A mammalian model of optic-flow utilization in the control of locomotion

Summary Gibson (1966, 1979) and Lee (1976) have described the potential usefulness of optic-flow information for the control of locomotion. One variable that might be particularly important for an animal approaching a target is time-to-collision, which Lee argues is most efficiently specified by the tau margin (the inverse of the relative rate of expansion of the target image on the retina). In humans, most empirical studies of optic flow have required perceptual judgements or have examined catching/intercepting behaviours. In animals, most studies have been strictly observational. This is particularly true for mammals, where there has been no experimental work of any kind looking at the control of locomotion. The present experiment demonstrates that the Mongolian gerbil (Meriones unguiculatus) uses time-to-collision information to control deceleration as it runs towards a target. The development of this animal model will aid investigation of the neural circuitry underlying optic flow utilization in motor control.     

Behavioural interaction between the NMDA antagonist MK-801 and the dopaminergic antagonist haloperidol: support for a balance model

One hundred and four male Sprague-Dawley rats were divided into three experiments. The first two experiments were to assess the effect of different MK-801 doses (0.1-0.3 mg/kg) and combinations of MK-801/ haloperidol (0.3/0.1-0.5 mg/kg) on locomotor behaviour. The animals from the third experiment were administered either saline, MK-801 (0.3 mg/kg), haloperidol (0.5 mg/kg) or MK-801/haloperidol (0.3/0.5 mg/kg). Locomotor activity measurements showed that the NMDA antagonist MK-801 induced a dose-dependent hyperactivity, while haloperidol, the D-2 dopamine receptor antagonist, induced hypoactivity. Significantly the highest doses of combined MK-801/haloperidol treatment (0.3/0.5 mg/kg) showed behavioural equivalence to the saline animals in both total locomotion, locomotion patterns and within-session habituation. Thus, the behavioural effects of each drug given alone were cancelled when the drugs were given together. This cancellation effect could not be ascribed to direct drug interference effects on dopamine metabolism since the ex vivo biochemical data revealed that the combined MK-801/haloperidol (0.3/0.5 mg/kg) treatment increased dopamine metabolism to the same extent as haloperidol given alone. None of the drug treatments, however, had any effect on brain serotonin metabolism. Serum measurement indicated that dopamine, homovanillic acid, 3,4-dihydroxyphenyl-acetic acid, 5-hydroxyindole-3-acetic acid, norepinephrine and corticosterone were not differentially affected by the drug treatment. Haloperidol-treated animals, however, had higher serum serotonin concentration than saline-treated animals. Taken together, these results support the hypothesis that the effect of MK-801 on behaviour is independent of biochemical changes in dopaminergic neuro transmission per se. Rather, the present results support the hypothesis of a glutamatergic-dopaminergic balance which when disturbed leads to behavioural changes along an excitatory-inhibitory behavioural gradient.     

Staff responsibility to exercise

Recent attention has been focused on the importance of exercise for improving the physical functioning of renal patients. The involvement of the dialysis staff in encouragement and implementation of programs is critical to the success of patient efforts in improving physical functioning. Staff responsibility initially consists of various developmental steps that are focused on gaining staff support and developing a plan that matches the needs and the resources available to the unit. Each staff member plays a critical role in the development, implementation, and evaluation of the exercise program. A concerted effort from all staff to incorporate exercise as a routine part of the patient care will enhance the potential of success and patient participation.     

Phorbol ester stimulated Cip1 expression in p53-negative leukemic cells

In differentiating leukemic cells, cyclin-dependent kinase interacting protein (Cip1) is induced and stimulates a G(1) arrest. TPA treated U937 monoblastoid cells expressed Cip1, hypophosphorylated retinoblastoma protein (Rb), arrested in G(1) and differentiated. PKC-zeta cells are U937 cells that overexpress the zeta isoform and display alterations in endogenous PKC isoform expression. TPA treated PKC-zeta cells undergo apoptosis without differentiating. TPA treated PKC-zeta cells express Cip1 and display substantial hypophosphorylation of Rb but fail to arrest in G(1). Thus, a novel phorbol ester dependent signalling pathway exists in which Cip1 induction is associated with the absence of a G(1) arrest and induction of apoptosis rather than differentiation.     

Cervical Cancer among Asian American Women: A Neglected Publica Health Problem?

PURPOSE OF THE PAPER: Relatively little attention has been paid to cervical cancer control in Asian American populations. We summarize available cervical cancer incidence and mortality dat, present information on levels of Pap testing use, and review factors that may be associated with cervical cancer screening participation. METHODS: We reviewed the literature pertaining to cervical cancer and Pap testing among Asian populations in North America. PRINCIPAL FINDINGS: Cancer registry data suggest that women from Southease Asia have a nearly five­fold increased risk of invasive cervical cancer (when compared to non­Hispanic White women). Filipino and Korean populations also have elevated risks. The excess invasive cervical cancer burden appears to be concentrated among women aged 40 and older. Pap testing use by Asians is less than for all toher racial/ethnic groups in the U.S., and recent studies suggest that over one­third of Vietnamese immigrants have never been screened. Barriers to Pap testing participation by less acculturated Asian women include a lack of familiarity with Western preventive concepts, a lack of knowledge concerning cervical cancer, embarrassment in association with gynecologic exams, the role of women in some Asian cultures, the cost of health care, and language difficulties. CONCLUSIONS: There is a considerable need for ethnoculturally appropriate cervical cancer control programs targeting Asian American populations. RELEVANCE TO ASIAN PACIFIC ISLANDER AMERICAN POPULATIONS: This paper is relevant to Asian American women from East, South, Southeast, and Island Asia.     

Appendicitis: Higher risk in Mexican Americans?

Objectives. Mexican Americans (MAs), compared to white non‐Hispanics (WNHs), have higher rates of biliary disease, noninsulin dependent diabetes, and endstage renal disease but lower rates of lung cancer, hip fractures, and mortality from coronary heart disease. Relatively little research has been done to identify other ethnic differences in disease incidence. We used surgical procedure rates to confirm known ethnic differences and to explore our clinical suspicion that MAs have higher rates of appendectomy than WNHs.

Methods. We used a registry of surgical procedures at two teaching hospitals in South Texas to calculate proportional operation ratios (PORs) for MAs versus WNHs. These two hospitals are the primary source of acute hospital care for the indigent in the area. The POR is arithmetically identical to proportional incidence and mortality ratios.

Results. MAs underwent appendectomy proportionally more often than WNHs at both hospitals (POR = 1.41 and 1.75, p < 0.0001). Other significant PORs were consistent with known ethnic disease differences in biliary tract operations, vascular access for chronic hemodialysis, lung cancer, and coronary artery bypass.

Conclusions. These findings support the hypothesis that MAs may undergo appendectomy more often than WNHs and so may be at higher risk of appendicitis.     

Use of resident physicians: an evaluation of the effects of a significant increase

Medical school graduates have become increasingly dependent on former community hospitals for residency programs because charitable institutions attached to medical schools are disappearing. It is not known what impact residencies have on hospitals that were community hospitals. We interviewed private practice physicians, residents, nurses, patients, and other groups in a large former community hospital. Overall, the interviews indicated good support for the hospital's new teaching function. Furthermore, the residents were viewed in very favorable terms by all groups. There were two problem areas. One, some residents seem less sensitive to human relations than private practice physicians and other hospital groups. Two, many private practice physicians are concerned over the number of hospital-salaried physicians and the outpatient care offered by residents supervised by hospital-salaried physicians. This research suggested several recommendations that, if followed, would serve to increase the value of the residency in meeting patient needs in the most effective manner.     

Some reasons for the lack of progress in the treatment of acute myelogenous leukemia: a review of three consecutive trials of the treatment of poor prognosis patients

The failure of three consecutive treatment protocols to significantly increase the complete remission rate for poor prognosis newly diagnosed patients with acute myelocytic leukemia led to a detailed investigation of the causes of treatment failure. In the majority of cases treatment failure was attributable to "clinical resistance" to therapy. Upon close examination two types of "clinical resistance" were discernible: the failure of chemotherapy to produce adequate cytotoxic effects ("classical" drug resistance), and treatment failure attributed to the rapid regrowth of leukemia cells subsequent to the substantial killing of leukemia cells by cytotoxic therapy ("biological" resistance). Each form of resistance accounted for one-half of the treatment failures.     

Clinical studies of a fast homoarginine-sensitive alkaline phosphatase in patients with cancer

The activity of an isoenzyme of alkaline phosphatase (FHAP) was measured in serum samples obtained from 1692 individual subjects. The median FHAP concentration in patients with untreated or recurrent cancer (2.73 IU/liter) was two-fold higher than in hospitalized control patients with illnesses other than cancer (1.17 IU/liter) and three-fold higher than in healthy control subjects (0.93 IU/liter). Among patients with either breast or colorectal cancer who were clinically disease free following their initial therapy, the median FHAP concentration (1.54 IU/liter) was intermediate between the median FHAP concentration in patients with untreated or recurrent cancer and that of healthy control subjects. In order to illustrate the potential clinical application of FHAP as a diagnostic cancer marker, we have selected a serum FHAP concentration of 2.22 IU/liter as a reference value above which only 3% of healthy control subjects would have a "positive" test. Utilizing this reference value, 58% of the patients in the present study with untreated or recurrent cancer would have a positive FHAP test, whereas only 11%, of hospitalized patients with illnesses other than cancer would have a positive test. These data suggest that FHAP may be equivalent to the carcinoembryonic antigen as a diagnostic cancer marker.