Water deficit inhibits cell division and expression of transcripts involved in cell proliferation and endoreduplication in maize endosperm.

Water deficit at the early post-pollination stage in cereal grains decreases endosperm cell division and, in turn, decreases the capacity for storage material accumulation. Post-mitotic replication of nuclear DNA (endoreduplication) may also play a role in stress effects. To gain a better understanding of the extent to which cell proliferation and endoreduplication are affected by water deficit, nuclear numbers and size were examined in endosperms of maize (Zea mays L.) by flow cytometry and the transcript levels of genes which have recognized roles in the cell cycle were quantified. Water deficit from 5-13 d after pollination (DAP) decreased the rate of endosperm cell division by 90% and inhibited [3H]-thymidine incorporation into DNA from 9-13 DAP. The proportion of nuclei engaging in endoreduplication and nuclear DNA content increased steadily from 9-13 DAP in controls, but water deficit initially increased the proportion of endoreduplicating nuclei at 9 DAP, then halted further entry into endoreduplication and S-phase cycling from 9-13 DAP. Transcript levels of alpha-tubulin, and the S-phase gene products histone H3 and PCNA were not affected by water deficit until 13 DAP, whereas those of ZmCdc2, a cyclin dependent kinase (CDK) with regulatory roles in mitosis, were inhibited substantially from 9-13 DAP. Cell proliferation and associated processes were inhibited at initial stages of the stress episode, whereas endoreduplication and associated S-phase processes were not inhibited until the stress was more advanced. It was concluded that endosperm mitosis has greater sensitivity than endoreduplication to water deficit.

The effect of combinations of Fusarium mycotoxins (deoxynivalenol, zearalenone and fumonisin B1) on growth of brewing yeasts.

The interactive effect of combinations of the Fusarium mycotoxins deoxynivalenol (DON), zearalenone (ZEA) and fumonisin B1 (FB1) on growth of brewing yeasts was examined. Yeast growth was assessed by measurement of dry weight or relative growth, cell number, viability and conductance change of the growth medium using direct and indirect methods. The interactive effect of a combination of these mycotoxins was subject to the ratio of toxins in the mixture and the toxicity of individual toxins on yeast growth. When a combination of mycotoxins at low concentration was added into the growth medium, no significant inhibitory effect on growth was observed compared to controls. However, when a combination of high concentrations of DON and ZEA which individually inhibited yeast growth was examined, the interactive effect was shown to pass from antagonism to synergism depending on the ratio of the toxins in the mixture. As a synergistic interaction between these Fusarium mycotoxins was observed only at high concentrations, which were far higher than would be expected in good quality grain, they are not a concern when related to yeast growth under the brewing conditions studied.

Regulation of endoreduplication in maize (Zea mays L.) endosperm. Isolation of a novel B1-type cyclin and its quantitative analysis.

To investigate the involvement of cyclin in mitotic and endoreduplicative cell cycle control, we have isolated a mitotic cyclin clone from a maize endosperm cDNA library. The deduced amino acid sequence of this clone identifies a novel B1-type cyclin with distinctly different sequence in regions with putative involvement in intracellular localization. This cyclin, designated Zeama;CycB 1;3 (CycZme1), was shown by RNA gel blots and quantitative RT-PCR to be specific for tissues engaging in cell proliferation. It accumulated in metaphase-arrested cells and declined rapidly upon release into G1 phase. During the transition from mitosis to endoreduplication in maize endosperm, CycZme1 transcript declined precipitously while transcripts associated with S phase (histone-H3 and PCNA) and multiple phases of the cell cycle (Cdc2, alpha-tubulin) remained at moderate to high levels. We conclude that CycZme1 down-regulation is involved in the cellular transition to endoreduplication.

Alternative splicing of cyclin transcripts in maize endosperm.

Cyclins are the regulatory subunits of cyclin-dependent protein kinases. In investigations of the expression of a cyclin gene during maize endosperm development, we detected a cyclin transcript with a 63-bp deletion in the region encoding the conserved 'cyclin box' where cyclin interacts with p34cdc2, the catalytic domain of the cyclin-dependent protein kinase. Analysis of cDNA and genomic sequences, and other observations, indicated that the deletion was caused by alternative splicing of a retained intron in the normally spliced transcript. Whereas the normally spliced cyclin RNA was mitotically functional, as indicated by its ability to promote maturation of Xenopus oocytes, the alternatively spliced transcript was unable to promote maturation. In addition to maize endosperm, the alternatively spliced cyclin was detected in apical meristem, mature leaf, root tip and mature root.

Production of patulin and cytochalasin E by Aspergillus clavatus during malting of barley and wheat.

Production of patulin and cytochalasin E by four strains of Aspergillus clavatus during small-scale laboratory malting of barley at 16 and 25 degrees C was investigated. Fungal biomass, measured as ergosterol, appeared to be greater at 25 than at 16 degrees C, but marked differences were observed between the degree of colonization by the different strains. Patulin was detected in extracts by HPLC. Net production was greater at 16 degrees C, but amounts were strain dependent. Except for one strain, cytochalasin E was detected only in barley malted at 25 degrees C. In experiments with wheat inoculated with two A. clavatus strains, ergosterol levels in the green malts were generally greater than in corresponding barley malts. Patulin was again detected in all samples, with the equivalent of 22.4 mg/kg being detected in one sample at 16 degrees C, but cytochalasin E was only found at 25 degrees C, the highest level detected being 13.8 mg/kg. In samples of barley spiked with toxin and kilned at 80 degrees C for 24 h, only about one-fifth of the amount of toxin recovered from corresponding unkilned controls was detected. It is indicated that differences in both contaminant strains and temperature in different maltings may account for disparities between symptoms reported for individual outbreaks of mycotoxicosis associated with malting by-products.

MR diagnosis of recurrent tears in the knee: value of intraarticular contrast material.

OBJECTIVE: After surgical resection or repair of a torn meniscus, the healed area may have areas of abnormal signal intensity on MR images. Consequently, routine MR imaging is not reliable for detecting recurrent meniscal tears. As a result, we studied the efficacy of MR imaging with intraarticular contrast material (MR arthrography) for detecting recurrent tears of the meniscus. SUBJECTS AND METHODS: Thirty-seven patients who previously had a meniscal tear treated by either meniscal resection or repair had conventional MR imaging and MR arthrography with 40-50 ml of a 1:100 solution of gadopentetate dimeglumine in saline. All patients had arthroscopy shortly after the MR studies. Follow-up arthroscopic surgery was performed within an average of 6.6 weeks after the MR arthrograms. The routine MR images and MR arthrograms were reviewed separately and randomly, and these results were compared with the arthroscopic findings. Meniscal morphology, signal intensity, and the presence of joint fluid tracking into recurrent tears were evaluated. RESULTS: The overall accuracy in diagnosing recurrent meniscal tears in the post-operative meniscus was 66% when conventional MR imaging was used and 88% when MR arthrography was used. In patients who had only minimal meniscal resection, both methods had an accuracy of 89%. In patients who had more extensive meniscal resection, accuracy was 65% with conventional MR imaging and 87% with MR arthrography. In four patients who had only a small meniscal remnant, the accuracy was 50% with routine MR imaging and 100% with MR arthrography. On conventional MR images, the presence of an effusion tracking into a meniscal tear had a sensitivity and positive predictive value of 90% for detection of recurrent meniscal tears; however, the sensitivity was only 41%. CONCLUSION: Our results show that the sensitivity of MR imaging in detecting meniscal tears after surgery varies with the extent of the resection. Sensitivity was considerably improved when intraarticular contrast material was used. MR arthrography should be considered as an alternative to arthroscopy in patients who have had resection or repair of the meniscus.

Magnetic resonance arthrography of the shoulder.

Recently, there have been attempts to improve the accuracy of MR imaging by distending the glenohumeral joint with fluid prior to imaging. This article reviews the techniques employed in performing MR arthrography, imaging characteristics of MR arthrography, and diagnostic use of the procedure.

Injuries of the superior portion of the glenoid labrum involving the insertion of the biceps tendon: MR imaging findings in nine cases.

The goal of this investigation was to describe the MR appearance of traumatic fraying or detachment of the superior portion of the glenoid labrum including the insertion of the tendon of the long head of the biceps. This condition is caused either by an acute injury or by repeated overhead motion during participation in sports. In nine patients with such a lesion, the arthroscopic report and MR images were available for review. These patients were 22-64 years old (mean, 38). In four patients only fraying was noted during arthroscopy, in four patients the superior part of the labrum was detached together with the insertion of the biceps tendon, and in one case there was a bucket-handle tear of the superior portion of the labrum. The MR images were retrospectively evaluated by three osteoradiologists in conference. Signal changes within the labrum and detachment of the labrum were noted, and the findings were compared with the results of arthroscopy. MR imaging did not allow recognition of simple fraying. In two of the five cases with arthroscopic findings of detachment of the superior labrum from the glenoid rim, differentiation between complete and partial labral detachments was not possible even with MR arthrography. However, in these cases the patient's age and history led to the correct diagnosis. We conclude that early traumatic abnormalities of the superior portion of the labrum cannot be detected with MR imaging. Complete detachment, however, can be demonstrated if the patient's age and history are taken into consideration.

Rotator cuff disease: assessment with MR arthrography versus standard MR imaging in 36 patients with arthroscopic confirmation.

Standard proton-density- and T2-weighted magnetic resonance (MR) imaging and MR arthrography were used to depict rotator cuff disease in 36 shoulders in 36 patients; the findings were compared with arthroscopic findings in every patient. In 19 rotator cuffs normal at arthroscopy, MR arthrography revealed no tear in 16 patients, a partial tear in one patient, and a full-thickness tear in two patients. Standard proton-density- and T2-weighted images were normal in 15 of these patients and revealed a partial tear in two patients and a full-thickness tear in two patients. In 13 partial tears found at arthroscopy, MR arthrography showed a partial tear in six patients, no tear in five patients, and a full-thickness tear in two patients; standard MR imaging revealed a partial tear in one patient, no tear in 10 patients, and a full-thickness tear in two patients. All four full-thickness tears proved with arthroscopy were correctly diagnosed with both MR imaging methods. The main advantage of MR arthrography was better depiction of partial tears in the articular surface.

Chronic wrist pain: spin-echo and short tau inversion recovery MR imaging and conventional and MR arthrography.

The accuracy of T1-, proton-density-, and T2-weighted magnetic resonance (MR) imaging sequences and gadolinium-enhanced MR arthrography in evaluation of the triangular fibro-cartilage complex (TFCC) and the scapholunate (SL) and lunotriquetral (LT) ligaments was studied in 15 patients with chronic wrist pain. Arthrography and arthroscopy were used as standards of reference. Twelve patients also underwent imaging with short tau inversion recovery (STIR) sequences. MR imaging was more reliable in evaluation of the morphology of the TFCC and SL ligament than in that of the LT ligament. With arthrography as the standard, sensitivity was 0.721, specificity was 0.947, and accuracy was 0.887 for the TFCC; these values were 0.500, 0.864, and 0.765 for the SL ligament and 0.519, 0.455, and 0.490 for the LT ligament. No visualization of the SL ligament indicated a tear, but this sign was not helpful in evaluation of the LT ligament. Fluid in the distal radioulnar joint had a high association with TFCC tears. Accuracy with MR arthrography was higher than with the other sequences. STIR images were effective in evaluation of the TFCC. The combination of proton-density-and T2-weighted images appears to be useful because morphologic characteristics and the presence of fluid can be evaluated.

Magnetic resonance imaging of the foot and ankle: correlation of normal anatomy with pathologic conditions.

Abnormalities of the foot and ankle can be difficult to diagnose by conventional examination and x-rays. Recently, magnetic resonance imaging (MRI) has emerged as a diagnostic tool for soft tissue and bony imaging. One hundred and ten normal feet and ankles were studied to define normal MRI anatomy. An additional 150 MRI scans were performed to diagnose and characterize various abnormal conditions. MRI demonstrated excellent definition of normal structures and pathologic entities. Surgical correlation with the MRI was done in 42 patients. MRI appears to be a useful examination for patients with certain soft tissue and bony abnormalities. A special oblique view also has been developed to assist in the diagnosis of injuries to the tibialis posterior, flexor hallucis longus, and flexor digitorum longus tendons.

Osteonecrosis of the knee after arthroscopic surgery: diagnosis with MR imaging.

Spontaneous osteonecrosis about the knee typically is a disease of the elderly characterized by an acute onset of pain. The exact cause of this condition has long been debated, although a causative relationship between meniscal tears and spontaneous osteonecrosis about the knee has been postulated. Seven patients with knee pain, meniscal tears, and chondromalacia without initial evidence of osteonecrosis at magnetic resonance (MR) imaging underwent arthroscopic surgery with meniscal recontouring or repair and cartilage shaving. These patients returned within 2-14 months with recurrent pain in the treated knee. MR imaging then demonstrated abnormalities consistent with osteonecrosis. Osteonecrosis of the femoral condyle or tibial plateau may be a late sequela of meniscal injury in association with chondromalacia and arthroscopic surgery. This diagnosis should be suspected in patients with recurrent knee pain after arthroscopic repair of meniscal tears. The precise relationship of this pattern of osteonecrosis to that previously described as spontaneous requires further investigation.

Surgical decompressive procedures for cervical spondylotic myelopathy. A study using magnetic resonance imaging.

Twenty-two patients who underwent a surgical decompressive procedure for cervical spondylotic myelopathy were studied with magnetic resonance imaging to evaluate the effectiveness of their decompressive procedures. Twelve patients were judged as adequately decompressed by magnetic resonance imaging criteria. Ten patients exhibited evidence of residual cord indentation. This along with cord atrophy, gliosis, and abnormal spine curvature presumably contributed to residual deficit in several patients. One patient underwent a second decompressive procedure for residual cord indentation, which subsequently improved, as seen on his second postoperative magnetic resonance image. Magnetic resonance imaging was useful in distinguishing mechanical problems from intrinsic cord damage or atrophy. Magnetic resonance imaging should be used after operation in patients with residual deficit to detect patients who may be considered for a second decompressive procedure.

MR arthrography of the shoulder: comparison with conventional MR imaging.

Twenty-three patients underwent both conventional MR imaging of the shoulder and MR shoulder arthrography for clinically suspected labral or rotator cuff abnormalities. Images obtained before and after contrast administration were studied independently, and without knowledge of clinical findings, by two radiologists for the presence of abnormalities of the glenoid labrum or rotator cuff. Results were correlated with surgical findings in all patients. Nine patients had surgically proved labral tears. MR arthrography detected all nine labral abnormalities, while six of the nine were missed on conventional MR imaging. Fourteen patients had surgically proved rotator cuff tears. MR arthrography detected 11 of the 14 tears and missed three partial tears on the bursal surface. Conventional MR imaging detected nine cuff tears and missed five tears; two of these were complete rotator cuff tears and three were partial tears of the undersurface of the rotator cuff. Our results suggest that MR arthrography enhances the accuracy of MR in the evaluation of the glenoid labrum and rotator cuff tendon.

Quantification of airborne moulds in the homes of children with and without wheeze.

A population survey of 1000 7 year old children found a significant excess of wheeze among children whose homes were reported to be mouldy (odds ratio 3.70, 95% confidence limits 2.22, 6.15). The airborne mould flora was quantified by repeated volumetric sampling during the winter in three rooms of the homes of 88 children. All of these had previously completed spirometric tests before and after a six minute free running exercise challenge. Total airborne mould counts varied from 0 to 41,000 colony forming units (CFU)/m3, but were generally in the range 50-1500 CFU/m3, much lower than the concentrations found outdoors in summer. The principal types of fungi identified are all known to be common out of doors, and most were found on at least one occasion in most of the homes. Median and geometric mean total mould counts were not related to reports of visible mould in the home, or to a history of wheeze in the index child. The heterogeneous group of non-sporing fungi (mycelia sterilia) were the only airborne fungi present at significantly higher concentrations in the homes of wheezy children (geometric mean 2.1 v 0.7 CFU/m3. A non-significant increase in total mould counts was observed in the homes of children with a 10% or greater decline in FEV1 after exercise (geometric mean 354 v 253 CFU/m3). Questionnaire reports of mould in the home may be a poor indicator of exposure to airborne spores. The total burden of inhaled mould spores from indoor sources is probably not an important determinant of wheeze among children in the general population. Although the association with mycelia sterilia could be a chance finding, these non-sporing isolates may include a potent source of allergen.

The use of MRI to assist in diagnosis of pigmented villonodular synovitis of the knee joint.

Pigmented villonodular synovitis (PVNS) of the knee joint remains a difficult and elusive entity to define and characterize. This entity most often appears in the young adult knee with nonspecific clinical features, including a painful range of motion and perhaps a sensation of locking. Detection and diagnosis of this localized soft-tissue mass are difficult because plain roentgenograms may be totally within normal limits. The case of a 21-year-old woman illustrates the use of magnetic resonance imaging (MRI) as an effective technique to define and characterize PVNS. Advantages of MRI include high-resolution/high-contrast multiplanar sections that depict bone, marrow, ligaments and tendons, fat, menisci, and articular cartilage in one image. In addition, MRI is noninvasive and requires no ionized radiation. MRI is an excellent clinical tool for the evaluation of intraarticular tumors of the knee joint.

Morphological studies on clinical isolates of Aspergillus fumigatus.

Morphological variation was examined in 19 strains of Aspergillus fumigatus Fres. isolated from the sputum of five patients with aspergilloma. For each patient a series of variant strains was obtained which exhibited gross differences in growth rate, colour and texture of the colony. On microscopical examination, some of the strains were found to produce markedly abnormal fruiting heads which were uncharacteristic for the species. Scanning electron microscopy revealed that the variant produced conidia of anomalous size, shape and surface-sculpturing. The significance of the isolation of morphological variants of A. fumigatus in sputum and their selection in vivo are discussed.

Magnetic resonance imaging of the pediatric spine.

The authors conclude that MRI is the imaging mode of choice for the evaluation of extradural and intramedullary tumors and for the screening of all children with suspected spinal pathology.

MR of craniopharyngiomas: tumor delineation and characterization.

MR imaging and CT (with and without contrast enhancement) were performed in 20 patients with an established or clinically suspected diagnosis of craniopharyngioma. Fifteen had biopsy-proven craniopharyngioma and five had presumed craniopharyngioma based on clinical and CT findings. In two cases MR was superior to contrast-enhanced CT in demonstrating the tumor. A variable appearance on T1-weighted MR images reflected the pathologic appearance of craniopharyngiomas. High intensity on T1-weighted images corresponded to high cholesterol content or presence of methemoglobin. MR was the preferred method in the evaluation of tumor extent, especially in the cavernous sinus and posterior clival region. CT was superior to MR in detecting the presence of calcification, which with the clinical history correctly suggested the diagnosis of craniopharyngioma. Both MR and CT studies are desired initially to establish the diagnosis and to evaluate tumor extent. MR was the preferred method in detecting the presence of recurrent tumor.