The prognostic significance of morphological features in childhood acute lymphoblastic leukaemia

A consecutive series of 209 children with acute lymphoblastic leukaemia (ALL) presenting to a regional referral unit between 1970 and 1977 was studied. The following morphological features in the initial bone marrow were recorded: blast size, percentage periodic acid-Schiff (PAS) and oil-red-O (ORO) positivity, percentage of blasts with vacuoles, and acid phosphatase positivity. The blasts were also coded according to the FAB (L13) classification. When analysed separately, increasing blast size was significantly related to the length of first remission (P = 0.01). However, this was almost entirely due to its association with the FAB L2 type of disease which also had a highly significant influence on length of first remission (P less than 0.0001) independent of all other factors. Patients with L3 disease had blasts with heavy vacuolation, ORO positivity and displayed monoclonal surface immunoglobulin and their prognosis was very poor. The percentage of vacuolated blasts and ORO positivity otherwise showed no influence on prognosis. Fine granularity of PAS staining in lymphoblasts showed no prognostic value but the trend of longer remission duration with increase in percentage of PAS coarse granularity and blocks, was statistically significant (P = 0.006). This relationship was partly due to a correlation with the presence of mediastinal mass and L2 disease, but was still independent of all other prognostic factors. In a smaller number (39) of the series of patients on whom cell surface markers were available, we were unable to demonstrate a correlation between T-derived blasts and the L1 and L2 classification; but there was a strong correlation with polar acid phosphatase positivity in T-derived blasts.

Emergency presentations by vulnerable road users: implications for injury prevention

Most emergency presentations by vulnerable road users were the result of collisions that did not involve a motor vehicle. Many injuries occurred off-road without police attendance. Hence, reliance on official police records would underestimate the magnitude and scope of these injuries. Suggestions to provide a safer road environment are given.

Enhancement of cALL immunogenicity by co-culture with a CD154 expressing 293 cell line

Pre-B cell acute lymphoblastic leukaemia (cALL) commonly occurs in young patients and although successful conventional therapies are available (such as cytotoxic drugs and bone marrow transplantation) for a proportion of patients (approximately 30%) these are ultimately unsuccessful. Recurrence of disease is a result of the failure of the immune system to recognize these abnormal cells and down-regulation of crucial molecules required for cognate CD4(+) T cell recognition has been postulated as a means of immune escape. In this study we show that an embryonic kidney cell line (293 cells) transfected with CD154 (40 L.1) are capable of not only maintaining the viability of primary ALL cells in culture but can also up-regulate the expression of a number of crucial molecules involved in antigen recognition. We show that 40 L.1 cell stimulation of primary ALL cell cultures can not only enhance the allogeneic and autologous MLR response to such cells but will also induce CTL effectors which are capable of lysing wild-type autologous ALL cells. It is therefore conceivable that such an approach could be used to generate an active anti-tumour response in patients, following conventional therapy, reducing the incidence of recurrence.

Design and validation of immunological tests for the detection of Porcine endogenous retrovirus in biological materials

The present study details the design and demonstrates function for a series of reagents and methods to allow the detection of exposure to antigens specific for Porcine endogenous retrovirus (PERV). The detection of PERV is carried out by the means of a variety of immunological screening methods including, indirect immunofluorescence, Western blotting and enzyme linked immunosorbent assay (ELISA) for the detection of antibodies in serum specific for PERV gag and env antigens. Alternatively, PERV-specific antisera for gag and env can be used to detect viral antigen in serum or other samples. PERV env peptides with potential specificity for the known PERV types are also described. Antisera against the peptides can be used to detect PERV antigens directly or to characterise viral type. Using electron microscopy coupled with labelled PERV-gag-specific antisera it was possible to visualise PERV virions.

Haploinsufficiency of CBFA2 causes familial thrombocytopenia with propensity to develop acute myelogenous leukaemia

Familial platelet disorder with predisposition to acute myelogenous leukaemia (FPD/AML, MIM 601399) is an autosomal dominant disorder characterized by qualitative and quantitative platelet defects, and propensity to develop acute myelogenous leukaemia (AML). Informative recombination events in 6 FPD/AML pedigrees with evidence of linkage to markers on chromosome 21q identified an 880-kb interval containing the disease gene. Mutational analysis of regional candidate genes showed nonsense mutations or intragenic deletion of one allele of the haematopoietic transcription factor CBFA2 (formerly AML1) that co-segregated with the disease in four FPD/AML pedigrees. We identified heterozygous CBFA2 missense mutations that co-segregated with the disease in the remaining two FPD/AML pedigrees at phylogenetically conserved amino acids R166 and R201, respectively. Analysis of bone marrow or peripheral blood cells from affected FPD/AML individuals showed a decrement in megakaryocyte colony formation, demonstrating that CBFA2 dosage affects megakaryopoiesis. Our findings support a model for FPD/AML in which haploinsufficiency of CBFA2 causes an autosomal dominant congenital platelet defect and predisposes to the acquisition of additional mutations that cause leukaemia.

Symptomatic HIV infection in infancy--clinical and laboratory markers of infection

OBJECTIVE

To investigate the usefulness of immunological tests in the diagnosis of HIV infection in young symptomatic children (< 15 months of age).

DESIGN

Tests were evaluated in HIV-infected (HIV antibody- and PCR-positive) patients and non-infected individuals.

SETTING

Hospitalised patients in a referral centre (Red Cross War Memorial Children's Hospital, Cape Town).

PATIENTS

All admissions under 15 months of age who had HIV antibody requested were eligible, provided there was sufficient serum (150 microliter) for further study. Overall, there were 201 symptomatic cases and 49 healthy controls. Twenty of the symptomatic cases were HIV antibody-positive and 19 of these were HIV-infected on the basis of a positive PCR for HIV viral product.

RESULTS

Of the tests we evaluated (total IgG, IgM, IgA and rheumatoid factors of the same classes), raised total IgG level (cut-off 18 g/I or above) was the most useful. We used a commercial radial immunodiffusion plate which was found to have excellent reproducibility (inter-assay coefficient of variation 3.2%). The test detected 16 of 19 infected infants (sensitivity 84%, negative predictive value 98%). With the exception of the finding of oral thrush (odds ratio 7; P < 0.001), the clinical signs at presentation did not distinguish those who were HIV antibody-positive from those who were negative.

CONCLUSIONS

In our study of hospital admissions, the finding of elevated IgG and HIV antibody was diagnostic of HIV infection. (The positive predictive value of the combination was 100%.) Likewise, the presence of raised IgG levels and oral candidosis had a high specificity for HIV infection (98%) but the sensitivity was low (37%). Measurement of total IgG levels by radial immunodiffusion is simple, relatively inexpensive (< 10% of the cost of PCR), helpful in diagnosing HIV infection in symptomatic infants and able to be performed in areas with minimal laboratory back-up.

A comparison of oral and intravenous iron supplementation in preterm infants receiving recombinant erythropoietin

OBJECTIVE

To determine whether intravenously administered iron supplements would improve the hematologic response to recombinant erythropoietin in stable preterm infants.

METHODS

Forty-two preterm infants (<33 weeks' gestation, birth weight < 1500 gm, hematocrit <38%) were treated with recombinant human erythropoietin (Eprex), 600 U/kg per week, and randomly assigned to receive either an oral preparation of ferrous lactate (elemental iron, 12 mg/kg per day) or an intravenous preparation of iron sucrose (6 mg/kg per week).

RESULTS

Hematocrits, reticulocyte counts, and transfusions were similar in the oral group (OG) and the intravenous group (IVG). However, markedly higher serum ferritin concentrations were noted in the IVG (p <0.001), and by completion of the study the arithmetic mean values were 265 +/- 127 microg/L versus 137 +/- 65 microg/L in the IVG and the OG, respectively. The numbers of hypochromic erythrocytes increased in both groups during the study but were significantly higher in the OG (p = 0.04). Mean daily weight gain in the IVG (27 +/- 6.4 gm/day) was greater than in the OG (22.9 +/- 4.78 gm/day; p = 0.04).

CONCLUSIONS

High doses of both orally administered iron and intravenously administered iron sucrose appear to supply sufficient iron for erythropoiesis in stable infants. Storage iron may become depleted after oral supplementation. The intravenous preparation appears to be safe and maintains serum ferritin concentrations, and it may be indicated for patients with low ferritin levels and for those not established on enteral feedings.

Is the use of recombinant human erythropoietin in anaemia of prematurity cost-effective?

In a double-blind placebo-controlled study we showed a 3-fold decrease in blood transfusions (BTFs) given to preterm infants with anaemia of prematurity who received recombinant erythropoietin. However, only 50% of placebo recipients required a BTF. Data from the placebo group indicated that either mean daily weight gain < or = 7.5 g/day before study entry or haematocrit < or = 50% at birth was associated with BTFs (P < 0.001). We calculated that giving erythropoietin to patients in the treatment group with either of these variables prevented 24 of 28 BTFs and that it would cost R184 to prevent 1 BTF. The cost of each BTF was R187 (blood filtered to remove white cells and reduce cytomegalovirus transmission). Therefore, the costs of the two treatments were similar, but as the risk of transmitting infection is lower with erythropoietin, we recommend its use in selected preterm infants.

Marked eosinophilia in an immunosuppressed patient with strongyloidiasis

Strongyloidiasis in immunocompromised patients is typically associated with a fulminant clinical course and little eosinophilia. We describe an immunocompromised patient with strongyloidiasis in whom the infection was only minimally symptomatic in association with a dramatic increase in eosinophil count.

Flavone acetic acid (FAA) with recombinant interleukin-2 (rIL-2) in advanced malignant melanoma. III: Cytokine studies

Twelve patients undergoing IL-2 and flavone acetic acid (FAA) combination immunotherapy for advanced melanoma were studied throughout treatment for the induction of measurable levels of bioactive TNF, GM-CSF and IL-6 in their serum. This was to assess the extent of secondary cytokine induction in these patients and the possible role of such cytokines in both the toxic and therapeutic responses. The nature of the treatment schedule enabled these cytokines to be measured in response to FAA alone, FAA/IL-2 and FAA alone following IL-2/FAA activation of target cells. A small rise in the serum levels of these cytokines was seen on the initial course of FAA/IL-2 but this was minor compared to the marked elevation in levels 2-8 h following the initiation of the third course of FAA given with or without IL-2 and at a time point which coincided with maximum toxicity in those patients who experienced it. These results show that FAA alone can induce cytokine release from primed target cells. This may be associated with the therapeutic effect and/or toxicity of the agent.

Effects of acute bolus and chronic continuous intrathecal baclofen on genitourinary dysfunction due to spinal cord pathology

A prospective, blinded study was done to examine the effects of acute bolus and chronic continuous intrathecal baclofen on genitourinary function in 10 patients with severe spasticity due to spinal cord pathology. Genitourinary function was assessed by symptom questionnaires and urodynamic studies performed after a bolus dose of baclofen and 6 to 12 months after continuous intrathecal baclofen. Results were compared to placebo for acute bolus testing or to pre-continuous intrathecal baclofen values. In all patients with irritative voiding and urge incontinence uninhibited bladder contractions were eliminated. Of 3 patients with an indwelling urethral catheter for incontinence due to detrusor hyperreflexia 1 was converted to intermittent self-catheterization. Whereas bladder capacity, compliance, sensation and voiding pressures were not different after continuous intrathecal baclofen, when a mean of all patients was compiled, a 72% increase in capacity and 16% improvement in compliance were observed in subjects without cervical spinal cord pathology. Detrusor-sphincter dyssynergia was abolished in 40% of the patients. Continuous intrathecal baclofen may represent a novel approach to the management of patients with a neurogenic bladder who have decreased bladder compliance and detrusor hyperreflexia not controlled by oral medications.

Expression of granulocyte-macrophage colony-stimulating factor in rheumatoid arthritis: regulation by tumor necrosis factor-alpha

Granulocyte-macrophage colony-stimulating factor (GM-CSF), in addition to being a growth factor for granulocytes and macrophages, is an activator of cells of the monocyte/macrophage lineage and induces HLA class II expression and cytokine synthesis in these target cells. Macrophage activation and class II expression are prominent features in rheumatoid arthritis (RA) joints, but the mechanism of their stimulation is not understood, since interferon-gamma, the major stimulus of class II expression, is not usually detectable at the protein level in synovial cell culture supernatants. We have, therefore, studied GM-CSF expression in cultures of cells derived from joints affected by RA and osteoarthritis (OA), and show that GM-CSF is produced spontaneously both by RA synovial cells and to a lesser extent by OA synovial cells in the absence of extrinsic stimuli. GM-CSF production continues for the 5-day duration of the culture period. Using neutralizing antibodies to tumor necrosis factor (TNF)-alpha we demonstrated that GM-CSF production in RA synovial cell cultures is dependent on the continued presence of active TNF-alpha. This result supports our concept that continued activation of the cytokine network is a marked feature of RA, and that TNF-alpha plays a pivotal role in this network, by regulating the production of other pro-inflammatory cytokines, such as interleukin 1, as demonstrated previously, and GM-CSF.

Cytokine assays: role in evaluation of the pathogenesis of autoimmunity

Cytokines are protein mediators involved in inflammation, the immune response, cell growth, repair and fibrosis. All of these processes are ongoing in active autoimmune diseases such as rheumatoid arthritis (RA), and so it would be expected that many cytokines would be actively produced in RA joints or Graves' disease (GD) thyroid glands. The cDNA cloning of cytokines has permitted the generation of pure recombinant molecules, and of newer more sensitive assays, and spurred the rapid development of knowledge in this field. Here we review the molecular strategies devised to study the possible role of cytokines in the pathogenesis of RA and GD, and describe some of the initial results. After 'cataloguing' the relative abundance of various cytokines, we sought to discover which cytokines are of major importance in pathogenesis. For that purpose we used neutralizing anti-cytokine antibodies and found that TNF alpha is one of the major signals regulating the production of IL-1 in the RA but not in the osteoarthritic (OA) joint. In order to further understand the dynamics of the cytokine network, the localization of the cytokine-producing cells by immunostaining and in situ hybridization has also been performed. The latter techniques are particularly valuable for attempting to establish the role of the target cell, such as thyroid epithelium, in the pathogenesis of disease. Cytokines act on cells via binding to high-affinity receptors. The last two years has been the cDNA cloning of many molecules encoding cytokine receptor chains, and it is now possible to begin to evaluate the other half of the cytokine pathway. Taken together, there are now exciting opportunities for the molecular dissection of the cytokine events occurring in auto-immune tissues.

Cytokine production in the rheumatoid joint: implications for treatment

Cytokines are protein mediators that play a part in inflammation, the immune response, cell growth, repair, and fibrosis. All of these are continuing processes in active rheumatoid arthritis (RA), and so it would be expected that many cytokines would be actively produced in RA joints. Here, the molecular strategies devised to study the possible role of cytokines in the pathogenesis of RA, are reviewed and some of the initial results described. The relative abundance of various cytokines is 'catalogued' and then attention is turned to an attempt to discover which cytokines are of major importance in the pathogenesis. Neutralising antibodies to cytokines were used for that purpose, and it was found that tumour necrosis factor alpha (TNF alpha) is one of the major signals regulating the production of interleukin-1 in the RA, but not in the osteoarthritic joint. To understand further the dynamics of the cytokine network localisation of the cytokine producing cells by immunostaining--for example, TNF alpha, is currently being established.

Multifunctional cytokines in haemopoiesis

The number of cytokine molecules identified and cloned grows almost weekly. Studies using pure preparations have shown that single entities, e.g. TGF beta and IL-1 act on a wide variety of target cells whereas other cytokines, e.g. G-CSF have a more restricted target cell population. The outcome of stimulation of a cell by a cytokine depends on the target cell type, the presence of other coexisting cytokines and, as the release of cytokines may be targeted in the direction of the stimulus, the orientation of producer and target cells. These modulating phenomena may enable a small number of cytokines to specifically define a much larger number of responses, so that maximum 'value' is obtained from the successful evolution of cytokine and receptor molecules. The current nomenclature has little regard for this, the names of cytokines often deriving from the first property observed in vitro. In many cases these are not the most important properties of the molecule and can be misleading, e.g. transforming growth factor beta, which is growth inhibitory in some systems; the antiviral action of interferon gamma is relatively minor compared to its role as a macrophage activation factor; and interleukin-1 is produced by, and acts on, many cells outside the lymphohaemopoietic system. In addition, although there is often a high degree of homology, the repertoire of activities may vary between species. For example, IL-5 is a growth factor for eosinophils, both in humans and mice, however, in the mouse it also acts as a B-cell differentiation factor--a property which has been less easy to identify in human IL-5.(ABSTRACT TRUNCATED AT 250 WORDS)

T cells and lymphokines

T lymphocytes are one of the richest sources of protein mediators. Many of their effects, such as T cell help, growth stimulation, macrophage activation or suppression are caused by the release of these molecular mediators, which include the interleukins IL-2, IL-3, IL-4, IL-5, IL-6, interferons alpha and beta (IFN alpha and beta), tumour necrosis factor (TNF), lymphotoxin (LT), granulocyte macrophage colony stimulating factor (GM-CSF) and transforming growth factor beta (TGF beta). These molecules are only produced transiently after activation of the cells, and the CD4 (cluster differentiation antigen 4) cells are the richest sources of cytokines.

Rearrangement of the breakpoint cluster region and expression of P210 BCR-ABL in a "masked" Philadelphia chromosome-positive acute myeloid leukemia

The Philadelphia (Ph) translocation t(9;22)(q34;q11) occurs frequently in chronic myeloid leukemia (CML) but is less common in acute lymphoblastic leukemia (ALL) and rare in acute myeloid leukemia (AML). In most cases of CML and some cases of Ph+ ALL the protooncogene ABL from 9q34 is translocated to the breakpoint cluster region (bcr) of the BCR gene at 22q11 to form a chimeric gene encoding a novel 210-kd protein (P210 BCR-ABL) with enhanced tyrosine kinase activity. In other patients with Ph+ ALL and Ph+ AML, the breakpoint probably occurs in the first intron of the BCR gene; this results in a smaller chimeric gene which encodes a P190 BCR-ABL. We studied a patient with AML (FAB M6) arising de novo who had a "masked" Ph chromosome in association with extensive karyotypic changes. The leukemic cells initially showed rearrangement of the bcr, presence of a hybrid mRNA, and expression of the P210 BCR-ABL. These changes were absent in remission. These results support the concept that the BCR-ABL chimeric gene plays a crucial role in leukemogenesis but suggest that factors other than the position of the breakpoint in the BCR gene determine the lineage of the target cell for malignant transformation.

Role of HLA class II and cytokine expression in rheumatoid arthritis

HLA class II expression is notable in rheumatoid arthritis. We have investigated the mechanism of HLA class II regulation in the joints and found local synthesis, as judged by mRNA levels to be high. The role of antigen presentation in maintaining class II mRNA was explored, and blocking presentation by using monoclonal antibodies to HLA class II inhibited synthesis of mRNA for HLA-DR alpha chain. HLA class II expression is maintained by cytokines and so cytokine production in rheumatoid joints was investigated. It was chosen to use mRNA analysis by slot blotting as a screening assay, and the expression of many cytokines was detected. Levels of these were maintained in culture in the absence of extrinsic stimulation.

Intracranial pressure after atracurium in neurosurgical patients

In order to investigate the usefulness of atracurium for neurosurgical anesthesia, we studied its impact on intracranial pressure (subarachnoid bolt) mean arterial pressure (radial artery catheter) and cerebral perfusion pressure (mean arterial pressure-intracranial pressure) in 20 patients undergoing elective craniotomy for brain tumor excision. General anesthesia was induced with thiopental, 4 mg/kg intravenously, and maintained with 70 percent nitrous oxide in oxygen. Ventilation was controlled by face mask, with end-tidal CO2 held constant. Once intracranial pressure and mean arterial pressure had stabilized, the response to atracurium, 0.5 mg/kg intravenously, was continuously recorded for 5 min in 10 patients. An additional 10 patients received no atracurium and served as matched controls. Thiopental caused reductions in ICP in both groups of patients. Comparing the responses of the patients who received atracurium with those who did not, we found that atracurium had no significant effect on intracranial pressure, mean arterial pressure or cerebral perfusion pressure. Based on these data we conclude that atracurium appears to be preferable to the other available neuromuscular blocking agents that have been evaluated for neurosurgical anesthesia.

Serial incidence of bone marrow GM-CFC prior to the development of acute non-lymphoblastic leukaemia in a child treated for non-Hodgkin's lymphoma

A child treated for NHL developed acute non-lymphoblastic leukaemia 27 months after stopping treatment. Serial in vitro bone marrow studies showed a normal incidence of GM-CFC following treatment. However, GM-CFC incidence dropped at least 15 months prior to the development of leukaemia. This was associated with an asymptomatic neutropenia but no disturbance of bone marrow morphology. It is concluded that sub-clinical disturbances of bone marrow function may play an important part in leukaemogenesis.

Long-term bone-marrow damage in children treated for ALL: evidence from in vitro colony assays (GM-CFC and CFUF)

We have studied granulocyte-macrophage progenitor cells (GM-CFC) in serial bone marrow aspirates from 43 children who had been treated for acute lymphoblastic leukaemia (ALL). All patients were in full remission, not receiving anti-leukaemic therapy and 42 out of the 43 had normal peripheral blood counts. Thirty-seven patients have received standard amounts of chemotherapy and 6 have received additional therapy for relapses occurring in the first treatment-free interval. In the former group estimation of GM-CFC incidence did not provide evidence of long-term residual bone-marrow damage. In the latter, however, the mean incidence of GM-CFC was significantly reduced. This reduction was also apparent when the incidence of GM-CFC was related to the incidence of non-haemopoietic progenitor cells within the marrow (CFU-F).

Thiamine responsive anaemia: a study of two further cases

A brother and sister of Pakistani origin suffered from sensorineural deafness, diabetes mellitus and a macrocytic anaemia. Their bone marrows showed megaloblastic erythropoiesis and contained many ringed sideroblasts. Electron microscope studies of the bone marrow revealed (1) iron-laden mitochondria in many erythroblasts, (2) non-specific abnormalities indicative of dyserythropoiesis in some erythroblasts, and (3) evidence of ineffective erythropoiesis. The deoxyuridine suppression test indicated that the megaloblastic changes were not caused by an impairment of the methylation of deoxyuridylate. Studies of nucleic acid synthesis in the bone marrow cells showed that the rate of incorporation of [3H]thymidine into DNA was increased and that the rates of incorporation of [14C]glycine and [14C]adenine into both DNA and RNA were essentially within the normal range. The anaemia did not respond to therapy with hydroxocobalamin, folic acid or pyridoxine but responded to 25 mg thiamine, daily, by mouth. In one of the cases a post-thiamine marrow aspirate showed a considerable improvement in both the megaloblastic and sideroblastic changes.

Routine bone marrow examination in the management of acute lymphoblastic leukaemia of childhood

Eighty-four children with acute lymphoblastic leukaemia (ALL) who had relapsed in bone marrow were studied to assess whether treatment would be more successful if relapse was detected before the disease became clinically evident. Patients whose relapse was detected by routine bone marrow examination before the disease became apparent were compared with those whose relapse was suspected from clinical examination or peripheral blood findings. In the former there was a lower percentage of blast cells in the marrow (p less than 0.02) and the patients suffered less from complications of the disease, but there was no difference in the incidence or duration of second remissions between the two groups.

Viability of red cells stored in diminished concentration of citrate

A comparison was made between the post-transfusion survival of red cells stored in standard ACD-A and in modified ACD-A, containing two-thirds the amount of citrate. Measurements of survival after 28 d storage in both solutions were made in each of six subjects. Mean post-transfusion survival with the two solutions was almost identical. When the results in one subject in whom survival was particularly bad with both solutions were omitted mean values at 24 h were 74.0% for standard ACD-A and 74.9% for modified ACD-A. It is concluded that viability is just as well maintained in modified ACD-A as in standard ACD-A. The results also provide further evidence of large differences between donors with respect to the maintenance of red cell viability during storage.

A case of atypical polyagglutinability due to Tk-transformation

A case of acquired transient polyagglutinability in a group O, Rh(D) positive female patient, Wa, is described. An unusual finding in the preliminary serological investigation was the non-reaction of the cells with peanut (Arachis hypogaea) extract. The patient's red cells were strongly agglutinated by normal human and rabbit sera from which anti-T had been removed. Electrophoretic mobility studies and tests with polybrene indicated that their sialic acid content was normal. The use of a specific antiserum raised in a rabbit to Wa cells and cross-absorption tests showed that the patient's erythrocytes shared similar antigenic determinants to red cells treated with supernatants from pure cultures of Bacteroides fragilis. The in vitro-modified red cells reacted strongly with BS II lectin prepared from Bandeiraea simplicifolia seeds thus providing confirmatory evidence for Tk transformation on Wa cells. It is concluded that the Tk receptor is probably a more frequent feature of acquired transient polyagglutinability than has hitherto been recognized.

Fetomaternal transfer of glucose analogues by sheep placenta

The steady-state permeability of the placenta to radiolabeled 3-O-methyl--D-glucopyranose (3MeG), alpha-methyl-D-glucopyranoside (AMG), and D-xylose was measured in chronically catheterized conscious sheep near term. Fetomaternal flux was calculated by application of Fick's principle to the uterine circulation after injection to the fetus. At a fetal glucose concentration of 10.2 +/- 1.25 mM, the permeability of 3MeG was half the maximal value of 59.5 +/- 11.2 ml/min found by extrapolation to zero glucose concentration. The permeability to 3MeG is considerably greater than is compatible with restricted diffusion, which together with the competitive effect of D-glucose suggests a carrier-mediated transfer mechanism. The permeability to AMG was less than 0.1 ml/min. The specificity pattern of sugar transport from the fetal side of the sheep placenta is different from that reported for gut lumen or kidney tubule in other species. D-Xylose is not metabolically inert after its injection into the fetal lamb.

Permeability of the sheep placenta to unmetabolized polar non-electrolytes

1. The rate of appearance in uterine venous blood of radioactively labelled, polar, non-electrolytes has been measured following their injection into the foetal circulation in the chronically catheterized sheep near term. Uterine blood flow was measured by an antipyrine technique. 2. Estimates of a placental permeability constant not corrected for area were 61-2 +/- 5-5 ml. min-1 (mean +/- S.E. of mean) for [14C] urea, 1-85 +/- 0-16 for [14C]erythritol and 0-21 +/- 0-03 for [3H]mannitol. Results are also presented for [14C]ethylene glycol, [14C]L-glucose, [14C]mannitol, [51Cr] EDTA and [3H] and [14C]sucrose. 3. In four sheep, permeability measurements for several solutes were made and the results were analysed in terms of restricted diffusion via cylindrical, water-filled pores. Calculation of pore radius was made by a minimum variance method and values ranging from 0-43 to 0-45 nm were obtained. 4. Stability and absence of protein binding of probe molecules was investigated by gel permeation on Sephadex columns.

Enteric-coated aspirin overdose and gastric perforation

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