Childhood leukemia and dental considerations

Leukemia is the major form of cancer in children in Britain and mirrors the percentage of children affected in the USA. This report outlines some of the medical aspects of leukemia and its treatment and gives a guide to the dentist, who may have the responsibility of dealing with leukemic children and their families.

Lead poisoning in a dog

A case of lead poisoning caused by ingestion of a lead roof-washer is described in a one-year-old, spayed Fox Terrier bitch, presented with nervous signs, and basophilic stippling of red blood cells. Blood concentrations of lead were in the low toxic range. Radiography of the abdomen revealed radio-dense objects in the stomach, which on gastrotomy included a lead roof-washer. Prior to removal of the foreign bodies, the dog showed remarkable improvement on non-specific symptomatic treatment alone, and recovered well after surgery, only to die unexpectedly several hours later. Concentrations of lead in the liver and kidneys were extremely high, and histology revealed typical intracellular inclusions and organ degeneration. In the light of these findings, it is suggested that all cases of suspected or confirmed lead poisoning be given specific chelation therapy.

The pathology of experimental Lasiospermum bipinnatum (Thunb.) Druce (Asteraceae) poisoning in sheep. II. Pulmonary and miscellaneous lesions

Poisoning with the plant Lasiospermum bipinnatum was studied in 9 lambs at various dose levels. Dyspnoea and tachypnoea, which were dose-related, were observed in 4 of the lambs. Gross and microscopic pulmonary lesions were found in all the lambs receiving plant material originating from one source but not in those given plant from another locality. The severity of the lesions appeared to be dose-dependent. Macroscopic lesions included pulmonary and mediastinal emphysema, congestion and oedema. Microscopically Clara cell hypertrophy and hyperplasia, and interstitial pneumonia were the most outstanding findings. It is speculated that the pulmonary lesions were induced by a furanosesquiterpene or tryptophan or a combination of both of these toxins in the dosed plant material. Miscellaneous and inconsistent lesions observed in the experimental animals included widespread haemorrhage (1 lamb), transudations into the body cavities and adrenocortical hyperplasia.

The pathology of experimental Lasiospermum bipinnatum (Thunb.) Druce (Asteraceae) poisoning in sheep. I. Hepatic lesions

Poisoning with the plant Lasiospermum bipinnatum was studied in 9 lambs. Intraruminal doses, varying from 1-12 g/kg/day of dried plant, were administered to 8 animals and 1 was fed 2.5 g/kg/day of the material mixed with maize meal for 13 days. Periodic serum analyses were done to monitor liver function. Lambs given 6-12 g/kg/day died or were killed in extremis. Clinical signs included progressive anorexia and depression in all these lambs and icterus in 2 animals. Lambs given 1-4 g/kg/day were sacrificed after about 2 weeks. Clinical signs in these animals were minimal or absent. Hepatosis was found in all the lambs, the severity of which correlated with levels of plant administered. Centrilobular necrosis and haemorrhage occurred in 2 of the 4 lambs given high doses; single cell necrosis of hepatocytes was observed with intermediate doses, and diffuse degeneration, which was more severe peripherally, was seen at various doses. In 1 lamb, degeneration was most severe midzonally. Bile ductule epithelial proliferation was observed in 7 of the 9 poisoned animals. Marked hypertrophy of hepatocellular smooth endoplasmic reticulum was seen in 3 lambs given low doses. The hepatic lesions were compared with those reported for poisoning by other hepatotoxic plants belonging to the family Asteraceae and found to be indistinguishable.

The effect of magnesium sulfate infusion on systemic and renal prostacyclin production

Recent in vitro studies have suggested that magnesium sulfate (MgSO4) infusions may increase prostacyclin production. We studied the effect of MgSO4 infusion on prostacyclin (PGI2) metabolite excretion in women with either pregnancy induced hypertension or preterm labor. Excretion of renal and systemic metabolites of PGI2 was measured prior to and following the start of MgSO4 infusion in the two groups. An increased in renal PGI2 metabolite preterm labor excretion was noted in the hypertension group but no change was noted in systemic PGI2 excretion in either group. These data fail to support a generalized, short term increase in endothelial cell PGI2 production as the basis for the beneficial effect of MgSO4.

Eye movement indices of mental workload

Four investigations were carried out to assess the feasibility of using eye movement measures as indices of mental workload. In the first experiment, saccadic extent was measured during free viewing while subjects performed low, moderate and high complexity, auditory tone counting as the workload tasks. The range of saccadic extent decreased significantly as tone counting complexity (workload) was increased. In the second experiment the range of spontaneous saccades was measured under three levels of counting complexity with a visual task that did not require fixation or tracking. The results indicated that the extent of saccadic eye movements was significantly restricted as counting complexity increased. In the third experiment, the effects of practice were examined and decreased saccadic range under high tone counting complexity was observed even when significant increases in performance occurred with practice. Finally, in experiment 4, the first experiment was repeated with additional optokinetic stimulation and the saccadic range was again observed to decrease with tone counting complexity. The results indicated that the extent of spontaneous and elicited eye movements was significantly restricted as counting complexity increased. We conclude that this measure may provide a valuable index of mental workload.

Impaired plasma cholesteryl ester transfer with accumulation of larger high density lipoproteins in some families of baboons (Papio sp.)

Baboons from some families have a higher concentration of plasma high density lipoproteins (HDL) on a chow diet and accumulate large HDL (HDL1) when challenged with a high cholesterol and high saturated fat (HCHF) diet. HDL1 from high HDL1 animals contained more (1.5-fold) cholesteryl ester than HDL (HDL2 + HDL3) from high or low HDL1 animals. HDL from high HDL1 baboons had lower triglyceride content than that from low HDL1 baboons. HDL3 or HDL labeled with [3H]cholesteryl linoleate was incubated with entire lipoprotein fraction (d less than 1.21 g/ml) or very low density lipoprotein + low density lipoprotein (VLDL + LDL) (d less than 1.045 g/ml) and with lipoprotein-deficient serum (LPDS), and the radioactive cholesteryl ester and mass floating at d 1.045 g/ml (VLDL + LDL) after the incubation was measured. The transfer of cholesteryl esters from either HDL or HDL3, prepared from plasma of high HDL1 animals fed chow or the HCHF diet, was slower than the transfer from either HDL or HDL3 of low HDL1 animals, regardless of the source of transfer activity or the ratio of LDL:HDL-protein used in the assay. Addition of HDL from high HDL1 baboons into an assay mixture of plasma components from low HDL1 baboons decreased the transfer of cholesteryl ester radioactivity and mass from HDL to VLDL and LDL. In addition to HDL, a fraction of intermediate density lipoprotein (IDL) and denser HDL were also effective in inhibiting the transfer. These observations suggest that accumulation of HDL1 in high HDL1 baboons fed an HCHF diet is associated with a slower transfer of cholesteryl esters from HDL to LDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of cell-specific markers for alveolar epithelium in fetal rat lung

In adults, the alveolar epithelium is composed of types I and II cells which differ structurally and functionally although they appear to belong to the same cell lineage. Using cell-specific markers (type I cells, monoclonal antibody; type II cells, Maclura pomifera lectin [MPA]), we have determined when and in what pattern their binding sites occur during development of the fetal rat lung. Rather than first appearing on days 19 to 20, when morphogenesis of type I cells occurs and lamellar bodies provide positive identification of type II cells, the markers appeared on day 15 (for type I cell marker) and day 16 (for type II cell marker). The type I cell marker was widespread by day 17 and was sufficiently abundant to be detected on a Western blot. MPA binding appeared more gradually and was often found on isolated cells. On serial sections of day 20 lung, the markers appeared to be localized to the same cells. The early appearance of cell-specific markers suggests an early onset of the developmental program that leads to full differentiation of types I and II cells. Co-expression of both cell-specific markers suggest that fetal cell lineage may differ from the scheme proposed by others that type II cells serve as type I cell precursors during development.

Lamellar bodies of cultured human fetal lung: content of surfactant protein A (SP-A), surface film formation and structural transformation in vitro

Lamellar bodies were isolated from dexamethasone and T3-treated explant cultures of human fetal lung, using sucrose density-gradient centrifugation. We examined their content of surfactant apoprotein A (SP-A), and their ability to form surface films and to undergo structural transformation in vitro. SP-A measured by ELISA composed less than 2% of total protein within lamellar bodies; this represented, as a minimum estimate, a 2-12-fold enrichment over homogenate. One- and two-dimensional gel electrophoresis also suggested that SP-A was a minor protein component of lamellar bodies. Adsorption of lamellar bodies to an air/water interface was moderately rapid, but accelerated dramatically upon addition of exogenous SP-A in ratios of 1:2-16 (SP-A:phospholipid, w/w). Similar adsorption patterns were seen for lamellar bodies from fresh adult rat and rabbit lung. Lamellar bodies incubated under conditions that promote formation of tubular myelin underwent structural rearrangement only in the presence of exogenous SP-A, with extensive formation of multilamellate whorls of lipid bilayers (but no classical tubular myelin lattices). We conclude that lamellar bodies are enriched in SP-A, but have insufficient content of SP-A for structural transformation to tubular myelin and rapid surface film formation in vitro.

Perceptual consequences of a temporal processing deficit in reading disabled children

Recent research suggests that some children who are reading disabled exhibit sensory deficits associated with poor temporal processing. The performance of disabled readers on various perceptual tasks is consistent with a temporal processing deficit hypothesis. Visual masking paradigms were utilized to obtain direct measures of the temporal aspects of processing in normal and disabled readers, and showed that the visual processing of disabled readers is characterized by a longer integration time and a slower processing rate for both simple and word-like stimuli. Image blurring, which reduces the contrast of high spatial frequencies, reestablished normal temporal processing of words in disabled readers.

Interferon-gamma and synthesis of surfactant components by cultured human fetal lung

We examined the effects of interferon-gamma (IFN-gamma) on development of the surfactant system in alveolar epithelial cells of fetal lung. Explants of second-trimester human fetal lung were cultured for 1 to 6 days in serum-free medium containing recombinant human IFN-gamma (0.03 to 30 ng/ml) and/or dexamethasone (10 or 100 nM). Treatment for 3 days with IFN-gamma alone, dexamethasone alone, and IFN plus dexamethasone increased the content of surfactant protein A (SP-A, 28 to 36 kD) by approximately 3-, 2.5-, and 10-fold, respectively. The biphasic response pattern of SP-A to dexamethasone (stimulation initially and inhibition with continued culture) was not altered by the presence of IFN-gamma. IFN-gamma also stimulated accumulation of SP-A mRNA (2.7-fold at 24 h) but did not affect the levels of mRNAs for surfactant protein B (18 kD) and surfactant protein C (5 kD). To assess the effect of IFN-gamma on synthesis of surfactant lipids, we determined the content of phosphatidylcholine, the rate of labeled choline incorporation into phosphatidylcholine, saturation of newly synthesized phosphatidylcholine, and the activity of fatty acid synthetase, a glucocorticoid-inducible enzyme. Treatment of explants for 5 days with IFN-gamma had no effect on these parameters. Studies by light and electron microscopy revealed little difference between control and IFN-treated explants with regard to cell viability and epithelial cell differentiation. We conclude that IFN-gamma has a selective stimulatory effect on SP-A among surfactant components.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of isoluminant-background color on metacontrast and stroboscopic motion: interactions between sustained (P) and transient (M) channels

The magnitudes of metacontrast masking and of stroboscopic motion were investigated as a function of the color of isoluminant backgrounds on which the stimuli consisting of rectangular-shaped luminance decrements appeared. White, green, and red backgrounds were employed. Background isoluminance was obtained by minimal flicker settings with heterochromatic flicker of uniform fields. Both metacontrast and stroboscopic motion were decreased when red as compared to white or green backgrounds were used. Within the context of current sustained-transient channel approaches to visual masking and motion, these results indicate that the activity of transient channels is attenuated by red relative to white or green backgrounds. Moreover, these psychophysical findings may correspond to the suppressive effects of diffuse red light on neural activity in the transient M pathway of monkey.

The fetal board

The fetal board is a multidisciplinary approach to complex perinatal clinical problems. It has a model in the tumor board, which has been used in many institutions to plan and coordinate care for patients with a malignancy. The pregnancy with a known or suspected abnormal fetus represents a clinical setting in which consultants from several disciplines have a potential role in the ultimate outcome. Therefore, a fetal board provides prospective opportunities for clinical diagnosis, counseling, and comprehensive care of the maternal patient and her fetus before, during, and after delivery. The fetal board's purpose is to incorporate the expertise of various specialties and subspecialties to provide optimum care for the abnormal fetus. The board also provides educational opportunities to all involved in patient care, including perinatologists, obstetricians, neonatologists, pediatricians, nursing staff, social service providers, and other health professionals.

Monoclonal antibodies specific to apical surfaces of rat alveolar type I cells bind to surfaces of cultured, but not freshly isolated, type II cells

The alveolar surface of the lung is lined by two classes of epithelial cells, type I and type II cells. Type I cells cover more than 97% of the alveolar surface. Although this cell type is felt to be essential for normal gas exchange, neither unique identifying characteristics nor functions have been described for the type I cell. We have produced monoclonal antibodies to (a) component(s) of molecular weight 40,000 and 42,000 of the apical surface of rat alveolar type I cells. The antibodies are specific to the lung in Western blots of organ homogenates. In immunocytochemical studies of frozen lung at the level of both light and electron microscopy, the monoclonal antibodies appear to react specifically with the apical plasma membrane of type I cells. Airway, vascular, interstitial cells, type II cells and macrophages are not immunoreactive. Western blots of isolated type I cells (approx. 70% pure) also demonstrate immunoreactivity at molecular weights of 40,000 and 42,000. When the lung is injured, type I cells may be damaged and sloughed from the alveolar surface. Alveolar repair occurs when the second type of alveolar cell, the type II cell, divides. Cell progeny may retain type II cell morphology or may differentiate into type I cells. Western blots of freshly isolated type II cells (approx. 85% pure) do not display immunoreactivity with our monoclonal antibodies. However, type II cells maintained in culture acquire immunoreactivity to monoclonal antibodies, demonstrating that type II cells in vitro have the capacity to develop a characteristic associated with type I cells in situ. The availability of markers for a specific membrane component of type I cells should facilitate the study of many questions on alveolar functions, development and response to injury.