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Biomedical subjects

J H Allen

Publications and source records attributed to J H Allen.

At least 19 recordsLinked to original sources
PubMed2004

Cannabinoid hyperemesis: cyclical hyperemesis in association with chronic cannabis abuse.

BACKGROUND AND AIMS: To explore the association between chronic cannabis abuse and a cyclical vomiting illness that presented in a series of cases in South Australia. METHODS: Nineteen patients were identified with chronic cannabis abuse and a cyclical vomiting illness. For legal and ethical reasons, all patients were counselled to cease all cannabis abuse. Follow up was provided with serial urine drug screen analysis and regular clinical consultation to chart the clinical course. Of the 19 patients, five refused consent and were lost to follow up and five were excluded on the basis of confounders. The remaining nine cases are presented here and compared with a published case of psychogenic vomiting. RESULTS: In all cases, including the published case, chronic cannabis abuse predated the onset of the cyclical vomiting illness. Cessation of cannabis abuse led to cessation of the cyclical vomiting illness in seven cases. Three cases, including the published case, did not abstain and continued to have recurrent episodes of vomiting. Three cases rechallenged themselves after a period of abstinence and suffered a return to illness. Two of these cases abstained again, and became and remain well. The third case did not and remains ill. A novel finding was that nine of the 10 patients, including the previously published case, displayed an abnormal washing behaviour during episodes of active illness. CONCLUSIONS: We conclude that chronic cannabis abuse was the cause of the cyclical vomiting illness in all cases, including the previously described case of psychogenic vomiting.

Adolescent↗
PubMed2000

A functional cra gene is required for Salmonella enterica serovar typhimurium virulence in BALB/c mice.

A minitransposon mutant of Salmonella enterica serovar Typhimurium SR-11, SR-11 Fad(-), is unable to utilize gluconeogenic substrates as carbon sources and is avirulent and immunogenic when administered perorally to BALB/c mice (M. J. Utley et al., FEMS Microbiol. Lett., 163:129-134, 1998). Here, evidence is presented that the mutation in SR-11 Fad(-) that renders the strain avirulent is in the cra gene, which encodes the Cra protein, a regulator of central carbon metabolism.

Animals↗
PubMed1992

Prediction and evaluation of solar particle events based on precursor information.

Protection from the radiation effects of solar particle events for deep space mission crews requires a warning system to observe solar flares and predict subsequent charged particle fluxes. Such a system relates precursor information observed in each flare to the intensity, delay, and duration of the subsequent Solar Particle Event (SPE) at other locations in the solar system. A warning system of this type is now in operation at the NOAA Space Environment Services Center in Boulder, Colorado for support of space missions. It has been used to predict flare particle fluxes at the earth for flares of Solar Cycle 22. The flare parameters used and the effectiveness of the current warning system, based on Solar Cycle 22 experience, are presented, with an examination of the shortcomings. Needed improvements to the system include more complete observations of solar activity, especially information on the occurrences of solar mass ejections; and consideration of the effects of propagation conditions in the solar corona and interplanetary medium. Requirements for solar observations and forecasting systems on board the spacecraft are discussed.

Astronomical Phenomena↗
PubMed1987

Phenytoin removal during plasma exchange.

Plasma exchange is currently being used to treat a variety of disorders including immune complex and hematologic disorders. It has been shown that the removal of plasma removes drugs bound to plasma proteins. This case documents the removal of phenytoin during plasma exchange therapy. Total and free phenytoin serum concentrations were obtained before and after each exchange. Aliquots were obtained from each pass, and total phenytoin concentrations were determined. The total phenytoin serum concentration increased during the first exchange, while the total concentration decreased as a result of the second exchange. It was determined that approximately 27.7 mg and 30.4 mg of phenytoin were removed by the first and second plasma exchanges, respectively.

Adolescent↗
PubMed1986

Primary glioma: diagnosis with magnetic resonance imaging.

Seventeen patients with surgically documented primary glial-origin brain tumors were evaluated by magnetic resonance imaging and high-resolution computed tomography. The exclusion of CT ring-enhancing lesions directed the focus of this study toward lower grade tumors that were more difficult to diagnose. The computed tomography abnormalities were often subtle and included areas of low attenuation, mass effect, and focal enhancement. Spin-echo sequences with both heavy T1 and T2 weighting were utilized. Prolonged T1 and T2 values were observed in all tumors. The T2-weighted spin-echo 1000/120 sequence was the most sensitive in tumor detection and was positive in all cases. Magnetic resonance imaging was superior to computed tomography in tumor detection, tumor localization, assessment of tumor extent, and determination of associated changes, ie, brain stem encroachment. All the magnetic resonance sequences used showed an increase in severity of imaging changes with increasing tumor grade. The T2-weighted sequence showed progressive margin irregularity, whereas the T1-weighted (inversion recovery) sequence showed increasing severity of internal tissue changes. The superior resolution of these changes by magnetic resonance imaging may have implications for better assessment of tumor grade in the future than is currently possible with computed tomography.

Adolescent↗
PubMed1984

Magnetic resonance imaging of multiple sclerosis: a study of pulse-technique efficacy.

Forty-two patients with the clinical diagnosis of multiple sclerosis were examined by proton magnetic resonance imaging (MRI) at 0.5 T. An extensive protocol was used to facilitate a comparison of the efficacy of different pulse techniques. Results were also compared in 39 cases with high-resolution x-ray computed tomography (CT). MRI revealed characteristic abnormalities in each case, whereas CT was positive in only 15 of 33 patients. Milder grades 1 and 2 disease were usually undetected by CT, and in all cases, the abnormalities noted on MRI were much more extensive than on CT. Cerebral abnormalities were best shown with the T2-weighted spin-echo sequence (TE/TR = 120/1000); brainstem lesions were best defined on the inversion-recovery sequence (TE/TI/TR = 30/400/1250). Increasing TE to 120 msec and TR to 2000 msec heightened the contrast between normal and abnormal white matter. However, the signal intensity of cerebrospinal fluid with this pulse technique obscured some abnormalities.

Adult↗
PubMed1983

Intervertebral disk-space infection: CT changes. Work in progress.

Seven patients who had spinal interspace infections underwent clinical, laboratory, and radiographic examinations, and findings are reported. Lytic fragmentation of adjacent vertebral bodies is a characteristic appearance on CT scans. Sagittal-coronal reformations confirm the end-plate irregularity and establish the diagnosis. Since the changes of diskitis are delayed and often obscured by accompanying degenerative disease on plain radiographs, CT appears to offer a diagnostic modality that shortens the usual delay from onset of symptoms to diagnosis.

Adult↗
PubMed1983

Limited value of CT brain scans in the staging of small cell lung cancer.

Computed tomography of the brain was performed as part of the initial staging evaluation of 84 patients with small cell lung cancer. Brain scans indicative of metastatic disease were obtained in 12 (14%) patients, two of whom had no neurologic signs or symptoms. One of these had no other extrathoracic disease. Brain scans without evidence of metastatic disease were obtained in 72 patients, 58 (80.5%) of whom had no signs or symptoms suggestive of metastatic intracranial disease. In the 14 patients with neurologic symptoms but negative computed tomographic scans, other explanations than brain metastases were found. It was concluded that head scanning is a sensitive and accurate method of detecting central nervous system metastases in patients with small cell lung cancer. However, head computed tomography should not be included as part of the initial staging evaluation of the neurologically asymptomatic patients. In only one of 60 such patients did the brain scan change the initial clinical staging, which included chest films, liver and bone scans, and bone marrow biopsy.

Adult↗
PubMed1982

Computed tomography in the diagnosis of congenital cytomegalic inclusion disease.

We present two cases of congenital CID, one in a 4-month-old male infant and the other in a 6-week-old male infant. The diagnoses were confirmed by means of computed tomography, cultures, and serologic methods. The relatively noninvasive character of CT makes it an ideal diagnostic method in the neonate. With the improved visualization afforded by CT, specificity on radiographic grounds alone may become possible.

Calcinosis↗
PubMed1981

The role of sonography and the radiologist-ultrasonologist in the detection and follow-up of intracranial hemorrhage in the preterm neonate.

Intracranial hemorrhage (ICH), specifically hemorrhage in the subependymal germinal matrix, is a common disorder affecting preterm neonates. The authors discuss the relative virtues and limitations of portable, real-time ultrasonography (US) and computed tomography (CT) in detection and follow-up of sequelae of this disorder. The importance of cooperative effort on the part of the radiologist-ultrasonologist, neonatologist, pediatric neurologist, neurosurgeon and ultrasound technologist is emphasized.

Cerebral Hemorrhage↗
PubMed1980

Macrocephaly with head growth parallel to normal growth pattern: neurological, developmental, and computerized tomography findings in full-term infants.

Fifteen infants with macrocephaly had a head growth pattern parallel to 2 SDs above normal. In eight patients with initial and subsequent normal findings on neurological and developmental examinations, computerized tomography (CT) showed slight ventricular dilation and increased width of the subarachnoid space anteriorly. The other seven patients had abnormal results from neurological or developmental examinations. The CT findings in two were similar to those in the first group; in four, other abnormalities were observed; and one had a normal scan. None of the 15 infants required shunting. In infants with this head growth pattern, a similar CT scan with ventricular dilation and widened subarachnoid space could be found in patients with normal or abnormal results from neurological and developmental examinations. Those infants with this CT scan pattern and normal neurological and developmental findings appear to have a benign condition.

Cephalometry↗
PubMed1980

Cerebellar degeneration due to chronic phenytoin therapy.

Five patients developed cerebellar degeneration while being treated with phenytoin. All had high plasma levels of the drug, and none was having seizures of a type that could have caused systemic hypoxia at the time the cerebellar syndrome appeared. Cerebellar degeneration was confirmed by the finding of atrophy on CT scan and by persistence of cerebellar signs when plasma phenytoin levels were decreased. We suggest that chronic phenytoin therapy can cause cerebellar degeneration. The question of whether phenytoin or the cumulative effect of hypoxia from repeated convulsions causes cerebellar degeneration should not be posed as one of exclusive alternatives, since hypoxia is a well-known cause of cerebellar atrophy. Instead, the question should be whether or not phenytoin can also be responsible. The cases reported here suggest that it can.

Adult↗
PubMed1980

Diagnostic imaging in pediatric emergencies.

Evaluation of pediatric emergencies by diagnostic imaging technics can involve both invasive and noninvasive procedures. Nuclear medicine, conventional radiography, ultrasound, computerized axial tomography, and xeroradiography are the major nonangiographic diagnostic technics available for patient evaluation. Appropriate decisions regarding choice of these imagining technics can be made only if the advantages and limitations of each are known. We will emphasize the use of computerized axial tomography, nuclear medicine, xeroradiography, and ultrsound in the evaluation of emergencies in the pediatric age group. Basic principles with specific reference to clinical disorders will be presented. Since the radiologist is the primary consultant with regard to diagnostic imaging, his knowledge of these modalities can greatly influence patient care and clinical results.

Abdomen↗