[Recording of synaptic currents with extracellular electrodes]

Recordings made by multielectrodes distributed in depth of the cortex are used for the system level study of the brain. The distribution of the extracellular potential obtained contains information about the input signals of pyramidal neurons in the cortex, the synaptic currents. A method of the estimation of the synaptic current distribution is described, which is based on the solution of the reverse problem for a system of homogeneously distributed parallel cylinders as a model of dendrites of the pyramidal neurons. The estimations are compared to the data both known from literature and obtained by an independent model.

Impact of telomerase status on canine osteosarcoma patients

BACKGROUND

We demonstrated previously that canine osteosarcoma (OSA) cell lines and samples from clinical patients are predominantly telomerase positive. In contrast, the majority of OSA samples from human patients appear to be telomerase negative, maintaining telomere length by an alternative lengthening of telomeres (ALT) mechanism. The purpose of the current study was to examine the telomerase status of a large number of OSA samples from dogs and determine if telomerase status can serve as a prognostic factor.

HYPOTHESIS

The majority of clinical canine OSA appendicular lesions will be telomerase positive, and telomerase positivity will negatively impact disease outcome.

ANIMALS

Sixty-seven dogs with appendicular OSA presenting to the Colorado State University Animal Cancer Center for treatment.

METHODS

The Telomeric Repeat Amplification Protocol was performed on tissue samples from primary canine appendicular OSA to determine the presence of telomerase activity. Telomere restriction fragment (TRF) analysis was utilized to determine telomere length and detect ALT. Outcome data were obtained in a retrospective manner and correlated with telomerase status.

RESULTS

Seventy-three percent of canine OSA samples were telomerase positive. Telomerase status did not have an impact on disease-free interval or survival time. Nine of 10 telomerase-negative samples examined were consistent with an ALT phenotype, based on TRF analysis.

CONCLUSIONS AND CLINICAL IMPORTANCE

These results are consistent with the hypothesis that the majority of canine OSA are telomerase positive, suggesting that telomerase may be a valuable target for canine OSA therapy. Additionally, telomerase status does not appear to be a prognostic factor in canine OSA.

Proximal anterior cruciate ligament avulsion fracture in a skeletally immature athlete: a case report and method of physeal sparing repair

Traumatic rupture of the anterior cruciate ligament (ACL) in adulthood is relatively common and surgical reconstruction is frequently required to allow return to high-level activities. There is growing evidence to suggest that ACL rupture in children is more common than previously thought and a poor outcome is associated with conservative management. The site of rupture in childhood is predominantly tibial avulsion, but mid-substance tears have also been reported. We report a case of a proximal ACL avulsion in an 11-year-old athlete and discuss a method of extra-physeal repair. There are very few previous reports of proximal avulsion fractures in skeletally immature patients.

In situ characterization and mapping of iron compounds in Alzheimer's disease tissue

There is a well-established link between iron overload in the brain and pathology associated with neurodegeneration in a variety of disorders such as Alzheimer's (AD), Parkinson's (PD) and Huntington's (HD) diseases [1]. This association was first discovered in AD by Goodman in 1953 [2], where, in addition to abnormally high concentrations of iron in autopsy brain tissue, iron has also been shown to accumulate at sites of brain pathology such as senile plaques [3]. However, since this discovery, progress in understanding the origin, role and nature of iron compounds associated with neurodegeneration has been slow. Here we report, for the first time, the location and characterisation of iron compounds in human AD brain tissue sections. Iron fluorescence was mapped over a frontal-lobe tissue section from an Alzheimer's patient, and anomalous iron concentrations were identified using synchrotron X-ray absorption techniques at 5 mum spatial resolution. Concentrations of ferritin and magnetite, a magnetic iron oxide potentially indicating disrupted brain-iron metabolism, were evident. These results demonstrate a practical means of correlating iron compounds and disease pathology in-situ and have clear implications for disease pathogenesis and potential therapies.

Purification of the RelB and RelE proteins of Escherichia coli: RelE binds to RelB and to ribosomes

The direct interaction of the Escherichia coli cytotoxin RelE with its specific antidote, RelB, was demonstrated in two ways: (i) copurification of the two proteins and (ii) a positive yeast two-hybrid assay involving the relB and relE genes. In addition, the purified RelE protein exhibited ribosome-binding activity in an in vitro assay, supporting previous observations suggesting that it is an inhibitor of translation.

Dementia, quantitative neuroimaging, and apolipoprotein E genotype

BACKGROUND AND PURPOSE

Quantitative MR imaging differences in an elderly population of subjects with various clinical disorders (including dementia, particularly Alzheimer's disease and vascular dementia) and disorders of mild cognitive impairment were examined. Potential quantitative MR differences were assessed by presence or absence of the apolipoprotein E (APOE) epsilon4 allele and by level of cognitive deficit.

METHODS

One hundred eighty subjects with a diagnosis of dementia or other clinical disorders were identified from an eligible population of 5,677 elderly individuals. Age, duration of disease, and head size (where appropriate) were considered as covariates. APOE genotype was determined by polymerase chain reaction using buccal material. Axial and coronal intermediate- and T2-weighted MR images were quantified using a multispectral segmentation algorithm. Cognitive status was assessed by means of a modified Mini-Mental Status Examination.

RESULTS

All types of dementing illness showed significant volume reductions in the majority of structures examined, particularly in the total brain, hippocampus, and white and gray matter, and increased CSF and ventricular volumes. Subjects with mild cognitive impairment showed fewer atrophic changes but were still distinguishable from the 24 control subjects. Presence of an epsilon4 allele was associated with smaller hippocampal volume in subjects with Alzheimer's disease and vascular dementia within just 1 year of disease onset. For other analyses, atrophy related to the presence of the epsilon4 allele disappeared after controlling for age and length of disease.

CONCLUSION

The effects of the epsilon4 allele on brain morphology may be subtly expressed early in the development of dementia, but do not specifically affect cerebral atrophy thereafter. Cognitive impairment is associated with atrophy irrespective of diagnosis and presence of epsilon4.

A cluster of leptospirosis among abattoir workers

In early December 1998, the Northern Rivers Public Health Unit (north-eastern New South Wales) was alerted to a possible cluster of leptospirosis cases by the supervising scientist of the Western Pacific Region World Health Organization/Food and Agricultural Organization Collaborating Centre for Reference and Research on Leptospirosis. Investigation revealed a cluster of eight leptospirosis cases diagnosed during October and November 1998. All were employees of a local meat works. Leptospira serovars isolated included pomona and hardjo. Symptoms included headache, fever, muscle pain, sore eyes, abdominal pain, vomiting, jaundice, and rash. Five of the eight cases were hospitalised. The infection could not be traced to any particular source. Unfortunately, records of stock killed during the exposure periods were not available. All cases reported exposure to large volumes of animal urine during the course of their work. Protective clothing provided included an apron, gloves, and rubber boots. All of the patients said they wore rubber boots and seven of the eight wore the apron provided. Only two patients reported wearing gloves, the remainder thought these were too difficult to work in.

Metabolic responses to fructose-1,6-diphosphate in healthy subjects

Fructose-1,6-diphosphate (FDP) is an important naturally occurring intracellular metabolite with a direct regulatory role in many metabolic pathways. The most important and widely studied of the FDP effects has been its regulation of glycolysis, particularly the enzyme that synthesizes FDP--phosphofructokinase (PFK). Since it was observed experimentally that FDP does indeed modulate carbohydrate metabolism, we investigated whether FDP would similarly enhance carbohydrate utilization in man. The study used indirect calorimetry and was open to healthy adults (N = 45) of either sex and above legal age. After a steady metabolic state was obtained, 5 g of FDP (10%) was infused into a brachial vein. In 10 subjects, glucose (5 g) or FDP (5 g) was sequentially infused. The rapid intravenous infusion of FDP produced a slight but significant decrease in heart and respiration rates (P < .05). A significant increase in the serum concentration of inorganic phosphate (P < .0001) and the intraerythrocytic concentration of adenosine triphosphate (ATP) (P < .01) was also observed. The FDP infusion produced a decrease in plasma cholesterol and triglycerides (P < .001 and P < .01, respectively). The indirect calorimetric data indicate that the infusion produced a highly significant increase in the respiratory quotient ([RQ] P < .0001) and the energy derived from carbohydrates (P < .0001) and a significant decrease in the energy derived from lipids (P < .0001). Glucose infusion did not cause changes in any of the parameters. These data indicate that carbohydrate metabolism is stimulated by FDP.

Carotid artery stenting in patients with high neurologic risks

Forty-four patient with high neurologic risks (Mayo class IV) successfully underwent carotid artery stenting with combined major stroke and death rates of 4.5%. Late follow-up at a mean of 23 +/- 1.8 months showed 1 non-neurologic death, but no neurologic events or repeat stenting procedures.

Choroidal neovascularization secondary to Candida albicans chorioretinitis

PURPOSE

To study the clinical histories and courses of six patients with choroidal neovascularization secondary to endogenous Candida albicans chorioretinitis.

METHODS

The medical records, fundus photographs, and fluorescein angiograms of six patients who developed C. albicans chorioretinitis secondary to candidemia and who subsequently developed choroidal neovascularization in one or both eyes were reviewed.

RESULTS

The six patients ranged in age from 18 to 79 years. Four were women and two men; all but one showed evidence of bilateral chorioretinal scarring secondary to C. albicans chorioretinitis. All patients had been treated successfully with systemic antifungal therapy (amphotericin B). Two weeks to two years after the chorioretinitis, choroidal neovascularization developed in one eye (four cases) or both eyes (two cases). The neovascularization on initial examination was subfoveal in four eyes, extrafoveal in three eyes, and juxtafoveal in one eye. Laser photocoagulation was used in four of the eight involved eyes. In these cases, the active choroidal neovascularization was brought under control. In one eye, the patient had submacular surgery for excision of the choroidal neovascular membrane. Final visual acuities ranged from 20/20 to 20/200 in treated eyes and from 20/50 to 20/400 in untreated eyes.

CONCLUSION

Choroidal neovascularization is a potential cause of late visual loss in patients who have had C. albicans sepsis and endogenous C. albicans chorioretinitis. Eyes that have chorioretinal scarring from C. albicans chorioretinitis should be watched for the development of choroidal neovascularization. Laser photocoagulation or perhaps surgical excision of the neovascular complex may be of benefit in selected cases.

Effect of cocaine on left ventricular function. Relation to increased wall stress and persistence after treatment

BACKGROUND

To determine whether alterations in left ventricular (LV) function after a cocaine infusion are due to reduced myocardial contractility or changes in loading conditions, we examined LV function in 30 morphine-sedated, closed-chest dogs. We also wanted to determine the time course of the effects of cocaine on LV function after the infusion was stopped.

METHODS AND RESULTS

Two-dimensional echocardiography and hemodynamics provided LV fractional shortening and end-systolic wall stress data. Radionuclide ventriculography was also performed. Four groups of dogs received saline or cocaine infusions of 10, 30, or 100 micrograms.kg-1.min-1. Cocaine was infused for 90 minutes with ECG and arterial pressure monitoring. Animals were monitored for an additional 120 minutes after the infusion ended. Arterial pressure rose over the course of the experiment in all four groups, but saline and cocaine 10 micrograms.kg-1.min-1 did not significantly change ejection fraction. Cocaine 30 and 100 micrograms.kg-1.min-1 acutely increased arterial pressure and heart rate but decreased ejection fraction from 0.64 +/- 0.06 to 0.45 +/- 0.08 and from 0.65 +/- 0.10 to 0.46 +/- 0.11, respectively. Additionally, cocaine 100 micrograms.kg-1.min-1 decreased fractional shortening from 36 +/- 9% to 23 +/- 12%. However, cocaine 30 and 100 micrograms.kg-1.min-1 also increased wall stress from 42 +/- 15 to 65 +/- 11 g/cm2 and from 37 +/- 15 to 90 +/- 33 g/cm2, respectively. These results were analyzed by use of the relation between wall stress and fractional shortening as an index of contractility. Fractional shortening after cocaine infusion was displaced downward as a result of increased wall stress rather than changes in contractility. In addition, alteration of afterload with phenylephrine (6 micrograms/kg) and sodium nitroprusside (10 micrograms/kg) before and during infusion of cocaine 100 micrograms.kg-1.min-1 showed similar regression lines for wall stress to fractional shortening.

CONCLUSIONS

Ejection-phase indexes of LV function were reduced by cocaine in this model of conscious, sedated dogs, but effects were attributable to increased wall stress rather than to reduced myocardial contractility. These effects persisted for at least 2 hours after the infusion was stopped.

The major electrolytes: sodium, potassium, and chloride

Electrolytes are substances that dissociate in solution and have the ability to conduct an electrical current. These substances are located in the extracellular and intracellular fluid. Within the extracellular fluid, the major cation is sodium and the major anion is chloride. The major cation in the intracellular fluid is potassium. These electrolytes play an important role in maintaining homeostasis. In this article, the etiology, signs, symptoms, and treatments for imbalances of these three electrolytes are reviewed.