Phasing the 30S ribosomal subunit structure

The methods involved in determining the 850 kDa structure of the 30S ribosomal subunit from Thermus thermophilus were in many ways identical to those that are generally used in standard protein crystallography. This paper reviews and analyses the methods that can be used in phasing such large structures and shows that the anomalous signal collected from heavy-atom compounds bound to the RNA is both necessary and sufficient for ab initio structure determination at high resolution. In addition, measures to counter problems with non-isomorphism and radiation decay are described.

Crystal structure of the 30 S ribosomal subunit from Thermus thermophilus: purification, crystallization and structure determination

We describe the crystallization and structure determination of the 30 S ribosomal subunit from Thermus thermophilus. Previous reports of crystals that diffracted to 10 A resolution were used as a starting point to improve the quality of the diffraction. Eventually, ideas such as the addition of substrates or factors to eliminate conformational heterogeneity proved less important than attention to detail in yielding crystals that diffracted beyond 3 A resolution. Despite improvements in technology and methodology in the last decade, the structure determination of the 30 S subunit presented some very challenging technical problems because of the size of the asymmetric unit, crystal variability and sensitivity to radiation damage. Some steps that were useful for determination of the atomic structure were: the use of anomalous scattering from the LIII edges of osmium and lutetium to obtain the necessary phasing signal; the use of tunable, third-generation synchrotron sources to obtain data of reasonable quality at high resolution; collection of derivative data precisely about a mirror plane to preserve small anomalous differences between Bijvoet mates despite extensive radiation damage and multi-crystal scaling; the pre-screening of crystals to ensure quality, isomorphism and the efficient use of scarce third-generation synchrotron time; pre-incubation of crystals in cobalt hexaammine to ensure isomorphism with other derivatives; and finally, the placement of proteins whose structures had been previously solved in isolation, in conjunction with biochemical data on protein-RNA interactions, to map out the architecture of the 30 S subunit prior to the construction of a detailed atomic-resolution model.

Recognition of cognate transfer RNA by the 30S ribosomal subunit

Crystal structures of the 30S ribosomal subunit in complex with messenger RNA and cognate transfer RNA in the A site, both in the presence and absence of the antibiotic paromomycin, have been solved at between 3.1 and 3.3 angstroms resolution. Cognate transfer RNA (tRNA) binding induces global domain movements of the 30S subunit and changes in the conformation of the universally conserved and essential bases A1492, A1493, and G530 of 16S RNA. These bases interact intimately with the minor groove of the first two base pairs between the codon and anticodon, thus sensing Watson-Crick base-pairing geometry and discriminating against near-cognate tRNA. The third, or "wobble," position of the codon is free to accommodate certain noncanonical base pairs. By partially inducing these structural changes, paromomycin facilitates binding of near-cognate tRNAs.

Crystal structure of an initiation factor bound to the 30S ribosomal subunit

Initiation of translation at the correct position on messenger RNA is essential for accurate protein synthesis. In prokaryotes, this process requires three initiation factors: IF1, IF2, and IF3. Here we report the crystal structure of a complex of IF1 and the 30S ribosomal subunit. Binding of IF1 occludes the ribosomal A site and flips out the functionally important bases A1492 and A1493 from helix 44 of 16S RNA, burying them in pockets in IF1. The binding of IF1 causes long-range changes in the conformation of H44 and leads to movement of the domains of 30S with respect to each other. The structure explains how localized changes at the ribosomal A site lead to global alterations in the conformation of the 30S subunit.

The structural basis for the action of the antibiotics tetracycline, pactamycin, and hygromycin B on the 30S ribosomal subunit

We have used the recently determined atomic structure of the 30S ribosomal subunit to determine the structures of its complexes with the antibiotics tetracycline, pactamycin, and hygromycin B. The antibiotics bind to discrete sites on the 30S subunit in a manner consistent with much but not all biochemical data. For each of these antibiotics, interactions with the 30S subunit suggest a mechanism for its effects on ribosome function.

Functional insights from the structure of the 30S ribosomal subunit and its interactions with antibiotics

The 30S ribosomal subunit has two primary functions in protein synthesis. It discriminates against aminoacyl transfer RNAs that do not match the codon of messenger RNA, thereby ensuring accuracy in translation of the genetic message in a process called decoding. Also, it works with the 50S subunit to move the tRNAs and associated mRNA by precisely one codon, in a process called translocation. Here we describe the functional implications of the high-resolution 30S crystal structure presented in the accompanying paper, and infer details of the interactions between the 30S subunit and its tRNA and mRNA ligands. We also describe the crystal structure of the 30S subunit complexed with the antibiotics paromomycin, streptomycin and spectinomycin, which interfere with decoding and translocation. This work reveals the structural basis for the action of these antibiotics, and leads to a model for the role of the universally conserved 16S RNA residues A1492 and A1493 in the decoding process.

Structure of the 30S ribosomal subunit

Genetic information encoded in messenger RNA is translated into protein by the ribosome, which is a large nucleoprotein complex comprising two subunits, denoted 30S and 50S in bacteria. Here we report the crystal structure of the 30S subunit from Thermus thermophilus, refined to 3 A resolution. The final atomic model rationalizes over four decades of biochemical data on the ribosome, and provides a wealth of information about RNA and protein structure, protein-RNA interactions and ribosome assembly. It is also a structural basis for analysis of the functions of the 30S subunit, such as decoding, and for understanding the action of antibiotics. The structure will facilitate the interpretation in molecular terms of lower resolution structural data on several functional states of the ribosome from electron microscopy and crystallography.

A new approach to alcoholism detection in primary care

This article describes a model that brings together the chemical dependency, mental health, and primary care services of a staff model HMO for the purpose of establishing a primary care clinic-based program to assist physicians in early detection of chemical dependency and frequent psychiatric disorders. The model creates a partnership between a master's-level professional social worker (MSW) and a designated family physician from the clinic. Their focus is on provider education, consultation, and on assisting patients with referrals to the appropriate services. Parameters of success include changes on referral patterns, use of the MSW's services, and clinic satisfaction. In addition, there are indications that early intervention has had a positive impact on subsequent use of other health care system's resources.

Comparisons of urinary versus serum cortisol in older persons

The present analysis compared urine- versus serum-based amounts of the stress hormone cortisol in two older adult samples, given that urine as a sample medium is a less expensive and less invasive method of determining cortisol amounts relative to serum. Seventy-three older adults provided urine samples as part of an ongoing study to assess levels of cortisol as a function of intellectual efficacy/performance; these data were compared to serum cortisol levels obtained from 96 older adults in a separate study examining health beliefs and cortisol levels. Analyses indicated that the cortisol levels did not differ across samples, i.e., cortisol amounts measured in serum or urine yielded similar, typical (within normal ranges) results. The data, though preliminary, indicate that urine may provide an alternative to serum when assessing cortisol in older persons.

MRA of the intracranial circulation in asymptomatic patients with sickle cell disease

BACKGROUND

MR angiography (MRA) provides a mechanism for non-invasively studying blood flow, thus providing a new opportunity to study the intracranial circulation in asymptomatic sickle cell disease (SCD) patients. Although conventional angiography is the gold standard for the depiction of vascular anatomy, this is too invasive for an asymptomatic population.

OBJECTIVE

To establish the range of appearances in asymptomatic SCD patients and to correlate brain MRI results (either sub-clinical abnormalities or normal brain parenchyma) with the MRA findings.

MATERIALS AND METHODS

Brain MRI and MRA of the intracranial circulation was performed on 22 patients (13 male and 9 female, median age 7.5 years, range 1.3-20 years). Fourteen were homozygous SS and eight were SC. The median haematocrit at the time of MRI was 25.9 (range 13.8-33.3).

RESULTS

On MR imaging, four patients had infarcts in eight vascular territories (six anterior and two posterior). In 3/4 of anterior vascular territories with infarction, long ( >/= 6 mm) segments of abnormal signal were seen at the internal carotid artery bifurcation with associated reduced distal flow. Short focal areas of abnormal signal were commonly seen where vessels branched, bifurcated or curved and were not associated with infarcts. These areas probably represent turbulence-related dephasing secondary to high velocity flow found in SCD.

CONCLUSION

Long segments ( >/= 6 mm) of abnormal signal with reduced distal flow correlated with sub-clinical infarction.

Fast spin echo vs conventional spin echo in cervical spine imaging

The major attraction of fast-spin-echo (FSE) imaging is reduced acquisition time; however, careful review of the literature reveals many weaknesses: phase-encoded blurring, truncation artefact, bright fat signal, reduced magnetic susceptibility and increased motion artefact. Our aim was a prospective, blinded comparison of FSE and conventional spin echo (CSE) in the cervical spine. Both sequences were performed in 43 patients (19 males and 24 females; mean age 45 years, range 15-66 years). Twenty-eight patients were studied at 1.5 T and 15 at 0.5 T. Typical sequence parameters were: at 1.5 T, TR/TE 2000/90 CSE and 3000/120 FSE, and at 0.5 T, 2200/80 CSE and 2800/120 FSE. Time saved on the FSE was used to increase the matrix and the number of acquisitions. Two neuroradiologists evaluated the images for pathology, artefacts, disc signal intensity, thecal sac compression and image quality. Ten patients had cord lesions; 2 (20 %) were missed on CSE. In 4 of 10 patients with moderate/severe thecal sac compression, the degree of stenosis was apparently exaggerated on CSE. The mean degree of confidence for the CSE sequences was 1.8 and for the FSE 1.1, where 1 is optimal. For cervical spine imaging, FSE should be preferred to CSE.

Cerebral infarction in patients with AIDS

PURPOSE

To establish the frequency, distribution, and pathogenesis of cerebral infarction as confirmed with MR imaging in a cohort of patients with acquired immunodeficiency syndrome (AIDS).

METHODS

We reviewed all (71) abnormal cranial MR studies obtained at our institution in human immunodeficiency virus (HIV)-positive patients over a 2-year period and recorded the number and distribution of ischemic lesions, any associated abnormalities, and the MR angiographic findings, where available. Patients' charts were studied for relevant clinical data, biochemical and culture results, and potential etiologic factors.

RESULTS

Twenty-two infarcts were seen in 13 of the 71 patients. Of these 22, the basal ganglia area was affected in 15, the middle cerebral artery territory in two, and the vertebrobasilar territory in five. Five patients had concomitant evidence of infection, six others used cocaine or were intravenous drug abusers. MR angiography was performed in eight patients; two of these had multiple lesions consistent with vasculitis, two had isolated lesions that corresponded with their parenchymal infarct, and four had normal findings.

CONCLUSIONS

The frequency of infarction was 18%, higher than previously reported. The pathogenesis of infarction was multifactorial. Underlying infectious causes were identified in 39% of patients. Two patients had an idiopathic vasculitis.

Carotid MRA--what advantages do the turbo field-echo and 3D phase-contrast sequences offer?

Our purpose was to investigate some of the newer MR angiography (MRA) techniques for studying the carotid arteries. Forty-two arteries in seven asymptomatic, healthy volunteers were studied using five MRA sequences: two conventional time-of-flight sequences, 2D time-of-flight (2DTOF) and 3D time-of-flight (3DTOF); 2D and 3D magnetisation-prepared, segmented time-of-flight sequences (2DTFE and 3DTFE); and a 3D phase contrast angiography (3DPCA) sequence. A protocol that could be realistically employed in a routine clinical situation was chosen. 2DTOF had significantly (P < 0.05) better signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) than 2DTFE. 3DTOF demonstrated better SNR than 3DTFE but 3DTFE demonstrated better CNR than 3DTOF. 3DPCA provided maximal anatomical coverage. No one sequence provided optimal anatomical coverage, accurate demonstration of the carotid bulb and maximal SNR and CNR. The combination of 3DPCA and a 3D inflow sequence was best. 2DTOF sequences are useful when only one brief sequence is practicably feasible.

MR appearances of the temporal evolution and resolution of infectious spondylitis

OBJECTIVE

We undertook this study to document the MR appearances of evolving or resolving infectious spondylitis.

MATERIALS AND METHODS

A retrospective review was carried out of all patients with infectious spondylitis who had undergone MR imaging from 1991-1993 at Boston University Hospital and Boston City Hospital Imaging Foundation. The study population consisted of 25 patients (seven females and 18 males). There was a bimodal age distribution with peaks at 34 and 59 years old (age range, 25-81 years old). The causative organism was isolated in 20. Sixteen had Staphylococcus aureus, two had mycobacterium tuberculosis, and two had gram-negative bacilli. Follow-up MR imaging was performed in 20. Nine had two studies, three had three, five had four, two had five, and one had six. The median length of follow-up was 8 weeks (range, 2-104 weeks). Follow-up MR appearances were correlated with clinical outcome.

RESULTS

Early imaging revealed atypical appearances. Fourteen of 20 (70%) improved; the first sign of response to treatment was a reduction in the inflammatory soft tissue (8/14, 57%). Changes in the bones or discs concurrently progressed in six of eight patients (75%) including involvement of a new disc level in four (50%). A definitive sign of healing was a peripheral rim of high T1 signal in bone (5/14, 36%). Gadolinium enhancement persisted long after resolution of changes in the soft tissues, for up to a median of 17.5 weeks (range, 8-80 weeks). A subgroup of six IV drug users showed unique radiologic features.

CONCLUSION

The early appearances of infectious spondylitis may be atypical. Resolution of soft-tissue change and fat deposition in the bone marrow are reliable signs of healing. Bone or disc changes can progress despite clinical improvement. Gadolinium enhancement can increase and persist after symptom resolution.

Magnetization transfer contrast MR in lesions of the head and neck

PURPOSE

To compare lesion-to-background contrast with and without magnetization transfer (MT) in lesions of the head and neck.

METHODS

Twenty lesions (16 malignant, 4 benign) were evaluated in 17 patients (11 men, 6 women; mean age, 58 years; age range, 39-76 years). In 13 patients, MR imaging was performed at 0.1 T with continuous-wave, off-resonance MT; in 4 patients, MR imaging was performed at 1.5 T with on-resonance, binomial MT prepulses. Fifteen sequences were conducted before the administration of gadopentetate dimeglumine; 13 were conducted after the administration of that contrast material. The ratio of signal intensity with the MT pulses (Ms) to signal intensity without the MT pulses (Mo) was calculated, as were the lesion-to-background contrast and the contrast-to-noise ratios.

RESULTS

Ms/Mo showed both wide variability and considerable overlap among different lesion types. Images from MT sequences showed better contrast than those from non-MT sequences in 23 of 28 lesions (12 of 15 before and 11 of 13 after the administration of contrast material). The mean contrast improvement percentages (+/- standard deviation) were 165.5% (+/- 58%) on unenhanced images and 186.6% (+/- 84.8%) on contrast-enhanced images. The mean improvements in contrast-to-noise ratios were 156% (+/- 60%) on unenhanced images and 171.6% (+/- 98.1%) on contrast-enhanced images.

CONCLUSION

MT improved contrast between nodes or tumors showing an MT effect and background tissue (usually fat) not showing an MT effect. MT also improved contrast between contrast-enhanced neoplastic lesions and background tissue that showed an MT effect.

Clinical utility of a new contrast option from magnetization transfer contrast

Two magnetization transfer (MT) contrast effects, a T2-like effect and the improved contrast observed when gadolinium is used with MT, are combined in a single sequence. Forty patients (22 males:18 females; mean age, 45 years (23-87)) with suspected intracranial pathology underwent MRI on a 1.5 Tesla system. Of 46 lesions; seven were ischemic, five infective, seven neoplastic, four hemorrhagic, four multiple sclerosis, seven human immunodeficiency virus (HIV) leukoencephalopathy, nine normal/miscellaneous, and three gliosis. A conventional spin-echo sequence (TR 900 TE 15) was used with on-resonance binomial MT pulses. The sequence was performed postgadolinium +/- MT. The signal intensity ratios +/- MT were: white matter, 0.62 +/- 0.03; gray matter, 0.75 +/- 0.04; ischemia, edema, and demyelination, 0.75 (0.57-0.86); and gadolinium/methemoglobin, 0.85 (0.81-0.98). Areas which exhibited MT had T2-like contrast and those that did not maintained expected contrast for the given parameters. The result was a combination of T2-like contrast, gadolinium enhancement, and dark cerebrospinal fluid (CSF) providing both increased sensitivity to lesions which exhibited both contrast features and improved delineation of periventricular lesions. Furthermore, the differential signal between T2-like contrast of edema and gadolinium enhancement in neoplastic or infective lesions was maintained.

Is transcranial Doppler a worthwhile addition to screening tests for cerebrovascular disease?

PURPOSE

Carotid duplex imaging has become the standard diagnostic evaluation for patients with suspected cerebrovascular disease. Transcranial Doppler ultrasonography expands the noninvasive diagnostic capabilities to the intracranial circulation. The purpose of this study was to evaluate the results of routine transcranial Doppler studies on patients referred for noninvasive cerebrovascular evaluation.

METHODS

A total of 670 patients had routine transcranial Doppler examinations as part of their noninvasive cerebrovascular evaluation. Patients were categorized clinically and according to their severity of extracranial internal carotid artery stenosis (< 50%, 50% to 79%, 80% to 99%, occlusion). Transcranial Doppler examinations were classified as normal or abnormal (intracranial stenosis, collateral pathway, > 30% velocity difference normal or abnormal (intracranial stenosis, collateral pathway, > 30% velocity difference between sides, flow reversal, and velocities +/- SD from normal).

RESULTS

Forty-eight percent of the patients were women, and 52% were men. The average age was 65.5 years. Fifty-four percent of the patients were white, 42% were black, 3% were Hispanic, and 1% were other. Forty-eight percent presented with hemispheric symptoms, 34% had no symptoms, and 18% had nonhemispheric symptoms. Forty-five percent (304 of 670) had an interpretable transcranial Doppler examination. The ability to insonate the basal cerebral arteries through the temporal bone was significantly reduced in women (p < 0.0001), black patients (p < 0.0001), and older patients (p < 0.0001). The results of forty-four percent of interpretable examinations were normal, 19% demonstrated side-to-side velocity differences, 13% showed collateral pathways, 11% showed velocities +/- 2 SD, 10% showed an intracranial stenosis, and 4% showed reversed flow pattern. Although 56% of the patients had notable findings, no patient had their diagnostic or therapeutic plan altered by the transcranial Doppler results.

CONCLUSION

Less than 50% of the patients referred for first-time cerebrovascular examination had access for an interpretable transcranial Doppler examination. Though the number of positive findings is reasonably high, no material impact on diagnostic or treatment plans was seen in the patients in this series. These results indicate that selection criteria for examination of the intracranial arteries should be refined and that transcranial Doppler scanning should not be incorporated as part of the "routine" noninvasive cerebrovascular examination.

The piezoelectric pulse sensor device: a prospective evaluation

The goal of this prospective study of the piezoelectric pulse sensor device was to determine its technical applications and its ability to detect lower extremity occlusive arterial disease. Ten extremities (five volunteers) were evaluated to assess the ability to place the sensor in the correct anatomic position on a foot without a palpable pulse during cuff occlusion so that pulsatile flow would be detected following cuff deflation; its sensitivity as an end-point detector for pulsatile perfusion; and whether there is a linear qualitative pulse wave response with increasing perfusion pressures. Forty extremities (20 patients) with suspected occlusive arterial disease were studied to evaluate its capability of detecting perfusion as compared with the presence of a palpable pulse, an audible Doppler signal, and a foot volume waveform. The placement of the sensor on 10 normal limbs with temporary arterial occlusion resulted in a recordable waveform following cuff deflation in 100% of the dorsalis pedis arteries and in 10% of the posterior tibial arteries. The piezoelectric pulse sensor was as sensitive for detecting pulsatile perfusion as an audible Doppler signal and demonstrated a linear change in the waveform's amplitude and shape with incremental changes in perfusion pressure. In the 40 extremities with ankle/brachial indices ranging from 0.00 to 1.35, there was uniform agreement between pulse volume and Pulse Check waveforms. The piezoelectric pulse sensor is a sensitive method for monitoring lower extremity arterial perfusion when supplied by the dorsalis pedis artery; however, it is inadequate for the posterior tibial artery.(ABSTRACT TRUNCATED AT 250 WORDS)

MR angiography of normal pelvic arteries: comparison of signal intensity and contrast-to-noise ratio for three different inflow techniques

OBJECTIVE

Two-dimensional (2D) time-of-flight (TOF) MR angiography has been the standard technique for evaluating arteries of the lower extremity. However, this technique is limited by artifacts resulting from vessel pulsation, as well as by relatively poor vessel-to-background contrast. The purpose of this study was to evaluate two cardiac-gated inflow techniques to determine whether they exhibited better contrast and signal performance than the standard technique of 2D TOF MR angiography of the iliac arteries.

SUBJECTS AND METHODS

Fourteen subjects who had no clinical evidence of vascular disease had standard 2D TOF, gated 2D TOF, and gated 2D turbo field-echo MR angiography. Images were evaluated for signal-intensity ratio, signal-to-noise ratio, and contrast-to-noise ratio, in addition to qualitative evaluation.

RESULTS

Turbo field-echo MR angiography exhibited significantly higher signal-intensity, signal-to-noise, and contrast-to-noise ratios than did either gated or standard MR angiography for all vessel segments. We found no significant difference between gated and standard 2D TOF techniques for any vessel segment. Qualitative features of turbo field-echo MR angiography included improved visualization of horizontal vessel segments compared with the standard 2D TOF technique, less effective venous saturation compared with either the gated or standard 2D TOF technique, and increased ghosting artifacts compared with the gated 2D TOF technique.

CONCLUSION

Two-dimensional turbo field-echo MR angiography exhibits improved signal and contrast for evaluation of normal iliac segments compared with standard or gated 2D TOF MR angiography. This technique should replace standard 2D TOF MR angiography for evaluation of the iliac arteries.

Magnetic resonance imaging of pathologic conditions of the Achilles tendon

The advent of magnetic resonance imaging (MRI) has improved imaging of the Achilles tendon. Various pathologic conditions of the Achilles tendon and their MRI characteristics are described. The superior resolution of the tendon provided by MRI can aid in the diagnosis of Achilles tendon disorders, which include complete or partial rupture of the tendon as well as postoperative assessment of tendinous healing, tendinitis and tenosynovitis, and various tumors of the Achilles tendon.

Screening for prostate cancer: is ultrasound the answer?

The high incidence and subsequent mortality from prostate cancer in progressively older US males is a serious health concern. Prognosis is related to extent of spread of the disease at the time of diagnosis and to pathologic grading of the tumor cells. The argument for early detection is somewhat clouded by a high incidence of latent prostate cancer related to increasing age, which may or may not progress to clinical disease. Recent applications of ultrasound technology have greatly improved our ability to image the prostate gland and raised the possibility of using ultrasound to screen for prostate cancer. The conclusions of this investigation are that ultrasound should not yet replace annual digital rectal examination as the primary screening tool, but ultrasound is a useful diagnostic adjunct. This recommendation may change with further application of the technology and as more information is gathered.

Health promotion in an HMO. Ad astra per aspera

The shift in emphasis towards disease prevention and health promotion is forcing changes in the traditional health provider model. At Group Health Cooperative of Puget Sound (GHC), a 349,000 member staff model HMO, consensus development on health promotion issues is the responsibility of a permanent Committee on Prevention (COP). By spreading the workload over multiple subcommittees that involve cross-sections of the medical, nursing, and other professional staff, the COP has prepared the groundwork for a number of major health care decisions at GHC. The COP has also been the starting point for programs such as the GHC Breast Cancer Screening Program, colon cancer screening, a senior influenza immunization program, and an institutional ban on smoking.

Magnetic resonance imaging in a family with hereditary cerebral arteriovenous malformations

Because of a family history of neurologic problems and the documentation of three vascular lesions in one patient, we evaluated 18 members representing three family generations with magnetic resonance imaging. Of these, eight were normal, two had abnormalities probably not related to arteriovenous malformation, one scan was suboptimal, and the remaining eight had evidence of hemorrhagic lesions characteristic of arteriovenous malformation. Four of these patients had multiple lesions, and three patients with lesions had no neurologic symptoms. The findings suggest an autosomal dominant mode of inheritance in this unique case of familial cerebral arteriovenous malformation.

A clinically effective breast cancer screening program can be cost-effective, too

The logistics of complying with current American Cancer Society breast cancer screening recommendations in a large health maintenance organization, serving more than 50,000 women age 40 or older, are described. An alternative screening approach estimated to be at least as health-effective as the American Cancer Society recommendations has been developed and appears to solve the problem and is financially feasible. Cost-effectiveness depends on optimal use of mammography and health-care personnel resources. The authors show how the start-up and maintenance costs of an organized program can be offset by future cost savings resulting from reduced long-term disability in patients diagnosed at Stages 0-1 as opposed to Stages 2 and later. Careful selection of the delivery model before implementation can make a breast cancer screening program cost-effective as well as health-effective.

Intracranial histiocytosis X: a case report

A case of intracranial histiocytosis X that presented radiologically with thickening of the pituitary stalk is presented. The radiologic findings, including a blush seen on angiography, are described.

An improved radioimmunoassay for the anabolic agent hexoestrol, using a monoclonal antibody

A monoclonal antibody was raised against hexoestrol coupled to bovine serum albumin. The antibody cross-reacted with the stilbenes, diethylstilboestrol (10%) and dienoestrol (4%), but had no cross-reaction (less than 0.01%) with other anabolic agents. A radioimmunoassay method using the monoclonal antibody has been validated and used to measure residues of hexoestrol in the urine of treated cattle. The limit of detection was 0.6 pg/ml urine at the 95% confidence limit. The results were compared with those obtained using polyclonal antibodies. Although there was a good correlation between the results, the use of monoclonal antibody gave more reliable results than those obtained with available polyclonal antibodies. The monoclonal antibody, because of its quality and theoretically limitless supply, is very suitable for use in large scale screening or monitoring programmes for regulating the use of hexoestrol.

Interobserver discrepancies in distance measurements from lumbar spine CT scans

Lumbar spine computed tomographic (CT) scans of 10 patients were examined independently at two levels by five experienced radiologists. At each level the minimum midline sagittal diameter was measured, and at each intervertebral space the left foramen was measured for its minimum diameter. Statistically significant differences were found between the measurements of different observers, differences that in a number of cases could have led to disagreement over whether or not stenosis was present. There were reasonably strong correlations between different observers' readings of midline sagittal diameters but generally not of foraminal diameters. Reasons for discrepancies between observers in spine CT measurements are reviewed briefly.

Embolization of medullary carcinoma of the thyroid invading the trachea. Report of a case

A case is presented of medullary thyroid carcinoma causing severe hemoptysis by invading the trachea. After embolization with polyvinyl alcohol there was marked diminution of tumor vascularity. The embolized portions were significantly revascularized two months later, however.

Computed tomography of aqueous humour outflow pathways

The anterior chamber of adult Rhesus monkeys (Macaca mulatta) was perfused with a radio-opaque contrast medium (Amipaque; mol. wt 789 daltons) at controlled intraocular pressure (IOP), and its subsequent distribution examined by computed tomography. In the living monkey no contrast medium was detectable outside the anterior chamber, even after prolonged (8 hr) perfusion. However, if the animal was then killed, and the IOP maintained artificially at its previous level, opacity appeared immediately throughout the anterior segment. Subsequent scans showed the contrast medium to diffuse into the anterior orbital tissues, and to move posteriorward through the globe wall and extraocular muscles. None entered the vitreous body and very little progressed behind the point at which the extraocular muscles exited from Tenon's capsule. Elevation of IOP did not appear to accelerate this posterior diffusion. It is inferred that in vivo contrast medium passing into the posterior, non-conventional aqueous drainage pathway is cleared immediately by the circulating blood in the uvea and possibly also the extraocular muscle. Tenon's capsule may provide a barrier to further intra-orbital diffusion.

Vertical foramina in the lumbosacral region: CT appearance

Several computed tomographic (CT) examples of vertically oriented foramina in the neural arches of the lumbosacral vertebrae are presented. The literature is reviewed briefly, and the possible clinical and embryologic significance of these foramina is discussed.

CT detection of retroperitoneal gas associated with gas in intervertebral disks

Three cases are presented with computed tomographic evidence of gas in retroperitoneal soft tissues in association with the so-called "vacuum phenomenon" (Knutsson sign) in lumbar disks. We review the explanations of Knutsson sign and offer an explanation of how extradiscal gas can occur in association with it.

Preparation and properties of monoclonal antibodies to the anabolic agent zeranol

Monoclonal antibodies have been produced using two haptens, zeranol-7-hemisuccinate coupled to bovine serum albumin and zeranol-16-carboxypropyl ether coupled to human serum albumin. An assessment of cross-reactivity demonstrated that the monoclonal antibody raised against the 7-hemisuccinate derivative reacted with zeranol (100%), talernol (12%), zearalenone (17%), zearalanone (100%) and alpha- and beta-zearalenol (17% and less than 0.01%, respectively). In contrast the antibodies to the 16-carboxypropyl ether derivative reacted only with zeranol (100%) and also with a alpha-zearalenol (13-16%). All monoclonal antibodies were more specific than the polyclonal antibodies raised to the same haptens by conventional methods using sheep.

Association between scrotal circumference, live weight and sperm output in cattle

The relationships between scrotal circumference and live weight and sperm output were examined in 3 samples of bulls selected for use in AI. In Study 1 the linear correlation between live weight and scrotal circumference in 418 British Friesian bulls at about 400 days of age was +0.28, and the circumference of the scrotum was related to the live weight of the bull by +0.179 +/- 0.060 mm/kg live weight. At 400 days of age the mean (+/- s.e.) live weight and scrotal circumference of 22 British Friesian bulls in Study 2 was 412 +/- 7 kg and 332 +/- 4 mm respectively. Rates of growth were 1.11 +/- 0.023 kg/day and 0.426 +/- 0.023 mm/day. The correlation (+0.42) between the size of the scrotum and the no. of spermatozoa/ejaculate was not significant. British Friesian (average age 90 years) and Hereford (average age 6.5 years) bulls were examined in Study 3. For the 25 Herefords, the correlation between the number of usable straws over a 6-month period and the scrotal circumference was +0.43, compared with +0.21 among the 28 British Friesians. It is concluded that scrotal circumference is unlikely to be an accurate predictor of sperm output in AI bulls.

Aicardi's syndrome; radiologic manifestations

Features of Aicardi's syndrome include infantile spasms associated with pathognomonic chorioretinopathy, abnormalities of the corpus callosum with heterotopia of gray matter, and characteristic electroencephalographic findings. Vertebral abnormalities are also part of the syndrome, which is apparently limited to female infants. Subnormal mental development appears in all cases. It was first described in 1969 in French. Isolated cases in the literature have been associated with facial asymmetry, plagiocephaly, and the Dandy-Walker syndrome. Experience with two patients suggests that a search for cases among patients with chorioretinopathy and infantile spasms will show the syndrome to be more common than currently reported.