Empathy, Defending, and Functional Connectivity While Witnessing Social Exclusion

Peers are present for most bullying episodes. Peers who witness bullying can play an important role in either stopping or perpetuating the behaviour. Defending can greatly benefit victimized peers. Empathy is strongly associated with defending. Yet, less is known about defenders' neural response to witnessing social distress, and how this response may relate to the link between empathy and defending. Forty-six first-year undergraduate students (M_age = 17.7; 37 women), with varied history of peer defending, underwent fMRI scanning while witnessing a depiction of social exclusion. Functional connectivity analysis was performed across brain regions that are involved in cognitive empathy, empathetic distress, and compassion. History of defending was positively associated with functional connectivity (Exclusion > Inclusion) between the left orbitofrontal cortex (OFC) - medial prefrontal cortex (MPFC), and right OFC - left and right amygdalae. Defending was negatively associated with functional connectivity between the left OFC - anterior cingulate cortex. The relationship between history of defending and empathy (specifically, empathetic perspective taking) was moderated by functional connectivity of the right OFC - left amygdala. These findings suggest that coactivation of brain regions involved in compassionate emotion regulation and empathetic distress play a role in the relationship between empathy and peer defending.

Structure-function relationships of insulin-like growth factor binding protein 6 (IGFBP-6) and its chimeras

Insulin-like growth factor binding protein 6 (IGFBP-6) is a high-affinity IGFBP with substantially greater affinity for insulin-like growth factor-II (IGF-II) than IGF-I. IGFBP-6(3) is a chimera which has a 20 amino acidC -terminal portion of IGFBP-6 switched with the homologous area of IGFBP-3, P3. Unlike IGFBP-4(3), in which the P3 region was exchanged for the homologous region of IGFBP-4 (P4), IGFBP-6(3) does not bind to endothelial cells. Double mutations were made with the P3 region exchanged as well as a second area differing from IGFBP-3 to form IGFBP-6(3)A and IGFBP-6(3)B, by replacing this area with the homologous region of IGFBP-3. Neither [(125)I]IGFBP-6(3)A nor IGFBP-6(3)B specifically bound to endothelial cells. However, each double mutant competed for [(125)I]IGFBP-3 binding to cultured cells. In the perfused heart, transendothelial transport of IGFBP-6 and IGFBP-6(3) was only 25% of similar transendothelial transport of perfused IGFBP-3. We conclude that chimeras of IGFBP-6 and IGFBP-3(6) clearly differ from IGFBP-4(3) in their ability to bind specifically to endothelial cells and in their capacity to undergo transendothelial transportation in the perfused heart.

Distribution of chimeric IGF binding protein (IGFBP)-3 and IGFBP-4 in the rat heart: importance of C-terminal basic region

IGF binding proteins-3 and -4, whether given in the perfused rat heart or given iv in the intact animal, cross the microvascular endothelium of the heart and distribute in subendothelial tissues. IGF binding protein-3, like IGF-I/II, localizes in cardiac muscle, with lesser concentrations in CT elements. In contrast, IGFBP-4 preferentially localizes in CT. In this study, chimeric IGF binding proteins were prepared in which a basic 20-amino-acid C-terminal region of IGF binding protein-3 was switched with the homologous region of IGF binding protein-4, and vice-versa, to create IGF binding protein-3(4) and IGF binding protein-4(3). Perfused IGF binding protein-3(4) behaved like IGF binding protein-4, localizing in connective tissue elements, whereas IGF binding protein-4(3) now localized in cardiac muscle at concentrations identical to perfused IGF binding protein-3. To determine whether these small mutations altered the affinity of the chimera for cells, the ability of (125)I-IGF binding protein-3(4) and (125)I-IGF binding protein-4(3) to bind to microvascular endothelial cells was determined and compared with IGF binding protein-3. IGF binding protein-3(4) retained 15% of the binding capacity of IGF binding protein-3, whereas IGF binding protein-4(3) bound to microvessel endothelial cells with higher affinity and greater total binding than that of IGF binding protein-3. We conclude that small changes in the C-terminal basic domain of IGF binding protein-3 and the corresponding region of IGF binding protein-4 can alter their affinity for cultured cells and influence their tissue distribution in the rat heart.

Vascular endothelial growth factor and basic fibroblast growth factor differentially modulate early postnatal coronary angiogenesis

The roles of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF [FGF-2]) in early postnatal regulation of coronary angiogenesis were investigated by administering neutralizing antibodies to these growth factors between postnatal days 5 and 12. Immunohistochemistry and Western blotting both revealed decreases in VEGF protein in the hearts of rats treated with either antibody. In contrast, bFGF mRNA increased in both treated groups, whereas VEGF mRNA was unchanged. Using stereological assessment of perfusion-fixed hearts, we found that both anti-VEGF and anti-bFGF inhibited the rapid and marked capillary growth that occurs during this time period and that the effects of the two neutralizing antibodies are not additive. Arteriolar growth, as indicated by a lower length density, was inhibited by anti-bFGF, but not anti-VEGF. When both anti-VEGF and anti-bFGF were administered, arteriolar length density was not significantly lower, but the population of small arterioles (<15 microm) was markedly reduced, whereas the percentage of large arterioles (26 to 50 microm) more than doubled. Thus, inhibition of both growth factors negated or limited the formation of small arterioles and facilitated an expansion of the largest arterioles. These in vivo data are the first to document that during the early neonatal period, (1) both VEGF and bFGF modulate capillary growth, (2) bFGF facilitates arteriolar growth, and (3) the two growth factors interact to establish the normal hierarchy of the arteriolar tree.

Interinstitutional study to compare the effectiveness of a radiology-anatomy module of instruction

RATIONALE AND OBJECTIVES

The purpose of this study was to validate the effectiveness of a proven radiology-anatomy instructional module during I st-year gross anatomy courses at Emory University College of Medicine and the University of Iowa College of Medicine.

MATERIALS AND METHODS

This prospective study involved 108 Emory students and 177 Iowa students. The instructional content was the same at both institutions. Each student was randomly assigned into one of three groups at each institution, and each group received a unique, randomized, five-item pretest. All students were posttested as part of their gross anatomy laboratory examination, and the posttests consisted of all 15 items used in the three five-item pretests.

RESULTS

No statistically significant pretest effects were demonstrated by t tests. Posttest performances across items ranged from 73% to 96% correct for Emory students and 67% to 98% for Iowa students. Performance levels on the posttests were significantly higher than on pretests, and few significant differences were found in the performance of the two populations.

CONCLUSION

The radiology-anatomy instructional module integrated into the gross anatomy courses for 1st-year Emory University and University of Iowa students was not instructor or institution dependent.

Effects of TGFbeta2 on collagen synthesis in cultured normal and wounded fetal mouse palates

OBJECTIVE

It has been demonstrated in a number of models that fetal wounds heal with little or no scar. Since collagen is an integral part of the extracellular matrix in adult scar formation, we studied the synthesis and localization of collagen in an in vitro mouse palate model for fetal wound healing.

METHODS

Palates, dissected from fetal mice at 15, 16, and 17 days of gestation and from newborn mice, were cultured in medium containing serum (for 8 hours); this was followed by culture in serum-free medium (for 12 hours). One-half of the samples from each age group were wounded in the midline. All samples were placed in serum-free medium containing 20 microCi/mL 3H-proline for 8 hours. In addition, palates from 15-day gestation and from newborn mice were also incubated with transforming growth factor TGF-beta2 (10 ng/mL). Palates were washed with saline, homogenized, and radioactivity was counted. Proline uptake was calculated for each sample as counts per milligram of protein and was subjected to statistical analysis (three-way analysis of variance). Samples of the homogenate were subjected to sodium dodecyl sulfate-gel electrophoresis and Western blotting in order to determine the types of collagen that were synthesized. Immunohistochemical localization of collagen types I, III, and VI was carried out on paraffin-embedded samples from each group.

RESULTS

There were no significant differences in proline uptake between wounded mouse palates and nonwounded mouse palates at any age, and there was no histological evidence of regeneration of the palate at the site of the wound. Proline uptake was significantly greater in untreated wounded palates at 15 days' gestation than it was in newborns. After treatment with TGF-beta2, proline uptake was significantly greater in both wounded and nonwounded palates in the newborn group and had no effect on collagen synthesis in palates from 15-day gestation animals. Collagen types I and III were localized in histological specimens using immunohistochemistry and on nitrocellulose using Western blotting. No type VI collagen was demonstrated by Western blotting, but it was localized around blood vessels and on basement membranes using immunohistochemistry.

CONCLUSION

Treatment with TGF-beta2 significantly increased collagen synthesis, as assessed by 3H-proline uptake, in cultured palates from newborn mice as compared with palates from untreated newborn mice and from both treated and untreated palates of 15-day gestation mice. These data suggest a differential response to TGF-beta2 by mouse palates as a function of fetal development.

Development of an immunocontraceptive vaccine. Current status

Development of an effective and modern contraceptive vaccine is a key factor in the global issue of regional population growth as well as agricultural, medical, economic and social development. A review was done of the current medical literature concerning development of an immunocontraceptive vaccine and relative molecular biology technology. Various approaches have been taken to identify candidate-specific antigens for immunocontraceptive development, such as sperm, zona pellucida and hormonal antigens. Suppressed fertility and the reversibility of these effects on mammalian species, including humans, have been demonstrated. The successful results obtained so far support the continued investigation for an effective immunocontraceptive vaccine.

Vascular endothelial growth factor expression coincides with coronary vasculogenesis and angiogenesis

Vascular endothelial growth factor (VEGF) plays an important role in early embryonic vasculogenesis. To establish its temporal expression and localization in the heart during development, we studied rat hearts from the first embryonic day (E) of myocardial vascular tube formation through the early postnatal period. Ventricular VEGF immunoreactivity was noted in the epicardium and the thin underlying myocardium in E10 ventricles. During the earliest stages of vascularization (E13-E16) immunoreactivity was highest in the compact myocardium nearest the epicardium, and subsequently (E18 and thereafter) became more evenly distributed transmurally. By birth (E22) immunoreactivity was most intense around microvessels. Similarly, VEGF mRNA localization, demonstrated by in situ hybridization, was initially highest near the epicardium and then became more evenly distributed transmurally by late gestation. Within the interventricular septum, the highest expression occurred in the middle of the wall where it correlated with the greatest vascularization. Northern blot analysis showed that from E12 through the first 10 days of postnatal life, VEGF was two to three times higher than in the adult. Western blot analysis showed that VEGF tended to be higher in the atria than the ventricles, and negligible in the outflow tract. Our data indicate that VEGF localization and expression 1) correspond to the pattern of vascularization in the embryonic/fetal heart, and 2) remain high during the early postnatal period when capillary proliferation is high. Because VEGF is stimulated by hypoxia, its preferential mRNA expression near the epicardium, that is, farthest from the ventricular lumen and the O2 source, fits with the hypothesis that a hypoxic gradient is a driving force in the transmural vascularization process.

Migration and ultrastructural localization of the c-kit receptor protein in spermatogenic cells and spermatozoa of the mouse

PURPOSE

The c-kit receptor is a proto-oncogene important in germ cell migration and maturation and has also been demonstrated on the acrosomal region of mature sperm. The purpose of the present study was to examine the ultrastructural location of the c-kit receptor in mouse testis and sperm.

MATERIALS AND METHODS

Testis and sperm from mature male mice were examined for the c-kit receptor utilizing electron microscopy and Western blot analysis techniques. Thin sections of mouse testis and sperm were stained with immunogold-labeled anti-c-kit antibodies. The protein from these testes and sperm was also utilized for Western blot analysis.

RESULTS

The c-kit protein was localized within the mouse testes to the type A spermatogonia, the round spermatids, and the mature testicular spermatozoa. The c-kit receptor was noted to migrate from the lumen of the acrosomal vesicles in the early spermatids to the plasma membrane of the late spermatids. It was also noted in the acrosomal region of the testicular spermatozoa, as well as the sperm from the epididymis. Sperm undergoing the acrosome reaction demonstrated association of the c-kit receptor with the plasma membrane of the acrosome, but not on the acrosomal membrane itself. Western blot analysis demonstrated protein bands of 150 kDa in testis and intact sperm.

CONCLUSIONS

The present study confirms the presence of the c-kit receptor in mouse testis and sperm. It also demonstrates that this receptor is localized to the region of the developing acrosome.

Temporal expression of inducible nitric oxide synthase in mouse and human placenta

The aim of this study is to investigate the changes in expression and activity of inducible nitric oxide synthase (iNOS) in the developing murine embryo and mouse and human placenta. Using reverse transcription-polymerase chain reaction (RT-PCR), Northern blotting, and in-situ hybridization (ISH) we identified iNOS mRNA in mouse placenta at 9.5, 12, 14, 16, 18 and 20 days post coitum. Northern blot analysis demonstrated that the quantity of murine iNOS transcript was expressed at a stable level between days 12-20 although the level of calcium-independent NOS activity declined with advancing gestation. RT-PCR detected iNOS-specific mRNA in murine embryonic stem cells, but not in embryos at later stages (4-cell or blastocyst). ISH failed to show iNOS-specific mRNA in either murine placenta or the underlying myometrium on day 7, but did so in the trophoblast by day 9.5. Later in gestation, extensive labelling was observed in both spongiotrophoblast and trophoblast giant cells. iNOS mRNA was also detected both in immature human placentae (16-18 weeks) and at term, predominantly in syncytiotrophoblasts and placental artery smooth muscle. In conclusion, iNOS is constitutively expressed in mouse and human placenta at a time and in a location that suggests a role in placentation.

Fetal hemorrhage and platelet dysfunction in SLP-76-deficient mice

The adapter protein SLP-76 is expressed in T lymphocytes and hematopoietic cells of the myeloid lineage, and is known to be a substrate of the protein tyrosine kinases that are activated after ligation of the T-cell antigen receptor. Transient overexpression of SLP-76 in a T-cell line potentiates transcriptional activation after T-cell receptor ligation, while loss of SLP-76 expression abrogates several T-cell receptor-dependent signaling pathways. Mutant mice that lack SLP-76 manifest a severe block at an early stage of thymocyte development, implicating SLP-76 in signaling events that promote thymocyte maturation. While it is clear that SLP-76 plays a key role in development and activation of T lymphocytes, relatively little is understood regarding its role in transducing signals initiated after receptor ligation in other hematopoietic cell types. In this report, we describe fetal hemorrhage and perinatal mortality in SLP-76-deficient mice. Although megakaryocyte and platelet development proceeds normally in the absence of SLP-76, collagen-induced platelet aggregation and granule release is markedly impaired. Furthermore, treatment of SLP-76-deficient platelets with collagen fails to elicit tyrosine phosphorylation of phospholipase C-gamma2 (PLC-gamma2), suggesting that SLP-76 functions upstream of PLC-gamma2 activation. These data provide one potential mechanism for the fetal hemorrhage observed in SLP-76-deficient mice and reveal that SLP-76 expression is required for optimal receptor-mediated signal transduction in platelets as well as T lymphocytes.

Decreased expression of the c-kit receptor is associated with increased apoptosis in subfertile human testes

OBJECTIVE

To examine the expression of the c-kit receptor and its ligand, stem cell factor, and their possible relation with apoptosis in infertile men.

DESIGN

Prospective laboratory study.

SETTING

Urology laboratory in a university hospital.

PATIENT(S)

Men undergoing testicular biopsy during an investigation of subfertility.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Expression of the c-kit receptor protein, stem cell factor, and apoptosis in the testes.

RESULT(S)

The c-kit receptor was strongly present in Leydig cells and type A spermatogonia of normal testes, with decreased staining in Leydig cells and type A spermatogonia of testes with maturational arrest, and staining in only Leydig cells of Sertoli cell-only specimens. Stem cell factor was demonstrated in Leydig cells and Sertoli cells in all specimens. Western blotting demonstrated the 150-kd c-kit protein in the normal testes and the testes with maturational arrest, but not in the testes with the Sertoli cell-only pattern. Stem cell factor was expressed in all specimens, with a protein size of 45 kd. Increased apoptosis was demonstrated in type A spermatogonia and spermatocytes of tissue with maturational arrest compared with normal testicular tissue.

CONCLUSION(S)

C-kit receptor expression is decreased in subfertile testicular tissue compared with normal testicular tissue. Stem cell factor expression is present in Leydig cells and Sertoli cells. Increased apoptosis is seen in tissue with maturational arrest compared with normal tissue.

Cryotherapy in basal cell carcinoma

Cryotherapy has proved to be an effective tool in the management of various dermatoses. We report 6 patients with histopathologically proven basal cell carcinoma of variable sizes treated with liquid nitrogen cryotherapy by the open spray technique. Lesions tended to heal with depigmentation and scar formation. However depigmented areas often repigmented over a period of time.

Infused IGF-I/IGFBP-3 complex causes glomerular localization of IGF-I in the rat kidney

Insulin-like growth factor I (IGF-I) increases renal blood flow, glomerular filtration rate (GFR), and proximal tubule reabsorption of phosphate in humans and rodents. The biological effects of IGF-I are likely to be influenced by cellular localization of IGF-I within the kidney. We therefore tested whether the renal localization of infused IGF-I could be altered if given with selected IGF-binding proteins (IGFBPs). Rats were treated with intravenous injections of 125I-labeled IGF-I, 125I-IGFBP-3, or 125I-IGFBP-4 alone or with complexes of 125I-IGF-I and IGFBP-3 or IGFBP-4. The cellular localization of IGF and the IGFBP within the kidney was then determined. 125I-IGF-I, 125I-IGFBP-4, and 125I-IGF-I/IGFBP-4 complexes were found almost exclusively in vacuolar structures (endosomes) of proximal renal tubules. In contrast, about one-third of renal 125I-IGFBP-3 and 125I-IGF-I/IGFBP-3 was localized to glomeruli. When 125I-IGF-I was given alone, 3% was found in glomeruli and 89% in proximal tubules. When given as 125I-IGF-I/IGFBP-3, 29% was in glomeruli and 65% in proximal tubules. We conclude that the cellular localization of IGF-I within the kidney can be directed to glomerular elements if the IGF-I is given with IGFBP-3.

Antigen mapping in hereditary epidermolysis bullosa

Standard immunofluorescence tests are not positive in the various inherited epidermolysis bullosa (EB). Using antibodies to known antigens present in the basement membrane zone, antigen mapping can be done by immuno fluorescence, to determine the level of blistering and establish the diagnosis. We report three cases of junctional EB and one case of dystrophic EB in whom the diagnosis was confirmed by antigen mapping.

Direct immunofluorescence in lesional and uninvolved skin in dle

Direct immunofluroscence was evaluated in 16 patients with DLE including 1 case of lupus profundus and 4 with disseminated DLE. A BMZ band with multiple immunoreactants was demonstrated in lesional skin in 14 patients (87.5%), while 2 had only single immunoreactants. C3 and lgM were the commonest reactants followed by lgG, lgA and fibrinogen. A perifollicular prominence was seen in several patients. Four patients showed a band in uninvolved skin. This may indicate a potential to develop SLE. ANA was also positive in 5 patients but ds DNS was negative.

Direct evidence for nitric oxide synthase in vagal afferents to the nucleus tractus solitarii

The anatomical relationship between vagal afferents and brain nitric oxide synthase containing terminals in the nucleus tractus solitarii was studied by means of anterograde tracing combined with immunocytochemistry and immuno-electron microscopy. Biotinylated dextran amine was injected into the nodose ganglion with a glass micropipette. Four to eight days following the injection, regions of the nucleus tractus solitarii containing biotinylated dextran amine-labelled vagal afferents and those containing nitric oxide synthase-immunopositive terminals were congruent. Many neurons exhibiting nitric oxide synthase immunoreactivity were found within the biotinylated dextran amine-containing terminal field. However dense labeling of terminals with biotinylated dextran amine precluded determination if the terminals were nitric oxide synthase-immunoreactive. Therefore, we combined degeneration of vagal afferents after removal of one nodose ganglion with nitric oxide synthase immuno-electron microscopy. Axon terminals that possessed characteristic vesicle clusters and were partially or completely engulfed by glial processes were identified as degenerating vagal afferents. Degenerating axon terminals comprised 38% of the total axon terminals in the nucleus tractus solitarii in a sample of sections; and of the degenerating axon terminals, 67% were nitric oxide synthase-immunoreactive. Nitric oxide synthase immunoreactivity was present in 41% of the non-degenerating axon terminals. Prominent staining of dendrites for nitric oxide synthase immunoreactivity indicated that much of the nitric oxide synthase in the nucleus tractus solitarii is not derived from peripheral afferents. Of the total number of dendritic profiles sampled, half were nitric oxide synthase-immunoreactive. Our data support the hypothesis that nitric oxide or nitric oxide donors may be present in primary vagal afferents that terminate in the nucleus tractus solitarii. While this study confirms that vagal afferents contain brain nitric oxide synthase, it demonstrates for the first time that the majority of nitric oxide synthase immunoreactivity in the nucleus tractus solitarii is found in intrinsic structures in the nucleus. In addition, our data show that second or higher order neurons in the nucleus tractus solitarii may be nitroxidergic and receive both nitroxidergic and non-nitroxidergic vagal input.

Early coronary angiogenesis in response to thyroxine: growth characteristics and upregulation of basic fibroblast growth factor

Although a substantial coronary angiogenesis occurs after thyroid hormone treatment, its regulation and relationship to cardiac hypertrophy are not understood. This study was designed to determine (1) the onset of capillary proliferation, (2) the sites of capillary proliferation, and (3) whether basic fibroblast growth factor (bFGF) upregulation occurs in response to thyroxine administration. Male Sprague-Dawley rats were injected daily with L-thyroxine (T4, 0.2 mg/kg s.c.). Bromodeoxyuridine labeling of capillary endothelial cells increased during the first 24 hours of treatment and peaked after 2 days of treatment. Northern blot analysis revealed a slight increase in bFGF mRNA during this period, followed by a doubling of expression by 48 hours, at which time bFGF protein was also increased. In situ hybridization, used to localize bFGF mRNA, showed an increase in transcripts within 24 hours after T4. This enhancement was uniform in the epimyocardium and endomyocardium. Histochemical analysis (double staining for alkaline phosphatase and dipeptidyl peptidase) of frozen sections, used to discriminate capillary profiles as arteriolar and venular, respectively, showed that growth occurred in the latter, since the percentage of capillary profiles positive for dipeptidyl peptidase was higher than the control value after 4 days of T4 administration. These data indicate that in the thyroxine model of cardiac hypertrophy (1) capillary DNA synthesis occurs after a single injection of thyroxine, (2) capillary growth coincides with an upregulation in bFGF mRNA and increase in bFGF protein, and (3) proliferation occurs in the venular capillaries.

The c-kit receptor and its possible signaling transduction pathway in mouse spermatozoa

The presence and role of the c-kit protein was investigated in the mature sperm of the mouse. The c-kit monoclonal antibody (mAb) ACK2 reacted specifically with the acrosomal region and the principal piece of fixed noncapacitated sperm but did not react with the acrosome region in acrosome-reacted sperm. ACK2 significantly inhibited the acrosome reaction; this inhibition was relieved by the calcium ionophore A23187. The kit ligand stem cell factor (SCF) significantly increased the percentage of sperm undergoing acrosome reaction. This increase was partially inhibited by the calcium channel inhibitor (verapamil), the PI3k inhibitor (wortmannin), and the PLC inhibitor (U-73122). ACK2 predominantly recognized c-kit proteins of 33, 48, and 150 kDa by Western blotting of mouse sperm extracts. The 48- and 150-kDa protein bands were released into the media and tyrosine autophosphorylated at low basal levels during acrosome reaction. On stimulation with SCF, the level of c-kit phosphorylation increased significantly. These findings suggest that c-kit is present in mature sperm, and its binding to SCF may result in the activation of PLC gamma 1 and PI3K, leading to receptor autophosphorylation, and ultimately may play a role in capacitation and/or the acrosome reaction.

Expression and function of the c-kit proto-oncogene protein in mouse sperm

The presence and role of the c-kit protein were examined in mature sperm of the mouse. Monoclonal antibodies (mAbs) against the c-kit protein were used to perform immunohistochemical staining, electron microscopy studies, and Western blot analysis. The acrosomal region of both fixed and unfixed noncapacitated sperm stained with the antibodies. No acrosomal staining was noted in acrosome-reacted (AR) sperm. Electron microscopy studies demonstrated immunogold label on the plasma membrane of the acrosome and confirmed the lack of binding following the acrosome reaction. Proteins corresponding to 33 kDa, 48 kDa, and 150 kDa were detected by the antibodies utilizing Western blot analysis. The 48-kDa and 150-kDa proteins were released into the media during sperm capacitation, and release from the acrosome was dependent upon the acrosome reaction. The mAbs significantly inhibited the acrosome reaction and increased sperm agglutination. Monoclonal antibody ACK1 significantly inhibited the motility of the sperm, whereas mAbs ACK2 and NCL-ckit did not. These results suggest that c-kit-related proteins are present in mature sperm and may play a role in capacitation and/or the acrosome reaction.

Localization and expression of the c-kit receptor protein in human and rodent testis and sperm

OBJECTIVES

To examine the localization and expression of the c-kit receptor protein in the testes of the mouse, rat, and human, and then compare these among the three species.

METHODS

Testis tissue from all three species was obtained through biopsy or orchiectomy. Immunohistochemistry was used for the localization, using a monoclonal antibody to the c-kit receptor. The expression of the c-kit receptor protein was examined in the testes and sperm with Western blot analysis.

RESULTS

Localization was noted in the early spermatogenic cells, most likely type A spermatogonia, as well as in the acrosomal region of more mature germ cells, such as the round spermatids. The c-kit receptor was localized in analogous sites in all three species. The Western blot data revealed testicular expression of the c-kit receptor protein in all three species as well. Similar bands were recognized on the Western blots of all three species in testes at approximately 75 kDa and approximately 90 kDa, and sperm at approximately 90 kDa only.

CONCLUSIONS

The c-kit receptor protein is expressed in the early spermatogenic cells, as well as the later stages of spermatogenesis, specifically, the acrosomal granules of the round spermatids, and the acrosomal region of testicular spermatozoa, in the mouse, rat, and human. All three species exhibit similar expression of the c-kit receptor protein in both testis and sperm, although to a varying degree. We believe that these observations allow direct valid comparisons concerning the expression of the c-kit receptor to be made cautiously to the human condition from experimental data obtained from rodents.

Increased expression of nitric oxide synthase in the gracile nucleus of aged rats

Aging is associated with disturbances in autonomic cardiovascular control. The purpose of this study was to test the hypothesis that changes in nitric oxide occur with aging in brainstem nuclei involved in autonomic cardiovascular control. The principal and unexpected finding in this study was that NADPH-diaphorase reactivity, which is considered a marker of neuronal nitric oxide synthase activity, was decidedly increased in the neuronal bodies of the gracile nucleus but decreased in the axons and axon terminals in old compared with young rats. In situ hybridization also revealed that nitric oxide synthase gene expression was enhanced predominantly in the gracile nucleus neurons of aged rats. The differences between the young and old rats were most dramatically evident in the gracile nucleus, but not evident in other brainstem nuclei. The significance of this finding as it might relate to autonomic or other specific neural dysfunction with aging is not evident at this time.

Up-regulation of nitric oxide synthase and its mRNA in vagal motor nuclei following axotomy in rat

Effects of vagotomy on nitric oxide synthase (NOS) protein and mRNA levels in the dorsal motor nucleus of vagus (DMV) and nucleus ambiguus (NA) of rats were examined by nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining, brain NOS (bNOS) immunostaining and in situ hybridization. NADPH-d staining and bNOS immunoreactivity increased in neurons of the ipsilateral DMV and NA 5, 10, and 20 days after vagotomy. These changes were not observed in unoperated or sham-operated rats. In situ hybridization showed that bNOS mRNA levels were also elevated in neurons of DMV and NA on the operated side. Our results suggest that transection of vagal efferents up-regulates bNOS and its mRNA expression in the DMV and NA.

The role of transforming growth factor alpha in rat craniofacial development and chondrogenesis

To explore the possible role of transforming growth factor alpha (TGF-alpha) in craniofacial development, its expression in the craniofacial region of rat embryos from embryonic day (d) 9 to d 20 was examined by in situ hybridisation and immunostaining. The TGF-alpha transcripts were first detected in the neural fold of embryonic d 9 and 10 embryos. In the craniofacial region, the TGF-alpha transcripts were not detected until embryonic d 16 in mesenchyme surrounding the olfactory bulb, within the olfactory bulb, the nasal capsule, vomeronasal organ, and vibrissal follicle. In addition, TGF-alpha message was detected in mesenchyme in the vicinity of Meckel's cartilage, and in the dental epithelium and lamina. This expression pattern of TGF-alpha transcripts persisted until embryonic d 17 but disappeared by d 18. The presence of TGF-alpha protein largely coincided with TGF-alpha message although, unlike the message, it persisted throughout later embryogenesis in the craniofacial region. The possible function of TGF-alpha in chondrogenesis was explored by employing the micromass culture technique. Cartilage nodule formation in mesenchymal cells cultured from rat mandibles in the presence of TGF-alpha was significantly inhibited. This inhibitory effect of TGF-alpha on chondrogenesis was reversed by addition of antibody against the EGF receptor, which crossreacts with the TGF-alpha receptor. The inhibitory effect of TGF-alpha on chondrogenesis in vitro was further confirmed by micromass culture using mesenchymal cells from rat embryonic limb bud. Taken together, these results demonstrate the involvement of TGF-alpha in chondrogenesis during embryonic development, possibly by way of a specific inhibition of cartilage formation from mesenchymal precursor cells.

Expression of c-KIT and its ligand, stem cell factor, in normal and subfertile human testicular tissue

The c-KIT proto-oncogene encodes for a transmembrane receptor and is associated with maturation of several cell types, including germ cells. The ligand of the receptor has been identified as stem cell factor (SCF). Loss or alteration of the expression of either of these factors leads to anemia, albinism, and/or sterility in mice. We examined the expression of c-KIT and SCF by immunohistochemistry in specimens from normal and infertile human testis. All specimens were obtained in the evaluation of male subfertility. We were able to demonstrate staining for c-KIT in Leydig cells in all specimens. Normal testis stained for c-KIT in the cytoplasm of early spermatogenic cells, as well as the acrosomal granules of the round spermatids and the acrosome of testicular spermatozoa. However, staining in testis demonstrating maturation arrest failed to demonstrate acrosomal staining, and Sertoli-only specimens demonstrated staining for c-KIT in Leydig cells only. The results for SCF demonstrated an overall uniform staining of Leydig cells in all specimens. The intensity of staining of Sertoli cells increased from normal to maturation arrest to Sertoli-only specimens. Germ cell staining was consistently negative. We hypothesize that these staining patterns for SCF are due to either lack of staining of the receptor-ligand complex or overexpression of the kit ligand in tissue that does not express the kit receptor. It appears that the c-kit receptor is expressed in the acrosome of developing germ cells, as well as in Leydig cells and early spermatogenic cells, suggesting a role in the acrosome reaction, as well as germ cell maturation and differentiation.

Coronary vascularization during development in the rat and its relationship to basic fibroblast growth factor

OBJECTIVE

Our overall aims were to elucidate the temporal and spatial sequence of coronary vascularization during development in the rat, and to determine whether basic fibroblast growth factor expression corresponds to any phase of the vascularization process.

METHODS

Immunohistochemical, histochemical, morphometric and in situ hybridization analyses were performed on prenatal and postnatal hearts of various ages.

RESULTS

Coronary vascularization, which begins at embryonic day 13 (E13) with blood island-like structures in the epicardium, progresses from this layer toward the endocardium as indicated by a transmural gradient of vascular volume throughout the ventricles. Vascular smooth muscle first appears in E17 hearts at the time a capillary-like plexus coalesces and penetrates the aorta to form the main coronary arteries. These vessels maintain an anastomatic morphology and must undergo subsequent remodeling in order to assume adult branching characteristics. The early postnatal period is characterized by development of the arterial tree and the enzymatic differentiation of the arteriolar and venular ends of the capillary bed. Although bFGF is expressed both prenatally and postnatally, the highest mRNA expression was noted during the early period of vascularization (E14 and E15), and the early neonatal period (1-6 days) which corresponds to a period of substantial microvascular growth.

CONCLUSIONS

Coronary vascularization follows a temporal sequence which includes transmural expansion of the capillary bed, arteriolar formation subsequent to vascular penetration of the aorta, and postnatal growth, differentiation, and remodeling. Since high levels of bFGF expression are correlated with key time points in coronary vascular growth, bFGF may play an important role in this process.

Transport of transferrin across the blood-thymus barrier in young rats

The interaction of transferrin-peroxidase (Tf-HRP) with the capillary endothelium of the rat thymus was analyzed by diaminobenzidine (DAB) cytochemistry and electron microscopy. The thoracic aortas of young rats were cannulated and the upper bodies perfused with the Tf-HRP conjugate. In the thymus, plasmalemmal vesicles of the endothelium mediated the endocytosis and transport of Tf-HRP. Transcytosis of Tf-HRP appeared to occur by micropinocytosis, without morphological evidence of involvement by endothelial endosomes. DAB reaction product was commonly present in the subendothelial interstitial space and, in addition, was often localized in clathrin coated pits and vesicles in epithelial reticular cells that surround the thymic capillaries. In perfusions done at 4 degrees C, no binding of Tf-HRP to the lumenal membranes of capillaries was detected. The transport of Tf-HRP across the capillary endothelium in the thymus was not inhibited by competition with excess native transferrin; however, the uptake of Tf-HRP by epithelial reticular cells was completely inhibited by excess transferrin. Transferrin receptors were localized in the thymus by indirect immunocytochemistry using OX-26, a mouse anti-rat transferrin receptor monoclonal antibody. No transferrin receptors were detected on the capillary endothelium but diffuse reaction product was localized on the subjacent epithelial reticular cells. These results indicate that transport of Tf-HRP across the thymus capillary wall is independent of transferrin receptors at the level of the endothelial cells but that subsequent uptake of Tf-HRP by epithelial reticular cells is a transferrin receptor dependent process.

Conversion of diacylglycerol to phosphatidylcholine on the basolateral surface of epithelial (Madin-Darby canine kidney) cells. Evidence for the reverse action of a sphingomyelin synthase

When N-6[7-nitro-2,1,3-benzoxadiazol-4-yl]aminohexanoyl-phosphatidic acid (C6-NBD-PA) is inserted into the plasma membrane of fibroblasts, it is metabolized by the cells to C6-NBD-diacylglycerol (DG), -triacylglycerol, -phosphatidylcholine (PC), and -phosphatidylethanolamine (PE) (Pagano, R. E., Longmuir, K. J., and Martin, O. C. (1983) J. Biol. Chem. 258, 2034-2040). In Madin-Darby canine kidney (MDCK) cells incubated at 10 degrees C with C6-NBD-PA, up to 70% of the newly synthesized C6-NBD-PC but no C6-NBD-PE could be depleted from the basolateral cell surface by the addition of bovine serum albumin to the medium. Preincubation of the cells with [3H]choline for 2 h at 37 degrees C prior to C6-NBD-PA addition at 10 degrees C labeled non-depletable C6-NBD-PC with a specific activity of > 10 times that of the depletable C6-NBD-PC on the basolateral cell surface, indicating that the latter had not been synthesized by the CDP-choline pathway. C6-NBD-DG could substitute for C6-NBD-PA as substrate for both intracellular and surface C6-NBD-PC synthesis. In addition, C6-NBD-PC synthesis on the cell surface was independent of the location of the C6-NBD-chain on the 1- or 2-position, indicating that the reaction occurred by transfer of phosphorylcholine. Using C6-NBD-ceramide, C6-NBD-sphingomyelin (SM) synthesis also was discovered on the basolateral but not on the apical cell surface. The conversion of PC plus ceramide to DG and SM on the basolateral MDCK cell surface suggests that the synthesis of C6-NBD-PC on this surface occurred via the reverse reaction of a SM synthase. Indeed, the surface C6-NBD-PC synthesis was reduced to 40-50% by addition of C6-NBD-ceramide or hydrolysis of cell surface SM by exogenous neutral sphingomyelinase. Since DG activates protein kinase C and ceramide indirectly inhibits this kinase but activates other kinase(s) and phosphatase(s), the phosphocholine transferase at the cell surface may have a regulatory role in signal transduction.

Immunolocalization of GLUT-1 glucose transporter in rat skeletal muscle and in normal and hypoxic cardiac tissue

We compared the expression and cell-type localization of GLUT-1 mRNA and protein between cardiac and skeletal muscle of normal rats. Also, since we recently showed that cardiac GLUT-1 is upregulated in rats exposed to hypobaric hypoxia, we examined the cellular localization of GLUT-1 in cardiac tissue of normal and hypoxic rats. Confocal light microscopy and double immunofluorescent labeling revealed intense localization of GLUT-1 around neurofilament immunoreactivity within gastrocnemius muscle consistent with the previously described localization of large amounts of GLUT-1 in perineurial sheaths of skeletal muscle. However, using the same methods, we were unable to visualize GLUT-1 adjacent to nerve fibers in numerous sections of right or left ventricles or atria. Compared with skeletal myoctes, however, GLUT-1 immunofluorescence among cardiomyocytes was much more intense, particularly along the plasma membrane and especially intercalated discs. GLUT-1 immunofluorescence was also seen within the walls of arterioles within the heart. The predominant localization of GLUT-1 expression to cardiomyocytes in heart tissue was confirmed by in situ mRNA hybridization to digoxigenin-conjugated GLUT-1 cDNA. Northern blot analysis demonstrated that GLUT-1 mRNA was increased severalfold in the cardiac tissues compared with skeletal muscle. Although we detected GLUT-1 protein by immunoblotting of detergent extracts of the heart, we could not detect GLUT-1 in similar extracts of skeletal muscle. The cell type distribution of GLUT-1 in hearts of hypoxic rats was not different by immunohistochemistry from normals. These data indicate that 1) the cell-type distribution of GLUT-1 in the heart differs markedly from that in skeletal muscle. GLUT-1 in cardiac tissue, unlike skeletal muscle, is predominantly expressed within myocytes. 2) Cardiac GLUT-1 is not located along nerve fibers. 3) GLUT-1 mRNA and protein levels in cardiac tissue are considerably greater than in skeletal muscle. 4) The hypoxia-induced increase in cardiac GLUT-1 that we previously reported must occur within cardiomyocytes.

Apical-basal membrane polarity of membrane phosphatases in isolated capillary endothelium: alteration in ultrastructural localisation under culture conditions

Capillaries from freshly isolated rat epididymal fat were subjected to protocols that allowed ultrastructural localisation of alkaline phosphatase and 5'-nucleotidase. Alkaline phosphatase was almost entirely restricted to the capillary luminal membrane and vesicles associated with this membrane. 5'-nucleotidase was localised on the basal or abluminal membrane and associated vesicles. Arterioles and occasional venules were also present in the cell isolates, and arteriole localisation of 5'-nucleotidase was identical to that in capillaries. In venules, 5'-nucleotidase often failed to exhibit a polarised distribution and was present on both membrane domains. In confluent cultured endothelial cells, 5'-nucleotidase was not expressed in a predominantly polarised arrangement. Alkaline phosphatase was found on apical surfaces and regions of lateral cell contact. The results of these studies show that capillary endothelial cells exhibit enzyme polarity of their surface membranes which is subject to change on introduction of the cells to tissue culture.

Receptor-mediated endocytosis of transferrin at the blood-brain barrier

Rat brains were perfuse with a transferrin-peroxidase conjugate (Tf-HRP) to characterize morphologically the endocytic pathway of transferrin in blood-brain barrier endothelial cells. Electron microscopic evaluation of rat brains perfused with Tf-HRP at 4 degrees C and subsequently warmed to 37 degrees C for brief periods of time (2 minutes) showed sequestration of Tf-HRP in clathrin coated pits and vesicles on the luminal membrane of the brain endothelium. After 5 minutes of warming, diaminobenzidine (DAB) reaction product was present in vesicular structures 250–500 nm in diameter and in associated tubules morphologically identified as large or sorting endosomes. Recycling endosomes were also heavily labelled at this time point. Almost no DAB reaction product remained in the cerebral endothelial cells when the warming period was longer than 15 minutes. Other rat brains were perfused with Tf-HRP at 30 degrees C for 15 minutes prior to fixation and DAB cytochemistry. In these studies, brain endothelial cells contained large amounts of DAB reaction product, mostly localized in 50–100 nm vesicles and tubules, often in the Golgi region of the cells. Coated pits and vesicles and large endosomes were also heavily labelled. Transcytosis of Tf-HRP was not identified in either perfusion protocol. Ultrastructural, indirect immunocytochemical localization of transferrin receptors showed that the transferrin receptor is highly polarized at the blood-brain barrier and is localized only on the apical membrane, in contrast to other polarized epithelial cells, like hepatocytes, in which the receptor is present on the basolateral membrane. The evidence supports an iron transport model in which iron-loaded transferrin is taken up by receptor-mediated endocytosis at the luminal membrane of brain capillaries. The iron then dissociates from transferrin in endosomal compartments and is transcytosed by unknown mechanisms, while the transferrin is retroendocytosed.

Insulin-like growth factor binding protein (IGFBP)4 accounts for the connective tissue distribution of endothelial cell IGFBPs perfused through the isolated heart

Insulin-like growth factor binding protein 4 (IGFBP4) was purified to homogeneity from conditioned media of bovine pulmonary artery endothelial cells and shown to have the N-terminal amino acid sequence DEAIHCPPCS, a sequence unique to IGFBP4. The IGFBP4 was separated into predominantly glycosylated and nonglycosylated fractions, with each fraction separately perfused through isolated, beating rat hearts. Both forms of IGFBP4 crossed the capillary boundary of the heart and distributed primarily in subendothelial connective tissue components with a connective tissue/cardiac muscle distribution ratio of 20:1 for the glycosylated fraction and 27:1 for the nonglycosylated fraction. Perfused IGFBP1, 2, 3, and IGF-I also crossed the capillary boundary but in contrast to IGFBP4, preferentially localized in cardiac muscle with a connective tissue/muscle ratio of approximately 1:3. We conclude that the connective tissue distribution previously reported for IGFBPs in conditioned media of pulmonary artery endothelial cells is due to IGFBP4.

Studies of the mechanism of iron transport across the blood-brain barrier

The mechanism by which iron enters the central nervous system from the blood is not well understood. Iron in blood plasma is totally bound to transferrin (Tf), a major plasma glycoprotein. Tf receptors are present on the blood-brain barrier (BBB) endothelium. It is not known whether iron separates from Tf during its passage across the endothelial cells and then enters the brain by another mechanism, or whether the two proteins enter the brain together. We characterize here the morphological pathway for endocytosis of a monomeric horseradish peroxidase-transferrin conjugate by the rat BBB endothelium. Our results indicate that this conjugate binds to Tf receptors on the luminal BBB, is internalized via clathrin-coated vesicles, enters early or sorting endosomes, and, subsequently, late or recycling endosomes near the Golgi apparatus. No evidence is found for Tf transcytosis. It is likely that iron separates from Tf in early endosomes, which are assumed to be acidic, as they are in other cells, and enters the brain by an as yet undefined pathway. A clonal line of brain capillary endothelial cells that mimics the BBB when grown on permeabilized membranes can transcytose iron provided as Fe55-Tf. This cell line may provide a useful system to determine the pathway that iron uses to enter the brain. We also present evidence that cultured chick embryo forebrain neurons contain a large number of a unique Tf receptor.

Receptor-mediated endocytosis of insulin by cultured endothelial cells

Label-fracture immunochemistry and pre-embedding indirect immunocytochemistry were applied to investigate insulin uptake by endothelial cells. Freeze fracture replicas showed that a small percentage of native insulin receptors are associated with non-coated pits (4%) and coated pits (2%). After warming, receptor bound insulin became increasingly associated with such endocytotic vesicles. After 2 min the percentage of detectable insulin associated with non-coated and coated pits increased to 16% and 8%, respectively. Pre-embedding immunocytochemical localization of insulin gave results consistent with those obtained from the label-fracture studies. Both non-coated and coated vesicles appeared labelled after 5 min of warming. Non-coated vesicles contained 25% of the cell associated insulin while 9% was associated with coated pits and vesicles. After 10 min of warming, 9% of label was located in non-coated vesicles and 7% in coated vesicles. A large proportion (29%) of the label was found in tubular-vesicular endosomes at this time. After 15 min of warming, 30% of the remaining cell-associated gold label was found in multivesicular bodies. These experiments demonstrate that insulin uptake by endothelium is mediated by both coated and non-coated vesicles and that, once internalized, insulin is routed through endosomal pathways that primarily result in transcytosis.

Plasma membrane appearance of phosphatidylethanolamine in stimulated macrophages

Mouse peritoneal macrophages were labeled with [1-3H]ethanolamine, and the presence of radioactive [3H]phosphatidylethanolamine (PE) at the plasma membrane was monitored by reacting the cells with trinitrobenzene sulfonic acid (TNBS) under nonpenetrating conditions. Macrophages stimulated with either the calcium ionophore A23187 or zymosan demonstrated a larger proportion of radiolabeled PE in the plasma membrane than control, nonstimulated cells. In experiments in which macrophages were labeled with ethanolamine for increasing times, appearance of membrane 3[H]PE was stimulated as early as after 2 hr of labeling. Macrophages labeled for 24 hr, then stimulated and returned to fresh medium still reflected a higher amount of membrane 3[H]PE at 2 hr after the stimulation, suggesting stimulation results in long-term alterations in plasma membrane lipids. Protease-peptone-elicited macrophages, which are not stimulated by zymosan or ionophore, did not exhibit an increase in membrane 3[H]PE upon stimulation. The size of the TNBS-accessible radiolabeled PE pool increased proportionately with a second stimulation; however, a subsequent labeling of the cells with TNBS after brief warming increased the TNBS-accessible pool in control cells only. As shown in previous studies, macrophage stimulation resulted in an increased incorporation of lipid precursors into phospholipid. The mass of plasma membrane Tnp-PE relative to mass of PE was not increased in ionophore-treated macrophages in contrast to a small (approximately 22%) increase in zymosan-treated cells. These results are suggestive of alterations in lipid synthesis in stimulated macrophages and possible long-term changes in the structure and function of the plasma membrane of macrophages following stimulation.

Ultrastructural localization of arachidonic acid in stimulated macrophages

The distribution of 3[H] arachidonic acid incorporated into cultured mouse peritoneal macrophages was assessed upon stimulation of the cells with either the calcium ionophore A23187 or zymosan. After a labeling time of 24 h, cells were stimulated and processed for light and electron microscopic autoradiography. Grains were primarily localized over the plasma membrane and lipid-containing vesicles of both control and stimulated cells. In macrophages stimulated with ionophore, a decreased labeling density was evident in both of these cell compartments. Similar alterations in labeling pattern were observed in zymosan treated cells, although a larger decline in grain density occurred from the plasma membrane compartment. Immunocytochemical localization of PGE2, a major eicosanoid product released upon ionophore stimulation, revealed the presence of the prostaglandin in clear vesicular structures, many of which appear to be continuous with the plasma membrane. These results provide morphological evidence that different cellular pools of arachidonic acid may be differentially mobilized for eicosanoid production as a function of the mode of stimulation.

Tissue localization of perfused endothelial cell IGF binding protein is markedly altered by association with IGF-I

Perfused endothelial cell IGF binding proteins (ECBP) have been previously demonstrated to leave the microcirculation of the rat heart and distribute primarily in connective tissue elements of the heart. In the present study, ECBP have been crosslinked to IGF-I and the biologically inactive [1-27,gly4,38-70]-hlGF-I, an analog of IGF-I lacking the type I IGF receptor domain. The crosslinked ECBPs were perfused through the isolated rat heart and their tissue distributions determined. Both [ECBP-Analog] and [ECBP-IGF-I] left the microcirculation of the heart. [ECBP-Analog] preferentially localized in connective tissue elements with a muscle:connective tissue ratio of approximately 1:6, similar to the tissue distribution of perfused ECBP. In contrast, the [ECBP-IGF-I] complexes localized in cardiac muscle with a muscle to connective tissue ratio of approximately 3:1, virtually identical to the tissue distribution of IGF-I when the IGF-I is perfused through the heart in the absence of any binding proteins. We conclude that 1) ECBP in the presence of IGF will cross capillary boundaries and 2) the tissue distribution of [ECBP-IGF-I] is dictated by the IGF-I molecule.

Transcapillary permeability and subendothelial distribution of endothelial and amniotic fluid insulin-like growth factor binding proteins in the rat heart

Insulin-like growth factor (IGF) binding proteins (IGFBP) were purified from conditioned media of cultured bovine endothelial cells (ECBP) and from human amniotic fluid (IGFBP-1), and then labeled by radioiodination. 125I-ECBP and 125I-IGFBP-1 were perfused through isolated beating rat hearts for 1 and 5 min, and the hearts fixed and analyzed for 125I-BP content and distribution. One to 4% of the perfused 125I-ECBP and 125I-IGFBP-1 crossed the capillary boundary. The ECBPs predominantly localized as intact 125I-BP in connective tissue elements of the heart with less 125I-BP in cardiac muscle. The ratio of 125I-ECBP in connective tissue: muscle (normalized to percent vol of these compartments) was greater than or equal to 10:1. In contrast, the IGFBP-1 had a greater affinity for cardiac muscle with ratios of 125I-IGFBP-1 in connective tissue:muscle of approximately 1:2. When 125I-IGF-I, in the absence of any BPs, was perfused through the hearts approximately 3-5% left the microcirculation and was found in subendothelial tissues. 125I-IGF-I localized primarily to cardiac muscle with a distribution of connective tissue:cardiac muscle of about 1:3. The findings in the isolated perfused heart were confirmed in intact animals. After 125I-IGFBP-1 was injected into anesthetized rats and allowed to circulate for 5 min, substantial radioactivity was associated with the heart. As in the isolated heart, the IGFBP-1 preferentially localized to cardiac muscle with a connective tissue:cardiac muscle ratio of 1:3. We conclude that IGFBPs produced by endothelial cells and the IGFBP-1 contained in amniotic fluid can cross the capillary boundaries of the rat heart, and that the ECBPs preferentially localize in connective tissue elements of the myocardium, whereas IGFBP-1 predominantly localizes in cardiac muscle.

Insulin differentially alters transcapillary movement of intravascular IGFBP-1, IGFBP-2 and endothelial cell IGF-binding proteins in the rat heart

Insulin-like growth factor binding-proteins 1 and 2 (IGFBP-1, IGFBP-2) and endothelial cell IGF binding proteins (ECBP) were individually perfused through isolated beating rat hearts in the absence and presence of insulin. Insulin caused an increased movement of IGFBP-1 from the vascular space to tissues of the heart. Subendothelial content of IGFBP-1 was 110%, 126% (p less than .01) and 132% (p less than 0.05) of control hearts when perfused with 1, 10 and 100 ng/ml insulin, respectively. . In contrast, insulin treatment was associated with a decrease in ECBP content in cardiac tissue, being 83%, 62% (p less than 0.005) and 73% (p less than 0.05) of control when perfused with 1, 10 and 100 ng/ml insulin. The efflux of IGFBP-2 from the intravascular space was unaffected by insulin. The subendothelial tissue distribution of the transported binding proteins was not changed by insulin perfusion, with IGFBP-1 and IGFBP-2 localizing predominantly in cardiac muscle and ECBP having greater affinity for connective tissue elements. We conclude that in the perfused rat heart, insulin can differentially alter transcapillary movement of IGFBP-1, IGFBP-2 and endothelial cell IGF-binding proteins. Such insulin-facilitated changes could potentially mediate nutrient-dependent transport of IGF-I and IGF-II to peripheral tissues.