Biomedical subjects

A L Williams

Publications and source records attributed to A L Williams.

At least 73 records · Page 4Linked to original sources

PubMed1986

Development and testing of scoring systems for predicting infants with high-risk of sudden infant death syndrome in Melbourne.

Epidemiological surveys undertaken in Melbourne during the past 8 years have provided data on which a birth scoring system for infants at high-risk for sudden infant death has been derived. This scoring system was developed after testing scoring systems developed in Sheffield, UK, on Melbourne data and then extending these systems. Prospective trials carried out on a preliminary version of the extended system showed that it is effective in identifying infants at high-risk. The final version of the birth scoring system is capable of identifying a group of future live births which will have a risk of about one in 55 of sudden and unexpected death. The system is also capable of identifying infants with relatively low-risk.

Australia↗

PubMed1985

Control of isoleucine-valine biosynthesis in a valine-resistant mutant of Escherichia coli K-12 that simultaneously acquired azaleucine-resistance.

A mutant of Escherichia coli K-12 isolated as being growth resistant to L-valine (Valr) was shown also to exhibit growth resistance to 4-azaleucine (Azlr). Transductional analysis indicated that Azlr is cotransduced with Valr at a frequency of 100% and both are linked to leu, ara, and carA. This mutation conferring valine and azaleucine growth resistance resulted in increased levels of isoleucine and valine biosynthetic enzymes as well as those of valyl- and isoleucyl-tRNA synthetases during growth in minimal and enriched media. Acquisition of Vals/Azls results in the restoration of normal regulation of both classes of ilv enzymes and normal patterns of the tRNA Ile species. The overall regulatory patterns observed for individual isoleucine and valine gene products suggest differential participation of isoleucine and valine and/or isoleucyl- and valyl-tRNA's in control of expression of the respective structural genes.

Acetolactate Synthase↗

PubMed1985

Illness associated with contamination of drinking water supplies with phenol.

In January 1984 the River Dee in north Wales was contaminated with phenol, with subsequent contamination of the tap water received by about two million consumers. A retrospective postal survey of 594 households was undertaken to determine whether consumption of this contaminated water was associated with illness. Subjects in areas that received contaminated water reported significantly more gastrointestinal illness than those in a nearby unexposed area (32.6% v 8.7%, p less than 0.00001) as well as reporting a higher incidence of any symptoms (43.6% v 18.4%, p less than 0.00001). Symptoms were consistent with phenol poisoning and bore a strong temporal relation to the pollution of the supply, but they developed at concentrations of phenols previously considered to be safe by the water authorities concerned. Chlorophenols produced during the treatment of water may have aggravated the problem.

Disease Outbreaks↗

PubMed1985

Evidence for cAMP-mediated control of isoleucyl-tRNA synthetase formation in Escherichia coli K-12.

The ability of cAMP to inhibit isoleucyl-tRNA synthetase (IRS) formation has been demonstrated in wild type K-12 Escherichia coli and two adenyl-cyclase (cya) mutants. cAMP appeared not to have any effect on either the valyl- or arginyl-tRNA synthetase (VRS and ARS respectively). Addition of cAMP led to a reduction in rate of IRS synthesis but not VRS or ARS. Furthermore, derepression of IRS and VRS by isoleucine limitation was completely prevented by cAMP.

Amino Acyl-tRNA Synthetases↗

PubMed1985

Quantification of contrast in clinical MR brain imaging at high magnetic field.

The relative contrast between two tissues in a magnetic resonance (MR) image is shown to be quantifiable for any combination of pulse timing parameters, provided the intrinsic parameters are known. Based on multiple inversion-recovery and spin echo images, a region-of-interest T1, T2 and density analysis was conducted at 1.4T in selected patients with diagnosed neuropathology for various brain tissues. The resulting tissue parameters subsequently served to calculate the contrast-to-noise (C/N) ratio for typical tissue interfaces as a function of the operator-variable pulse timing parameters and the data were compared with the images. Although such calculations may be useful as a protocol selection aid, it is obvious that an optimized pulse protocol can only be established for a single tissue interface. The data also reveal that a T2-discriminating pulse sequence like Carr-Purcell-Meiboom-Gill with long repetition time, generally advocated as clinically most effective, may not always be ideal.

Brain Diseases↗

PubMed1985

The cervical neural foramina: correlation of microtomy and CT anatomy.

The CT appearance of the cervical neural foramina and contents is described in detail. Nineteen cervical spine specimens were studied with CT and corresponding cryomicrotomy in direct axial, sagittal, coronal, and oblique planes. Both ventral and dorsal nerve roots can be identified in the foramen's lower portion at or below the disk level. The dorsal nerve roots and ganglion contact the superior facet. The ventral nerve roots contact the uncinate process and bottom of the neural foramen. The ventral nerve roots, dorsal nerve roots and ganglion, and vertebral artery are resolved with current high-resolution CT.

Cadaver↗

PubMed1985

Intracranial calcification in the infant and neonate: evaluation by sonography and CT.

This study reports the sonographic and computed tomography (CT) findings in seven infants and neonates with intracranial calcifications and a spectrum of underlying disorders, including toxoplasmosis, cytomegalic inclusion disease, transverse/straight sinus thrombosis, and probable anoxia. Neurotropic infectious disease usually produced clumped or subependymal calcifications accompanied by sometimes bizarre ventricular configurations and prominent periventricular cystic encephalomalacia. Sonography failed to identify prospectively intracranial calcifications in two of the three patients without infection, although calcifications were visible in retrospect. Overall, CT provided optimum visualization of intracranial calcifications.

Brain Diseases↗

PubMed1985

Magnetic resonance imaging of the cavernous sinus.

The magnetic resonance (MR) appearance of the cavernous sinus was studied by correlating the MR images of normal volunteers and cryomicrotomic sections from six cadavers. In addition, MR images of patients with parasellar masses were compared with corresponding intravenously enhanced computed tomographic (CT) scans. The MR appearance of the cranial nerves in the cavernous sinuses is demonstrated, as well as MR signs of a parasellar mass, including obliteration of intracavernous venous spaces, displacement of the intracavernous internal carotid artery, and bulging of the lateral wall of the cavernous sinus. MR proved to be more effective than CT in delineating the parts of the cavernous sinus.

Aneurysm↗

PubMed1985

Orbital apex: correlative anatomic and CT study.

A detailed analysis of the coronal anatomic and CT appearances of the orbital apex is presented. In cadavers, coronal CT 9800 scans of the orbital apex and precisely corresponding cryomicrotomic sections were obtained. The CT appearance of the optic nerve, anulus of Zinn, and cranial nerves III-VI at the superior orbital fissure and orbital apex were determined. These anatomic structures were also demonstrated in clinical CT studies. Practical applications of the anatomic landmarks in evaluating orbital apex tumors are illustrated.

Cadaver↗

PubMed1984

Respiratory viruses and sudden infant death.

Viruses were shown to be present in the respiratory tract in 200 of 763 cases of the sudden infant death syndrome studied in the nine years 1974-82. Epidemiological and pathological evidence suggested that the distribution of viruses in the sudden infant death syndrome differs between infants aged 3 months or less and those aged over 3 months: the incidence of detection of virus was 14% in the younger group compared with 39% in the older group. The distribution of the viruses in these two groups was compared with that in 1341 live infants with respiratory virus infections. Adenovirus, influenza virus, parainfluenza virus, and rhinovirus had similar distribution among the victims of the sudden infant death syndrome and live controls. The incidence of detection of respiratory syncytial virus was increased in the older infants dying of the sudden infant death syndrome (90% of the cases detected) compared with the older group of live infants (53%). Antibody studies, detection of virus, and epidemiological data suggest that respiratory syncytial virus may be a precipitating factor of sudden death in older infants.

Age Factors↗

PubMed1984

Magnetic resonance imaging of the internal auditory canal.

Three patients with exclusively or predominantly intracanalicular neuromas and 5 with presumably normal internal auditory canals were examined with prototype 1.4- or 1.5-tesla magnetic resonance (MR) scanners. MR images showed the 7th and 8th cranial nerves in the internal auditory canal. The intracanalicular neuromas had larger diameter and slightly greater signal strength than the nerves. Early results suggest that minimal enlargement of the nerves can be detected even in the internal auditory canal.

Facial Nerve↗

PubMed1984

Cervical radiculopathy: computed tomography and myelography compared.

The accuracy of CT in the determination of cervical disk herniation has not been measured as it has in the determination of lumbar disk disease. Cervical myelograms and CT scans of patients with cervical radiculopathy secondary to disk herniation or spondylosis, which was verified by clinical examination, surgery, and in most cases EMG, were evaluated blindly and independently, results were analyzed statistically, and receiver operating characteristic (ROC) curves were calculated. CT without or with the use of intrathecal metrizamide was more accurate than myelography in the identification of lesions that caused cervical radiculopathy. In some patients, CT obviates the need for cervical myelography. With improvement in CT techniques and more experience in interpreting the images, CT will be increasingly important in the evaluation of cervical radiculopathy.

Cervical Vertebrae↗

PubMed1984

The normal conus medullaris: CT criteria for recognition.

The normal CT configuration and dimension of the conus medullaris and adjacent spinal cord were determined in 30 patients who had no clinical evidence of conus compression. CT studies were also correlated with anatomic sections in cadavers. The normal conus on CT has a distinctive oval configuration, an anterior sulcus, and a posterior promontory. The anteroposterior diameter ranged from 5 to 8 mm; the transverse diameter from 8 to 11 mm. Intramedullary processes altered both the dimensions and configuration of the conus.

Astrocytoma↗

PubMed1984

Magnetic resonance imaging of the optic nerves and chiasm.

Magnetic resonance imaging (MR) of the optic nerves and chiasm was compared with computed tomography (CT) in 4 healthy volunteers, 4 patients without orbital or chiasmal abnormalities, and 4 patients with tumor (anterior clinoid meningioma in 2, optic nerve glioma in 1, and optic nerve sheath meningioma in 1). MR was found to be effective in demonstrating the optic nerves and related structures, particularly the intracanalicular portion of the nerve which is difficult to see with CT. Best results were achieved with partial saturation recovery (SR) images; inversion recovery (IR) and spin echo (SE) techniques were less successful because of decreased spatial resolution (in the case of SE) as well as difficulty in seeing the anterior clinoid processes. As axial views cannot always distinguish the ethmoid sinus tissue from the optic nerve, it may be necessary to employ both axial and coronal images.

Adult↗

PubMed1984

Syringomyelia and hydromyelia: magnetic resonance evaluation.

Magnetic resonance (MR) imaging of 13 proved cases of syringomyelia or hydromyelia and one case of myelomalacia is described. Most intramedullary cysts were evident on sagittal partial saturation recovery (PSR) images. One cyst containing viscous fluid was not demonstrated on PSR images, but was suggested on a sagittal spin echo image. The case of myelomalacia was indistinguishable from a syrinx on axial PSR and spin echo images. Not all cases of syringomyelia and hydromyelia had the typical MR appearance previously described in the literature. Atypical cysts, spinal cord degeneration, and tumors may have a similar appearance on MR.

Cysts↗

PubMed1984

Jugular foramen: anatomic and computed tomographic study.

The computed tomographic (CT) appearance of the jugular foramen was examined in detail, and anatomic and CT sections were correlated. The pars nervosa and pars vascularis were identified, and, with intravenous contrast enhancement, a rapid sequence of scans at a gantry angle of +30 degrees to the canthomeatal line demonstrated cranial nerves IX, X, and XI. The osseous margins of the jugular foramen were best shown by CT at planes of sections parallel and positive (0 degrees - 30 degrees) of the canthomeatal line. CT can be used to evaluate osseous anatomy and the jugular foramen with precision sufficient to confidently exclude an intracanalicular mass.

Cadaver↗

PubMed1984

Current concepts in evaluation of the lumbar facet joints.

The lumbar facet joints have been recognized for many years to be an important source of chronic low back pain with sciatic radiation. The presence of unilateral chronic low back pain with sciatic radiation, but without objective neurological abnormality, is typical of symptomatic lumbar facet arthropathy. Computed tomography is much better able to demonstrate significant lumbar facet joint abnormalities than conventional radiographic examination. Computed tomographic findings in the lumbar facet joints appear to correlate better with clinical relief following intraarticular lumbar facet block than do findings on conventional studies. The combination of computed tomography and fluoroscopically controlled intraarticular lumbar facet block is becoming an important examination sequence in the accurate diagnosis of symptomatic lumbar facet arthropathy. The development of concepts regarding lumbar facet joint abnormalities are reviewed, and implications of the development of new procedures for studying lumbar facet disease in the patient with chronic low back pain and sciatica are discussed.

Arthrography↗

PubMed1983

Molecular characterization of ilvC specialized transducing phages of Escherichia coli K-12.

A series of lambda defective ilvC specialized transducing phage has been isolated which carry regions of isoleucine and valine structural and regulatory genes derived from the ilv cluster at minute 83 on the linkage map of the chromosome of Escherichia coli K-12. The ilv genes carried by these phages and their order have been determined by transduction of auxotrophs. The ilvC+ lysogen of an ilvC- strain gave rise, after heat induction of the lysogen, to transducing particles which carried the wild-type allele of the cya-marker. Further experiments have shown that the lambda defective ilvC phages were able to cotransduce a rho-15ts mutation as well as a rep-5 mutation. Hence, the order of the clockwise excision of the ilv cluster was found to be ilvC-rho-rep-cya. Enzyme levels in strains carrying the lambda defective ilvC phages indicated the the ilvC gene was not altered by the insertion of lambda into the ilv cluster. The isolation and digestion of lambda defective ilvC DNA by EcoRI and HindIII restriction endonucleases demonstrated that the specialized transducing phages carried part of the genome from the E. coli K-12 chromosome.

Adenylyl Cyclases↗