Response-specific sources of dual-task interference in human pre-motor cortex

It is difficult to perform two tasks at the same time. Such performance limitations are exemplified by the psychological refractory period (PRP): when participants make distinct motor responses to two stimuli presented in rapid succession, the response to the second stimulus is increasingly slowed as the time interval between the two stimuli is decreased. This impairment is thought to reflect a central limitation in selecting the appropriate response to each stimulus, but not in perceptually encoding the stimuli. In the present study, it was sought to determine which brain regions are specifically involved in response selection under dual-task conditions by contrasting fMRI brain activity measured from a response selection manipulation that increased dual-task costs, with brain activity measured from an equally demanding manipulation that affected perceptual visibility. While a number of parieto-frontal areas involved in response selection were activated by both dual-task manipulations, the dorsal pre-motor cortex, and to a lesser extent the inferior frontal cortex, were specifically engaged by the response selection manipulation. These results suggest that the pre-motor cortex is an important neural locus of response selection limitation under dual-task situations.

Development and integration of an extended embryo culture program

OBJECTIVE

To study and evaluate a sequential, extended embryo culture system.

DESIGN

Prospective study.

SETTING

University-affiliated IVF clinic.

PATIENT(S)

All couples who were treated between October 1997 and July 1998.

INTERVENTION(S)

A standard human tubal fluid plus 10% serum substitute supplement (SSS) culture medium was used. The embryos were transferred to extended culture medium (S2 or G2) on day 3.

MAIN OUTCOME MEASURE(S)

Blastocyst formation and implantation and pregnancy rates.

RESULT(S)

Forty percent of the 20 donated cryopreserved embryos progressed to the blastocyst stage by day 6. Clinically, 7 (5.6%) of the 125 cycles did not result in a transfer. Blastocyst formation rates ranged from 33%-63% in the five study groups. Implantation rates ranged from 15%-52% and pregnancy rates ranged from 37%-75%.

CONCLUSION(S)

Extended culture to day 5 or 6 results in acceptable blastocyst formation rates, implantation rates, and pregnancy rates.

An intrauterine insemination-ready cryopreservation method compared with sperm recovery after conventional freezing and post-thaw processing

OBJECTIVE

To test a sucrose-glycerol cryoprotectant for IUI-ready sperm preparation.

DESIGN

Semen aliquots from normozoospermic donors either were subjected to conventional semen freezing (TES and Tris yolk buffer in 7.4% final glycerol) with post-thaw processing or were preprocessed and frozen in HEPES-buffered human tubal fluid with 1% human serum albumin, 4% sucrose, and 6% glycerol. All aliquots were cooled to 4 degrees C, exposed to liquid nitrogen vapors, and stored in liquid nitrogen. Aliquots from each were processed by centrifugation resuspension or by centrifugation in Percoll (Pharmacia, Alameda, CA) before sperm parameters were analyzed.

SETTING

University-based andrology laboratory.

MAIN OUTCOME MEASURE(S)

Recovery of motile sperm.

RESULT(S)

Percoll processing produced preparations with higher percentages of motile cells; however, cryopreserved sperm had a lower recovery of motile sperm compared with Percoll-processed fresh semen or centrifugation/resuspension-processed fresh or frozen samples. The percentages of sperm with normal morphologies were significantly increased in the IUI-ready samples compared with samples frozen conventionally. The IUI-ready Percoll-processed sample produced the best results, with a final mean motility of 36% and an overall yield of motile sperm of 17.4%.

CONCLUSION(S)

The sucrose-glycerol-based cryoprotectant produced an IUI-ready preparation with motile sperm recovery comparable to that of conventional semen cryopreservation but with improved percent morphology.

Value of maternal serum alpha-fetoprotein levels of 5.0 MOM or greater and prenatal sonography in predicting fetal outcome

PURPOSE

To determine fetal outcomes and the capability of sonography to help predict these outcomes in patients with maternal serum alpha-fetoprotein (MSAFP) levels of 5.0 multiples of the median or greater.

MATERIALS AND METHODS

Real-time sonography was performed in patients with singleton and multiple gestations. After sonography, the pregnancy was monitored.

RESULTS

Inaccurate historical dating caused elevated MSAFP levels in 14 patients. In the remaining 72 singleton gestations, 42 fetuses (58%) had anomalies, 13 (18%) died in utero or after birth, three (4%) had intrauterine growth retardation or were premature, and 14 (19%) were normal, with no complications. A poor outcome occurred in 58 (80%) of the singleton pregnancies, and sonography depicted an abnormality in 49 (84%) of these patients.

CONCLUSION

Most pregnant patients with MSAFP levels of 5.0 MOM or greater have an unfavorable outcome. Sonography depicts most of these abnormal pregnancies.

1989 ARRS President's Award. The validity and utility of sonography in the diagnosis of appendicitis in the community setting

Two hundred six patients with suspected appendicitis were examined with sonography over a 6-month period in three community teaching hospitals. Of 41 patients in whom the surgeons judged the clinical findings severe enough to warrant immediate surgery (group A), 34 (83%) had appendicitis, and sonography had a sensitivity of 0.76, a specificity of 0.71, and an accuracy of 0.76. Of 165 patients in whom the surgeons judged the clinical findings severe enough to warrant hospitalization for observation but not immediate surgery (group B), 51 (31%) had appendicitis at subsequent surgery. Sonography had a sensitivity of 0.96, a specificity of 0.94, and an accuracy of 0.95. Of 49 surgeons surveyed, the mean testing threshold (i.e., the probability of appendicitis below which they would send the patient home without further tests or observation) was 0.11, and the mean treatment threshold (i.e., the probability of appendicitis above which they would operate immediately) was 0.82. The posttest probability of appendicitis with findings indicating appendicitis present on sonography was 0.93 in group A and 0.88 in group B, and with findings absent on sonography it was 0.62 in group A and 0.02 in group B. We conclude that in group A patients, the use of sonography remains controversial in the diagnosis of appendicitis, but in group B patients it is both valid and useful.

Increased prevalence of HLA-B27 in patients with ectopic ossification following traumatic spinal cord injury

The histocompatibility antigen HLA-B27 was determined in 43 patients with post-traumatic spinal cord injury (SCI). The prevalence of B27 was significantly increased in the SCI patients with ectopic ossification. Five of 21 patients with ectopic bone had B27 compared to none of the 22 patients without ossification (P = 0.021). This finding indicates that HLA-B27 is a genetically determined risk factor for the development of heterotopic ossification following injury to the central nervous system. Future studies may determine that HLA-typing can identify a group of patients at a high risk of a disabling complication of SCI who should be treated prophylactically to prevent ectopic bone.

Dermatologists in the United States, 1968 through 1973

From 1968 to 1973, the number of dermatologists in the United States per 100,000 population gradually increased from 1.6 to 1.8, with the West and Northeast regions showing relatively higher rates and the South and North Central regions showing relatively lower rates. The variation in rate, considered by geographic divisions, can be analyzed to identify areas in the United States that may be in need of additional dermatologists. Given the current number of dermatologists being certified by the American Board of Dermatology and given the current death rate, there appear to be a sufficient number of dermatologists to ensure future growth.

Immunochemical heterogeneity of calcitonin in plasma of patients with medullary thryoid carcinoma

Marked discrepancies (values up to four times higher in on assay than in the other) were observed when the plasma concentration of immunoreactive human calcitonin (iCT) was measured by two radioimm8noassays in 18 patients with medullary thyroid carcinoma. The two antisera used had different binding affinities for the NH2- and COOH-terminal regions of synthetic calcitonin monomer (CT-1-32). Except for this difference, the assays were identical and reacted equally with CT 1-32. Plasma samples from patients with medullary thyroid carcinoma were gel filtered on columns of Bio-Gel P-150, and the immunoreactivity in column effuent fractions was measured with both assays. The one utilizing the antiserum with prominent NH2-terminal binding affinity (and giving higher iCT values) recognized at least five molecular species that eluted with or before CT 1-32. The other assay, utilizing the antiserum with a COOH-terminal binding affinity, recognized two fo these molecular species-one eluting with CT 1-32 and the other in a position consistent with a dimer. A mixture of athreotic asthma and added CT 1-32 contained a single immunologic species that was recoqnized equally by both antisera. No forms smaller than CT 1-32 were detected in any study. The results suggest that iCT circulating in the plasma of patients with medullary thryoid carcinoma is hetergeneous. The absolute iCT concentration measured by radioimmunoassays depends on recognition of these distinct molecular species as well as on the specific binding affinities of the antiserum used to detect them. These observations may partially explain the variations among iCT values reported by different laboratories.