Enamel hypoplasia in ancestral Puebloan populations from southwestern Colorado: I. Permanent Dentition

Predictions of P. R. Killeen's (1994) mathematical principles of reinforcement were tested for responding on ratio reinforcement schedules. The type of response key, the number of sessions per condition, and first vs. second half of a session had negligible effects on responding. Longer reinforcer durations and larger grain types engendered more responding, affecting primarily the parameter alpha (specific activation). Key pecking was faster than treadle pressing, affecting primarily the parameter delta (response time). Longer intertrial intervals led to higher overall response rates and shorter postreinforcement pauses and higher running rates, and ruled out some competing explanations. The treadle data required a distinction between the energetic requirements and rate-limiting properties of extended responses. The theory was extended to predict pause durations and run rates on ratio schedules.     

Patterns of clinical metastasis in breast cancer: an analysis of 100 patients

Many patients diagnosed with breast cancer will develop metastases and these have diverse presentations. We have reviewed 100 consecutive patients who have died with metastatic breast cancer, to determine the frequency, sites and mode of presentation of recurrent disease. The commonest site of failure was loco-regional (n = 61), this usually presented with a mass, but a minority of patients also complained of pain. Bone metastases developed in 60 patients and produced bone pain, pathological fracture (n = 6) or cord compression (n = 5). Pulmonary metastases producing shortness of breath were diagnosed in 34 patients and were asymptomatic in a further 10. Intra-abdominal metastases were found at some time in 23 patients, most commonly in the liver (n = 20) and the majority complained of epigastric pain (n = 17). Brain metastases occurred in 23 patients and produced a wide range of symptoms including those of a space-occupying lesion (n = 10), cranial nerve palsy (n = 7), diabetes insipidus (n = 3), focal limb weakness (n = 2) and meningitis (n = 1). Three patients had choroid metastases producing reduced visual acuity. Recurrent breast carcinoma can present in a variety of ways, therefore any new symptom or sign should be considered to represent recurrence until proved otherwise.     

Outpatient parenteral antimicrobial therapy technology

Health care costs are continuing to spiral upward despite government and public insistence on cost containment. To meet the challenge, medical professionals and organizations are seeking opportunities for cost reduction and alternatives for delivery health care. This article discusses the tools that allow the effective delivery of care using the outpatient parenteral antimicrobial therapy (OPAT) model.