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Biomedical subjects

M M Brown

Publications and source records attributed to M M Brown.

At least 145 records · Page 8Linked to original sources
PubMed1988

Preoperative and postoperative levels of plasma protein and amino acid in esophageal and lung cancer patients.

The metabolic changes following thoracic surgery in three groups of patients (esophageal cancer, lung cancer, and hiatus hernia) have been studied. Before operation patients with esophageal cancer, but not those with lung cancer, had significantly lower plasma total protein and albumin than patients with hiatus hernia. After surgery plasma albumin and total protein fell in both esophageal cancer and hiatus hernia patients, a development attributed to poor nutrition and restricted calorie diet in these two groups of patients respectively. With the exception of alanine and arginine in lung cancer patients, and free tryptophan in lung and esophageal cancer patients, the preoperative concentrations of all plasma amino acids were similar in both groups of cancer patients and in those with hiatus hernia. After operation the concentrations of glutamine, total tryptophan, alanine, glycine, and arginine fell sharply, whereas those of phenylalanine, lysine, valine, and leucine were slightly or not at all affected by surgery. The immediate postoperative fall of plasma free amino acids is thought to be due to the increased rate of gluconeogenesis. The rise of free fraction of plasma tryptophan after surgery is related to the raised level of plasma free fatty acids and increased secretions of catecholamines, which is believed to follow surgery.

Aged↗
PubMed1988

Autopsy validation of MRI in central pontine myelinolysis.

In a fatal case of central pontine myelinolysis (CPM) a low field strength (0.08 Tesla) magnetic resonance image revealed reduction of image intensity in the pons with sparing of two central symmetrical areas in the ventral portion. The latter correlated with preservation of centrally located groups of longitudinal myelinated nerve fibres shown at autopsy. Although such sparing is well recognised in pathological studies of CPM it has never previously been demonstrated in life.

Adult↗
PubMed1988

Bell's palsy and HIV infection.

Unilateral infranuclear facial palsy developed in three young homosexual men. All three were positive for antibodies to human immunodeficiency virus (HIV). Two had persistent generalised lymphadenopathy, but the clinical criteria for the acquired immune deficiency syndrome (AIDS) were not fulfilled. There were no features of generalised neuropathy, and no other cause for facial palsy was evident. Recovery was excellent in each patient.

AIDS-Related Complex↗
PubMed1988

Assessment of cerebral haemodynamic reserve: correlation between PET parameters and CO2 reactivity measured by the intravenous 133 xenon injection technique.

Regional cerebral blood flow (CBF), oxygen utilisation, fractional oxygen extraction (OER) and cerebral blood volume (CBV) were measured by positron emission tomography (PET) in 21 patients with occlusive carotid artery disease. In the same patients, measurements of cerebral CO2 reactivity were performed using the intravenous xenon-133 technique. A significant correlation was found in symptomatic hemispheres between the CBF/CBV ratio and CO2 reactivity. Four patients had significant increases in OER and this was associated with a reduction in CBF/CBV ratio implying exhaustion of haemodynamic reserve. CO2 reactivity was reduced below 1.5% mm Hg in all four cases with raised OER but only in two cases with normal OER. In patients with CO2 reactivities above 1.5% mm Hg, OER was normal in all cases. It is concluded that measurements of CO2 reactivity provide a satisfactory method for assessing cerebral haemodynamic reserve.

Aged↗
PubMed1987

Peripheral proliferative retinopathies.

The cases of 100 consecutive persons (156 eyes) seen with peripheral proliferative retinopathy were reviewed in a retrospective fashion. Associated systemic and ocular diseases included sickling hemoglobinopathies (49%), branch retinal vein obstruction (20%), diabetes mellitus (9%), sarcoidosis (4%), intravenous drug abuse (4%), the ocular ischemic syndrome (1%), pars planitis (1%), Coats' disease (1%) and retinitis pigmentosa/retinal detachment (1%). In ten (10%) patients no obvious cause for the development of new blood vessel growth could be ascertained.

Adolescent↗
PubMed1986

The Salmonella typhimurium/mammalian microsomal assay. A report of the U.S. Environmental Protection Agency Gene-Tox Program.

The Salmonella assay has been in use for almost 15 years and can be defined as a routine test for mutagenicity and for predicting potential carcinogenicity. It detects the majority of animal carcinogens and consequently plays an important role in safety assessment. The test is also routinely used as the frontline screen for environmental samples (complex mixtures) isolated from air, water and food. This role will continue to remain an area of growth as or because sample volumes associated with these testing areas are generally very limited and more extensive testing is generally impossible. While this test, like all others, has some limitations, it is recommended that it be regularly included in all genetic testing batteries.

Animals↗
PubMed1986

Effectiveness of the Denver Developmental Screening Test with biologically vulnerable infants.

The Denver Developmental Screening Test (DDST) was initially developed specifically to identify children with mental retardation. However, its use in screening low birth weight and other biologically at-risk infants for motor problems is widespread. In view of the absence of biologically vulnerable children in the DDST standardization sample, and the limited validational support available for its use with children under 30 months of age, the purpose of this study was to investigate the effectiveness of the DDST in screening 62 Neonatal Intensive Care Unit graduates during infancy. Categorical results (Normal, Questionable, Abnormal), obtained in the home setting by DDST, were compared with results of Neonatal Intensive Care Unit Follow-up Clinic evaluations. There was a marked underselection of the DDST's categorical results in identifying those infants with suspect or abnormal findings on the more detailed clinic evaluations. However, the effectiveness of the screeners' clinical impression ratings (based on observations made during administration of the DDST) in identifying infants with positive criterion results was encouraging. These findings suggest that, although the DDST's categorical results may be of limited value in screening biologically vulnerable infants, administration of the DDST may provide a useful framework for more systematically observing and documenting significant qualitative aspects of an infant's developmental status, particularly for the screener who is less experienced in neuromotor assessment. These observations need to be defined further, and validated.

Developmental Disabilities↗
PubMed1986

Reactivity of the cerebral circulation in patients with carotid occlusion.

Cerebral blood flow (CBF) and the response to hypercapnia (cerebral reactivity) have been measured in 41 patients with unilateral or bilateral internal carotid artery occlusion in an attempt to identify those with limited collateral reserve. Normocapnic CBF was within normal limits in the majority of subjects. The response to hypercapnia varied from normal to absent, with impaired reactivity becoming increasingly likely when more than one artery was diseased. In 19 patients with unilateral carotid occlusion, hemisphere reactivity was well preserved in the majority, but was significantly lower on the side of the occlusion (mean 2.9%/mm Hg) compared to the normal side (mean 3.4%/mm Hg). Reactivity on the side of the occlusion was further reduced in 15 patients with occlusion and contralateral internal carotid artery stenosis (mean 1.7%/mm Hg) and was even lower in seven patients with bilateral occlusion (mean 1.1%/mm Hg). There was no difference in reactivity between asymptomatic hemispheres in the 41 patients (mean 2.7%/mm Hg) and hemispheres in which a previous stroke had occurred (mean 2.8%/mm Hg). In contrast the response in hemispheres subject to continuing transient ischaemic attacks was significantly impaired (mean 1.6%/mm Hg), suggesting that the cerebral symptoms in some of these patients may have had a haemodynamic origin more often than suspected from the clinical history.

Aged↗
PubMed1986

Escape from serial stimuli leading to food.

If the functional relations governing the strength of a conditioned reinforcer correspond to those obtained with other Pavlovian procedures (e.g., Kaplan, 1984), the termination of stimuli appearing early in the interval between successive food deliveries should be reinforcing. During initial training we presented four key colors, followed by food, in a recurrent sequence to each of 6 pigeons. This established a baseline level of autoshaped pecking. In later sessions, we terminated each of these colors or only the first color for a brief period following each peck, replacing the original color with a standard substitute to avoid darkening the key. Pecking decreased in the presence of the last color in the sequence but increased in the presence of the first. In accord with contemporary models of Pavlovian conditioning, these and other data suggest that the behavioral effects of stimuli in a chain may be better understood in terms of what each stimulus predicts, as measured by relative time to the terminal reinforcer, than in the exclusively positive terms of the traditional formulation (Skinner, 1938). The same model may also account for the initial pause under fixed-interval and fixed-ratio schedules of reinforcement.

Journal Article↗
PubMed1985

Regulation of cerebral blood flow in response to changes in blood viscosity.

Cerebral blood flow (CBF) was measured by the non-invasive xenon-133 technique in patients with increased blood viscosity as a result of paraproteinaemia or leukaemia. A highly significant inverse relation was found between CBF and arterial oxygen content in 59 paraproteinaemic patients. There was no significant correlation between CBF and whole blood viscosity, and no significant difference between CBF in paraproteinaemic patients and a matched group of anaemic patients. 7 leukaemic patients with up to threefold increases in whole blood viscosity were also found to have CBF appropriate to their degree of anaemia. The effects of treatment to reduce blood viscosity were studied in 7 paraproteinaemic and 5 leukaemic patients; changes in CBF were significantly related to changes in arterial oxygen content but not to changes in blood viscosity. These studies confirm the importance of arterial oxygen content in the determination of CBF, and demonstrate that regulatory mechanisms can maintain normal cerebral oxygen transport despite increased plasma and whole blood viscosity.

Adult↗
PubMed1985

Fundamental importance of arterial oxygen content in the regulation of cerebral blood flow in man.

The relationships between cerebral blood flow (CBF), arterial oxygen content, whole blood viscosity and the transport of oxygen to the brain have been studied in 54 subjects with variations in arterial oxygen content resulting from alterations in haemoglobin concentration ranging from 5.7 to 19.1 g/dl. A highly significant relationship was found between CBF and arterial oxygen content, CBF altering to maintain the rate of transport of oxygen to the brain within certain limits. No significant effect of changes in blood viscosity was evident. In a multiple regression analysis arterial oxygen content emerged as the major determinant of CBF and after this effect had been taken into account there was no significant influence of blood viscosity, arterial pCO2, age or mean arterial blood pressure. The results imply that the alterations in CBF found in subjects with anaemia and polycythaemia are primarily physiological and not caused by the accompanying alterations in blood viscosity. It is proposed that the response of the cerebral circulation to arterial oxygen content is mediated by a local mechanism sensitive to alterations in local tissue oxygen tension.

Adolescent↗