PDGF-alpha receptor and myelin basic protein mRNAs are not coexpressed by oligodendrocytes in vivo: a double in situ hybridization study in the anterior medullary velum of the neonatal rat

Platelet-derived growth factor (PDGF) is a growth-regulatory dimer with A and B subunits. PDGF-AA, acting via PDGF receptors of the alpha-unit subtype (PDGF-alphaR), is implicated in the differentiation of oligodendrocyte precursors and in the survival of newly formed oligodendrocytes, which gradually lose expression of PDGF-alphaR. However, it is unclear whether terminally differentiated oligodendrocytes express PDGF-alphaR in vivo. To address this question, and to help clarify the role of PDGF-AA in late oligodendrocyte differentiation, we have used double in situ hybridization with digoxigenin- and fluorescein-labeled riboprobes to relate PDGF-alphaR mRNA and myelin basic protein (MBP) mRNA expression in the isolated intact anterior medullary velum (AMV) of rats ages Postnatal Day (P) 10-12 and P30-32. In parallel experiments, AMV were immunolabeled with the oligodendrocyte-specific monoclonal antibody Rip to provide information on oligodendrocyte development and the extent of myelination. At P10, the AMV contained tracts in which axons ranged from unmyelinated to fully myelinated, whereas myelination was complete in P30-32 AMV. The first oligodendrocytes to express MBP mRNA or Rip were promyelinating oligodendrocytes, which had a "star-burst" morphology and had not yet begun to form myelin sheaths. As myelination proceeded, MBP mRNA became dispersed throughout oligodendrocyte units, comprising cell somata, processes, and internodal myelin sheaths. By P30-32, MBP mRNA had been redistributed to the myelin sheaths only, reflecting a change in the site of protein synthesis in mature myelinated axon tracts. At no stage of oligodendrocyte differentiation did we observe cellular coexpression of mRNA for PDGFalphaR and MBP. Our results indicated that oligodendrocytes lost the expression of PDGFalphaR prior to gaining that of myelin gene products, and preclude an action of PDGF-AA on Rip+/MBP+ star-burst promyelinating oligodendrocytes. The spatial and temporal expression of PDGF-alphaR mRNA in the AMV was inversely related to the pattern of maturation of both myelin and oligodendrocytes, and is consistent with PDGF-alphaR being expressed by pro-oligodendrocytes. A notable finding was the high level of expression of PDGF-alphaR mRNA in the AMV of juvenile rats, localized to cell bodies within the myelinated axon tracts, strongly suggesting that oligodendrocyte precursors persisted in the mature velum.

The unusual imaging appearance of primary retroperitoneal teratoma: report of a case

Primary retroperitoneal (RP) teratoma is a rare entity which has a distinctive imaging appearance. We describe herein the case of a 25-year-old man in whom a RP teratoma was found to have an extremely unusual imaging morphology by ultrasound and computed tomography (CT). The tumor was resected and histopathological examination confirmed the diagnosis of primary benign RP teratoma.

Hygiene- and food-related behaviors associated with blood lead levels of young children from lead-contaminated homes

Exposures associated with blood lead levels greater than 40 micrograms/dL in young children who live in lead-contaminated homes have been well documented. As the action level for lead is reduced, activities that contribute to lower levels of lead exposure must be identified. A child's eating habits and related hygiene behaviors are major hand-to-mouth activities that have been largely overlooked in the study of activities contributing to lead ingestion. To examine this subject, a survey questionnaire for caretakers of young children was developed. The objective of the questionnaire was to characterize food-related activities of young children and to identify behavioral indicators of lead exposure. The association between food- and hygiene-related behaviors and blood lead levels among 60 children between 13 and 36 months old with low-to-moderate blood lead levels was examined in homes that had been identified as containing lead in paint and house dust. The participants were enrolled in the Children's Lead Exposure and Reduction Study in Jersey City, New Jersey. Blood lead levels of children 13-24 months old did not differ significantly from those of children 25-36 months of age (10.1 and 11.3 micrograms/dL, respectively). Differences in eating habits and hygiene behaviors were found for the two age groups. Bivariate analyses found that the primary behavioral indicators of blood lead levels were determined by whether the child prepared his/her own food and whether the child ate food that had been on the floor. This factor was dependent on age. Children 13-24 months old had significantly elevated blood lead levels if these behaviors exhibited. No significant differences were found, however, for children 25-36 months old. Several food-related habits were also associated with blood lead levels. Eating hamburgers, doughnuts, peanut butter and jelly sandwiches, and cold cuts were associated with elevated blood lead levels in 13-24-month-old children, while eating vitamins, raw vegetables, and yogurt were associated with lower blood lead levels in this age group. For children 25-36 months old, eating hamburgers and peanut butter and jelly sandwiches was associated with elevated blood lead levels, while yogurt consumption was associated with lower blood lead levels.

Polydispersity of normal human conjunctival mucins

PURPOSE

To isolate all constituent mucins from human conjunctival mucus.

METHODS

Mucins were extracted from human conjunctiva in guanidine hydrochloride and protease inhibitors. The mucins were isolated by density gradient centrifugation, gel filtration, and ion exchange chromatography. Throughout purification, the mucin profile was monitored by agarose electrophoresis and vacuum blotting. Blots were probed for peptide and carbohydrate epitopes. The latter included IE3 and TKH2 specific for Tn and sialyl-Tn, respectively, considered tumor-related antigens. In vivo impression cytology specimens of normal conjunctival goblet cells also were probed with the same reagents. Oligosaccharides were released from isolated mucins by alkaline beta-elimination and then size fractionated.

RESULTS

Human conjunctival mucins consist of at least three size populations; the largest is excluded on Sepharose CL2B. The two largest populations are polydisperse. Their overall electrophoretic pattern is conserved between individuals. Similar charge distributions were detected in different buoyant density ranges from the density gradient centrifugation: a less charged population containing three components and a highly charged population with two components on agarose electrophoresis. Cross-reaction with IE3 and TKH2 was detected throughout purification in the largest mucins, which were presumably mature, and in impression cytology. Oligosaccharides from mucins in each buoyant density were largely in the monosaccharide and disaccharide range, consistent with Tn and sialyl-Tn standards.

CONCLUSIONS

Secreted human conjunctival mucins are polydisperse, with discrete components appearing consistently in pooled and individual samples. They have a unique oligosaccharide pattern containing Tn and sialyl-Tn. This indicates normal roles in normal human ocular mucins for these antigens, which are disease markers in other tissues.

Certification for child protective services staff members: the Texas initiative

Cases coming to the attention of child protective service agencies are increasingly complex and difficult, while the number of trained staff members has decreased substantially over the last 10 years. Some states are attempting to improve the situation by implementing a certification process for staff members in child welfare service. This article describes the Texas initiative to do so, identifies problems in planning and implementation, and discusses implications for practice.

Effect of glucose on uptake of radiolabeled glucose, 2-DG, and 3-O-MG by the perfused rat liver

In the transition from the fasting to the fed state, plasma glucose levels rise, and the liver converts from an organ producing glucose to one of storage. To determine the effect of glucose on hepatic glucose uptake, radiolabeled glucose, 2-deoxyglucose, and 3-O-methylglucose were injected into perfused rat livers during different nontracer glucose levels, and the concentrations in the outflow were measured. A mathematical model was developed that described the behavior of the injected compounds as they traveled through the liver and was used to simulate and fit the experimental results. The rates of membrane transport, glucokinase, glucose-6-phosphatase, and the consumption of glucose 6-phosphate were estimated. Membrane transport for all of the tracers decreased as nontracer glucose increased, demonstrating competitive inhibition of the glucose transporter. In contrast, the consumption of injected [2-14C]glucose increased when glucose was elevated, demonstrating that glucose caused an activation of enzyme activity that overcame the competitive inhibition of transport and phosphorylation. When glucose was elevated, the rate coefficient of glucokinase did not decrease, indicating that glucokinase was stimulated by glucose. Both changes would lead to the increased glycogen synthesis and decreased glucose production rate observed in vivo during the fasted-to-fed transition.

Transfer of horseradish peroxidase from oligodendrocyte to axon in the myelinating neonatal rat optic nerve: artefact or transcellular exchange?

In this paper we make the surprising observation that intracellular injection of horseradish peroxidase (HRP) into a single myelinating oligodendrocyte also resulted in localised HRP labelling at the nodes of Ranvier of some axons of the unit. It appeared that HRP had been transferred to the nodal axoplasm from the paranodal loops of the HRP-filled oligodendrocyte. Three HRP-filled oligodendrocytes from isolated optic nerves of 14-day-old rats were analysed by serial section electron microscopy, and HRP was observed in the axonal cytoplasm at three of the nodes of Ranvier delineated by one of the cells. At labelled nodes, HRP was of a uniform intensity throughout the nodal axoplasm. Axonal labelling gradually diminished along the paranodal regions and was not evident in the contiguous internodal axoplasm beyond 20 microns from the node. The myelin sheaths, paranodal loops, and axons appeared normal at labelled nodes, and the paranodal loops and astrocyte perinodal processes adjacent to those of the HRP-filled oligodendrocyte unit did not contain HRP. There was no evidence of extracellular HRP or tissue damage in the surrounding neuropil, and axons neighbouring those enwrapped by the HRP-filled oligodendrocyte did not contain HRP. The possibility that axonal labelling was an artefact of either iontophoretic injection or tissue preparation is discussed. This provocative finding is not definite proof of exchange, but the balance of evidence supports the possibility that there was transcellular exchange of HRP at paranodes between the labelled oligodendrocyte and some of the axons in the unit. The rarity of HRP transfer to axons suggests that it may be a transient or labile event. It is not clear whether oligodendrocyte to axon macromolecular exchange has real physiological and/or pathological significance.

Cholesterol-lowering intervention program. Effect of the step I diet in community office practices

BACKGROUND

A randomized study was conducted to test the feasibility of cholesterol lowering in physician office practices using the National Cholesterol Education Program Adult Treatment Panel 1 guidelines.

METHODS

Twenty-two physician practices in phase 1 and 23 in phase 2 were recruited from communities in Western Pennsylvania and West Virginia. These physicians treated a total of 450 adults in phase 1 (190 men and 260 women) and 480 adults in phase 2 (184 men and 296 women) with hypercholesterolemia. Three models (Usual Care [phase 1], Office Assisted [phase 2], and Nutrition Center [phase 2]) for implementing the National Cholesterol Education Program Adult Treatment Panel 1 guidelines were tested over an 18-month period. The baseline serum cholesterol levels were as follows: 6.51 mmol/L (252 mg/dL) in the Usual Care Model; 6.80 mmol/L (262 mg/dL) in the Office Assisted Model; and 6.96 mmol/L (269 mg/dL) in the Nutrition Center Model.

RESULTS

In the patients who were not taking lipid-lowering medication, the mean cholesterol response was significantly different between the 3 models (P < .01). Serum cholesterol levels declined by 0.14 mmol/L (5.4 mg/dL) in the Usual Care Model; by 0.31 mmol/L (12 mg/dL) in the Office Assisted Model; and by 0.54 mmol/L (20.9 mg/dL) in the Nutrition Center Model. Two factors-length of time to follow-up measurement and change in weight-were independently related to cholesterol response across all models. African Americans demonstrated a significantly smaller response than whites in the Usual Care Model, while men demonstrated greater declines in serum cholesterol levels than women in the Office Assisted Model. Patient satisfaction was very favorable in both enhanced conditions; however, those treated in the the Nutrition Center Model were more satisfied (P < .05) with program components.

CONCLUSIONS

The impact of nutrition intervention delivered through physician practices on serum cholesterol levels is less than clinically desirable, and new approaches with more aggressive therapy should be tested and implemented.

Hyperopia correction by noncontact holmium:YAG laser thermal keratoplasty. Clinical study with two-year follow-up

BACKGROUND

Thermal keratoplasty to correct hyperopia has been attempted with nonlaser and laser devices. Problems have included long-term regression and irregular induced astigmatism. The present clinical study was performed to investigate the safety, efficacy, and stability of a noncontact mode of holmium: YAG laser energy delivery and a modified laser thermal keratoplasty treatment procedure for correction of low hyperopia.

METHODS

Seventeen patients underwent noncontact holmium: YAG laser thermal keratoplasty in their nondominant eyes for correction of hyperopia of up to 3.00 diopters. Treatment parameters included simultaneous delivery of eight holmium: YAG laser spots in a symmetrical octagonal array with a centerline diameter of 6mm, 10 pulses of laser light at 5-Hz pulse repetition frequency, and pulse energies of 159 to 199mJ. Follow-up was 2 years in 15 of 17 patients.

RESULTS

In the 15 eyes examined at 2 years after surgery, mean uncorrected distance Snellen visual acuity improved from 20/125-1 to 20/50-2. The mean change in spherical equivalent of subjective manifest refraction was -0.79 diopter. Eleven of these 15 eyes (73%) had a mean refractive correction of -1.1 diopters (range, -0.38 to -2.63 diopters); regression between 14 days and 2 years was 0.2 diopter. Four eyes (27%) had no persistent refractive correction (within +/- 0.25 diopter). Mean induced refractive astigmatism was 0.18 diopter. None of the eyes lost two or more lines of spectacle-corrected distance vision. The amount of refractive correction at 2 years after surgery was correlated to the treatment pulse energy and the volume of the opacified corneal tissue observed immediately after treatment.

CONCLUSIONS

This technique of noncontact laser thermal keratoplasty produced safe, effective, and persistent corrections of low hyperopia in the majority of treated eyes.

Mesenteric plexiform neurofibroma: computed tomography appearance

Gastrointestinal involvement in von Recklinghausen's disease is usually in the form of neurofibromas and leiomyomas. Very rarely, plexiform neurofibromas may be seen involving the bowel wall and myenteric plexus with secondary minor involvement of the mesentery. This report describes the computed tomography morphology of a plexiform neurofibroma extensively involving the mesentery with minor involvement of the bowel wall.

An in vitro model of the rat dorsal root entry zone reveals developmental changes in the extent of sensory axon growth into the spinal cord

The dorsal root entry zone (DREZ) forms the junction between the dorsal roots of the peripheral nervous system and the spinal cord. In rats older than 1 week, lesioned primary sensory axons regenerate within the dorsal roots but stop at the DREZ, and are thus unable to reconnect with the spinal cord. To analyze the causes of this failure, we have developed a culture model of the interaction of sensory axon growth cones with the intact DREZ, whereby dissociated dorsal root ganglion neurons from rats of various ages are grown on longitudinal cryosections of rat spinal cord, incorporating the DREZ and attached dorsal roots, from neonatal, 1-week-old (P6), or adult animals. Neurites of all ages grew along the roots to the DREZ, where their ability to cross into the spinal cord depended on both their age and that of the spinal cord substrate. Neurites from neonatal neurons failed to cross either the P6 or adult DREZ, but a substantial proportion crossed the immature neonatal DREZ. Early embryonic neurites exhibited substantial crossing on both immature and adult DREZ. These findings strongly suggest that soon after birth, the normal mammalian DREZ acquires growth inhibitory activity that is recognized by the axons of postnatal but not early embryonic sensory neurons.

Peripheral nerve explants grafted into the vitreous body of the eye promote the regeneration of retinal ganglion cell axons severed in the optic nerve

We have conducted experiments in the adult rat visual system to assess the relative importance of an absence of trophic factors versus the presence of putative growth inhibitory molecules for the failure of regeneration of CNS axons after injury. The experiments comprised three groups of animals in which all optic nerves were crushed intra-orbitally: an optic nerve crush group had a sham implant-operation on the eye; the other two groups had peripheral nerve tissue introduced into the vitreous body; in an acellular peripheral nerve group, a frozen/thawed teased sciatic nerve segment was grafted, and in a cellular peripheral nerve group, a predegenerate teased segment of sciatic nerve was implanted. The rats were left for 20 days and their optic nerves and retinae prepared for immunohistochemical examination of both the reaction to injury of axons and glia in the nerve and also the viability of Schwann cells in the grafts. Anterograde axon tracing with rhodamine-B provided unequivocal qualitative evidence of regeneration in each group, and retrograde HRP tracing gave a measure of the numbers of axons growing across the lesion by counting HRP filled retinal ganglion cells in retinal whole mounts after HRP injection into the optic nerve distal to the lesion. No fibres crossed the lesion in the optic nerve crush group and dense scar tissue was formed in the wound site. GAP-43-positive and rhodamine-B filled axons in the acellular peripheral nerve and cellular peripheral nerve groups traversed the lesion and grew distally. There were greater numbers of regenerating fibres in the cellular peripheral nerve compared to the acellular peripheral nerve group. In the former, 0.6-10% of the retinal ganglion cell population regenerated axons at least 3-4 mm into the distal segment. In both the acellular peripheral nerve and cellular peripheral nerve groups, no basal lamina was deposited in the wound. Thus, although astrocyte processes were stacked around the lesion edge, a glia limitans was not formed. These observations suggest that regenerating fibres may interfere with scarring. Viable Schwann cells were found in the vitreal grafts in the cellular peripheral nerve group only, supporting the proposition that Schwann cell derived trophic molecules secreted into the vitreous stimulated retinal ganglion cell axon growth in the severed optic nerve. The regenerative response of acellular peripheral nerve-transplanted animals was probably promoted by residual amounts of these molecules present in the transplants after freezing and thawing. In the optic nerves of all groups the astrocyte, microglia and macrophage reactions were similar. Moreover, oligodendrocytes and myelin debris were also uniformly distributed throughout all nerves. Our results suggest either that none of the above elements inhibit CNS regeneration after perineuronal neurotrophin delivery, or that the latter, in addition to mobilising and maintaining regeneration, also down regulates the expression of axonal growth cone-located receptors, which normally mediate growth arrest by engaging putative growth inhibitory molecules of the CNS neuropil.

Computed tomography morphology of the adrenal glands of patients with Addison's disease

To study the morphology of the adrenal glands of patients with Addison's disease an ultrasound and a computed tomographic scan of the adrenal glands were performed in 28 patients with Addison's disease. Thirteen patients had bilateral, asymmetric adrenal enlargement. In six of these patients, areas of necrosis and calcification were also seen. Six patients had atrophic glands with calcification and nine patients had normal/atrophic glands without calcification. After instituting appropriate treatment, computed tomography (CT) was repeated between 6 months and 3 years later in 10 of the 13 patients with adrenal enlargement. A reduction in gland size was noted in all patients and one had functional recovery. We conclude that the appearance of the adrenal glands on CT depends not only on the nature of the underlying disease but also on the duration of the illness and the type of treatment.

Role of the duplicated CCAAT box region in gamma-globin gene regulation and hereditary persistence of fetal haemoglobin

Hereditary persistence of fetal haemoglobin (HPFH) is a clinically important condition in which a change in the developmental specificity of the gamma-globin genes results in varying levels of expression of fetal haemoglobin in the adult. The condition is benign and can significantly alleviate the symptoms of thalassaemia or sickle cell anaemia when co-inherited with these disorders. We have examined structure-function relationships in the -117 HPFH gamma promoter by analysing the effect of mutating specific promoter elements on the functioning of the wild-type and HPFH promoters. We find that CCAAT box mutants dramatically affect expression from the HPFH promoter in adult blood but have little effect on embryonic/fetal expression from the wild-type promoter. Our results suggest that there are substantial differences in the structure of the wild-type gamma promoter expressed early in development and the adult HPFH promoter. Together with previous results, this suggests that gamma silencing is a complex multifactorial phenomenon rather than being the result of a simple repressor binding to the promoter. We present a model for gamma-globin gene silencing that has significant implications for attempts to reactivate the gamma promoters in human adults by pharmacological means.

Diffuse pneumocephalus due to meningitis: CT findings

Diffuse pneumocephalus due to infection by gas forming organisms is very unusual. We report computed tomography (CT) findings of such a case in an infant with Clostridium meningitis.

Axon-glial relationships in the anterior medullary velum of the adult rat

The anterior medullary velum is a thin sheet of CNS tissue which roofs the rostral part of the IVth ventricle and contains fascicles of myelinated fibres which, in part, arise from the nucleus of the IVth cranial nerve. This study used histochemical, immunohistochemical, and intracellular dye-injection techniques to describe cellular interrelationships in the velum in whole-mounts and in sections. Rip antibody-stained whole mounts provided a unique description of both oligodendrocyte units (defined as an oligodendrocyte and the complement of myelinated internodal segments it forms), and consecutive myelin sheaths along the same axon. A broad range of unit morphologies was categorised into four arbitrary groups, according to classical criteria, which comprised small cells supporting the short, thin myelin sheaths of 15-30 small diameter axons (Type I), through intermediate types (II & III), to the largest cells forming the long, thick myelin sheaths of 1-3 large diameter axons. Rip antibody and ferric ion-ferrocyanide staining, together with intracellular dye injection, revealed oligodendrocyte process branching patterns and their mode of engagement of myelin sheaths, nodes of Ranvier, and the spatial disposition of the outer cytoplasmic rims of myelin sheaths. The latter formed a conspicuous spiral ridge on the exterior surface of myelin sheaths which connected with the paranodal loops at each heminode. Large bundles of axons decussated through the velum, the bulk of which were IVth nerve fibres which constituted the IVth nerve rootlet. The PNS/CNS transitional zone of the IVth nerve was located 0.25-0.50 mm along the root, where astrocytic end-feet defined an abrupt margin, convex towards the periphery, where the heminodes of central and peripheral myelin were apposed, and where the basal lamina tubes of the Schwann cell units were discontinued. The basal processes of ependymal cells lining the ventricular wall of the velum, passed between axon bundles before abutting on the basal lamina of the pia. Many of these processes branched and ran along the axonal bundles. A monolayer of microglia occupied a subependymal stratum in which the non-overlapping dendritic territories of each cell formed a regular mosaic throughout the velum without any obvious interaction with either axons or other glial cells. Astrocytes were also uniformly distributed; their fine processes made up a dense lattice amongst axons, often running parallel and within the fibre bundles; stouter ones had terminal end-feet which undercoated the basal lamina of both the glia limitans externa and the blood vessels in the velum.