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Biomedical subjects

B E Jones

Publications and source records attributed to B E Jones.

At least 109 records · Page 6Linked to original sources
PubMed1994

Thrombosis of parietal, but not striate, cortex impairs acquisition of a 14-unit T-maze in the rat.

We evaluated parietal cortex (PCTX) involvement in learning a shock-motivated, 14-unit T-maize in young F344 rats. In Experiment 1, each rat was placed into a stereotaxic instrument, and the scalp was retracted before either the photosensitive dye, rose bengal, or saline (CON) was provided via a jugular catheter. After 60 s, halogen lamps were used to illuminate the cranium bilaterally over PCTX for 40 min to activate the dye and generate a thrombus in dye-injected rats. Active avoidance pretraining in a straight runway occurred 12 days after surgery. Each rat was provided acquisition (ACQ) trials in the 14-unit T-maze 24-h later. The PCTX rats were impaired relative to CON in errors, run time, alternation errors, and shock frequency measures in the 14-unit T-maze, but not in shock duration. The thrombosis extended to areas comprising anteromedial and posterior PCTX, and also into the striate cortex (SCTX). In Experiment 2, rats were divided into four groups: a PCTX group that received bilateral illumination; PCTX+SCTX and SCTX groups that were illuminated at midline; and a CON group that received the surgery and either dye or illumination. Only PCTX differed from CON, with maze performance similar to Experiment 1. The thrombosis for the PCTX group in Experiment 2 was confined to anteromedial and posterior PCTX. Thus, PCTX, but not SCTX, was implicated in ACQ of this maze task, suggesting that PCTX might be involved in the robust age-related impairments in ACQ previously observed.

Age Factors↗
PubMed1994

Distribution of cholinergic, GABAergic and serotonergic neurons in the medial medullary reticular formation and their projections studied by cytotoxic lesions in the cat.

As part of a larger study concerning the role of neurons in the medial medullary reticular formation in sleep-wake states, the distribution and projections of cholinergic, GABAergic and serotonergic neurons were studied within the lower brainstem of the cat. Cells were plotted with the aid of an image analysis system through the medullary reticular formation and raphe in adjacent sections immunostained for choline acetyltransferase, glutamic acid decarboxylase and serotonin. Immunostained fibres and varicosities were examined and quantified by microdensitometry in regions of the medulla, pons and upper spinal cord in normal and quisqualate-injected animals to assess the loss of local and distant projections following cytotoxic destruction of neurons in the medial medullary reticular formation. Choline acetyltransferase-immunoreactive neurons are unevenly and sparsely distributed, though none the less in significant numbers (estimated at approximately 9080 in total), through the medial medullary reticular formation, and are present in all tegmental fields, including the gigantocellular (approximately 3700) and magnocellular (approximately 1760) rostrally and the ventral (approximately 3240) and paramedian (approximately 380) caudally, and are absent in the midline raphe. Glutamic acid decarboxylase-immunoreactive neurons are more evenly and densely distributed in large numbers (estimated at approximately 18,720) through the medial medullary reticular formation, being present in the gigantocellular (approximately 5960), magnocellular (approximately 8260), ventral (approximately 2280) and paramedian (approximately 2220) tegmental fields, and are also numerous within the raphe magnus and pallidus-obscurus nuclei (approximately 3880). Serotonin-immunoreactive cells are sparse in the medial medullary reticular formation (estimated to total approximately 1540), where they are mainly located in the magnocellular tegmental field (approximately 1340), and are concentrated in larger numbers within the raphe nuclei (approximately 8060). Cholinergic varicose fibres were moderately densely distributed through the medial medullary reticular formation, as well as through more distant lateral, rostral and caudal brainstem and upper spinal regions. After cytotoxic lesions focussed in the gigantocellular and magnocellular tegmental fields, a loss of approximately 55% of the cholinergic neurons in the medial medullary reticular formation was associated with a minor decrease (approximately 35% in optical density measures) of local cholinergic fibres. Small and variable reductions in varicose fibres (and their optical density measures) were detected in distant structures (including the pontine lateral, gigantocellular and subcoerular tegmental fields and the caudal spinal trigeminal nucleus), that were none the less correlated with the number of intact medial medullary cholinergic cells, suggesting that these cells may project to distant brainstem targets, in addition to providing a minor proportion of the local cholinergic innervation of the medial medullary reticular formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Importance of cholinergic, GABAergic, serotonergic and other neurons in the medial medullary reticular formation for sleep-wake states studied by cytotoxic lesions in the cat.

Previous evidence has suggested that neurons in the medial medullary reticular formation play a critical role in the modulation of forebrain and spinal cord activity that occurs during the sleep-waking cycle and particularly in association with the state of paradoxical sleep. The importance of these neurons, including cholinergic, serotonergic and GABAergic cells [Holmes C. J. et al. (1994) Neuroscience 62, 1155-1178] for sleep-wake states was investigated after their destruction with the neurotoxin quisqualic acid injected into the medullary gigantocellular and magnocellular tegmental fields in cats. To assess the effects of the neuronal loss, polygraphic recording and behavioural observations were performed in baseline and for three weeks after the lesion, and the changes in these measures were correlated with the volume of destruction of medullary regions and the numbers of chemically identified cells within those regions. Following the cytotoxic lesions, which affected approximately 60% of the medullary gigantocellular and magnocellular tegmental fields, there was a significant reduction in the amount of paradoxical sleep (to a mean of 64% of baseline) during the first postlesion week, that recovered variably across cats in the second and third weeks. There was little to no change in the amount or organization of waking and slow wave sleep. The individually variable amounts of postlesion paradoxical sleep were correlated positively with the number of surviving cholinergic cells, negatively with the number of surviving serotonergic cells and positively with the ratio of surviving cholinergic or GABAergic cells to serotonergic cells. The most marked effect of the lesion was a substantial increase in the amplitude of the nuchal electromyogram during slow wave sleep (to 198%) and paradoxical sleep (to 378% of baseline in the first postlesion week). The increase in muscle tone was associated with movements of the head, neck or limbs during paradoxical sleep. Although, in some cats, the abnormal neck muscle tone decreased with time, limb movements continued to occur during paradoxical sleep for the duration of the experiment. The ratio of the total number of remaining cholinergic or GABAergic cells to serotonergic cells correlated negatively with the increased muscle tone and/or movements. It was concluded that the neurons of the medial medullary reticular formation contribute to, but are not necessary for, the generation of paradoxical sleep, and have particular importance for the regulation of muscle tone and inhibition of movement during this state.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Efficacy of brain-derived neurotrophic factor and neurotrophin-3 on neurochemical and behavioral deficits associated with partial nigrostriatal dopamine lesions.

Brain-derived neurotrophic factor (BDNF) promotes the survival of dopamine (DA) neurons, enhances expression of DA neuron characteristics, and protects these cells from 6-hydroxydopamine (6-OHDA) toxicity in vitro. We tested the ability of BDNF or neurotrophin-3 (NT-3) to exert similar protective effects in vivo during chronic delivery of 6-OHDA to the rat neostriatum. Chronic infusions of BDNF or NT-3 (12 micrograms/day) above the substantia nigra were started 6 days before and continued during an 8-day chronic intrastrial infusion of 6-OHDA. In control and neurotrophin-treated animals, 6-OHDA treatment selectively depleted 50-60% of nigrostriatal DA nerve terminals but produced little if any loss of pars compacta DA cell bodies. This partial DA lesion resulted in three rotations per minute toward the lesioned hemisphere after treatment with the DA release-inducing drug d-amphetamine. Compared with supranigral infusions of vehicle, BDNF and NT-3 decreased the number of these ipsiversive rotations by 70 and 48% and increased by 20- and 10-fold, respectively, the number of contraversive rotations observed after amphetamine injection. When challenged with the DA receptor agonist apomorphine, BDNF- and NT-3-treated animals also exhibited a seven- and 3.5-fold increase in the number of contraversive rotations relative to the vehicle group, respectively. Compared with vehicle, BDNF increased striatal levels of homovanillic acid (HVA; 86%), 3,4-dihydroxyphenylacetic acid (DOPAC; 42%), and 5-hydroxyindoleacetic acid (5-HIAA; 32%) and the HVA/DA (43%) and 5-HIAA/serotonin (34%) ratios in the DA-denervated striatum. NT-3 augmented only striatal 5-HIAA levels (24%). Neither factor altered the 6-OHDA-induced decrease in striatal DA levels or high-affinity DA uptake and thus did not protect against the destruction of DA terminals and did not alter striatal D1 or D2 ligand binding. Choline, GABA, and glutamate uptake in the striatum were not altered by the lesion or neurotrophin treatment. Thus, BDNF and to a lesser extent NT-3 reverse rotational behavioral deficits and augment striatal DA and 5-HT metabolism in a partial DA lesion model.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Fluconazole combined with flucytosine for treatment of cryptococcal meningitis in patients with AIDS.

Treatment of cryptococcal meningitis with amphotericin B or fluconazole is often unsuccessful; in only 35%-40% of cases do CSF cultures become negative by 10 weeks after initiation of such therapy. We conducted a prospective, open-label clinical trial involving persons with AIDS to determine whether the rate of clinical success would improve when fluconazole (400 mg daily) was combined with flucytosine (150 mg/kg daily). At the conclusion of 10 weeks of therapy, 75% (95% confidence interval, 58%-87%) of 32 subjects' CSF cultures were negative. The Kaplan-Meier estimate of clinical success at 10 weeks was 63% (95% confidence interval, 48%-82%). The median time to negativity of the CSF culture was 23 days. Toxic side effects that were sufficiently severe to lead to the withdrawal of flucytosine were observed in nine subjects (28%). In this pilot study of fluconazole combined with flucytosine, the rate of clinical success at 10 weeks was greater than that previously reported with regard to the use of fluconazole alone or amphotericin B alone.

AIDS-Related Opportunistic Infections↗
PubMed1994

The use of inhaled radioisotopes for measuring the effect of sputum induction on tracheobronchial clearance rates.

Inhaled radioisotopes were employed to study the role of tracheobronchial clearance in sputum induction, a technique used to diagnose Pneumocystis carinii pneumonia in patients with acquired immune deficiency syndrome (AIDS). Seven normal nonsmoking male subjects inhaled a nebulized aerosol of technetium-labelled human serum albumen, which was cleared from the lung solely by tracheobronchial clearance. The aerosol's particle size distribution ensured both alveolar and proximal airway deposition, the site of P. carinii organisms and tracheobronchial clearance mechanisms, respectively. Pulmonary emission counts were measured for 12 continuous 5-min periods before, and immediately after, sputum induction with nebulized 3% saline. A further 10-min scan was performed at 24 h to determine the alveolar fraction of deposited aerosol. Tracheobronchial clearance rates (log10[activity]/time) were calculated after log linear regression, for the time periods before, during and after sputum induction, having corrected for isotope decay and alveolar deposition. Results were analysed by the Wilcoxon rank sum test. Tracheobronchial clearance rates increased significantly in all subjects during sputum induction, with a mean 65.5% reduction in pulmonary activity over this period. Mean clearance gradients for the three time periods before, during and after sputum induction were -1.2 x 10(-3) min-1, -15.0 x 10(-3) min-1 and 0.4 x 10(-3) min-1, respectively (P < 0.025), which probably underlies the principal mechanism for success of the technique.

Administration, Inhalation↗
PubMed1994

Tuberculosis in patients with HIV infection who receive corticosteroids for presumed Pneumocystis carinii pneumonia.

To determine if the use of corticosteroids for presumed Pneumocystis carinii pneumonia exacerbated undiagnosed tuberculosis or increased the likelihood of reactivation tuberculosis, we reviewed medical records of 144 hospitalized HIV-infected patients who received antipneumocystis therapy. Ninety-four patients (Group C) received corticosteroids and 50 patients (Group NC) did not. One hundred and thirty-seven patients (97%) had acid-fast stains and mycobacterial cultures performed. Group C and Group NC were similar in ethnicity, distribution of HIV risk factors and CD4 cell count. Eight (9%) Group C patients and seven (14%) Group NC patients had culture-proven tuberculosis during their hospitalization. After a median followup of 16 mo after discharge, one (2%) Group C patient and two (4%) Group NC patients developed tuberculosis. Only one patient in Group C died of tuberculosis, despite receiving antituberculosis therapy. We conclude that the use of corticosteroids for presumed P. carinii pneumonia does not increase morbidity from undiagnosed tuberculosis or increase the frequency of reactivation tuberculosis.

AIDS-Related Opportunistic Infections↗
PubMed1994

A prospective evaluation of antituberculosis therapy in patients with human immunodeficiency virus infection.

The purpose of this study was to determine the efficacy and toxicity of a standard antituberculosis regimen in patients with human immunodeficiency virus (HIV) infection. We prospectively evaluated 89 patients with tuberculosis and HIV infection at an urban medical center. Eighty-two patients received isoniazid, rifampin, and pyrazinamide, with or without ethambutol, for 2 mo, followed by isoniazid and rifampin for 7 mo. Seven patients received other regimens because of drug resistance or intolerance. Therapy was self-administered in 57 patients and directly observed in 32 cases. All patients showed rapid clinical improvement during the first month of therapy, and sputum cultures reverted to negative after 3 mo in 52 of 54 patients from whom specimens were obtained. Adverse reactions to isoniazid or rifampin prompted alterations in antituberculosis regimens in five patients (6%). Forty patients (45%) died during follow-up, and tuberculosis was a potential contributory cause of death in three cases. Treatment failure occurred in five patients (6%), four of whom were noncompliant with therapy. The fifty patient had an isoniazid-resistant organism. No relapses occurred in 916 patient-months of follow-up posttreatment. We thus conclude that the 9-mo regimen used for treatment of drug-susceptible tuberculosis in HIV-infected patients is effective and well tolerated.

AIDS-Related Opportunistic Infections↗
PubMed1994

T cell cytokine responses in persons with tuberculosis and human immunodeficiency virus infection.

Tuberculosis causes more extensive and life-threatening disease in patients with HIV infection than in immunocompetent persons. To investigate the hypothesis that these severe manifestations of tuberculosis may be due to alterations in cytokine production, we evaluated cytokine patterns in HIV-infected tuberculosis patients. Upon stimulation with Mycobacterium tuberculosis in vitro, PBMC from HIV-infected tuberculosis patients had reduced proliferative and type 1 responses, compared with HIV-seronegative tuberculosis patients. The reduction in proliferative responses was independent of the CD4 cell count, but the reduced type 1 response was a direct result of CD4 cell depletion. There was no enhancement of type 2 cytokine production in HIV-infected patients, although production of IL-10 was prominent in all tuberculosis patients. In HIV-infected tuberculosis patients, M. tuberculosis-induced proliferative responses were significantly enhanced by neutralizing antibodies to IL-10 but not by antibodies to IL-4 or by recombinant IL-12. The M. tuberculosis-induced type 1 response was augmented both by antibodies to IL-10 and by recombinant IL-12. Tuberculosis in the context of HIV infection is characterized by diminished type 1 responses, probably induced by immunosuppressive cytokines produced by macrophages/monocytes, rather than by type 2 cells.

Cytokines↗
PubMed1994

Vitreal insulin-like growth factor binding proteins (IGFBPs) are increased in human and animal diabetics.

Although patients with diabetic retinopathy have been reported to have elevated vitreal IGF-I levels, it is not known whether diabetes also affects the levels of vitreal IGF binding proteins (IGFBPs) which control IGF's bioavailability. To address this issue, vitreal IGFBP levels were assayed in human diabetics, rats with streptozotocin-induced diabetes and galactose-fed dogs with diabetic-like retinopathy. Using 125I-IGF-II ligand blots, it was found that human diabetics have a 4-fold increase in vitreal IGFBP levels. Also, western blots on human diabetic vitreous reveal increased levels of IGFBP-2 and proteolytic fragments of IGFBP-3. IGF binding assays on vitreous from streptozotocin-treated rats (three months in duration) also indicate a 5-fold increase in IGF binding activity. IGF ligand blots using vitreous from rats with a shorter duration of diabetes (one month) show a 63% increase in IGFBP binding and a marked decrease in serum IGFBP binding. IGF ligand blots and IGFBP-2 and -4 western blots using vitreous from galactose-fed dogs with diabetic-like retinopathy exhibit a 6-fold increase in vitreal IGFBPs. The observation that vitreal IGFBPs are elevated in diabetic humans and rats without overt retinopathy suggests that these increases are not the result of a preexisting end-stage retinopathy but rather are an early ocular event in the diabetic process. Increases in vitreal IGFBPs thus could participate in the proliferative aspects of diabetic retinopathy by virtue of their putative intrinsic bioactivity or their capacity to alter IGF bioavailability.

Adult↗
PubMed1993

Collapse of parallel folding channels in dihydrofolate reductase from Escherichia coli by site-directed mutagenesis.

The rate-limiting steps in the folding of dihydrofolate reductase from Escherichia coli have been shown to involve the conversion of a set of four intermediates to a corresponding set of native conformers via four parallel channels [Jennings et al. (1993) Biochemistry 32, 3783-3789]. Fluorescence and absorbance studies of the unfolding and refolding of the C85S/C152E double mutant at various final urea concentrations reveal two slow folding reactions, two fewer than observed in the wild-type protein. Refolding in the presence of substoichiometric levels of the inhibitor methotrexate shows that the two remaining slow reactions correspond to two parallel channels which lead to a pair of native conformers capable of binding the inhibitor. A combination of stopped-flow circular dichroism and cofactor binding studies confirms that the four parallel channels observed in the wild-type protein have collapsed into two channels in the mutant. Kinetic and equilibrium studies of the single cysteine mutants suggest that replacements of Cysteine-85 which perturb the hydrophobic core containing this side chain are responsible for the simplification of the kinetic mechanism. These results demonstrate that at least two of the parallel folding channels in dihydrofolate reductase arise when tertiary structure develops and are not dependent upon cis/trans isomerization at prolyl peptide bonds.

Circular Dichroism↗
PubMed1993

Management methods of reducing radionuclide contamination of animal food products.

Examples are given of general management methods that will reduce the contamination of domestic food producing animals. Such methods will decrease the radiation exposure of the animal which could be of importance for its health and long-term production of food but more importantly in the short term they will decrease transfer of radioactive contamination to animal food products, i.e. milk, meat, offal and eggs. The most important radionuclides contaminating food products of animal origin, 90Sr, 131I and 137Cs, are specifically discussed in detail. By choosing proper general management methods it is possible to decrease the transfer of contaminating radionuclides to animal food products by an order of magnitude or more.

Animal Feed↗
PubMed1993

Countermeasures for reducing radioactive contamination of farm animals and farm animal products.

A summary is given of the range and effectiveness of different available countermeasures which can reduce the radiation dose arising from the radioactive contamination of food products from animals. The choice of which countermeasure is suitable for each particular situation will depend on many factors. Consideration should be given not only to the effectiveness of each countermeasure in terms of reduction of radionuclide content, but also to its practicality and cost, particularly where deposition levels are high or where high contamination levels in animal food products persist for a long period of time. Effective countermeasures which can reduce radiocaesium contamination of milk and meat from farmed animals by more than a factor of 10 have been developed, tested and used during the last 30 years. Less progress has been made in identifying effective binders for reducing levels of the other important contaminating radionuclides, such as I and Sr, in animal food products.

Animal Feed↗
PubMed1993

Pharmacological and immunohistochemical evidence for serotonergic modulation of cholinergic nucleus basalis neurons.

Identified electrophysiologically by low threshold bursts and transient outward rectification, cholinergic nucleus basalis neurons were recorded and labelled intracellularly in guinea-pig basal forebrain slices. By means of a triple labelling immunofluorescent technique, serotonin-immunoreactive fibres were visualized in close proximity to the soma and dendrites of the biocytin-labelled, choline acetyl transferase (ChAT)-immunoreactive cells. By bath application, 5-hydroxytryptamine (5-HT) produced a direct hyperpolarization of the identified cells which was mimicked by 5-HT1A receptor agonists, suggesting that it may inhibit the tonic firing but also modulate the low threshold bursting of the cholinergic nucleus basalis neurons.

Animals↗
PubMed1993

A reexamination of the folding mechanism of dihydrofolate reductase from Escherichia coli: verification and refinement of a four-channel model.

The mechanism of folding of dihydrofolate reductase from Escherichia coli was reinvestigated by studying the unfolding and refolding kinetics using absorbance and fluorescence spectroscopies. The original kinetic model proposed that folding involved a series of native, intermediate, and unfolded forms which interconverted through four independent channels linked by slow cis/trans isomerization reactions at Xaa-Pro peptide bonds [Touchette, N. A., Perry, K. M., & Matthews, C. R. (1986) Biochemistry 25, 5445]. Recently, alternative sequential models have been proposed [Frieden, C. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 4413; Kuwajima et al. (1991) Biochemistry 30, 7693] which challenge the original proposal. Stopped-flow studies of the intrinsic tryptophan fluorescence demonstrated the presence of three (and tentatively four) kinetic phases in unfolding which correlated well with four phases previously observed in refolding experiments. By monitoring the binding of the inhibitor methotrexate during folding at varying relative concentrations of inhibitor to protein, it was found that the selective loss of the slow-folding phases at substoichiometric levels could only be explained by a four-channel folding model. Double-jump experiments (native-->unfolded-->native) showed that the four refolding channels are populated within 20 s at 15 degrees C and are not likely to be due to proline isomerization. Reverse double-jump experiments (unfolded-->native-->unfolded) demonstrated that interconversions between native conformers are more rapid than originally proposed. Interestingly, the majority of the protein folds through a channel to a native conformer that is minimally populated at equilibrium. This implies that although the folding of dihydrofolate reductase is ultimately under thermodynamic control, kinetic factors contribute to the transient populations of native species during folding.

Binding Sites↗
PubMed1993

Codistribution of GABA- with acetylcholine-synthesizing neurons in the basal forebrain of the rat.

In recent years, GABAergic neurons have been identified in the basal forebrain where cholinergic cortically projecting neurons are located and known to be important in mechanisms of cortical activation. In the present study in the rat, the relationship of the GABA-synthesizing neurons to the acetylcholine-synthesizing neurons was examined by application of a sequential double staining immunohistochemical procedure involving the peroxidase-antiperoxidase technique for glutamic acid decarboxylase (GAD) and choline acetyltransferase (ChAT). In these double and adjacent single immunostained series of sections, the GAD+ and ChAT+ cells were mapped, counted and measured with the aid of a computerized image analysis system. Through the entire basal forebrain, there was no evidence for colocalization of GAD and ChAT in the same neurons. Instead, a large population of GAD-immunoreactive neurons is codistributed with ChAT-immunoreactive neurons and outnumbers them by a factor of two: approximately 39,000 GAD+ cells to 18,000 ChAT+ cells. Although the GAD+ and ChAT+ neurons lie intermingled within fascicles of the major longitudinal and transverse forebrain fiber systems in subregions of the basal forebrain, the GAD+ cells are more highly concentrated within different sectors of the pathways and regions than the ChAT+ cells. Although GAD+ neurons resemble ChAT+ neurons in certain regions, both being bi- or multipolar and, on average, medium-sized cells, the GAD+ neurons are, in the majority (51%), small-sized cells (< 15 microns in length) and as a population significantly smaller than the ChAT+ neurons. These results suggest that many GABAergic neurons may represent interneurons in the basal forebrain and potentially exert an inhibitory influence on adjacent cortically projecting cholinergic neurons. Medium- to large GAD+ cells, which resemble similar ChAT+ cells, are also present and represent the majority of the GAD+ cells in the nucleus of the diagonal band of Broca, magnocellular preoptic nucleus, and olfactory tubercle, but represent the minority in the anterior and posterior substantia innominata and globus pallidus. Given their prominent size, such GABAergic cells may also exert an inhibitory influence outside the basal forebrain as projection neurons and potentially in parallel with cholinergic neurons, to certain regions of the cerebral cortex. Accordingly, GABAergic cells may be considered as constituents of the magnocellular basal nucleus and potentially important elements within the ventral extrathalamic relay from the brainstem reticular formation to the cerebral cortex.

Acetylcholine↗
PubMed1993

Distribution of IGF-I and -II, IGF binding proteins (IGFBPs) and IGFBP mRNA in ocular fluids and tissues: potential sites of synthesis of IGFBPs in aqueous and vitreous.

Levels of insulin-like growth factor-I and II (IGF-I and IGF-II) in bovine aqueous humor are twice those found in the vitreous (aqueal IGF-I = 0.62 nM, vitreal IGF-I = 0.30 nM; aqueal IGF-II = 0.028 nM, vitreal IGF-II = 0.017 nM). IGF-I and II binding assays and IGF-II Western ligand blots indicate that aqueous and vitreous humor have equal overall levels of binding (binding assays, mean +/- S.E.M. bound/free per 50 microliters of fluid: vitreal IGF-II = 7.28 +/- 1.6, IGF-I = 0.3 +/- 0.078; aqueal IGF-II = 7.21 +/- 0.072; IGF-I = 0.3 +/- 0.078). In addition, the ligand blots reveal that aqueous and vitreous have markedly different complements of specific IGF binding proteins (IGFBPs). Aqueal levels of a 34 kDa IGFBP, immunologically identified as IGFBP-2, exceed those in the vitreous by two-fold. In contrast, the vitreous exhibits a two- to three-fold higher level of smaller (28-24 kDa), yet unidentified, IGFBPs. Aqueal and vitreal IGFBP patterns are also different from those found in serum. IGFBP-2 found in the aqueous and vitreous may be synthesized by ciliary body and/or cornea since these structures contain high levels of IGFBP-2 mRNA. Lens epithelial cells may also contribute IGFBP-2 to the aqueous since they also contain IGFBP-2 mRNA, albeit at substantially lower levels than the cornea and ciliary body. The retina has the lowest level of IGFBP-2 mRNA. IGF-II binding assays of cornea, ciliary body, retina and retinal pigment epithelium (RPE) indicate that the cornea has the highest level of binding (mean +/- S.E.M. IGF-II B/F per 50 micrograms protein: cornea = 84.52 +/- 28.8; iris/ciliary body complex = 0.61 +/- 0.078; retina = 0.47 +/- 0.096; RPE = 0.069 +/- 0.019). IGF-II ligand blots confirm these tissue-specific differences in binding and show that each ocular tissue contains IGFBP-2. In addition, ligand blots indicate that each ocular tissue contains a complex and distinctive population of IGFBPs. For example, the cornea and retina (but not the ciliary body, aqueous or vitreous) contain a 46 kDa IGFBP that may be IGFBP-3. The finding that cornea and retina also contain IGFBP-3 mRNA suggests that these structures may synthesize IGFBP-3 for local use within the eye.

Animals↗