapse of the laryngeal soft tissues. This is best done at the time of initial cancer resection. At the time of extended frontal lateral hemilaryngectomy, an exact template of the resected cartilage is made. From this, a composite nasal septal cartilage graft is utilized to restore the laryngeal superstructure. The anterior commissure is reconstructed by scoring the septal cartilage. It has been our experience with this procedure that the neoglottis remains both competent and functional.

Cartilage↗

PubMedDate not supplied

Asymmetric leaves1 mediates leaf patterning and stem cell function in Arabidopsis.

Meristem function in plants requires both the maintenance of stem cells and the specification of founder cells from which lateral organs arise. Lateral organs are patterned along proximodistal, dorsoventral and mediolateral axes. Here we show that the Arabidopsis mutant asymmetric leaves1 (as1) disrupts this process. AS1 encodes a myb domain protein, closely related to PHANTASTICA in Antirrhinum and ROUGH SHEATH2 in maize, both of which negatively regulate knotted-class homeobox genes. AS1 negatively regulates the homeobox genes KNAT1 and KNAT2 and is, in turn, negatively regulated by the meristematic homeobox gene SHOOT MERISTEMLESS. This genetic pathway defines a mechanism for differentiating between stem cells and organ founder cells within the shoot apical meristem and demonstrates that genes expressed in organ primordia interact with meristematic genes to regulate shoot morphogenesis.

Arabidopsis↗