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Biomedical subjects

D E Jackson

Publications and source records attributed to D E Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1989

Highly conformationally constrained halogenated 6-spiroepoxypenicillins as probes for the bioactive side-chain conformation of benzylpenicillin.

The halogenated 6-spiroepoxypenicillins are a series of novel semisynthetic beta-lactam compounds with highly conformationally restricted side chains incorporating an epoxide. Their biological activity profiles depend crucially on the configuration at position C-3 of that epoxide. In derivatives with aromatic-containing side chains, e.g., anilide, the 3R-compounds possess notable Gram-positive antibacterial activity and potent beta-lactamase inhibitory properties. The comparable 3S-compounds are antibacterially inactive, but retain beta-lactamase inhibitory activity. Using the molecular simulation programs COSMIC and ASTRAL, we attempted to map a putative, lipophilic accessory binding site on the PBPs that must interact with the side-chain aromatic residue. Comparative computer-assisted modelling of the 3R-, and 3S-anilides, along with benzylpenicillin, indicated that the available conformational space at room temperature for the side chains of the 3R- and the 3S-anilides was mutually exclusive. The conformational space for the more flexible benzylpenicillin could accommodate the side chains of both the constrained penicillin derivatives. By a combination of van der Waals surface calculations and a pharmacophoric distance approach, closely coincident conformers of the 3R-anilide and benzylpenicillin were identified. These conformers must be related to the antibacterial, 'bioactive' conformer for the classical beta-lactam antibiotics. From these proposed bioactive conformations, a model for the binding of benzylpenicillin to the PBPs relating the three-dimensional arrangement of a putative lipophilic S2-subsite, specific for the side-chain aromatic moiety, and the 3 alpha-carboxylate functionality is presented.

Epoxy Compounds↗
PubMed1989

Intraspinal synovial cysts: MR imaging.

Juxtaarticular intraspinal synovial cysts are unusual lesions of the spine associated with facet arthropathy. These lesions can cause radicular symptoms and may masquerade clinically as other, more common entities. Synovial cysts have been detected at myelography and have been well characterized at computed tomography as posterolateral epidural masses, typically at L4-5. Six synovial cysts of the lumbar spine were demonstrated on magnetic resonance (MR) images. The signal-intensity patterns of these lesions are variable. MR imaging can be used to document the presence of hemorrhage within the cyst, which may relate to the exacerbation of symptoms. Air-filled synovial cysts may be difficult to detect and distinguish from facet arthropathy.

Adult↗
PubMed1989

Band heterotopias: a newly recognized neuronal migration anomaly.

Five patients with a continuous band of heterotopic neurons between the lateral ventricles and the cerebral cortex are described. All patients presented with intractable seizures and moderate-to-severe developmental delay. The identification of this anomaly is difficult because of its symmetry and the minimal abnormality of the gyral pattern of the cortex. The possible embryogenesis of the anomaly is discussed. The identification of these band heterotopias is important because of the intractable nature of the seizure disorder and the poor prognosis for the patient.

Brain Neoplasms↗
PubMed1989

Cerebral Erdheim-Chester disease: persistent enhancement with Gd-DTPA on MR images.

A case of Erdheim-Chester disease with intracerebral masses containing characteristic lipid-laden histiocytes is presented. These unusual lesions remained enhanced on magnetic resonance images obtained 8 days after injection of gadolinium diethylenetriaminepentaacetic acid (DTPA) dimeglumine. Chemical analysis of a biopsy specimen revealed a high concentration of gadolinium. Findings suggest that the Gd-DTPA complex or possibly a gadolinium-containing metabolite may be retained for extended periods in this unusual type of histiocytic lesion.

Brain↗
PubMed1988

EnvZ functions through OmpR to control porin gene expression in Escherichia coli K-12.

The regulatory proteins OmpR and EnvZ are both required to activate expression of the genes for the major outer membrane porin proteins, OmpF and OmpC, of Escherichia coli K-12. Here we show that OmpR, under certain conditions, could activate porin expression in the complete absence of EnvZ. In addition, the pleiotropic phenotypes conferred by a particular envZ mutation (envZ473) required the presence of functional OmpR protein. These results lead us to conclude that EnvZ and OmpR act in sequential fashion to activate porin gene expression; i.e., EnvZ modifies or in some way directs OmpR, which in turn acts at the appropriate porin gene promoter.

Bacterial Outer Membrane Proteins↗
PubMed1988

Normal maturation of the neonatal and infant brain: MR imaging at 1.5 T.

The pattern of normal white-matter maturation as demonstrated with high-field-strength magnetic resonance (MR) imaging was investigated. Eighty-two neurologically normal infants were examined with a 1.5-T unit with use of spin-echo T1-weighted and T2-weighted pulse sequences. The infants ranged in age from 4 days to 2 years. The images were assessed for qualitative changes of white matter relative to gray matter in 14 anatomic areas of the brain and correlated with the patient's age. The MR images showed that changes of brain maturation occur in an orderly manner, commencing in the brain stem and progressing to the cerebellum and the cerebrum. Changes caused by brain myelination were seen earlier on T1-weighted images than on T2-weighted images, possibly because of T1 shortening by the components of the developing myelin sheaths. The later changes on the T2-weighted images correlated best with the development of myelination as demonstrated with histochemical methods. T1-weighted images were most useful in the monitoring of normal brain development in the first 6-8 months of life; T2-weighted images were more useful after 6 months. The milestones in the MR appearance of normal maturation of the brain are presented. Persistent areas of long T2 relaxation times are seen superior and dorsal to the ventricular trigone in all infants examined and should not be mistaken for ischemic change.

Brain↗
PubMed1988

A comparison of patients in private and public psychiatric facilities.

OBJECTIVE: To compare hospitalised patients in private and public facilities. METHOD: Retrospective medical record review of 100 patients admitted consecutively to both a private psychiatric hospital and a public facility in South Australia in January, 1985. RESULTS: There is a paucity of data about privately treated patients with psychiatric illness. Although several studies have suggested that patients treated in private are similar to those seen at public facilities, thus challenging some of the myths about private practice, a recent Australian study emphasised the differences between private and publicly treated hospitalised patients. The present comparison of hospitalised patients in private and public hospitals, whilst demonstrating some differences, was more marked by the similarities in clinical features. The relevance of the different results, the manner in which they may be interpreted, and the implications for administrative decisions which may affect patients with psychiatric illness are discussed.

Adult↗
PubMed1986

Hemobilia. An unusual cause of segmental bile duct obstruction.

Hemobilia is reported as an unusual cause of segmental bile duct obstruction. The finding of focal "hot spots" caused by delayed washout of the tracer from the obstructed segments is discussed. Whenever the clinical triad of pain, intermittent jaundice, and gastrointestinal bleeding is associated with the above findings, the diagnosis of hemobilia should be entertained.

Adult↗
PubMed1986

A simplified method for the routine determination of effective renal plasma flow.

Quantitative renal data (i.e., glomerular filtration rate or effective renal plasma flow) often would be useful ancillary information when radionuclide renography is carried out. The added time, and therefore cost, of obtaining quantitative information might be the main reason a department does not routinely perform a quantitative study, although there is no added radiation or risk to the patient. To simplify the procedure for determining effective renal plasma flow with I-123 orthoiodohippurate (OIH), the published methodology was modified to eliminate the repetitive preparation of a standard solution. This allows the routine incision of effective renal plasma flow (ERPF) determination in I-123 OIH renography with minimal impact on departmental operations.

Humans↗
PubMed1986

Staging of non-small cell bronchogenic carcinoma. Relationship of the clinical evaluation to organ scans.

Organ scans are generally performed on patients with bronchogenic carcinoma only when clinical evaluation is suspicious for metastases. However, it is not clear whether the clinical abnormalities will direct attention to the single organ which should be scanned, or if all three organs (bone, brain, liver) should be evaluated if any clinical abnormality is present. We investigated the use of triple organ radionuclide scanning and computerized tomography (CT) of the brain in the initial staging of patients with non-small cell bronchogenic carcinoma with no obvious metastases. Of 122 patients with newly diagnosed lung cancer, 53 met our criteria for further study. Thirty-three (62 percent) of these had at least one clinical abnormality suggestive of metastasis. Bone scanning detected metastases in seven (21 percent) and head CT in two additional patients (6 percent). Brain and liver scanning had no yield. In only five of these nine patients did the clinical abnormality direct attention to the organ with detectable metastases. Twenty of the 53 (38 percent) patients had a negative routine clinical evaluation, yet bone scanning showed metastases in three (15 percent). We concluded that clinical abnormalities are not specific for the organ in which metastases may be detected, so three scans (bone, liver, CT of the brain) should be obtained if there is any suspicion of metastasis based on history, physical examination, and laboratory tests. The value of bone scanning in clinically normal patients deserves further study.

Adult↗
PubMed1986

Hemobilia associated with hepatic artery aneurysms: scintigraphic detection with technetium-99m-labeled red blood cells.

Biliary tract bleeding is an unusual cause of upper gastrointestinal hemorrhage. Rupture of hepatic artery aneurysms is one of the least common etiologies of hemobilia. Both cholescintigraphy and [99mTc]red blood cell scintigraphy are useful in the diagnosis of this rare disorder. The combination of focal obstruction on cholescintigraphy and intermittent visualization of the major bile ducts on red blood cell scintigraphy should suggest the diagnosis of hemobilia and prompt an angiogram to determine the cause.

Adult↗