Bellmanism: the distortion of reason.

Single-issue compound or class related anxieties about chemical exposures are often the focus of concern for groups that seek to affect the regulatory process itself or the regulatory status of compounds that have passed through it. A characteristic of these groups is an imperfect understanding and use of science, in particular in the evaluation of data. Studies which have been discredited are cited repeatedly and the role of confounding factors is not generally acknowledged. The regulation of medicines, devices, pesticides and some household chemicals depends on the use of a methodology that follows strict protocols. This involves testing in many systems including mammals, other vertebrates, invertebrates, soil macrobiota or ground water, as examples, with often well-defined schemes of interpretation which facilitate extrapolation between species. A complex risk evaluation will then be made for different groups (by age, sex, or occupation, say) or targets (patients, farmers, consumers and vulnerable non-human species). Focusing on an effect in a single group may suggest interventions which will be damaging for others.

Improving vascular grafts: the importance of mechanical and haemodynamic properties.

In the last 40 years, as techniques and materials have improved, the success rate of vascular prostheses with a diameter greater than 6mm has risen steadily, 5-year survival rates exceeding 95% in most centres. With smaller grafts no comparable improvement has occurred, the majority failing within 5 years, usually as a result of intimal hyperplasia and, ultimately atherosclerosis, in and around the downstream anastomosis. Clinical evidence suggests that the patency rates of small grafts are improved by matching the elastic properties of the graft to that of the artery into which it is placed. Although there is little reliable evidence that 'elastic mismatch' per se is the cause of intimal hyperplasia, it is generally accepted that mechanical factors are important in its genesis. These include disturbed flow at the anastomosis leading to fluctuations in shear stress at the endothelium (a known cause of intimal hyperplasia in normal arteries), injury due to suturing and stress concentration at the anastomosis. Few suitable materials or techniques have yet been developed to improve the long-term survival rates of small grafts. Recent advances in tissue engineering in which prostheses are manufactured by culturing vascular smooth muscle cells on a tubular scaffold of biodegradable polymer may ultimately make it possible to manufacture biologically and haemodynamically compatible grafts with diameters as small as 1mm.

The effects of maternal protein deprivation on the fetal rat pancreas: major structural changes and their recuperation.

There is evidence that low birth weight and poor growth in early life cause a long-term predisposition to non-insulin-dependent diabetes. Morphological changes were assessed in fetal rat pancreas subjected to both pre- and post-natal maternal protein deprivation (LP). Further groups were subjected to purely prenatal maternal protein deprivation (preLP) and purely postnatal maternal protein deprivation (postLP), as well as a control group. The results show that the LP and postLP groups had fewer but larger islets than the control group, while the preLP group had more numerous, smaller islets. All three low protein groups had more irregularly shaped islets than the control group. There was a reduction in the amount of beta cells within each islet in all three protein-deprived groups. The LP and postLP groups showed a reduction in the percentage of islet tissue and beta cells per pancreas, but the percentage of islet tissue expressed per unit body weight was similar in all four groups. These results show that in maternal protein deprivation, homeostatic mechanisms ensure a constant amount of pancreatic endocrine tissue per unit of body weight. However, there remain major structural changes in the size, shape, and composition of the islets. These results support the theory that early development profoundly affects the structure of the pancreas and may play a role in the later development of adult diseases, such as non-insulin-dependent diabetes mellitus.

Is the incidence of primary adenocarcinoma of the lung increasing?

Primary carcinoma of the bronchus is a major cause of death in males and females. Several studies report an increase in the incidence of adenocarcinoma and have suggested that this reflects changes in smoking habits or, alternatively, that it is a spurious rise due to changes in diagnostic criteria. To examine the latter suggestion we reviewed three cohorts of bronchial carcinoma from 1970, 1980 and 1990, using immunocytochemical techniques to refine diagnosis. We found that squamous cell carcinoma had been consistently overdiagnosed and adenocarcinoma and adenosquamous carcinoma consistently underdiagnosed in all groups. Also, many tumours showed evidence of divergent differentiation with both squamous and glandular components present. There was a small, but real temporal increase in the proportion of adenocarcinoma over the 10 years between 1970 and 1980, but this was not sustained between 1980 and 1990.

Early onset systemic Candida infection in extremely preterm neonates.

UNLABELLED: Classically, systemic Candida infections in preterm neonates occur at a mean age of 1 month. Over an 18-month period in a Regional Neonatal Intensive Care Unit we encountered seven cases of severe Candida infection, all in babies below 26 weeks gestation and weighing less than 0.75 kg. The median age of onset was 7 days (range 0-17), with thrombocytopenia, coagulopathy, hypotension, oedema, and skin breakdown being prominent features. CONCLUSION: The thin cutaneous barrier may contribute to early onset of systemic Candida infection in preterm infants. The characteristic skin appearance may assist early diagnosis.

Effects of exercise and fetal spinal cord implants on the H-reflex in chronically spinalized adult rats.

This study investigated the modulation of hindlimb reflex excitability after transection of the spinal cord in adult rats. After transection, the H-reflex exhibited decreased depression at high stimulation frequencies compared to intact animals. Groups of animals which received a spinal cord transection followed by either an exercise regimen for the hindlimbs or a fetal spinal cord implant, showed high stimulation frequency depression similar to controls. This suggests that each of these palliative strategies helped to "normalize' the excitability of specific spinal reflexes.

Postmortem diffusion of ingested and aspirated paint thinner.

Post mortem diffusion of paint thinner (toluene/ethyl acetate/isobutanol 8:1:1 v/v) from gastric residue (25 ml or 100 ml) and airways contamination (25 ml) was assessed in a human cadaver model, with sampling after 24 h at room temperature. Four torso blood samples showed less toluene diffusion after gastric instillation (0.5-3.8 micrograms/ml) than after tracheal instillation (10.5-421 micrograms/ml). Isobutanol diffused more readily than toluene with four torso blood samples 1.8-256 micrograms/ml after gastric instillation and 26-576 micrograms/ml after tracheal instillation. Following 25 ml gastric instillation, toluene concentrations (microgram/ml or microgram/mg) were: pericardial fluid 0.7-4.0; bile 0.5-0.6; urine 0-0.6; brainstem 1.1; lung 0.4-4.4; liver 0-162; spleen 0.6-0.7; kidneys 0.4-0.6; peri-renal fat 0.3-30.3; psoas muscle 0.3-0.8; concentrations of toluene and isobutanol were markedly higher in the left lobe of the liver than the right. Ethyl acetate was mostly undetectable in tissue samples but variably present in five blood samples: 0-21.2 micrograms/ml following 25 ml or 100 ml gastric instillation and 0-198 micrograms/ml following 25 ml tracheal instillation. Ethyl acetate was always detectable in pericardial fluid but not always detectable in gastric contents. We conclude that post mortem diffusion of toluene from gastric residue or airways contamination is unlikely to compromise the analytical validity of femoral venous blood samples, brain, or liver from deep within the right lobe. Analysis of pericardial fluid and gastric contents allows identification of ethyl acetate and isobutanol thus implicating thinner solution.

Vascular smooth muscle cells cultured on elastin membranes.

Smooth muscle cells from thoracic aortas of 12-week-old rats were cultured on elastin membranes for up to 21 days. The cell cultures were examined using light microscopy, transmission and scanning electron microscopy. The contractile phenotype characteristic for resident arterial wall muscle cell changed to the synthetic phenotype. In the synthetic state, the muscle cells contain few filaments, but a substantial amount of organelles are involved with synthesis. The cells grown on elastin substrates showed a multilayered pattern with the formation of nodules. Cell degeneration was present from day eight and increased with time. At the end of the experiment, the center of the multilayered areas showed degenerative changes with numerous foam cells of smooth muscle origin, areas of necrosis and a considerable amount of calcium deposit. Our experimental model would be valuable in the investigation of the pathological changes associated with smooth muscle cell proliferation in vessels.

Cell to stroma contacts in the tunica media of the hypertensive rat thoracic aorta.

The variation in mechanical stress to which the aortic wall is subjected requires that forces be transmitted between its components by means of relatively strong but compliant attachments. We have used transmission electron microscopy in order to study the cell to stroma contacts (smooth muscle cell-elastic fiber contact) in the tunica media of normotensive and hypertensive aortas of Sprague-Dawley rats. Hypertension was produced with a silver clip positioned around the left renal artery and the vessels were fixed by intravital perfusion at normal and elevated pressure. In ultrathin sections, the density of cell to stroma contacts per 100 microns cell perimeter and per 100 cell profiles were determined using an image analysis computer. In the hypertensive group the density of cell to stroma contacts fell considerably when compared with the control group. This research provides insights into the conditions under which high blood pressure may produce medial injuries and, perhaps, be a factor in the precipitation of dissections.

Myoendothelial contacts in the human fetal aorta.

Intracellular communication is an essential process in both embryological development and for the maintenance of normal tissue physiology. We have established the presence of this type of communication between endothelial cells and vascular smooth muscle cells in man and have here investigated the close contacts between endothelial and smooth muscle cells in the aorta of the 10-week-old human fetus. Transmission electron microscopy revealed myoendothelial contacts in the form of cytoplasmic projections, usually originating from the muscle cells. The nature of the cell-cell contacts was via simple appositions with an intercellular space of 6-15 nm. Myoendothelial contacts are sites for communication between elements of the intima and media, ensuring that paracrine secretion can occur and that the vessel wall, during growth and development, works as a unit.

Pathology of the ear in murine mucopolysaccharidosis type VII. Morphologic correlates of hearing loss.

BACKGROUND: Patients with mucopolysaccharidosis commonly have hearing impairment but the morphologic alterations in the ear caused by these lysosomal storage diseases are incompletely defined. EXPERIMENTAL DESIGN: We studied a murine model of mucopolysaccharidosis VII with clinical features, including conductive hearing loss and biochemical, and pathologic features similar to those seen in human mucopolysaccharidoses. Gross morphology, radiography, light and electron microscopy were used to define the pathologic alterations in the ear that correlate with auditory dysfunction in mucopolysaccharidosis VII. RESULTS: Cerumen occluded the external auditory canal and there was a severe otitis media. The bone encasing the middle and inner ear was sclerotic and opaque and the temporal bone and the ossicles and their joints contained cells distended by enlarged lysosomes. Hair cell damage and multifocal lysosomal distention in endoneural fibroblasts and spiral ganglion neurons characterized the mucopolysaccharidosis VII cochlea. CONCLUSIONS: The external auditory canal obstruction, otitis media, and ossicle articular alterations in mucopolysaccharidosis VII mice cause a conductive hearing loss. The hair cell damage and neuronal storage may contribute to sensorineural deafness. This model allows investigation of the pathophysiology of auditory dysfunction in mucopolysaccharidosis and the effects of therapies on hearing loss.

The observation of angiogenin and basic fibroblast growth factor gene expression in human colonic adenocarcinomas, gastric adenocarcinomas, and hepatocellular carcinomas.

Using digoxigenin-labelled, synthetic oligonucleotide probe cocktails of angiogenin and bFGF genes, the expression of the two genes was observed by in situ hybridization in ten colonic adenocarcinomas, seven gastric adenocarcinomas, and four hepatocellular carcinomas. The angiogenin gene was expressed in eight of the ten cases of colonic adenocarcinoma and in all of the four cases where dysplastic glands were found. Angiogenin expression was evident in four of the seven cases of gastric adenocarcinoma. bFGF expression was detected in only five of the seven gastric carcinoma cases. The mRNAs for angiogenin and bFGF were mainly cytoplasmic in distribution and were only occasionally seen in the nuclei of the positive cells. Neither the angiogenin gene mRNA nor the bFGF mRNA was expressed in the four cases of hepatocellular carcinoma. It is postulated that the angiogenin gene may play an important role in angiogenesis in colonic adenocarcinomas; in gastric cancers, both angiogenin and bFGF were involved in this process. For hepatocellular carcinomas, neither angiogenin nor bFGF production appeared to be related to angiogenesis.

Pathological sequelae of implantation of intracorporeal left ventricular assist devices in the calf.

Thromboembolic complications have previously been a major pathological complication of left ventricular assist device (LVAD) insertion and appear to be a consequence of the use of smooth polyurethane linings. Textured biomaterial surfaces are designed to attract a stable coagulum which becomes organized to form a neointima. We describe the pathological changes following experimental implantation of textured-surface LVADs in calves. The incidence of systemic embolization from such linings appears to be low. Surface modifications with cell seeding offer the possibility of further reduction in incidence of this problem. However, degradation of prosthetic valves may be a potential source of emboli and infection. With these complications minimized, the most significant pathological changes observed appear to relate to the device haemodynamics. At present renovascular changes associated with systemic hypertension appear to be the greatest potential problem for the long-term use of these devices.

The lining of textured surfaces in implantable left ventricular assist devices. An immunocytochemical and electronmicroscopic study.

OBJECTIVE: The aim was to examine and identify some components of biological linings developed upon the textured surfaces of a circulatory assist device. The development of biological linings upon a textured surface circulatory assist device was evaluated in patients implanted for periods ranging from 84 to 132 days. METHODS: Explanted devices were examined macroscopically. Light microscopy, transmission electron microscopy and immunocytochemistry techniques were employed to evaluate the histogenesis of the tissue deposits upon the device surfaces. Visible material was essentially limited to focal areas upon the static housing and the periphery of the pusher-plate diaphragm (Biomer). RESULTS: Microscopy of the linings showed fibrin-rich areas with platelets, monocytes and few spindle-shaped surface cells. Central areas were composed of multiple layers of spindle-shaped cells separated, mainly, by collagen. Giant-cell foreign-body reaction to Biomer fibrils was seen. CONCLUSION: Transmission electron microscopy and immunocytochemistry indicated the presence of at least two cell populations: fibroblasts and smooth muscle-like cells, or 'myofibroblasts'. There was no evidence of endothelial cell presence.

The relationship between wall tension, lamellar thickness, and intercellular junctions in the fetal and adult aorta: its relevance to the pathology of dissecting aneurysm.

It is known that the distribution of stress and strain in the vessel wall is not uniform. We believe that this explains the location of the plane of dissection in dissecting aneurysms of large elastic arteries. We have investigated the effects of non-uniformity of stress and strain on the thickness of each elastic lamella and on the distribution of intercellular junctions in the media of developing and adult rats, to seek evidence to support this hypothesis. Intercellular junctions were identified by transmission electron microscopy of whole wall sections. A morphometric study of elastic tissue distribution was made on an image analysis computer. Differences were analysed using one-way analysis of variance. There are between six and eight elastic lamellae in the aorta of rats. In the fetus, only the internal elastic lamella is complete; the others were not fully formed by term. In the adult, the inner five elastic lamellae were thicker than the remaining two or three, and smooth muscle cells in the thicker lamellar units had more cell-cell contacts of all types examined. These data support the concept of a difference in stress-resisting properties of the aortic wall on the junctions between the inner two-thirds and the outer third of the media. The findings indicate that, as proposed in theoretical models the innermost lamellae support the high tension. In the adult aorta, the structure is modified to enhance the capacity to resist stress in the internal two-thirds of the media.(ABSTRACT TRUNCATED AT 250 WORDS)

The development of an in-vitro perfusion system for studies on cultured cells.

The design and use of a perfusion system, using a modified flow chamber for studies on cultured animal cells, is described. Rat thoracic aorta smooth muscle cells were isolated by an explant method and grown on Thermanox coverslips. These were introduced into the flow chamber. A flow rate of 25ml/min and a shear stress of 14.6 dynes/cm2 (12 dyne = 10 microN) (both within physiological limits) were maintained. Cells remained attached to the coverslips after 8h of perfusion with culture medium. The effect of exposing rat smooth muscle cells to the cardiovascular toxin, allylamine, is also described. The components of the system are routinely available, simple to clean, easy to assemble and sterilize. The incorporation of an in-line sensor that monitors pH, PO2, PCO2 and temperature ensures that the perfusion conditions remain within physiological limits. Automation means that minimal supervision is required. This system provides a potential mechanism in which cultured vascular cells may be perfused under controlled haemodynamic conditions, and their response to a cytotoxin may be evaluated.

Myoendothelial contacts in arteriolosclerosis.

Human renal biopsies were examined electron microscopically to investigate close contacts between endothelial and smooth muscle cells in small arterioles. These myoendothelial contacts were seen in the form of cytoplasmic projections passing through fenestrae in the basal lamina. Most of these cell processes seem to arise from the endothelial cells. In the control vessels, the separation between the endothelial cells and smooth muscle cells of the tunica media is 0.09-0.27 microns. With arteriolosclerosis there is an increasing separation between the elements of the intima and the media, from 1.0 to 2.42 microns. In spite of this increasing separation, myoendothelial contacts maintain an intercellular space of 10-15 nm, as observed in the control vessels. At 2.42 microns of separation, the amount of extracellular material accumulated is such that the cells can no longer keep in contact. Break up of the myoendothelial contacts may be responsible for impairment of communication between the tunica intima and media in the vessel wall in arteriolosclerosis.