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PubMed1997

Urinary follicle-stimulating hormone for normogonadotropic clomiphene-resistant anovulatory infertility: prospective, randomized comparison between low dose step-up and step-down dose regimens.

A low dose step-up and step-down regimen for induction of ovulation using urinary FSH was compared in a prospective randomized fashion in 37 normogonadotropic clomiphene-resistant oligo- or amenorrheic infertile women. The objectives was to assess potential differences in duration of treatment, ovarian stimulation (serum FSH levels), and response [serum estradiol (E2) levels and number and size of follicles]. Monitoring (blood sampling and transvaginal sonography) took place on the day of initiation of treatment, the first day of ovarian response as assessed by ultrasound (i.e. the first day a follicle > or = 10 mm could be recognized), the day of hCG administration to induce ovulation, and 3 days thereafter. The median duration of treatment in the low dose step-up group was 18 (range, 7-41) days compared to 9 (range, 4-16) days in the step-down group (P = 0.003), and the total numbers of ampules administered were 20 (range, 7-69) and 14 (range, 7-33), respectively (P = NS). Serum FSH levels from the first day of sonographic ovarian response until the administration of hCG were constant (median increase, 2%/day) in patients receiving the low dose step-up protocol, but showed a decrease (median, 5%/day) in step-down cycles (P < 0.001). Monofollicular growth, defined as not more than one follicle 16 mm or larger on the day of hCG administration, was observed in 56% of low dose step-up and 88% of step-down cycles (P = 0.04). The percentage of patients with normal range periovulatory E2 serum levels (500-1500 pmol/L) was 33% in the low dose step-up group vs. 71% in the step-down group (P = 0.03). We conclude that a step-down protocol for gonadotropin induction of ovulation exhibits a more physiological, late follicular phase FSH serum profile than a low dose step-up protocol. This results in a shorter duration of treatment, a greater number of monofollicular cycles, and more cycles with periovulatory E2 levels within the normal range in the step-down protocol.

Adult↗
PubMed1983

Effect of step-down and step-up protein-energy feeding systems on egg-type pullet growth and laying performance.

Four egg-type pullet feeding systems were compared for the production of egg-type pullets. The dietary regimens consisted of either a step-down protein, high energy feeding program; a step-down protein, low energy program; a step-up protein, high energy program; or a step-up protein, low energy program. At 150 days of age all pullets were housed 2 birds per 25.4 X 45.7 cm laying cage and fed a standard layer diet (16% protein). The experiment utilized 2880 birds grown on the floor in a conventional growing house. At 140 days of age, birds subjected to the step-up protein feeding programs were 82 g smaller in mean body weight, had higher mortality, and consumed less feed than the birds on the step-down protein feeding programs. Body weights at 140 days of age were 1.17 and 1.09 kg for the step-down and step-up feeding programs, respectively. Energy levels fed had no significant effect on pullet weight, feed consumed, or mortality to 140 days of age. During the laying phase, hens that had been on the step-down protein feeding program reached 50% production 2.0 days earlier than birds subjected to the step-up protein feeding program. Hen-day production for the step-down and step-up pullet feeding systems based on 308 days' records was 76.09 and 76.86%, respectively. Feed efficiency and mature body weight were not significantly affected by grower feeding programs. The largest egg size and highest laying house mortality were noted in hens grown on the step-down protein feeding program.

Animals↗
PubMed2003

Measuring step kinematic variability on an instrumented treadmill: how many steps are enough?

Variability of step kinematics has been associated with falls by older adults. However, between-study differences with regard to the number of steps used to compute variability have varied by an order of magnitude. If the number of steps used to compute variability is too low there is the potential for a statistically spurious outcome. On the other hand, for subjects with mobility impairments a protocol requiring too many steps to estimate variability imposes an unnecessary burden on the subjects. We have determined the minimum number of steps needed to estimate the variability of spatial and temporal step kinematics. More than 700 steps were collected during level walking on an instrumented treadmill. Accurate estimation of step kinematic variability required at least 400 steps. The increased error in estimating the mean and standard deviations of the step kinematic variables with too few steps can impose an experimental cost with regard to statistical design considerations. The extent to which translation of these results can be made to the variability of spatial and temporal step kinematics collected during over-ground walking awaits further research.

Adult↗
PubMed2001

Influence of curriculum type on student performance in the United States Medical Licensing Examination Step 1 and Step 2 exams: problem-based learning vs. lecture-based curriculum.

INTRODUCTION: The results of the United States Medical Licensing Examination Step 1 and 2 examinations are reported for students enrolled in a problem-based and traditional lecture-based curricula over a seven-year period at a single institution. There were no statistically significant differences in mean scores on either examination over the seven year period as a whole. There were statistically significant main effects noted by cohort year and curricular track for both the Step 1 and 2 examinations. These results support the general, long-term effectiveness of problem-based learning with respect to basic and clinical science knowledge acquisition. CONTEXT: This paper reports the United States Medical Licensing Examination Step 1 and Step 2 results for students enrolled in a problem-based and traditional lecture-based learning curricula over the seven-year period (1992-98) in order to evaluate the adequacy of each curriculum in supporting students learning of the basic and clinical sciences. METHODS: Six hundred and eighty-nine students who took the United States Medical Licensing Examination Step 1 and 540 students who took Step 2 for the first time over the seven-year period were included in the analyses. T-test analyses were utilized to compare students' Step 1 and Step 2 performance by curriculum groups. RESULTS: United States Medical Licensing Examination Step 1 scores over the seven-year period were 214 for Traditional Curriculum students and 208 for Parallel Curriculum students (t-value = 1.32, P=0.21). Mean Step 2 scores over the seven-year period were 208 for Traditional Curriculum students and 206 for Parallel Curriculum students (t-value=1.08, P=0.30). Statistically significant main effects were noted by cohort year and curricular track for both the Step 1 and Step 2 examinations. CONCLUSION: The totality of experience in both groups, although differing by curricular type, may be similar enough that the comparable scores are what should be expected. These results should be reassuring to curricular planners and faculty that problem-based learning can provide students with the knowledge needed for the subsequent phases of their medical education.

Curriculum↗
PubMed2005

Age and stepping limb performance differences during a single-step recovery from a forward fall.

BACKGROUND: The purpose of this study was two-fold: 1) to evaluate any age-related differences in peak joint velocities of the stepping limb during single-step recovery from a forward fall, and 2) to determine if the ability to recover from a forward fall with a single step differs when stepping with the dominant or nondominant lower limb (LL). METHODS: Ten young (19-23 years old) and ten older (65-83 years old) men were released from forward-leaning positions and attempted to recover their balance with a single step. Lean magnitude was increased until the men failed to recover their balance with a single step. The men performed the experiment twice, once while stepping with the dominant LL and once while stepping with the nondominant LL, to determine if the ability to recover from a forward fall is limb dependent. Peak joint velocities during single-step recoveries were determined. RESULTS: No age-related differences in peak joint velocities were found during recovery from small lean magnitudes, but older men exhibited slower velocities during recovery from maximum lean magnitudes. There was no difference in the maximum lean magnitude achieved by the men when stepping with the dominant or nondominant LL. CONCLUSIONS: The previously reported age-related reduction in stepping speed seems to be due to localized reductions in maximum hip flexion velocity, knee flexion and extension velocity, and ankle plantar flexion velocity. Also, the ability of young and older men to recover from a forward fall with a single step does not seem to be limb dependent.

Accidental Falls↗
PubMed2006

Validity of the inexpensive Stepping Meter in counting steps in free living conditions: a pilot study.

OBJECTIVES: To evaluate if inexpensive Stepping Meters are valid in counting steps in adults in free living conditions. METHODS: For six days, 35 healthy volunteers wore a criterion Yamax Digiwalker and five Stepping Meters every day until all 973 pedometers had been tested. Steps were recorded daily, and the differences between counts from the Digiwalker and the Stepping Meter were expressed as a percentage of the valid value of the Digiwalker step counts. The criterion used to determine if a Stepping Meter was valid was a maximum deviation of 10% from the Digiwalker step counts. RESULTS: A total of 252 (25.9%) Stepping Meters met the criterion, whereas 74.1% made an overestimation or underestimation of more than 10%. In more than one third (36.6%) of the invalid Stepping Meters, the deviation was greater than 50%. Most (64.8%) of the invalid pedometers overestimated the actual steps taken. CONCLUSIONS: Inexpensive Stepping Meters cannot be used in community interventions as they will give participants the wrong message.

Adult↗
PubMedDate not supplied

Step-down and step-up therapy in moderate persistent asthma.

BACKGROUND: A step-down therapy may be more beneficial for the management of asthma than a step-up therapy. METHODS: Eighty-two asthmatic patients with moderate persistent asthma were enrolled in the study and randomized into three groups. One group of patients received 400 microg/day of beclomethasone dipropionate (BDP) for 4 weeks and then 800 microg/day for another 4 weeks (step-up group). The other two groups of patients received 1,200 microg/day of BDP for 4 weeks with or without short-term oral steroid (prednisolone, 0.5 mg/day for 1 week) and then 800 microg/day for another 4 weeks (step-down group). Severe exacerbation of asthma, asthma symptoms, respiratory function and rescue use of inhaled beta(2)-agonists were monitored. If asthma was well controlled, the dose of BDP was decreased every 3 months and if asthma was exacerbated, the dose of BDP was increased until 8 months after the initial treatment. RESULTS: Twenty-two patients during the run-in period, 4 patients in the step-up group, 2 patients in the step-down group treated with a high dose of BDP and no patients in the step-down group with oral steroids during first 4 weeks dropped out because of severe exacerbation of asthma. Although asthma symptoms and respiratory function significantly improved 8 weeks after the therapy in all groups, more significant and prompt improvements of these parameters were observed in patients of the step-down group than in patients of the step-up group after the first 2 weeks of treatment. Furthermore, step-down therapy with short-term oral steroid resulted in the lowest maintenance doses of BDP at 8 months of the three groups. CONCLUSIONS: These results suggest that step-down therapy starting with a high dose of inhaled steroid and short-term oral steroid is more effective in gaining prompt control of asthma and reducing the severe exacerbation of asthma and the maintenance dose of inhaled steroids than a step-up therapy starting with a low dose of inhaled steroids in patients with moderate persistent asthma.

Administration, Inhalation↗
PubMed1996

Visually guided stepping under conditions of step cycle-related denial of visual information.

We recently reported that subjects performing a task that requires visual guidance of each step onto irregularly placed "stepping stones" usually fixate the next target of footfall just before they lift the foot to be repositioned, i.e. towards the end of that limb's stance phase. When negotiating the same walkway without ambient lighting, and with each stone's location indicated by a central light spot (LED), stepping and eye movements were unchanged. Under conditions of intermittent visual denial, in which all LEDs (the only visual cues) were temporarily extinguished at irregular intervals, temporal changes in the normal stepping pattern were sometimes observed, but stepping was not always affected. The primary effect of visual denial was on the leg that was in stance (foot in place on a stepping stone) at the moment of LED extinction, rather than on the leg that was in swing, and was an increase in stance duration, suggesting an effect on planning during this stance of the next swing towards the next target rather than on execution of the ongoing swing of the other leg. Subjects rarely failed to step onto the targets. Prolongations of stance under visual denial lasting 400 or 500 ms were less than 200 ms, much less than the duration of denial; subjects did not simply wait for the footfall target to reappear. There was no effect for denial lasting 300 ms; subjects performed as well as with a constantly visible target. Under 400 and 500 ms denial, there was no effect when the targets disappeared in the first 100 ms of stance (of the foot to be repositioned); stance durations were indistinguishable from control. This suggests that there is no crucial visuomotor processing by the control system(s) for eye and limb guidance until the target reappeared near the usual end of stance, when feedforward planning of the next saccade and/or swing to a target reaches a crucial stage, and is affected by intrusion of the period of visual denial. With longer (800 ms) denial there was an effect regardless of when in stance it began. A smaller effect of 800 ms denial sometimes visible in swing duration is attributable to interlimb coordination. Accurate saccades, followed by accurate steps, to the next target are almost always made, even when the target is invisible. Our results demonstrate that uninterrupted on-line visual information is not necessary for accurate stepping even when (as here) each step requires visual guidance. Also, since stance prolongations did not always result, and they were always much shorter than the periods of denial, we conclude that the visuomotor control mechanism(s) are robust in the face of substantial denial of all visual information including normally preferred inputs (foveal or peripheral images) at the normally preferred times. The fact that a saccade is still made to an invisible target location implies that this is useful in itself, since it does not result in a visible foveal image. We propose that skilled, visually guided stepping onto irregularly placed targets is executed under predominantly feedforward visuomotor control mechanisms, and suggest that the ability to function effectively in this way is dependent upon the integrity of the lateral cerebellum.

Adult↗
PubMed1992

Accuracy of one-step versus two-step putty wash addition silicone impression technique.

This study compared the accuracy of one-step putty wash with two-step putty wash impression techniques. Five addition silicone impression materials-Mirror 3 (MR), Mirror 3 Extrude (ME), Express (E), Permagum (P), and Absolute(A)--were tested. A stainless steel model containing two full-crown abutment preparations was used as the positive control. Five replications for one-step and two-step putty wash impressions of the master model were made for each test material. Accuracy of the materials was assessed by measuring six dimensions on stone dies poured from impressions of the master model. Accuracy of addition silicone impression material is affected more by material than technique. Accuracy of the putty wash one-step impression technique was not different from the putty wash two-step impression technique except at one of the six dimensions where one-step was more accurate than two-step. Mirror 3 putty wash two-step impression presented less distortion than Mirror 3 Extrude putty wash one-step or two-step impression.

Analysis of Variance↗
PubMed2004

Effects of step length on stepping responses used to arrest a forward fall.

This study investigated effects of step length on the stepping response used to arrest an impending forward fall. Twelve healthy young (mean age 22, S.D. 3.3 years) males participated by recovering balance with a single step following a forward lean-and-release. Participants were instructed to step to one of three floor targets representing small, natural, and large step lengths. The effect of step length was examined on the primary outcome variables: pushoff time, liftoff and landing time, swing duration, balance recovery time, landing impulse, and center of mass (COM) characteristics. Pushoff and liftoff times were not affected by step length, although swing phase duration, landing and recovery times and the anterior-posterior (AP) impulse at landing increased with increasing step length. The results support the idea of an invariant step preparation phase. Given that our participants naturally chose not to utilize a step as short as they were capable of employing, healthy young individuals do not minimize recovery time nor strength requirements when selecting their step length.

Accidental Falls↗
PubMed1998

A comparative study of fixed-dose, step-down, and low-dose step-up regimens of human menopausal gonadotropin for patients with polycystic ovary syndrome.

OBJECTIVE: To compare the efficacy and safety of the fixed-dose, the step-down, and the low-dose step-up regimens of hMG for women with polycystic ovary syndrome (PCOS). DESIGN: Prospective randomized study. SETTING: Gunma University School of Medicine, Maebashi, Japan. PATIENT(S): Thirty-seven women with PCOS. INTERVENTION(S): The fixed-dose, the step-down. and the low-dose step-up regimens were administered. MAIN OUTCOME MEASURE(S): The number of growing follicles and serum hormone levels. RESULT(S): Serum FSH levels on the day of hCG administration were significantly higher in the fixed-dose regimen group than in the step-down and the low-dose step-up regimen groups, and the number of growing follicles (> or =11 mm) in the low-dose step-up regimen group was significantly smaller than in the fixed-dose regimen group. On the 7th day after hCG administration, the maximal diameter of the ovaries in the low-dose step-up regimen group was significantly smaller than in the fixed-dose and the step-down regimen groups, and the risk of excessive ovarian enlargement (> or =70 mm) was significantly lower in the low-dose step-up regimen group than in the fixed-dose regimen group. CONCLUSION: The low-dose step-up regimen of hMG for patients with PCOS may be the safest protocol among the three stimulation regimens for reducing multiple follicular development.

Adult↗
PubMed2003

Comparison of procedural errors resulting during root canal preparations completed by junior dental students in patients using an '8-step method' versus 'serial step-back technique.'.

AIM: To compare procedural errors occurring during preparation of root canals by junior dental students in patients using a new '8-step method' versus traditional 'serial step-back technique. METHODOLOGY: Junior dental students treated 291 root canals of maxillary and mandibular teeth in patients. A new '8-step method' was used to prepare 149 canals, whilst the traditional 'serial step-back technique' was used for 142 root canals. Instrumentation was carried out in both techniques using standardized stainless steel K-files and coronal flaring with Gates-Glidden reamers. In the apical one-third, a filing motion was used in the traditional technique: with the '8-step method,' reaming or filing motions were used in sizes up to 25 and only reaming in sizes larger than 25. All root canals were obturated with gutta-percha points and AH26 using a lateral condensation technique. Pre- and postoperative radiographs were made of each tooth. Procedural errors were recorded and statistically analysed using a binomic test for comparison of proportion. RESULTS: Significantly (P < (1.0001) more root canals maintained their original shape with no deviation (91%) with the'8-step method' compared to the traditional 'serial step-back technique' (61%). The procedural errors detected with the'8-step method' consisted of 10 canals with transportation (5%) and five with root perforations (2%); there were no canal obstructions. With the 'serial step-back technique: significantly (P < 0.0001) more errors occurred: 28 canals were transported (17%), 10 had root perforations (7%), and 16 canals were obstructed (6%). The differences in maintaining the original root canal shape between the two methods were significantly greater in molar versus anterior teeth. CONCLUSIONS: The new '8-step method' resulted in fewer procedural errors than the traditional 'serial step-back technique' when junior students prepared root canals in patients.

Dental Pulp Cavity↗
PubMed2005

One-step versus two-step culture of mouse preimplantation embryos: is there a difference?

BACKGROUND: A comparison has been made of the development of mouse zygotes in either one-step or two-step culture systems. METHODS: Embryo culture, blastocyst cell counts and embryo transfer were done. RESULTS: No significant differences were observed in the proportions of blastocysts, rates of hatching, numbers of cells in the inner cell mass (ICM) and trophectoderm (TE) that developed in protocols: one-step culture in potassium-enriched simplex optimized medium supplemented with glucose and amino acids (KSOMg(AA)), two-step culture in KSOMg(AA)/KSOMg(AA), and two-step culture in G1.2/G2.2. No gross abnormalities were observed in the fetuses that developed from zygotes in the one-step protocol using KSOMg(AA) and a two-step protocol using G1.2/G2.2. The body weights of these two groups of fetuses were not significantly different and no developmental abnormalities were observed. No significant differences were observed in the proportions of blastocysts, rates of hatching, numbers of cells in the ICM and TE that developed in protocols: one-step culture in KSOMg(AA), two-step culture in KSOMg(AA)/KSOMg(AA), and two-step culture in DM2/DM1. EDTA is not toxic to the initial cleavage stages of development at a concentration of 0.01 mmol/l in KSOMg(AA). CONCLUSIONS: Two-step culture protocols are sufficient for the support of preimplantation mouse development in vitro but they are not necessary.

Animals↗
PubMed2005

Stepping onto a single step: a kinematic study.

BACKGROUND AND PURPOSE: To describe the timings and ranges of linear displacements of the pelvis and feet occurring in a healthy older population when stepping up onto a step, and to describe variations noted in a small sample of subjects with hemiplegia. METHOD: An observational case series study design was used and the study took place in a gait laboratory in a general hospital. A convenience sample of 54 healthy volunteers (mean age 57.6 years, range 40-90 years; 26 males, 28 females) and six subjects with chronic hemiplegia (mean age 61.7 years, range 47-70 years; five males, one female) was recruited. Participants stepped up onto an 18 cm step. The following outcome measures were made: kinematic measures of stepping up cycle time; pelvic lateral displacement; width of foot base; and height of heel clearance by use of CODA (a three-dimensional movement analysis system). RESULTS: The mean (standard deviation, SD) stepping up cycle of healthy subjects was 1.68 seconds (+/- 0.22 seconds). The total range of pelvic lateral displacement during one stepping up cycle was 70 mm. Pelvic lateral displacement was asymmetrical, being significantly greater towards the initial weightbearing leg (p<0.0001). Older subjects (aged 60+ years) had less heel clearance (p<0.03) than younger subjects (aged <60 years). Stepping up performance by subjects with hemiplegia showed wide inter-subject variability, and was observed to be as much as three times slower to use as much as four times the range of pelvic lateral displacement and twice the foot base, and to be asymmetrical in timing of the stepping up cycle. CONCLUSIONS: This kinematic study describes a healthy stepping up pattern not previously reported. Age and hemiplegia influenced the amount and speed of movement adopted during the task. Information about the movement strategies used by the elderly and those with hemiplegia should guide physiotherapists in their management of physical function.

Adult↗
PubMed1994

Ultrastructure of IVM-IVF bovine blastocysts vitrified after equilibration in glycerol 1,2-propanediol using 2-step and 16-step procedures.

Two experiments were conducted to investigate the relationship between survival rates and ultrastructural appearance, using the freeze-replica technique, of bovine blastocysts after vitrification. In experiment 1, blastocysts obtained from in vitro-matured and in vitro-fertilized (IVM-IVF) bovine oocytes were either equilibrated in a stepwise manner in a vitrification solution (VS; 22.5% glycerol + 22.5% 1,2-propanediol) using 16 steps for 18 min in total (the 16-step method) or equilibrated with 10% glycerol + 20% 1,2-propanediol for 10 min and then exposed to VS (the 2-step method). The blastocysts were then vitrified by plunging them into liquid nitrogen. All samples were subsequently thawed in a water bath at 37 degrees C and cultured in vitro with a monolayer of cumulus cells. The survival rate obtained for blastocysts equilibrated by the 16-step method was 83.3% (25/30). In contrast, no blastocysts survived by the 2-step method (0/30). In experiment 2, freeze-replica observations were carried out on blastocysts vitrified by the 16-step method and the 2-step method. In all the blastocysts, no ice crystals were observed in the cytoplasm, blastocoelic cavity, or extracellular areas, which confirmed the occurrence of complete vitrification. Little ultrastructural change was observed in the plasma membrane of the blastocysts equilibrated by the 16-step method. In contrast, small vesicles and distinct intramembrane particle (IMP) aggregation were frequently observed in the plasma membranes of blastocysts equilibrated by the 2-step method. These results indicate that the successful cryopreservation of blastocysts following the 16-step equilibration requires not only complete vitrification, but also minimization of ultrastructural damage to the plasma membrane.

Animals↗
PubMed2006

Minimal step length necessary for recovery of forward balance loss with a single step.

Although the boundary conditions necessary to trigger a step in reaction to a forward balance loss have been predicted in previous research, the relationship between minimal step length needed for balance recovery with this single step and the center of mass (COM) motion state (i.e., its position and velocity) remains unknown. The purpose of this paper was to present a theoretical framework within which the minimal step length needed for balance recovery can be estimated. We therefore developed a simplified four-segment sagittal model of human body stepping for balance recovery. The work-energy principle of the Newtonian mechanics was employed in the simulation to determine the amount of excess mechanical energy that can be absorbed as a function of step length and the corresponding eccentric joint work that can be generated in a single step. We found that an increase in initial forward velocity and a greater forward shift of the COM require a corresponding increase in the minimal step length needed for balance recovery. Furthermore, the minimal step length is also a function of the muscle strength at the ankle: the lower the muscle strength, the greater the minimal step length required. Our theoretical framework reduces the complexity associated with previous studies relying on forward dynamics and iterative optimization processes. This method may also be applied to study aspects of balance control such as the prevention of balance loss in the posterior or mediolateral direction.

Accidental Falls↗
PubMed1996

Inhibition of the microsomal triglyceride transfer protein blocks the first step of apolipoprotein B lipoprotein assembly but not the addition of bulk core lipids in the second step.

The microsomal triglyceride transfer protein (MTP) is required for assembly and secretion of the lipoproteins containing apolipoprotein B (apoB): very low density lipoproteins and chylomicrons. Evidence indicates that the subclasses of these lipoproteins that contain apoB-48 are assembled in a distinct two-step process; first a relatively lipid-poor primordial lipoprotein precursor is produced, and then bulk neutral lipids are added to form the core of these spherical particles. To determine if either step is mediated by MTP, a series of clonal cell lines stably expressing apoB-53 and MTP was established in non-lipoprotein-producing HeLa cells. MTP activity in these cells was approximately 30%, and apoB secretion was 7-33% of that in HepG2 cells on a molar basis. Despite having robust levels of triglyceride and phospholipid synthesis, these cell lines, as exemplified by HLMB53-59, secreted >90% of the apoB-53 on relatively lipid-poor particles in the density range of 1.063-1.21 g/ml. These results suggested that coexpression of MTP and apoB only reconstituted the first but not the second step in lipoprotein assembly. To extend this observation, additional studies were carried out in McArdle RH-7777 rat hepatoma cells, in which the second step of apoB-48 lipoprotein assembly is well defined. Treatment of these cells with the MTP photoaffinity inhibitor BMS-192951 before pulse labeling with [35S]methionine/cysteine led to an 85% block of both apoB-48 and apoB-100 but not apoAI secretion, demonstrating inhibition of the first step of lipoprotein assembly. After a 30-min [35S]methioneine/cysteine pulse labeling and 120 min of chase, all of the nascent apoB-48 was observed to have a density of high density lipoproteins (1.063-1.21 g/ml), indicating that only the first step of lipoprotein assembly had occurred. The addition of oleic acid to the cell culture media activated the second step as evidenced by the conversion of the apoB-48 high density lipoproteins to very low density lipoproteins (d < 1.006 g/ml) during an extended chase period. Inactivation of MTP after completion of the first step, but before stimulation of the second step by the addition of oleic acid, did not block this conversion. Thus, inhibition of MTP did not hinder the addition of bulk core lipid to the primordial lipoprotein precursor particles, indicating that MTP is not required for the second step of apoB-48 lipoprotein assembly.

Animals↗
PubMed2005

Copy and recall performance of 6-8-year-old children after standard vs. Step-by-step administration of the Rey-Osterrieth complex figure.

The Rey-Osterrieth Complex Figure (ROCF; Rey 1941; Osterrieth, 1944) is frequently used in the neuropsychological assessment of children and adults. The present study was designed, in part, to examine the impact of providing organizational scaffolding to young children being tested with the ROCF. To this end, 6-, 7-, and 8-year-old children were administered the test either in the standard fashion, or using a format in which the 18 key elements of the figure were introduced sequentially. Participants included 132 children who were randomly assigned to the standard or step-by-step administration groups. Significantly higher accuracy and organization scores for both copy and recall were seen with the step-by-step format than with the standard format, even though children in the step-by-step condition took less time to execute their drawings. Retention of encoded information was not affected by age or testing format. The fact that 6-year-olds in the step-by-step condition performed as well as, or better than, 8-year-olds in the standard condition suggests that the primary problem young children experience with the ROCF lies with organizational strategy formation. Advantages of using the Step-by-step ROCF in clinical practice are discussed.

Child↗