Endogenous luteinizing hormone surges following administration of human chorionic gonadotropin: Further evidence for lack of loop feedback in humans

The existence of inhibitory short- and ultrashort-loop feedback mechanisms for luteinizing hormone (LH), while documented in animals, has been questioned in humans. Since human chorionic gonadotropin (hCG) binds to LH receptors but can be distinguished from LH in immunoassays, it is possible to identify LH surges in the face of exogenously administered hCG. The present study demonstrates LH surges at midcycle in normal volunteers and in women undergoing controlled ovarian hyperstimulation, given hCG. This provides further evidence for lack of loop feedback control of LH secretion in humans.     

Undetected ovulation in in vitro fertilization-embryo transfer patients

A retrospective evaluation was done of 102 consecutive in in vitro fertilization-embryo transfer (IVF-ET) treatment cycles that culminated in surgical intervention for oocyte pickup. In 35% of these patients, a disparity was noted in the number of mature follicles present on the day of human chorionic gonadotropin administration, compared with the day of surgery. This suggests the occurrence of undetected ovulation. An endogenous luteinizing hormone (LH) surge was detected in 14 of these patients. Another cohort showed evidence of early luteinization without a detected endogenous LH surge. Finally, a group without early luteinization was defined. Possible explanations for these outcomes and the implications for success of IVF-ET are discussed.     

Aerobic physical activity among third- to sixth-grade children

We observed the level of activity, and determined which of 24 third- to sixth-grade children were present during that activity, for two weekdays per child. No events of aerobic activity, as defined by nationally accepted criteria, were detected in that 48 days of observation. By a less stringent criterion, only half the children engaged in aerobic activity on any one day. With regard to who was active, there was no evidence for day-to-day consistency. Fathers were virtually absent during periods of activity. Issues relating to promoting aerobic activity are discussed.     

Adult heart disease prevention in childhood: a national survey of pediatricians' practices and attitudes

There is controversy about the role of pediatric care givers in reducing presumed risk factors for cardiovascular diseases in children. A national mail survey of 2,000 pediatricians was designed to determine the attitudes, current practices, and knowledge among primary care pediatricians regarding these risks. The response rate was 60% (779 primary care pediatricians). Responses indicated that a majority of pediatricians take a family history of cardiovascular diseases, assess BP, recommend exercise to school-aged children, and advise patients and parents against smoking. Few pediatricians felt confident in their ability to affect change in patient life-styles. There was a relatively low level of provision of dietary advice, and most pediatricians do not measure serum cholesterol levels, except in high-risk older children. A substantial minority do not discuss smoking, even with adolescents. Practices and attitudes varied with the age of the patient. Obesity was the topic most frequently chosen for continuing medical education. Older pediatricians were most likely to advocate and practice risk reduction in children. Attitudes and reported practices also varied by gender and geographic location of the pediatrician as well as the ethnic composition of the practice. Implications for continuing medical education are discussed.     

Hemolytic uremic syndrome due to an altered factor H triggered by neonatal pertussis

We report on a previously healthy newborn suffering from severe Bordetella pertussis infection who developed hemolytic uremic syndrome (HUS) a few weeks after the onset of whooping cough, with a fatal outcome. A factor H protein with abnormal mobility was found in the serum of the patient as analyzed by Western blotting, indicating that B. pertussis infection might have triggered HUS in a genetically predisposed patient. Received: 13 July 2000 / Revised: 3 October 2001 / Accepted: 9 October 2001     

Cocaine- and food-maintained responding under a multiple schedule in rhesus monkeys: environmental context and the effects of a dopamine antagonist

Abstract Rationale. Environmental context has been shown to influence responding under multiple schedules of food reinforcement and to modify the behavioral effects of drugs. However, no systematic study has been conducted under conditions of cocaine self-administration. The hypothesis was that changes in the magnitude of food reinforcement would affect cocaine-maintained response rates and influence the behavioral potency of a dopamine antagonist to decrease cocaine self-administration. Objective. A multiple schedule was used to evaluate the effects of changes in the magnitude of food reinforcement on the self-administration cocaine dose-response curve and on the behavioral potency of a dopamine receptor antagonist to decrease food- and cocaine-maintained responding. Methods. Rhesus monkeys (n=3) were trained to self-administer intravenous cocaine under a multiple fixed-interval (FI) 5-min schedule of food and cocaine presentation. Food (one or four pellets) was available in the first and third components and cocaine (saline, 0.01–0.3 mg/kg per injection) was available in the second and fourth components. After completion of cocaine dose-response curves, the effects of the dopamine D₂/D₃ receptor antagonist 2,3-dimethoxy-N-(9-p-fluorobenzyl)-azabicyclo[3.3.1]nonan-3β-yl benzamide (MABN) were examined. Results. Cocaine- and food-maintained responding varied as a function of dose and were characterized as inverted U-shaped functions; cocaine-maintained response rates were significantly influenced by the magnitude of food in the other component. The behavioral potency of MABN on food- and cocaine-maintained responding was not influenced by the magnitude of food reinforcement. Conclusions. These results suggest that cocaine self-administration under a multiple schedule with food reinforcement is influenced by the environmental context. These schedule interactions, however, did not alter the behavioral effects of a dopamine D₂/D₃ receptor antagonist. Electronic Publication     

NMDA receptor blockade in intact adult cortex increases trafficking of NR2A subunits into spines,postsynaptic densities,and axon terminals

Past in vitro studies have used immunofluorescence to show increased clustering of the NR1 subunits of NMDA receptors (NMDAR) following NMDAR blockade, indicating that NMDARs self-regulate trafficking to and from spines. However, since a substantial portion of spinous NMDAR subunits can reside at sites removed from plasma membranes, whether or not these immunofluorescent clusters are synaptic remains to be shown. Also, the NR2A/B subunits undergo activity-dependent switching at synapses, indicating that their subcellular distribution may be regulated differently from the NR1 subunits. We examined the issue of NMDAR autoregulation by determining whether in vivo NMDAR blockade enhances trafficking of the NR2A subunits toward spines and more specifically to postsynaptic densities (PSDs) of already mature synapses. Seven adult rats received unilateral intra-cortical infusion of the NMDAR antagonist, D-AP5 for 1/2-2 h and the inactive enantiomer or the solvent, alone, in the contralateral cortex. Using an electron microscope, approximately 5600 cortical spines originating from the two hemispheres of the seven adult animals were analyzed for the location of NR2A subunits. In six out of the seven cases analyzed, the D-AP5-treated neuropil exhibited increased immunolabeling at PSDs and a concomitantly great increase at non-synaptic sites within spines. NR2A subunits also increased presynaptically within 1/2 h but not after 1 h. These findings indicate that NR2A subunits in intact, adult cortical neurons are prompted to become trafficked into spines and axon terminals by NMDAR inactivity, yielding an increase of a readily available reserve pool and greater localization at both sides of synapses.     

Neurogenic cardiac injury

Opinion statement Cardiac injury may occur following many types of brain injury, although the most widely investigated form of neurocardiogenic injury is subarachnoid hemorrhage (SAH). Echocardiography may help prognosticate and aid in the treatment of SAH if left ventricular (LV) dysfunction is suspected or if troponin levels are elevated. Cardiac catheterization, however, is not routinely recommended in SAH patients with LV dysfunction and elevated troponin. The priority should be treatment of the underlying neurological condition, even in the setting of LV dysfunction. Cardiac injury that occurs following an SAH appears to be reversible. For patients that develop brain death cardiac evaluation under optimal conditions may help increase the donor pool.