Transcallosally evoked responses in the visual cortex of normal and monocularly enucleated rabbits

Summary In visual cortex of normal adult rabbits, callosal projections are restricted to a 2 mm wide band at the area 17/18 border. In adult rabbits which are monocularly enucleated (ME) on the day of birth, the callosal zone extends 4 mm into the medial region of area 17 in the cortex ipsilateral to the remaining eye. In this study, the function of these anomalous callosal projections in ME rabbits was investigated using electrophysiological techniques. A microelectrode was placed in the visual cortex ipsilateral to the enucleated eye at the 17/18 border, bipolar stimulating electrodes were placed in a homotopic location in the contralateral cortex, and averaged evoked responses (AERs) to stimulation were recorded. The stimulating electrodes were then moved mediolaterally in 1 mm steps, and the AERs were recorded for each location of the stimulating electrodes. In the normal rabbit, a maximal short latency evoked response was recorded when the stimulating electrodes were at a location homotopic to the recording electrode. When the stimulating electrodes were moved a distance of 1 mm or more from this optimal position, this short latency response was either absent or dramatically decreased in amplitude, reflecting the precise topographic pattern of the normal callosal projection. In contrast, in ME rabbits, a consistent response was evoked at the 17/18 border when the stimulating electrodes were moved as much as 3 mm medial to the homotopic position. Since antidromically activated responses and both pre- and post-synaptic orthodromically activated responses contribute to the AER, recordings were also made from single cells in some animals. Orthodromically activated single cell responses were evoked by electrical stimulation in the abnormal medial callosal zone of ME rabbits. The data indicate that abnormal callosal projections in ME rabbits can mediate functional interactions between nonhomotopic areas of the primary visual cortices.     

HLA Antigens in 16 Families with Xeroderma Pigmentosum

Xeroderma pigmentosum is an autosomal recessive disease. HLA-A and -B typing was performed on peripheral blood lymphocytes and platelets. Sixteen Tunisian families were typed with 37 patients and 108 relatives. Genetic transmission of the disease and of the HLA system seemed to be independent in this study. Comparison of HLA gene frequencies between (unrelated) parents of patients and a control population showed no difference, proving that there is no clear association in populations between deleterious XP genes and a particular HLA gene. However, an excess of identical HLA among pairs of diseased siblings would suggest that the disease is polymorphic and a form of the XP could be linked to HLA.     

Validation of intensity modulation on a commercial treatment planning system

For two years now, a study on intensity modulated radiotherapy (IMRT) has been in progress at the Antoine Lacassagne Hospital Center for Cancer Therapy (in Nice) in collaboration with the University of Nice-Sophia Antipolis. The kind of intensity modulation that was used is the "step and shoot" technique in which the modulated beam is created both by adding andjoining elementary fields. Before carrying out clinical tests, several problems regarding the production of modulated beams has to be mastered. The current developments of our study enable us to dosimetrically produce (in water phantom and in the PMMA phantom) complexmodulated whose segmentation was calculated by one commercial treatment planning system (TPS). Nevertheless, we showed and studied some critical discrepancies between standard clinical calculations and the calculations using field segmentation. We showed that with nonoptimal conditions of segmentation the discrepancies, which are due to the type of algorithm used, could bring about significant errors inside the field of up to 10% of maximum dose. Another point of our study is the quantification and resolution of differences between measurements and calculations due to the internal segmentation of calculated modulated fields and their realization on Linac. Once again, in none optimal conditions of segmentation and inside the field we obtained discrepancies up to 20% of maximum dose between calculations using field segmentation and measurements. That was mainly due to the tongue and groove effect and penumbra phenomena. This study allows us to show that the discrepancies between segmentation calculations and standard clinical calculations should be solved by the use of penumbra models during segmentation calculations. We will introduce both the study and its near-future perspectives.     

Analytical technique for quantification of selected resorbable calcium phosphate bone void fillers with the use of polarized-light microscopy

Synthetic calcium phosphate bone void fillers promote varying rates of bone formation and material resorption depending on chemistry, porosity, pore structure, and implant site. The objective of this study was to quantify the resorption of a novel ultraporous beta-tricalcium phosphate cancellous bone void filler with simultaneous quantification of bone formation in a canine humerus model. Potential measurement error involved in conventional histomorphometry using Von Kossa stains inspired the development of a new technique. This technique utilizes bright-field and polarized-light microscopy in conjunction with image analysis software, allowing more accurate histomorphometry. This technique was validated with two separate controlled experiments. Scanning electron microscopy further supported the results. The findings suggest that the use of polarized-light microscopy combined with image analysis software can be an effective tool in simultaneously quantifying calcium phosphate resorption and bone formation.     

Screening for Depression in the Medically Ill: a comparison of self-report measures, clinician judgment, and DSM-IV diagnoses

The performance of the self-report 10-item Depression in the Medically Ill scale was observed in 210 patients as part of clinical assessment by consultation-liaison psychiatry clinicians. Both the Depression in the Medically Ill scale and the Beck Depression Inventory for Primary Care were completed by the patient, and the clinicians made their judgment of the presence and severity of "clinical depression" and DSM-IV affective disorder diagnoses. Both the Depression in the Medically Ill scale and the Beck Depression Inventory for Primary Care detected 85% of patients with DSM-IV major depressive episode. The Depression in the Medically Ill scale was slightly superior to the Beck Depression Inventory for Primary Care in its relationship to clinicians' judgments of clinical depression caseness.     

Is ATP-sensitive K+ channel (K+ATP) recruitment a common mechanism for ECG-ST segment depression and elevation?

ATP sensitive (K(+)(ATP)) potassium cardiac channels are recruited when ATP levels are low as in ischemic injury and acute trauma. Such activation results in ECG-ST elevation and cardiac arrhythmias. K(+)(ATP) channel recruitment may be blocked by the sulfonylurea glibenclamide, permitting a wide variety of animal experimentation designed to test the genesis of ECG-ST segment elevations and depressions in diverse conditions including digitalis effect, acute arterial occlusion, tachycardias, and acute pericarditis. A specific series of animal experiments designed to test this hypothesis is proposed. Clinical implications are discussed.     

Kinetics of different specific immunological parameters after rabies vaccination in mice.

A significant protection to an intracerebral challenge of 70 mean lethal doses of a standard live rabies virus strain was obtained in BCG-pretreated mice or in normal mice which had been immunized with a single subcutaneous injection of a beta-propiolactone-inactivated rabies vaccine. Concomitantly, levels of delayed-type hypersensitivity (measured in vivo by the footpad test) and serum-neutralizing activity were evaluated at various times after immunization. All immune criteria were significantly augmented in the BCG-pretreated, rabies-immune mice as compared to normal, rabies-immune mice. However, peak levels of protection, delayed-type hypersensitivity, and serum-neutralizing activity did not occur at the same times. For instance, in the BCG-pretreated, rabies-immune mice, delayed-type hypersensitivity peaked on day 7, protection peaked on day 21, and serum-neutralizing activity peaked on day 60. In BCG-pretreated mice, which did not receive the rabies vaccine, positive delayed-type hypersensitivity, some protection, and serum neutralizing activity were observed 4 to 5 weeks after BCG pretreatment. The possible relationships between specific and nonspecific immunity provoked by rabies virus antigens, tissue culture cell-associated antigens (derived from the bovine fetal kidney cells in which the rabies virus was grown, and BCG are discussed.     

Control of spread of Methicillin Resistant Staphylococcus aureus (MRSA) in Burns Units

Results of four years' studies from a number of hospitals in Kenya have shown that nosocomial infections in burns units are due to Methicillin Resistant Staphylococcus aureus (MRSA). Through chromosomal DNA and plasmid DNA, the stain is highly resistant to sulphonamide ointment and other antibiotics. 90% of patients admitted in burns units get colonized or infected with MRSA. The strain prolongs the duration of patients in hospitals. The burns degenerate to second and third degree burns, thereby necessitating skin grafting. The environment has been found to be contaminated with this strain with some staff members having chronic throat infections. Minocycline was found to be effective in treating the infected staff members. Cleaning this environment with Sodium dichloroisocyanurate (precepts)/Sodium hypochlorite (JIK) reduced drastically the mechanical transmission of bacteria in the units. The duration of stay of the patient was reduced. This shows that MRSA which is spread in government and private hospitals can cheaply be controlled by the proper use of disinfectants, antiseptics, and use of effective antibiotics when necessary.     

Virtual patient simulator for distributed collaborative medical education

Project TOUCH (Telehealth Outreach for Unified Community Health; http://hsc.unm.edu/touch) investigates the feasibility of using advanced technologies to enhance education in an innovative problem-based learning format currently being used in medical school curricula, applying specific clinical case models, and deploying to remote sites/workstations. The University of New Mexico's School of Medicine and the John A. Burns School of Medicine at the University of Hawai'i face similar health care challenges in providing and delivering services and training to remote and rural areas. Recognizing that health care needs are local and require local solutions, both states are committed to improving health care delivery to their unique populations by sharing information and experiences through emerging telehealth technologies by using high-performance computing and communications resources. The purpose of this study is to describe the deployment of a problem-based learning case distributed over the National Computational Science Alliance's Access Grid. Emphasis is placed on the underlying technical components of the TOUCH project, including the virtual reality development tool Flatland, the artificial intelligence-based simulation engine, the Access Grid, high-performance computing platforms, and the software that connects them all. In addition, educational and technical challenges for Project TOUCH are identified.