Nicotinic and muscarinic cholinergic receptor binding in the human hippocampal formation during development and aging

High-affinity nicotine, alpha-bungarotoxin (alpha BT) and muscarinic receptor binding was measured in the human hippocampal formation in a series of 57 cases aged between 24 weeks gestation and 100 years. Changes in nicotine receptor binding during development and aging were more striking than differences in alpha BT and muscarinic binding. Nicotine binding was higher at the late foetal stage than at any other subsequent time in all areas investigated. In the hippocampus a fall in binding then occurred within the first six months of life, with little or no subsequent fall during aging, whereas in the entorhinal cortex and the presubiculum the major loss of nicotine binding occurred after the fourth decade. alpha BT binding was significantly elevated in the CA 1 region, but in no other region of the hippocampus, in the late foetus, and there was also a fall in alpha BT binding in the entorhinal cortex during aging from the second decade. The modest changes in total muscarinic binding, which appeared to reflect those in M1 and M3 + 4 rather than M2 binding, were a rise in the entorhinal cortex between the foetal stage and childhood and a tendency for receptors to fall with age in the hippocampus and subicular complex. These findings implicate mechanisms controlling the expression of nicotinic receptors to a greater extent than muscarinic receptors in postnatal development and aging in the human hippocampus.     

Epimerization via carbon-carbon bond cleavage. L-ribulose-5-phosphate 4-epimerase as a masked class II aldolase

Studies indicating that the E. coli L-ribulose-5-phosphate 4-epimerase employs an "aldolase-like" mechanism are reported. This NAD+-independent enzyme epimerizes a stereocenter that does not bear an acidic proton and therefore it cannot utilize a simple deprotonation-reprotonation mechanism. Sequence similarities between the epimerase and the class II l-fuculose-1-phosphate aldolase suggest that the two may be evolutionarily related and that the epimerization may occur via carbon-carbon bond cleavage and re-formation. Conserved residues thought to provide the metal ion ligands of the epimerase have been modified using site-directed mutagenesis. The resulting mutants show low kcat values in addition to a reduced affinity for Zn2+. These observations serve to establish that there is a structural link between between the active site geometry of the epimerase and the aldolase. In addition, the H97N mutant was found to catalyze the condensation of dihydroxyacetone and glycolaldehyde phosphate to produce a mixture of L-ribulose-5-phosphate and D-xylulose-5-phosphate. This observation of aldolase activity establishes that the epimerase active site is capable of promoting carbon-carbon bond cleavage. Furthermore, glycolaldehyde phosphate was shown to be a competitive inhibitor of the mutant enzyme (KI = 0.37 mM) but not of the wild-type enzyme. The mutation apparently causes the epimerase to become "leaky" and enables it to bind/generate the normal reaction intermediates from the unbound aldol cleavage products.     

Infants' detection of increments in low- and high-frequency noise

A visually reinforced operant paradigm was employed to examine the relationship between the difference limen (DL) for intensity and level of the standard during infancy. In Experiment 1, 7-month-old infants and adults detected increments in continuous noise presented via headphones at each of four levels ranging from 28 to 58 dB SPL. Noise stimuli were 2-octave bands centered at either 400 or 4000 Hz, and increments were 10 and 100 msec in duration. Infants' DLs were significantly larger than those of adult subjects and significantly larger for low- than for high-frequency stimuli. For the high-frequency noise band, infants' DLs were generally consistent with Weber's law, remaining essentially constant for standards higher than 28 dB SPL (3 dB SL) for 100-msec increments and 38 dB SPL (13 dB SL) for 10-msec increments. For low-frequency noise, infants' absolute thresholds were exceptionally high, and sensation levels of the standards were too low to adequately describe the relationship. In Experiment 2, 7-month-old infants detected 10- and 100-msec increments in 400-Hz noise stimuli presented in sound field. Infants' low-frequency DLs were large at low intensities and decreased with increases in level of the standard up to at least 30 dB SL. For both low- and high-frequency noise, the difference between DLs for 10- and 100-msec increments tended to be large at low levels of the standard and to decrease at higher levels. These results suggest that the relationship between the DL and level of the standard varies with both stimulus frequency and duration during infancy. However, stimulus-dependent immaturities in increment detection may be most evident at levels within approximately 30 dB of absolute threshold.     

Dorsalis pedis flap donor site: acceptable or not?

The dorsalis pedis flap has been used successfully for 20 years, both as a pedicled transfer for local foot reconstruction and as a free microvascular transfer. Proponents cite the reliable vascularity, versatility, ease of harvest, and thinness. Although significant donor-site morbidity has been recognized previously, published reports have inadequately documented the long-term effects of dorsalis pedis flap harvest. The purpose of the present study was to obtain long-term follow-up data regarding the donor site on a total of 10 male patients who underwent dorsalis pedis flap harvest during the period from 1982 to 1984. Standardized questionnaires and chart reviews were completed, and physical examinations and photographs of each patient were carried out when possible. Eight patients were reviewed, and seven of them were examined and photographed (mean follow-up 13 years). All patients had initially experienced delayed donor-site healing (mean 18 months; range 3 to 36 months). In addition, soft-tissue infections (five of eight cases), osteomyelitis (one of eight cases), wound breakdown (seven of eight cases), scarring and contracture (four of seven cases), pain or other uncomfortable sensations in the foot (six of seven cases), and requirement for reoperation (three of eight cases) were significant complications of the procedure. Most patients were able to attain their preoperative level of physical activity (five of eight cases). Although generally favorable reconstructive results were obtained in this series, the long-term follow-up of donor-site healing indicates that this flap should be used with caution. In particular, delayed donor-site healing, need for wound revision, and long-term and possibly permanent donor-site symptoms are common.     

The differential effects of cueing on recall in Parkinson's disease and normal subjects

Patients with Parkinson's disease (PD) are known to be impaired in supraspan verbal learning due to reduced availability of internal encoding capacity. PD patients may suffer from poor semantic, source and sequential processing capacity. Thirty-three patients with idiopathic PD and 42 matched normal control subjects (NC) were administered the California Verbal Learning Test under 3 conditions of graded cueing. While the PD patients benefited significantly and progressively from increasingly explicit cueing, the NC group did not since their performance was optimal even without cueing. Results are discussed in relation to frontal executive control of attentional resources and the establishment of encoding strategies.     

More than 10 years of unrecognized nosocomial transmission of legionnaires' disease among transplant patients

OBJECTIVE: To investigate a cluster of cases of legionnaires' disease among patients at a hospital. SETTING: A university hospital that is a regional transplant center. DESIGN: Retrospective review of microbiology and serology data from the hospital laboratories and prospective surveillance via the radiology department; a case-control study and environmental sampling within the hospital and from nearby cooling towers. RESULTS: Diagnosis of seven cases of legionnaires' disease in the first 9 months of 1996 led to recognition of a nosocomial outbreak that may have begun as early as 1979. Review of charts from 1987 through September 1996 identified 25 culture-confirmed cases of nosocomial or possibly nosocomial legionnaires' disease, including 18 in bone marrow and heart transplant patients. Twelve patients (48%) died. During the first 9 months of 1996, the attack rate was 6% among cardiac and bone marrow transplant patients. For cases that occurred before 1996, intubation was associated with increased risk for disease. High-dose corticosteroid medication was strongly associated with the risk for disease, but other immunosuppressive therapy or cancer chemotherapy was not. Several species and serogroups of Legionella were isolated from numerous sites in the hospital's potable water system. Six of seven available clinical isolates were identical and were indistinguishable from environmental isolates by pulsed-field gel electrophoresis. Initial infection control measures failed to interrupt nosocomial acquisition of infection. After extensive modifications to the water system, closely monitored repeated hyperchlorinations, and reduction of patient exposures to aerosols, transmission was interrupted. No cases have been identified since September 1996. CONCLUSIONS: Legionella can colonize hospital potable water systems for long periods of time, resulting in an ongoing risk for patients, especially those who are immunocompromised. In this hospital, nosocomial transmission possibly occurred for more than 17 years and was interrupted in 1996, after a sudden increase in incidence led to its recognition. Hospitals specializing in the care of immunocompromised patients (eg, transplant centers) should prioritize surveillance for cases of legionnaires' disease. Aggressive control measures can interrupt transmission of this disease successfully.     

Maternal nutritional status is inversely associated with lactational amenorrhea in Sub-Saharan Africa: results from demographic and health surveys II and III

Breast-feeding is positively associated with the duration of postpartum amenorrhea; thus it is a major determinant of fertility in countries where effective contraceptive methods are not widely available. The objective of these analyses was to examine the association between maternal nutritional status and lactational amenorrhea (LA) among breast-feeding women. Women who were not pregnant, who were breast-feeding, who were not using hormonal contraceptives and who had a child 相似文献   

Phospholipid pool, lipid peroxidation, and superoxide dismutase activity under various types of oxidative stress of the brain and the effect of low-energy infrared laser irradiation

The effect of low-energy infrared laser irradiation on the phospholipid pool, lipid peroxidation, and superoxide dismutase activity in the brain of white rats was studied in experimental ischemia, reperfusion, and acute edema. These models are characterized by oxidative stress; the contents of tri- and diphosphoinositides and sphingomyelins were lowered, whereas the levels of phosphatidylserine and phosphatidylethanolamine did not change, and the amount of phosphatidylcholine was increased. In acute brain edema, the contents of hydroperoxides and malonic dialdehyde in enzymatic and nonenzymic lipid peroxidation systems were increased in mitochondrial and microsomal fractions and the level of arachidonic acid was significantly elevated. Infrared laser irradiation contributes to the correction of the changes in the phospholipid pool; laser irradiation lowered the increased levels of hydroperoxides and malonic dialdehyde and elevated superoxide dismutase activity in the brain during ischemia, reperfusion, and acute edema of the brain. The data suggest that low-energy infrared laser irradiation has certain neuroprotective activity in various types of oxidative stress including ischemia, reperfusion, and acute edema of the brain.     

The effects of a single course of a calculus-softening scaling and root planing gel. A scanning electron microscopic study

The effect of a calculus scaling gel was evaluated as an adjunct to instrumentation in a double blind, split-mouth, clinical study. Fifteen comparable periodontally involved teeth from 5 patients were instrumented on the mesio-buccal root surface with the aid of either the test gel, placebo gel, or no gel until smoothness was achieved. Test or placebo gel was applied subgingivally for 10 minutes. Instrumentation time, ease, number of strokes, and gingival/tooth surfaces changes were recorded. Scanning electronic microscopic (SEM) evaluation of root surface topography was evaluated. The results demonstrated effective calculus removal in all treatment groups with no differences found between them. Instrumentation time, ease, and number of strokes were similar for all treatment groups. There were no harmful effects to soft or hard tissues. The results of this study do not support the use of calculus scaling gel as an adjunct to root instrumentation.