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Biomedical subjects

A Lawrence

Publications and source records attributed to A Lawrence.

At least 73 records · Page 4Linked to original sources
PubMed1988

Intracranial CSF volumes: natural variations and physiological changes measured by MRI.

Cranial CSF volumes, for the first time including CSF in the subarachnoid space, can be measured by Magnetic Resonance Imaging (MRI). The MRI sequence causes signal from the grey matter and white matter to cancel producing a contrast of 200: 1 between a unit of CSF and a unit of brain. We have assessed the variations between normal individuals and investigated some of the physiological factors that might influence cranial CSF volumes. Total CSF volumes were measured in 64 normal subjects, aged from 18-64 years (mean 38 years). Ventricular, cortical sulcal and posterior fossa volumes were also calculated separately. In 20 females with a normal menstrual cycle, CSF volumes were measured mid cycle and premenstrually; 10 post menopausal females and 10 males were rescanned after an interval of 2 weeks. Total cranial CSF volume were calculated before and during inhalation of 7% CO2 and before and during hyperventilation while breathing 60% O2, in 12 normal subjects. Total intracranial CSF volume ranged from 57.1-286.5 ml. Total intracranial and cortical sulcal CSF volumes increased more steeply with age than ventricular or posterior fossa CSF volumes. Males had more cranial CSF than females. Total CSF volume increased premenstrually in 19 females. Males and post-menopausal females did not have a significant change in CSF volume, on repeat examination. CO2 inhalation produced a mean increase of paCO2 of 17.2 mmHg and CSF volume decreased in all subjects (mean 9.4 ml). Cranial CSF volume increased in 11 subjects during O2 inhalation (range -0.5 to +26.7 ml mean 10.9 ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Brain and intracranial cavity volumes: in vivo determination by MRI.

Brain volume is altered by pathological processes such as swelling or atrophy yet until now this is a parameter which could only be determined at post mortem. This paper describes a non-invasive technique using MRI which permits the in vivo determination of brain volume (BV), intracranial cavity volume (ICV), ventricular, cortical sulcal and total intracranial CSF volumes. The technique was applied to 40 normal volunteers (20 males, 20 females) to investigate the variation of these parameters with age and sex after normalisation with respect to ICV. There was found to be a significant decrease in normalised brain volume between the ages of 20 and 60 years in males by 1.6% per decade. In females the decrease was less (0.5%) but was not statistically significant. This technique will make it possible, for the first time, to investigate prospectively the correlation between mental function and brain volume in illness and ageing.

Adult↗
PubMed1988

School health education to prevent the spread of AIDS: overview of a national programme.

The ultimate goal of CDC's School Health Education to Prevent the Spread of AIDS programme is to reduce the incidence of HIV infection among school-aged youth. Working objectives that integrate programme research and development activities are listed in the opposite Table. In 1982 it was estimated that of the 4.6 billion people in the world, about one billion were school-aged, and about 870 million of these youth were enrolled in schools. WHO, UNESCO, and the International Union for Health Education have recognized that schools could provide a critical means for ensuring that young people throughout the world understand the global AIDS pandemic they face, and what they can do to protect themselves, the families for which they will become responsible, and the communities in which they will reside. But if schools are to provide effective AIDS education, they will require the commitment and active collaboration of education and health leaders in local, national, and international agencies.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Immunoglobulin profile of tracheal aspirate fluid in intubated children.

Pulmonary lavage immunoglobulins IgG, IgA and IgM were measured in intubated ventilated neonates during their period of intubation (range 1-64 days, mean 12). The neonates were divided into two groups based on gestational age (group 1 26-32 weeks, group 2 33-40 weeks). IgG levels were high at birth, and decreased exponentially throughout the period of intubation. There was no statistical difference in IgG levels between the two groups. IgA and IgM levels were low at birth, and increased linearly, there being a significantly greater increase with age in Group 2 (the more mature gestationally) for both immunoglobulins. Two groups of older children were also studied (2-4 year olds, and 8-10 year olds). In the 2-4 year age group, IgG levels were similar to those seen in the immediate newborn period, were quantitatively greater than IgA and IgM, and were not significantly different from levels in the 8-10 year olds. IgA and IgM levels were also not significantly different between the two groups.

Aging↗
PubMed1987

Human cranial CSF volumes measured by MRI: sex and age influences.

Accurate measurements of CSF volumes would assist in the diagnosis of several important neurological conditions. Using Magnetic Resonance Imaging (MRI) we have devised a method to measure both total intracranial CSF volume and ventricular volume. This initial study, in normal humans, provides an answer to two longstanding questions: first, do these volumes differ between the sexes; second, do both total and ventricular CSF volumes increase with normal aging? We found that the total cranial CSF volume and skull size of males were significantly greater than those of females, but that there was not a statistically significant difference between the ventricular volumes of the sexes. Total cranial CSF volume increased steeply with age in both sexes but although there was an increase in ventricular volume with age in males, no significant increase with age could be demonstrated in females.

Adult↗
PubMed1985

Spectrum of catecholamine-secreting tumors of the organ of Zuckerkandl.

In a series of 24 pheochromocytomas, four were tumors in the organ of Zuckerkandl. Their presenting symptoms of headache, palpitation, diaphoresis, and anxiety were similar to symptoms of adrenal pheochromocytomas. Two patients had paroxysmal and two patients sustained hypertension. All four had elevated urinary vanillylmandelic acid, metanephrine or catecholamine levels. Two of the tumors were localized with angiography before the availability of computerized tomography. Two patients underwent initial computerized tomography, which was nondiagnostic. Later scans looking specifically for organ of Zuckerkandl tumors were positive. Organ of Zuckerkandl tumors, like other ectopic pheochromocytomas, have a higher rate of malignancy. Two of the four were malignant tumors. One patient died 4 years after operation, but the other patient remains stable despite metastatic disease 8 years after operation. The two patients with benign tumors remain well 2 and 3 years after resection and treatment with alpha-blockade.

Adult↗
PubMed1984

Persistent lymphadenopathy in homosexual men: a clinical and ultrastructural study.

Ultrastructural changes (tubuloreticular structures and tube and ring shaped forms) previously described in patients with acquired immunodeficiency syndrome (AIDS) are described for the first time in the lymph nodes and circulating lymphocytes of patients with persistent lymphadenopathy. These observations support the view that the persistent lymphadenopathy syndrome and AIDS are caused by the same transmissible agent(s).

Acquired Immunodeficiency Syndrome↗
PubMed1981

Morphology of spore-bearing structures in Streptomyces ipomoea.

Sporulating colonies of Streptomyces ipomoea were observed using light and scanning electron microscopy. In addition to the open loops and spiral chains of spores characteristic of S. ipomoea, globose structures resembling sporangia of the genus Streptosporangium were found. The "sporangia" had a smooth surface, were 5-6 micrometers in diameter, and consisted of an unbranched coiled hypha within an enveloping sheath. As the sporangia matured, septa formed in the internal sporogenous hypha forming coiled chains of spores morphologically similar to those formed on the typical spore chains. The sporangia germinated on agar, without releasing the nonmotile spores, by formation of several germ tubes at several locations on the sporangia.

Microscopy, Electron, Scanning↗
PubMed1979

Effect of blocking protein synthesis at nonpermissive temperatures on temperature-sensitive deoxyribonucleic acid mutants of Escherichia coli.

When protein synthesis was blocked in temperature-sensitive deoxyribonucleic acid synthesis mutants of Escherichia coli at nonpermissive temperatures, it reduced the amount of apparent subsequent chain elongation to approximately half that observed in the mutants either at nonpermissive temperatures alone or when protein synthesis was blocked at the permissive temperature. Blocking protein synthesis at the nonpermissive temperatures for periods of 40 min caused the loss of ability to reinitiate deoxyribonucleic acid synthesis at the permissive temperature.

Amino Acids↗
PubMedDate not supplied

Digital mapping of multi-parameter contrast functions in magnetic resonance (MR) imaging using a standard MR computer system and digital display.

A technique is described which utilises the full analysis and display capabilities of a commercial MRI system to produce digital maps of multi-parameter functions produced by MR contrast theory. The technique is utilised to determine the effects of nominating specific overall scan times on the optimum solutions as produced by the theory and it is shown that different solutions are obtained when the theory is applied using typical clinical constraints. The digital mapping approach is potentially of great value in prospectively determining pulse timing parameters to produce optimum contrast images, in producing contrast maps to aid retrospective image interpretation, and as a training aid for clinicians inexperienced in the interpretation MR images.

Computer Graphics↗
PubMedDate not supplied

The effect of acute ethanol (EtOH) exposure on protein kinase C (PKC) activity in anterior pituitary.

Alterations in the protein kinase C (PKC) pathway may interrupt anterior pituitary luteinizing hormone (LH) synthesis and/or secretion, which may impair normal reproductive function. Work by our laboratory and others has shown that EtOH has profound deleterious effects on the regulation of the hypothalamic-pituitary-gonadal (HPG) axis. The present study focuses on PKC translocation from the cytosol to the membrane of anterior pituitary after acute EtOH exposure. Serum levels of LH were measured at three time points (15, 30, and 90 min) after an IP injection of either saline or 3 g/kg EtOH in adult castrated male rats. LH levels dropped significantly (p < 0.03) in EtOH-injected compared to saline-injected control animals. In the same animals, EtOH significantly suppressed PKC localization at its active site at the pituitary cell membrane (p < 0.05). These findings suggest that the mechanism of EtOH's suppression of LH is mediated, at least in part, through a decrease in PKC translocation to the anterior pituitary cell membrane.

Animals↗