Localized calcium influx orients axon formation in embryonic hippocampal pyramidal neurons

A fundamental property of neurons is their polarization into distinct axonal and dendritic compartments which have characteristic structural and functional properties. The mechanisms regulating the formation of neuronal polarity are unknown. We used cultured embryonic rat hippocampal pyramidal neurons to test the hypothesis that a localized calcium influx can orient axon formation, and thereby direct the establishment of neuronal polarity. Transection of an initial axon, or focal application of A23187 or K+ to the initial axon, caused a new axon to form at a site distant from the initial axon. Fura-2 measurements of intracellular calcium revealed a localized calcium influx at the site of axon transection or focal application of A23187 or K+, and a calcium gradient spreading into the soma. New axon formation was inhibited when axons were transected in medium lacking calcium or containing calcium-elevating agents (conditions which prevented the formation of a calcium gradient). When calcium ionophore A23187 was applied focally to neurons which had not yet established an axon, the axon always formed at a site distant from the site of ionophore application; bath exposure to A23187 prevented axon formation. Taken together, these data demonstrate that a localized influx of calcium can suppress axon formation at the site of influx, and can thereby influence where the axon forms. These data suggest that gradients of intracellular calcium may be involved in orienting neuronal polarity.     

Monotherapy trials: endpoints.

Monotherapy antiepileptic drug (AED) trials can optimally provide information concerning efficacy and tolerability of one drug compared with placebo, as well as to different doses or rates of administration. Commonly, a drug is compared with one or more other drugs. The outcome measures will be dictated by the questions being asked. In most comparative studies, the single overall result that best defines success or failure is time of continuation on drug as expressed in a life table. Discontinuation before planned completion of the study implies insufficient efficacy or unacceptable adverse effects. A statistically significant difference between treatments provides important support for recommending the drug or dose with the best outcome. The criteria for continuation/discontinuation are defined in the design based on the expected outcome. The outcome of primary importance is efficacy in prevention of seizures or a decrease in severity. Complete control for the duration of the study is the ultimate goal but in some populations may not be possible. The number of subjects entering remission gives further information about long term outcome. Time to first (nth) seizure provides similar evidence of efficacy. Seizure rates allow comparisons of subjects retained for different lengths of time in the trial. Differences in seizure severity may be of clinical importance and multiple efforts have been made to develop instruments to accurately measure this outcome. Adverse effects of the drugs are the second major outcome. These can be expressed as incidence and/or prevalence. The presence and frequency of side effects will depend on how the study is designed and whether these effects are specifically sought by the investigators. Serious systemic safety outcomes are monitored, but the relative infrequency of occurrence and number of subjects in the trials usually do not provide enough power to detect statistically significant differences except for rash. Tolerability is more easily documented but is difficult to access accurately in the absence of placebo controls. Frequency, severity and persistence are measurable. Specific unwanted types of drug effects can be specifically studied using detailed neuropsychological test batteries. Some information concerning pharmacokinetic properties may be obtained but are better assessed in other types of trials. A final important outcome is the effect of drug therapy on quality of life. Although a favorable finding in this outcome is most desirable, the measures used are much less precise than those for efficacy and adverse effects.     

Chronic granulocytic leukemia: reassessment of morphologic and cytogenetic characteristics in Ph1-positive and Ph1-negative cases

33 cases of chronic granulocytic leukemia (CGL) were reassessed to determine if, by strict morphologic criteria. Philadelphia chromosome (Ph1)-negative CGL exists as a diagnostic entity and if Ph1-positive CGL could be distinguished from Ph1-negative CGL. Cases were reassessed using published criteria and, of 11 Ph1-negative cases, only 4 could be reclassified as myelodysplastic syndromes or undifferentiated chronic myeloproliferative disorder. Of the morphologic parameters evaluated, peripheral blood basophilia and bicytopenia proved to be good discriminators between Ph1-positive and Ph1-negative cases. As a group, Ph1-negative cases were more heterogeneous and tended to have lower hemoglobin, WBC, platelet count and absolute eosinophilia. Chromosomal abnormalities other than Ph1 were seen only in the Ph1-positive cases. Based on these findings, we conclude that Ph1-negative CGL constitutes a heterogeneous group, a subgroup of which is morphologically identical with the Ph1-positive CGL. The parameters that best discriminate between Ph1-positive and Ph1-negative cases are peripheral blood absolute basophilia and bicytopenia.     

Human Hippocampal Seizure Spread Studied by Depth and Subdural Recording: The Hippocampal Commissure

Eleven patients had seizures with unilateral temporal lobe onset recorded with simultaneous bilateral medial temporal depth electrodes and neocortical (subdural) electrodes at least on the side of seizure onset. Of a total of 55 seizures, four had simultaneous onset in neocortex and hippocampus, and 51 had onset in unilateral hippocampus. None originated solely in temporal neocortex. Three reproducible patterns of seizure spread from hippocampus were defined in which seizures spread initially to ipsilateral neocortex (32 seizures), spread first to contralateral hippocampus (13 seizures), or spread simultaneously to ipsilateral neocortex and contralateral hippocampus. Although the region of hippocampus in which seizures arose was constant, patterns of spread sometimes varied in the same patient. When contralateral neocortical involvement occurred, it was after or with contralateral hippocampus but never before. These results suggest the existence of an operational hippocampal commissure in humans.     

A comparison of smoking patterns in the People's Republic of China with the United States. An impending health catastrophe in the middle kingdom

Half of the global increase in tobacco use from 1976 to 1986 occurred in the People's Republic of China. In 1984, the first national smoking survey was conducted in China, involving over a half-million subjects. Sixty-one percent of Chinese males over age 15 smoke, with higher rates in all occupational groups than for corresponding groups in the United States. Current smoking patterns in China are similar to those in the United States during the 1950s, and these patterns forecast a steadily increasing epidemic of smoking-related deaths. It is estimated that by 2025, two million Chinese men will die annually from smoking. Foreign tobacco companies are mounting massive production and advertising campaigns in China. Government health education programs lack funds to counter these influences with sustained and comprehensive educational and interventional campaigns. To avert an impending national health catastrophe, China must launch a comprehensive smoking-control initiative aimed at public education, cessation, and legislation and policy.     

Monitoring gastrointestinal intraluminal PCO2: problems with airflow methods

Gastrointestinal intraluminal PCO2 (PiCO2) information is used to assess the adequacy of trauma patient resuscitation and to assist in choosing resuscitative interventions. Therefore, determining the limitations and potential caveats of different PiCO2 monitoring systems is clinically important. This study compared two PCO2 monitoring systems. The airflow device adds and then removes air samples to quantitate PCO2, whereas the fiber-optic device does not. METHODS: Airflow (TRIP Tonometer/Tonocap) and fiber-optic (Neotrend) systems were used. In vitro they were compared with each other and to two end-tidal CO2 monitors measuring the PCO2 of humidified air containing 5% and then 10% CO2. In vivo the two systems' catheters were surgically juxtaposed in 15 dogs' stomachs; paired PiCO2 readings were taken throughout hemorrhage and resuscitation. RESULTS: In vitro, paired PCO2 values from the airflow and fiber-optic devices correlated with each other (r = 0.99) and with end-tidal values (r = 0.99 with airflow, r = 0.95 with fiber-optic). In vivo, paired values differed significantly (P < 0.0001), correlating poorly for two devices simultaneously measuring the same variable (r = 0.61). Fiber-optic PiCO2 values were higher than airflow values (mmHg +/- SEM): 69.3 +/- 4.8 vs. 61.3 +/- 5.6 at the start of hemorrhage, 141.3 +/- 12.9 vs. 87.7 +/- 7.9 by end of hemorrhage, and 104.3 +/- 9.6 vs. 82.8 +/- 7.0 by end of resuscitation for fiber-optic and airflow, respectively. CONCLUSIONS: Despite agreement in vitro, airflow methods can influence PiCO2 values obtained in vivo. Passive sensing methods used to monitor PiCO2, such as fiber-optic methods, are preferable because they neither deliver O2 to, nor remove CO2 from the local microenvironment.     

Effect of lepirudin on the international normalized ratio

BACKGROUND: Many patients receiving direct thrombin inhibitor (DTI) therapy require transition to warfarin. This transition may be complicated by DTI-induced elevations in the international normalized ratio (INR). While the effect of argatroban on the INR has been characterized, data assessing the effect of lepirudin on the INR are limited. OBJECTIVE: To evaluate the effect of lepirudin on the INR. METHODS: Patients receiving lepirudin therapy between January 2000 and May 2001 were identified using the pharmacy database, and a retrospective chart review was conducted. Patients were included for analysis if they had paired activated partial thromboplastin time (aPTT) and INR data while receiving lepirudin monotherapy. RESULTS: Fifty-three paired aPTT and INR data points from 8 patients receiving lepirudin monotherapy were collected. The Organon MDA 180 instrument was used for aPTT and prothrombin time (PT) determination. Organon MDA Platelin L reagent was used for the aPTT and Organon Simplastin L reagent was used for the PT. The international sensitivity index (ISI) of the Simplastin L thromboplastin was 2.0. The mean +/- SD lepirudin dose was 0.05 +/- 0.04 mg/kg/h. Linear regression was used to identify the INRs that correspond to a therapeutic aPTT value of 45-75 seconds (1.5-2.5 times mean laboratory normal of 30 sec). The correlation between aPTT and INR was 0.77. An aPTT of 45-75 seconds with lepirudin correlated to an INR of 1.6-3.2. CONCLUSIONS: Based on laboratory results, when using a thromboplastin with an ISI of 2, lepirudin appears to elevate the INR in the absence of warfarin.     

The Monoglyceride Pathway of Fat Absorption in Man

The absorption of fat was studied in five male subjects with cannulation of the thoracic duct in the neck by the administration of doubly labeled monoglycerides, or triglyceride as well as labeled free glycerol or labeled free oleic acid, by gastric or duodenal intubation.Total recoveries of the administered glyceride radioactivity from the lymph lipids ranged from 35 to 53% for the glycerol label (tritium) and from 35 to 57% for the fatty acid label ((14)C). The recovery of administered radioactive free glycerol in lymph lipids was only 4.1%, even when given in mixture with bile salts, fatty acid, and monoglyceride.A comparison of the isotope ratios of the two components (glycerol and fatty acid) of the lymph glycerides with the ratios of these components of the original meal glyceride showed little change during the initial period of fat absorption, indicating that the doubly labeled monoglycerides passed into the lymph intact. During the later part of the period of major fat absorption, the ratios in lymph lipids changed due to loss of glycerol representation, indicating monoglyceride hydrolysis and portal venous diversion of free glycerol.Confirmation of the intact nature of 2-monoglyceride during absorption was made by analyzing the amount and position of the labeled fatty acid in the lymph triglycerides. The percentage of labeled fatty acid in the various positions of the lymph triglycerides was virtually identical with that of the meal during the initial period of fat absorption and then changed reflecting isomerization of fatty acids and subsequent complete hydrolysis of the glycerides.The 2-monoglyceride pathway appears to be the major route of fat absorption for man during normal digestion and absorption of dietary triglyceride.