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Biomedical subjects

G W Tyson

Publications and source records attributed to G W Tyson.

At least 19 recordsLinked to original sources
PubMed2001

Investigation of candidate division TM7, a recently recognized major lineage of the domain Bacteria with no known pure-culture representatives.

A molecular approach was used to investigate a recently described candidate division of the domain Bacteria, TM7, currently known only from environmental 16S ribosomal DNA sequence data. A number of TM7-specific primers and probes were designed and evaluated. Fluorescence in situ hybridization (FISH) of a laboratory scale bioreactor using two independent TM7-specific probes revealed a conspicuous sheathed-filament morphotype, fortuitously enriched in the reactor. Morphologically, the filament matched the description of the Eikelboom morphotype 0041-0675 widely associated with bulking problems in activated-sludge wastewater treatment systems. Transmission electron microscopy of the bioreactor sludge demonstrated that the sheathed-filament morphotype had a typical gram-positive cell envelope ultrastructure. Therefore, TM7 is only the third bacterial lineage recognized to have gram-positive representatives. TM7-specific FISH analysis of two full-scale wastewater treatment plant sludges, including the one used to seed the laboratory scale reactor, indicated the presence of a number of morphotypes, including sheathed filaments. TM7-specific PCR clone libraries prepared from the two full-scale sludges yielded 23 novel TM7 sequences. Three subdivisions could be defined based on these data and publicly available sequences. Environmental sequence data and TM7-specific FISH analysis indicate that members of the TM7 division are present in a variety of terrestrial, aquatic, and clinical habitats. A highly atypical base substitution (Escherichia coli position 912; C to U) for bacterial 16S rRNAs was present in almost all TM7 sequences, suggesting that TM7 bacteria, like Archaea, may be streptomycin resistant at the ribosome level.

Bioreactors↗
PubMed1984

Focal cerebral ischemia in the rat: topography of hemodynamic and histopathological changes.

We studied local cerebral blood flow, as measured by autoradiography with digital image processing and by tissue morphology, in six rats 4 hours after occlusion of the proximal middle cerebral artery. A consistent, three-dimensional pattern of graded reductions in local cerebral blood flow involved the affected hemisphere, with a densely ischemic zone (local cerebral blood flow less than 3 ml/100 gm/min) in the dorsolateral caudate putamen and the adjacent frontoparietal cortex. In the frontoparietal cortex, the normal laminar pattern of local cerebral blood flow was disrupted, and there was a transcortical gradient in flow, with pronounced ischemia in deeper layers and relatively preserved superficial flow. Comparisons of autoradiographic findings with histopathological abnormalities in adjacent frozen sections showed that the region of ischemic damage corresponded closely with the area of greatest reduction in blood flow. Although around this region local cerebral blood flow increased centrifugally, a striking finding was that flow density changed abruptly (a tenfold variation in flow within a 1 to 2 mm interval) at the edge of the pathological lesion. Penumbral conditions may therefore exist in only a very narrow zone 4 hours after onset of focal ischemia. After occlusion of a major cerebral artery, the pattern of local cerebral blood flow changes appears to depend on interactions among vascular architecture, reductions in perfusion pressure, alterations in metabolic demands, and variations in local vascular resistance.

Animals↗
PubMed1984

Contiguous scalp, skull, and epidural Hodgkin's disease.

A patient with Hodgkin's disease of the nodular sclerosing subtype presented with recurrent disease at the site of a previous blunt trauma to the head. The tumor involved the scalp and subjacent skull and epidural space. This particular presentation of Hodgkin's disease is probably unique, and involvement of the skull and cranial cavity by this subtype of Hodgkin's disease is rare.

Adult↗
PubMed1984

Sudden death in a child with an occult hindbrain malformation.

Chiari type I malformation in previously asymptomatic children can contribute to sudden death. We report a case of a 3-year-old child with this syndrome who died 48 hours after an apparently mild head injury. The case illustrates that, in children with abnormal head size or shape, it may be important to obtain skull films after even minimal craniocerebral trauma.

Arnold-Chiari Malformation↗
PubMed1983

Unilateral subdural hematoma without midline shift.

Two cases of radiographically isodense subdural hematoma are presented in which absence of displacement of midline cerebral structures was due not to bilateral lesions, but rather to "balancing" of the volumetric effect of a unilateral lesion by preexisting encephalomalacia. Attention to the past medical history and the computed tomography scan which showed evidence of unilateral loss of brain substance led to the proper diagnosis.

Adult↗
PubMed1982

Cerebrovascular permeability following MCA occlusion in the rat. The effect of halothane-induced hypotension.

A quantitative autoradiographic technique that utilizes carbon-14-aminoisobutyric acid (14C-AIB) as a tracer was used to study alterations in cerebral microvascular permeability in 15 rats. Five were "sham-operated" controls and 10 underwent microsurgical, unilateral occlusion of the proximal middle cerebral artery (MCA). Histological changes indicative of focal cerebral ischemia were observed in only the latter 10 animals. These changes were confined to tissue normally perfused by the occluded MCA. After MCA occlusion, five animals were also subjected to transient halothane-induced hypotension (mean arterial blood pressure 50 mm Hg) for 20 to 30 minutes. Only in these five animals were blood-to-brain transfer constants (ki) significantly increased (by approximately 100%) at 4 hours after MCA occlusion. The topographical distribution of this alteration in cerebral microvascular permeability corresponded closely with the histological changes. Neither proximal MCA occlusion nor halothane-induced hypotension alone was associated with any focal or diffuse increase in ki after 4 hours.

Aminoisobutyric Acids↗
PubMed1981

Emergency management of head injuries.

Sophisticated care of the head injury patient in the emergency department does not demand sophisticated knowledge of neurosurgery. Instead it depends upon: (1) Meticulous attention to the fundamental principles of resuscitation; (B) Prevention of secondary cardiopulmonary abnormalities which can further injure the traumatized brain; (C) Performance of serial neurologic examinations. (In the case of acute head injury, a simple neurologic examination performed repeatedly usually provides the physician with more useful information than a more elaborate examination performed only once). (D) Consultation with the neurosurgeon. If there is any possibility that neurosurgical consultation might enhance the emergency department management of the patient, one should not hesitate to contact him. There is no question that protocols for any phase of emergency management of central nervous system (CNA) trauma are of no values unless there is a high degree of compliance. This can only be achieved through persons dedicated to training emergency medical technicians, nurses and physicians in the optimal care that can be afforded these patients. If advances are to be made in decreasing the morbidity and mortality of the CNS trauma patient, those actively involved in emergency medicine are going to have to take an active role in training programs, seminars and clinical practice for physicians, emergency department nurses, and emergency medical technicians.

Coma↗
PubMed1980

Intraventricular extension of a ruptured basilar artery aneurysm.

Penetration of the floor of the third ventricle by a saccular basilar bifurcation aneurysm accounted for a primary intraventricular hemorrhage in a 75-year-old women. This unusual relationship between the aneurysm and the third ventricle was clearly demonstrated by a computed tomographic (CT) scan only after the interface between the aneurysm and the ventricle was projected in a plane parallel to the ventricular floor. The CT scan interpretation was corroborated by an autopsy study. The principle of varying the plane of projection in order to obtain optimum delineation of the relationships of an aneurysm is well established in angiography, but has not previously been reported in the study of aneurysms by CT scan.

Aged↗
PubMed1979

Spinal epidural abscess presenting as acute abdomen in a child.

Spinal epidural abscess is seldom encountered in children and rarely occurs in the absence of spinal pain. A case is described in which a child with a thoracic epidural abscess presented with abdominal rather than spinal pain. Thoracolumbar radicular inflammation and visceroparietal reflexes initiated by a s'spinal ileus' probably produced the symptoms and signs of acute intra-abdominal disease. Consideration of intraspinal disease is advisable in all cases of acute abdomen which exhibit atypical features.

Abdomen, Acute↗
PubMed1979

Citrobacter freundii meningitis in an adult.

We have described the first case of an adult patient with Citrobacter freundii meningitis, which was successfully treated without administration of intrathecal aminoglycoside.

Adult↗
PubMed1979

Primary cerebellar nocardiosis. Report of two cases.

The authors describe two cases of primary cerebellar nocardiosis. Confinement of Nocardia abscesses to a localized, accessible portion of the central nervous system should favor surgical cure of this aggressive and often fatal disease. In our two cases multilocularity, tenuous encapsulation, and proximity to the brain stem prevented complete primary excision. Nevertheless, the infections were effectively treated by intensive postoperative antibiotic therapy and, in one case, a second operation to excise the residual abscess. The need for the latter was suggested by the results of sequential computerized tomographic brain scans that were used to monitor the response to antibiotic therapy. In the absence of any apparent extracranial focus of infection and any overt condition that might impair immunological competence, nocardiosis is likely to be omitted from the preoperative differential diagnosis of a posterior fossa space-occupying lesion.

Adult↗
PubMed1979

The neurologic examination in patients with central nervous system trauma.

The neurological assessment of the head injured patient must be integrated into the emergency management and daily care of the patient. Neurosurgical nurses are in the best position to perform serial neurologic examinations and assess changes in the patient's clinical picture. If this added responsibility is assumed, neurosurgical nurses must take an active role in improving assessment skills. The improved assessment of the head injured patient will result in early intervention in the patient's course to avert potential problems, thus resulting in improved morbidity and eventual outcome. As neurosurgical nurses expand their roles in nursing, improved patient assessments are mandatory to deliver optimal patient care.

Humans↗