Parents'' sung performances for infants

We have cloned an unique gene encoding the heavy chain of a type II myosin in the fission yeast, Schizosaccharomyces pombe. The myo2+ gene encodes a protein of 1526 amino acids with a predicted molecular weight of 177 kDa and containing consensus binding motifs for both essential and regulatory light chains. The S. pombe myo2+ head domain is 45% identical to myosin IIs from Saccharomyces cerevisiae and Homo sapiens and 40% identical to Drosophila melanogaster Structurally, myo2+ most closely resembles budding yeast MYO1, the tails of both myosin IIs containing a number of proline residues that are predicted to substantially disrupt the ability of these myosins to form coiled coils. The myo2+ gene is located on chromosome III, 8.3 map units from ade6+. Deletion of approximately 70% of the coding sequence of myo2+ is lethal but myo2delta spores can acquire a suppressor mutation that allows them to form viable microcolonies consisting of filaments of branched cells with aberrant septa. Overexpression of myo2+ results in the inhibition of cytokinesis; cells become elongated and multinucleate and fail to assemble a functional cytokinetic actin ring and are either aseptate or form aberrant septa. These results suggest that a contractile actin-myosin based cytokinetic mechanism appeared early in the evolution of eukaryotic cells and further emphasise the utility of fission yeast as a model organism in which to study the molecular and cellular basis of cytokinesis.     

Resolution of abnormal MR signal intensity in patients with stress fractures of the femoral neck

OBJECTIVE: The purpose of this study was to describe the natural evolution of abnormal MR signal intensity after the diagnosis of a stress fracture of the femoral neck and to ascertain the time to resolution of that abnormal signal intensity. SUBJECTS AND METHODS: Ten patients who had been previously diagnosed with stress fractures of the femoral neck after positive MR scans of the hip were examined with MR imaging at regular intervals. In each patient T1-weighted and short inversion time inversion recovery (STIR) sequences were obtained until the abnormally bright, diffuse MR signal intensity (representing edema) disappeared from the STIR images. Time to resolution was correlated with each patient's age and presence or absence of a fatigue line on MR imaging. Statistical analysis was done using Fisher's exact test. RESULTS: Edema resolved in seven patients within 3 months of initial diagnosis, in two patients within 6 months, and in the remaining patient within 12 months. We found no statistically significant correlation between time to resolution and patient age or the presence of a fatigue line on MR imaging. Residual sclerosis occurred in five patients, all of whom had a fatigue line. Two of these patients developed bright T1 signal (fatty marrow conversion) around the area of sclerosis. In the remaining three patients, STIR images revealed a brightened fatigue line, which we presumed was caused by granulation tissue. CONCLUSION: In this study, 90% of patients showed resolution of abnormal MR signal intensity on STIR imaging within 6 months of the initial diagnosis of stress fracture of the femoral neck. Such data may prove helpful in examining patients with recurrent symptoms who undergo repeated MR scanning. When an abnormally bright, diffuse MR signal intensity on STIR imaging is seen more than 6 months after an original injury, such abnormal signal intensity is likely to represent new injury.     

In vitro antineoplastic activity of a novel lanthionine-containing peptide

It has been a long-term goal to discover peptides that can kill tumor cells while sparing normal tissues. Lan-7 is a novel, chemically stable peptide structurally related to somatostatin that contains a lanthionine bridge between the two cysteines in the peptide; TT-232 is a less stable analogue containing a disulfide bridge. The antitumor activity of Lan-7 was examined, relative to that of TT-232 and the clinically used analogue octreotide, against a panel of malignant human tumor cell lines and normal human hematopoietic precursors. Lan-7 was cytotoxic to all four tumor cell lines, with IC50 values ranging over a 2-fold range from 16 to 36 microM. The potency of Lan-7 was comparable to that of TT-232, and both of these agents were two to three times more potent than octreotide. At concentrations that were highly cytotoxic to tumor cells, Lan-7 produced no significant toxicity to normal human hematopoietic precursors. Lan-7 induced apoptosis in human ovarian carcinoma 2008 cells over the same concentration range at which it produced cytotoxicity, but it did so without activating G1, S, or G2 checkpoints, given that it produced no perturbation of cell cycle phase distribution. Cells engineered to overexpress P-glycoprotein were not more resistant to Lan-7 than isogeneic cells not expressing the mdr1 gene. These results make Lan-7 of interest as a potential cancer chemotherapeutic agent.     

Amniotic fluid alpha-fetoprotein determination at the time of genetic amniocentesis: has it outlived its usefulness?

The purpose of this retrospective study was to evaluate the utility of routine measurement of amniotic fluid alpha-fetoprotein levels at the time of second trimester genetic amniocentesis (mean gestational age, 17.3 weeks +/- 2.5 weeks standard deviation; median, 16.8 weeks; range, 15 to 22 weeks). During the study period 7174 patients underwent second trimester genetic amniocentesis. Outcome data were available in all cases. In 79 (1.1%) cases the amniotic fluid alpha-fetoprotein level was > or = 2.0 multiples of the median. Thirty-three of the 79 (42%) patients had normal ultrasonograms, and in 31 of 33 (94%) the amniotic fluid alpha-fetoprotein level was between 2.0 and 3.0 multiples of the median. Forty-six of the 79 (58%) patients had abnormal ultrasonographic findings, and of these, 82% were neural tube defects, abdominal wall defects, or cystic hygromas. Acetylcholinesterase was positive in 37 cases, all of which had abnormal ultrasonographic findings. None of the fetuses with negative findings on sonographic screening had detectable abnormalities at birth. In this study, with over 7000 patients, amniotic fluid alpha-fetoprotein and acetylcholinesterase levels did not increase the detection of fetal abnormalities. On the basis of these results, routine measurement of amniotic fluid alpha-fetoprotein level at the time of routine genetic amniocentesis (15 to 22 weeks) does not appear justified.     

Mapping the prion protein using recombinant antibodies

The fundamental event in prion disease is thought to be the posttranslational conversion of the cellular prion protein (PrPC) into a pathogenic isoform (PrPSc). The occurrence of PrPC on the cell surface and PrPSc in amyloid plaques in situ or in aggregates following purification complicates the study of the molecular events that underlie the disease process. Monoclonal antibodies are highly sensitive probes of protein conformation which can be used under these conditions. Here, we report the rescue of a diverse panel of 19 PrP-specific recombinant monoclonal antibodies from phage display libraries prepared from PrP deficient (Prnp0/0) mice immunized with infectious prions either in the form of rods or PrP 27-30 dispersed into liposomes. The antibodies recognize a number of distinct linear and discontinuous epitopes that are presented to a varying degree on different PrP preparations. The epitope reactivity of the recombinant PrP(90-231) molecule was almost indistinguishable from that of PrPC on the cell surface, validating the importance of detailed structural studies on the recombinant molecule. Only one epitope region at the C terminus of PrP was well presented on both PrPC and PrPSc, while epitopes associated with most of the antibodies in the panel were present on PrPC but absent from PrPSc.     

Recombinant scrapie-like prion protein of 106 amino acids is soluble

The N terminus of the scrapie isoform of prion protein (PrPSc) can be truncated without loss of scrapie infectivity and, correspondingly, the truncation of the N terminus of the cellular isoform, PrPC, still permits conversion into PrPSc. To assess whether additional segments of the PrP molecule can be deleted, we previously removed regions of putative secondary structure in PrPC; in the present study we found that deletion of each of the four predicted helices prevented PrPSc formation, as did deletion of the stop transfer effector region and the C178A mutation. Removal of a 36-residue loop between helices 2 and 3 did not prevent formation of protease-resistant PrP; the resulting scrapie-like protein, designated PrPSc106, contained 106 residues after cleavage of an N-terminal signal peptide and a C-terminal sequence for glycolipid anchor addition. Addition of the detergent Sarkosyl to cell lysates solubilized PrPSc106, which retained resistance to digestion by proteinase K. These results suggest that all the regions of proposed secondary structure in PrP are required for PrPSc formation, as is the disulfide bond stabilizing helices 3 and 4. The discovery of PrPSc106 should facilitate structural studies of PrPSc, investigations of the mechanism of PrPSc formation, and the production of PrPSc-specific antibodies.     

Magnetic resonance imaging of articular cartilage in the knee. An evaluation with use of fast-spin-echo imaging

The purpose of this study was to demonstrate that specialized magnetic resonance imaging provides an accurate assessment of lesions of the articular cartilage of the knee. Arthroscopy was used as the comparative standard. Eighty-eight patients who had an average age of thirty-eight years were evaluated with magnetic resonance imaging and subsequent arthroscopy because of a suspected meniscal or ligamentous injury. The magnetic resonance imaging was performed with a specialized sequence in the sagittal, coronal, and axial planes. Seven articular surfaces (the patellar facets, the trochlea, the femoral condyles, and the tibial plateaus) were graded prospectively on the magnetic resonance images by two independent readers with use of the 5-point classification system of Outerbridge, which was also used at arthroscopy. Six hundred and sixteen articular surfaces were assessed, and 248 lesions were identified at arthroscopy. Eighty-two surfaces had chondral softening; seventy-five, mild ulceration; fifty-three, deep ulceration, fibrillation, or a flap without exposure of subchondral bone; and thirty-eight, full-thickness wear. To simplify the statistical analysis, grades 0 and 1 were regarded as disease-negative status and grades 2, 3, and 4 were regarded as disease-positive status. When the grades that had been assigned by reader 1 were used for the analysis, magnetic resonance imaging had a sensitivity of 87 per cent (144 of 166), a specificity of 94 per cent (424 of 450), an accuracy of 92 per cent (568 of 616), a positive predictive value of 85 per cent (144 of 170), and a negative predictive value of 95 per cent (424 of 446) for the detection of a chondral lesion. Interobserver variability was minimum, as indicated by a weighted kappa statistic of 0.93 (almost perfect agreement). With use of this readily available modified magnetic resonance imaging sequence, it is possible to assess all articular surfaces of the knee accurately and thereby identify lesions that are amenable to arthroscopic treatment.     

Surgical management of aberrant sentinel lymph node drainage in cutaneous melanoma

BACKGROUND: Sentinel lymph node (SLN) mapping by lymphoscintigraphy has changed the surgical management of regional lymph node metastases for melanoma. SLNs lying outside of traditional nodal basins are now being identified. Our hypothesis is that when preoperative lymphoscintigraphy identifies aberrant SLNs, these nodes should be excised and, if histologically positive, lymphadenectomy of the aberrant nodal basin should be performed. METHODS: Patients with melanomas 1 mm or larger Breslow thickness and clinical stage N0M0 underwent lymphoscintigraphy and excision with SLN biopsy. Preoperative lymphoscintigraphy, intraoperative gamma probe, and intraoperative injection of isosulfan blue were performed to identify the SLN. Aberrant SLNs were defined as epitrochlear, supraclavicular, or popliteal nodes for extremity lesions and intramuscular nodes for truncal and head and neck lesions. RESULTS: Thirty-two patients were entered into the protocol. Seven (22%) were found to have aberrant nodes. Five of 19 patients with extremity melanoma had an aberrant SLN; 2 of 13 patients with truncal and head and neck melanoma had an aberrant SLN. CONCLUSIONS: This study demonstrates that (1) aberrant SLNs are encountered with similar frequency for extremity and truncal lesions, (2) biopsy should be performed on aberrant SLNs with intraoperative lymph node mapping with the gamma probe and blue dye, and (3) lymphadenectomy of the aberrant region should be considered if the aberrant SLN is positive.     

Variation in incidence of indinavir-associated nephrolithiasis among HIV-positive patients

BACKGROUND: Nephrolithiasis may be an important consequence of indinavir therapy; however little has been published on the variation in incidence between different populations of patients or the possible mechanisms of calculus formation. OBJECTIVE: To examine variation in the incidence of indinavir-associated nephrolithiasis (IAN) in HIV-positive patients in relation to hemophilia and hepatitis C virus (HCV) infection. METHODS: Clinical data were abstracted retrospectively from the medical records of all adult patients treated with indinavir from September 1995 to September 1997. Occurrence of first IAN, defined as flank pain and hematuria after initiation of therapy, was analyzed in relation to hemophilia status and HCV infection. RESULTS: There were 17 episodes of IAN (22%) among 79 patients treated with indinavir. Of 10 patients with hemophilia, 50% developed IAN as compared with 17% of patients without hemophilia (P = 0.03). Median days to first IAN was 22 (range 7-110 days) for hemophiliacs and 156 (range 5-611 days) for those without hemophilia. Data for HCV status were available for 74 out of 79 patients: 10 out of 27 (37%) patients with HCV developed IAN compared with six out of 42 (14%) without HCV (P = 0.02). CONCLUSION: Overall incidence of IAN was higher than that previously reported and was significantly greater in hemophiliacs than in non-hemophiliacs. HCV may be a contributing factor.