Intracranial Transplantation Research Articles

873. Synergistic and Antagonistic Effects of Neonatal Intracranial AAV Gene Therapy and Bone Marrow Transplantation in Sanfilippo Syndrome Type B Mice

873. Synergistic and Antagonistic Effects of Neonatal Intracranial AAV Gene Therapy and Bone Marrow Transplantation in Sanfilippo Syndrome Type B Mice

Silencing of Insulin-like Growth Factor-binding Protein-2 in Human Glioblastoma Cells Reduces Both Invasiveness and Expression of Progression-associated Gene CD24

Glioblastoma multiforme (GBM) is a malignant brain tumor characterized by rapid growth and extensive invasiveness. Overexpression of insulin-like growth factor-binding protein-2 (IGFBP-2) has been reported in GBM. However, it remains to be determined how IGFBP-2 is involved in the progression of GBM. We utilized short hairpin-RNA (shRNA) expression retroviral vectors to inactivate the IGFBP-2 gene permanently in two human GBM cell lines, U251 and YKG-1. The stable knockdown of IGFBP-2 resulted in decreased invasiveness, decreased saturation density of the cells in vitro, and decreased tumorigenicity in nude mice. Transcriptional profiling of both lines revealed several genes that were significantly down-regulated by inactivation of IGFBP-2. One such gene was CD24, which has been implicated in progression of various cancers. Indeed, CD24 was expressed in most GBM cases and the inactivation of CD24 in GBM cells suppressed cellular invasiveness, as was the case for IGFBP-2. Forced overexpression of CD24 led to increased invasiveness of both IGFBP-2-inactivated GBM cell lines and also A172, a human GBM cell line with low endogenous CD24. Further supporting the inter-relationship between IGFBP-2 and CD24, knockdown of IGFBP-2 suppressed the CD24 promoter activity. Moreover, both CD24 promoter activity and in vitro invasiveness were restored in knockdown cells by transfection with an IGFBP-2 expression plasmid. These results indicate that CD24 is modulated by IGFBP-2 and contributes to IGFBP-2-enhanced invasiveness of GBM cells.

Stem cells act through multiple mechanisms to benefit mice with neurodegenerative metabolic disease

Intracranial transplantation of neural stem cells (NSCs) delayed disease onset, preserved motor function, reduced pathology and prolonged survival in a mouse model of Sandhoff disease, a lethal gangliosidosis. Although donor-derived neurons were electrophysiologically active within chimeric regions, the small degree of neuronal replacement alone could not account for the improvement. NSCs also increased brain beta-hexosaminidase levels, reduced ganglioside storage and diminished activated microgliosis. Additionally, when oral glycosphingolipid biosynthesis inhibitors (beta-hexosaminidase substrate inhibitors) were combined with NSC transplantation, substantial synergy resulted. Efficacy extended to human NSCs, both to those isolated directly from the central nervous system (CNS) and to those derived secondarily from embryonic stem cells. Appreciating that NSCs exhibit a broad repertoire of potentially therapeutic actions, of which neuronal replacement is but one, may help in formulating rational multimodal strategies for the treatment of neurodegenerative diseases.

Stem Cells and Metastatic Cancer: Fatal Attraction?

Neural stem cells (NSCs) are generally defined by their dual capacity to self-renew and differentiate into more specialized cell types such as neurons and glia. NSCs have been the object of many studies aimed at neuron replacement therapy in several degenerative conditions of the central nervous system such as Parkinson disease, Alzheimer disease, multiple sclerosis, and amyotrophic lateral sclerosis. Pathotropism (movement towards diseased areas), a yet incompletely understood characteristic of NSCs, makes them particularly attractive candidates not only to replace damaged tissue in degenerative pathologies, but also to deliver therapeutic molecules in patients with disseminated metastatic cancer [1]. By 2000, several studies had shown that upon intracranial transplantation into animal models of brain cancer, NSCs are able to specifically migrate to sites of neoplasia [2–4], possibly in response to chemotactic signals emanating from cancer cells. Perhaps even more surprisingly, this tropism of neural stem cells can be exploited to target extracranial tumors of both neural and non-neural origins [5].

Effect of intracranial transplantation of CD34+ cells derived from human umbilical cord blood in rats with cerebral ischemia

作为可移植的干细胞的来源，在人的脐的绳索血(HUCB ) 的 CD34~+ 潜水艇人口广泛地被使用了治疗一些造血的系统疾病。然而， CD34~+ 房间是否保持治疗学的潜力到服的局部缺血，是未知的。学习是在 CD34~+cells 的移植以后观察神经功能的恢复的这的 Thepurpose 源于 HUCB 进是化学家在老鼠的服的组织。

Advances in the delivery of treatments for Parkinson’s disease

Innovative drug delivery in Parkinson’s disease (PD) has the potential to reduce or avoid many side effects of current treatment, such as wearing-off type fluctuations, dyskinesia, on-off phenomena or bouts of motor freezing. The traditional orally administered formulations of l-dihydroxyphenylalanine combined with a peripheral aromatic acid decarboxylase inhibitor remain the mainstay of treatments for PD. However, such combination therapies have been further formulated to extend their duration of action by including a catechol-O-methyltransferase inhibitor. Preventing the breakdown of dopamine has also been achieved by monoamine oxidase-B inhibition; this approach now having been formulated for sublingual use (Zelapar®, Valeant Pharmaceuticals). An alternative approach bypasses the oral route of administration and instead relies on continuous duodenal infusion (Duodopa®, Solvay, NeoPharma AB) for better therapeutic effect. The clinical use of dopamine agonists as antiparkinsonian drugs now incorporates a variety of delivery techniques. For example, apomorphine, which relies on parenteral administration for maximum bioavailability, may be delivered via rectal, intranasal, sublingual and subcutaneous (e.g., Apokyn®, Mylan Bertek) routes. Meanwhile, rotigotine and lisuride have both been formulated for delivery via skin patches. Finally, the authors examine more experimental delivery techniques, including the delivery of genes via viral vectors or liposomes, intracranial transplant of a variety of cells and of l-dihydroxyphenylalanine by prodrug-dispensing liposomes or pulmonary delivery (AIR®, Alkermes). The advent and application of these varied technologies will help encourage patient-specific means of treatment for PD.

Myofiberbreak-up: A marker of ventricular fibrillation in sudden cardiac death

Background Electrophysiologically, ventricular fibrillation is defined as a “chaotic, random, asynchronous electrical activity of the ventricles due to repetitive re-entrant excitation and/or rapid focal discharge”. To this point its morphological equivalent has not been defined. Material and method Several groups of different diseases and types of accidental death in normal subjects were studied. A complete autopsy was performed and the hearts were examined in 432 cases. A total of 16 myocardial samples per heart were processed for histological examination and sections were stained by haematoxylin and eosin or by specific stains. The frequency, location and extent of myocellular segmentation (stretching and/or rupture) of intercalated discs and associated changes of myocardial bundles and single myocells were investigated. A quantitative analysis was performed and the data were processed for statistical evaluation. Results The frequency of MFB was maximal in coronary (88%) and Chagas (76%) groups followed by the intracranial brain haemorrhage group (52%). The extent of myofiberbreak-up was maximal in coronary/Chagas groups followed by intracranial haemorrhage and transplant groups. Conclusions No correlation was seen between gender, age, heart weight, degree of coronary atherosclerosis, myocardial fibrosis, survival and MFB. If our postulate is correct, finding MFB in the myocardium might allow the diagnosis of a malignant arrhythmia followed by cardiac arrest due to ventricular fibrillation even in the absence of clinical information (sudden death out-of-hospital).

Isolation of immortalized, INK4a/ARF-deficient cells from the subventricular zone after in utero N-ethyl-N-nitrosourea exposure

Brain tumors, including gliomas, develop several months after rats are exposed in utero to N-ethyl-N-nitroso-urea (ENU). Although pathological changes cannot be detected until these animals are several weeks old, the process that eventually leads to glioma formation must begin soon after exposure given the rapid clearance of the carcinogen and the observation that transformation of brain cells isolated soon after exposure occasionally occurs. This model can therefore potentially provide useful insights about the early events that precede overt glioma formation. The authors hypothesized that future glioma cells arise from stem/progenitor cells residing in or near the subventricular zone (SVZ) of the brain. Cells obtained from the SVZ or corpus striatum in ENU-exposed and control rats were cultured in an epidermal growth factor (EGF)-containing, chemically defined medium. Usually, rat SVZ cells cultured in this manner (neurospheres) are nestin-positive, undifferentiated, and EGF-dependent and undergo cell senescence. Consistent with these prior observations, control SVZ cells undergo senescence by the 12th to 15th doubling (20 of 20 cultures). In contrast, three of 15 cultures of cells derived from the SVZs of individual ENU-treated rats continue to proliferate for more than 60 cell passages. Each of these nestin-expressing immortalized cell lines harbored a common homozygous deletion spanning the INK4a/ARF locus and was unable to differentiate into neural lineages after exposure to specific in vitro stimuli. Nevertheless, unlike the rat C6 glioma cell line, these immortalized cell lines demonstrate EGF dependence and low clonogenicity in soft agar and did not form tumors after intracranial transplantation. Data in this study indicated that immortalized cells may represent glioma precursors that reside in the area of the SVZ after ENU exposure that may serve as a reservoir for further genetic and epigenetic hits that could eventually result in a full glioma phenotype.

Intracerebral transplantation of porcine choroid plexus provides structural and functional neuroprotection in a rodent model of stroke.

Choroid plexus (CP) secretes a cocktail of neurotrophic factors. In the present study, CP from neonatal pigs was encapsulated within alginate microcapsules for in vitro and in vivo neuroprotective studies. In vitro studies involved serum deprivation of rat embryonic cortical neurons and treatment with a range of concentrations of conditioned media from CP. For in vivo studies, rats received a 1-hour middle cerebral artery occlusion followed by intracranial transplantation of encapsulated or unencapsulated CP, empty capsules, or no transplant. Behavioral testing was conducted on days 1 to 3 after transplantation. Cerebral infarction was analyzed using 2,3,5-triphenyl-tetrazolium chloride staining at 3 days after transplantation. Conditioned media from CP produced a significant dose-dependent protection of serum-deprived cortical neurons. Enzyme-linked immunosorbent assay confirmed secretion of GDNF, BDNF, and NGF from CP. Parallel in vivo studies showed that CP transplants improved behavioral performance and decreased the volume of infarction. Both encapsulated and unencapsulated CP transplants were effective; however, more robust benefits accompanied encapsulated transplants. These data are the first to demonstrate the neuroprotective potential of transplanted CP and raise the intriguing possibility of using these cells as part of the treatment regimen for stroke and other neurological disorders.

Mesenchymal stem cell engraftment in lung is enhanced in response to bleomycin exposure and ameliorates its fibrotic effects.

Previously we described a reliable method based on immunodepletion for isolating mesenchymal stem cells (MSCs) from murine bone marrow and showed that, after intracranial transplantation, the cells migrated throughout forebrain and cerebellum and adopted neural cell fates. Here we systemically administered MSCs purified by immunodepletion from male bleomycin (BLM)-resistant BALB/c mice into female BLM-sensitive C57BL/6 recipients and quantified engraftment levels in lung by real-time PCR. Male DNA accounted for 2.21 x 10(-5)% of the total lung DNA in control-treated mice but was increased 23-fold (P = 0.05) in animals exposed to BLM before MSC transplantation. Fluorescence in situ hybridization revealed that engrafted male cells were localized to areas of BLM-induced injury and exhibited an epithelium-like morphology. Moreover, purification of type II epithelial cells from the lungs of transplant recipients resulted in a 3-fold enrichment of male, donor-derived cells as compared with whole lung tissue. MSC administration immediately after exposure to BLM also significantly reduced the degree of BLM-induced inflammation and collagen deposition within lung tissue. Collectively, these studies demonstrate that murine MSCs home to lung in response to injury, adopt an epithelium-like phenotype, and reduce inflammation and collagen deposition in lung tissue of mice challenged with BLM.

Functional recovery after simultaneous transplantation with neuro-epithelial stem cells and adjacent mesenchymal tissues into infarcted rat brain.

Cerebral infarction results in impairment of motor and cognitive functions. We performed intracranial transplantation of multipotential neuro-epithelial stem cells with mesenchyme into experimentally large ischemic lesions to study their potential to relieve deficits. Wistar albino rats were subjected to transient middle cerebral artery occlusion for 60 minutes, producing an extensive ischemic lesion in the ipsilateral striatum and adjacent cerebral cortex. The rat mesencephalic neural plate at the early somite stage (embryonic day 10.5) together with adjacent ventral mesenchyme was used as donor material. We performed histological and immunohistochemical studies, with antibodies against tyrosine hydroxylase, and dopamine- and adenosine 3': 5'-monophosphate-regulated phosphoprotein 32 (DARPP-32; a striatal marker). Micro-angiograms were made by using Microfil silicone rubber. Morris Water-maze learning and treadmill task were employed to evaluate motor and cognitive functions. A viable non-tumoral mass was recognized in the rat striatum, up to as long as 156 days after transplantation. There were many cells positive for tyrosine hydroxylase or DARPP-32 in the graft. Some of the DARPP-32 positive cells within the graft had extended their dendrites into host tissues. In the micro-angiograms, many fine vessels were observed within the graft and dilated vessels meandered around the graft. Transplanted animals recovered significantly better in motor and cognitive functions than animals injected with only culture medium. Neuro-epithelial stem cells may follow several lines of differentiation; along the naturally genetically programmed line of differentiation, or along other cell lines depending on different environments. Grafting of neuro-epithelial stem cells with mesenchyme may merit a further study as a treatment for cerebral infarction.

Evidence for Target-Specific Nerve Fiber Outgrowth from Subpopulations of Grafted Dopaminergic Neurons: A Retrograde Tracing Study Using in Oculo and Intracranial Grafting

Efforts have been made to counteract the symptoms of Parkinson's disease by substituting the loss of dopaminergic neurons with fetal ventral mesencephalic grafts. One of the postulated limiting factors in this treatment is the relatively poor cell survival and limited graft-derived fiber outgrowth. Recent results documenting enhanced survival of grafted dopaminergic neurons showed no positive correlation to enhanced innervation of the striatal target. Therefore this study was undertaken to investigate whether all surviving grafted dopaminergic neurons projected to the striatal target. Hence, fetal ventral mesencephalic tissue was implanted adjacent to mature versus immature striatal tissue using in oculo and intraventricular grafting techniques. In in oculo grafting, fetal ventral mesencephalon was implanted simultaneously with fetal lateral ganglionic eminence (immature striatal target) or to already matured striatal in oculo grafts (mature striatal target). Furthermore, fetal ventral mesencephalon was implanted into the lateral ventricle adjacent to mature dopamine-depleted striatum. The retrograde tracer fluorogold was injected into the striatal portion of the in oculo cografts and into reinnervated areas of the adult brain. Immunohistochemistry revealed that a significantly larger proportion of tyrosine hydroxylase-positive neurons in the ventral mesencephalic graft was innervating in oculo immature striatal tissue, and hence was fluorogold-positive, in comparison with the number of tyrosine hydroxylase-positive neurons innervating mature striatal tissue. Moreover, intracranial transplantations showed that tyrosine hydroxylase-positive neurons were distributed within the grafts in dense clusters of cells. In most clusters tyrosine hydroxylase-positive cells were fluorogold-negative but calbindin-positive. In a few tyrosine hydroxylase-positive cell clusters, neurons were coexpressing fluorogold but were calbindin-negative. In conclusion, significantly more dopamine neurons projected to immature than to mature striatal tissue and thus, a subpopulation of grafted dopaminergic neurons was not projecting into adult striatum. Thus, the results from this study show that further attempts to enhance survival of grafted dopamine neurons in purpose to enhance graft-derived fiber outgrowth and efficacy should also consider different subtypes of dopamine neurons.

Intracranial bone marrow transplantation after traumatic brain injury improving functional outcome in adult rats.

The authors tested the hypothesis that intracranial bone marrow (BM) transplantation after traumatic brain injury (TBI) in rats provides therapeutic benefit. Sixty-six adult Wistar rats, weighing 275 to 350 g each, were used for the experiment. Bone marrow prelabeled with bromodeoxyuridine (BrdU) was harvested from tibias and femurs of healthy adult rats. Other animals were subjected to controlled cortical impact, and BM was injected adjacent to the contusion 24 hours after the impact. The animals were killed at 4, 7, 14, or 28 days after transplantation. Motor function was evaluated both before and after the injury by using the rotarod test. After the animals had been killed, brain sections were examined using hemotoxylin and eosin and immunohistochemical staining methods. Histological examination revealed that, after transplantation, BM cells survived, proliferated, and migrated toward the injury site. Some of the BrdU-labeled BM cells were reactive, with astrocytic (glial fibrillary acid protein) and neuronal (NeuN and microtubule-associated protein) markers. Transplanted BM expressed proteins phenotypical of intrinsic brain cells, that is, neurons and astrocytes. A statistically significant improvement in motor function in rats that underwent BM transplantation, compared with control rats, was detected at 14 and 28 days posttransplantation. On the basis of their findings, the authors assert that BM transplantation improves neurological outcome and that BM cells survive and express nerve cell proteins after TBI.

822 Intracranial Transplantation of Bone Marrow Cells Cultured with Neurotrophic Factors Improves Functional Outcome in Adult Male Wistar Rats after Traumatic Brain Injury

822 Intracranial Transplantation of Bone Marrow Cells Cultured with Neurotrophic Factors Improves Functional Outcome in Adult Male Wistar Rats after Traumatic Brain Injury

Experimental Gliosarcoma Induces Chemokine Receptor Expression in Rat Brain

Macrophage/microglial infiltration is a characteristic feature of brain tumors. The functional role(s) of these cells is complex and could include both trophic and suppressive effects on tumors. Information has recently emerged about the molecular signals that regulate the accumulation and function of monocytes in pathological disorders. Recent data indicate that the chemokine, monocyte chemoattractant protein-1 (MCP-1), a potent monocyte activating and chemotactic factor, is a primary regulator of the macrophage response in brain tumors. We hypothesized that if MCP-1 regulates macrophage/microglial infiltration, then expression of the specific MCP-1 receptor, CCR2, will be induced in peritumoral tissue and/or within brain tumors. Identification of a specific receptor that is preferentially expressed in brain tumors could be important both in terms of tumor biology and as a potential therapeutic target. We used an established experimental gliosarcoma model, induced by intracranial transplantation of cultured 9L cells into adult rat brain, to test this hypothesis. RT-PCR analysis showed high levels of both MCP-1 and CCR2 mRNA and Western blot analysis demonstrated increased CCR2 protein in tumor extracts. Immunocytochemistry showed CCR2 immunoreactive microglia in peritumoral tissue and, unexpectedly, that intrinsic tumor cells, rather than monocytes, were the predominant source of CCR2. These results demonstrate that CCR2 expression is markedly upregulated in this brain tumor model.

Allogeneic Astrocytoma In Immune Competent Dogs

We have induced in canines long-term immune tolerance to an allogeneic cell line derived from a spontaneous canine astrocytoma. Allogeneic astrocytoma cells were implanted endoscopically into the subcutaneous space of fetal dogs before the onset of immune competency (<40th gestational day). At adulthood, dogs rendered tolerant successfully serve as recipients of intracranial transplants of their growing allogeneic, subcutaneous tumor. Transplanted dogs subsequently develop a solid brain tumor with histological features similar to the original astrocytoma. This model may allow rapid development and evaluation of new therapies for brain tumors, as well as afford tumor biology studies that are untenable in smaller, immune incompetent, or inbred animals harboring less representative tumors.

Kidney Cografts Enhance Fiber Outgrowth From Ventral Mesencephalic Grafts to the 6-OHDA–Lesioned Striatum, and Improve Behavioral Recovery

Recent studies have demonstrated the presence of many different neurotrophic factors in the developing and adult kidney. Due to its production of this mixture of neurotrophic factors, we wanted to investigate whether fetal kidney tissue could be beneficial for neuritic fiber growth and/or cell survival in intracranial transplants of fetal ventral mesencephalic tissue (VM). A retrograde lesion of nigral dopaminergic neurons was performed in adult Fischer 344 male rats by injecting 6-hydroxydopamine into the medial forebain. The animals were monitored for spontaneous locomotor activity in addition to apomorphine-induced rotations once a week. Four weeks following the lesion, animals were anesthetized and embryonic day 14 VM tissue from rat fetuses was implanted stereotaxically into the dorsal striatum. One group of animals received a cograft of kidney tissue from the same embryos in the same needle track. The animals were then monitored behaviorally for an additional 4 months. There was a significant improvement in both spontaneous locomotor activity (distance traveled) and apomorphine-induced rotations with both single VM grafts and VM–kidney cografts, with the VM–kidney double grafts enhancing the motor behaviors to a significantly greater degree. Tyrosine hydroxylase (TH) immunohistochemistry and image analysis revealed a significantly denser innervation of the host striatum from the VM–kidney cografts than from the single VM grafts. TH-positive neurons were also significantly larger in the cografts compared to the single VM grafts. In addition to the dense TH-immunoreactive innervation, the kidney portion of cografts contained a rich cholinergic innervation, as evidenced from antibodies against choline acetyltransferase (ChAT). The striatal cholinergic cell bodies surrounding the VM–kidney cografts were enlarged and had a slightly higher staining density for ChAT. Taken together, these data support the hypothesis that neurotrophic factors secreted from fetal kidney grafts stimulated both TH-positive neurons in the VM cografts and cholinergic neurons in the host striatum. Thus, these factors may be combined for treatment of degenerative diseases involving both dopaminergic and cholinergic neurons.

Kidney cografts enhance fiber outgrowth from ventral mesencephalic grafts to the 6-OHDA-lesioned striatum, and improve behavioral recovery.

Recent studies have demonstrated the presence of many different neurotrophic factors in the developing and adult kidney. Due to its production of this mixture of neurotrophic factors, we wanted to investigate whether fetal kidney tissue could be beneficial for neuritic fiber growth and/or cell survival in intracranial transplants of fetal ventral mesencephalic tissue (VM). A retrograde lesion of nigral dopaminergic neurons was performed in adult Fischer 344 male rats by injecting 6-hydroxydopamine into the medial forebrain. The animals were monitored for spontaneous locomotor activity in addition to apomorphine-induced rotations once a week. Four weeks following the lesion, animals were anesthetized and embryonic day 14 VM tissue from rat fetuses was implanted stereotaxically into the dorsal striatum. One group of animals received a cograft of kidney tissue from the same embryos in the same needle track. The animals were then monitored behaviorally for an additional 4 months. There was a significant improvement in both spontaneous locomotor activity (distance traveled) and apomorphine-induced rotations with both single VM grafts and VM-kidney cografts, with the VM-kidney double grafts enhancing the motor behaviors to a significantly greater degree. Tyrosine hydroxylase (TH) immunohistochemistry and image analysis revealed a significantly denser innervation of the host striatum from the VM-kidney cografts than from the single VM grafts. TH-positive neurons were also significantly larger in the cografts compared to the single VM grafts. In addition to the dense TH-immunoreactive innervation, the kidney portion of cografts contained a rich cholinergic innervation, as evidenced from antibodies against choline acetyltransferase (ChAT). The striatal cholinergic cell bodies surrounding the VM-kidney cografts were enlarged and had a slightly higher staining density for ChAT. Taken together, these data support the hypothesis that neurotrophic factors secreted from fetal kidney grafts stimulated both TH-positive neurons in the VM cografts and cholinergic neurons in the host striatum. Thus, these factors may be combined for treatment of degenerative diseases involving both dopaminergic and cholinergic neurons.

Metastatic behavior of human tumors in congenitally athymic nude mice: intrinsic properties of the tumor cells and host immune reactivity.

Congenitally athymic nude (nu/nu) mice have been used extensively as hosts to study the metastatic properties of xenografted human tumors. It has not been fully explored to what extent the metastatic behavior of human tumor xenografts reflects the intrinsic properties of the tumor cells and to what extent it is influenced artificially by the host. The purpose of the work reported here was to evaluate the potential usefullness of athymic mice for qualitative and quantitative assessment of the intrinsic metastatic properties of human tumor cells. Four human melanoma cell lines (A-07, D-12, R-18, U-25) were included in the study. Quantitative intradermal and intracranial transplantation assays were used to determine the tumorigenicity and immunogenicity of the cell lines. The metastatic behavior of the cell lines was studied by inoculating cells intra-arterially or intravenously (artificial metastases) or intradermally (spontaneous metastases). The influence of the host on the incidence of metastases was assessed by inoculating cells intravenously in immunologically modified athymic mice. Both the intradermal and intracranial tumorigenicity differed substantially between the cell lines. The host immune reactivity against heterotransplantation was significantly lower for D-12 than for A-07, R-18 and U-25 cells. The incidence of metastases was influenced significantly by the host immune reactivity. The cell lines showed organ-specific metastatic patterns in athymic mice. The organs of preference were lungs for A-07 and D-12 cells, lymph nodes for R-18 cells, and brain for U-25 cells. The organ-specific metastatic pattern in athymic mice reflected the pattern of distant metastases in the donor patients. In addition, all cell lines gave rise to metastases in abdominal organ sites, but without organ specificity. The incidence of abdominal metastases was influenced significantly by the tumorigenicity of the cell lines. In conclusion, athymic mice appear to be excellent hosts for assessment of the organ specificity in the metastatic behavior of human tumors. The metastasis frequency of human tumors in athymic mice, however, might be a misleading quantitative measure of the intrinsic metastatic propensity of the tumor cells, owing to the cell-line-dependent host immune reactivity.

The pupillary light response: assessment of function mediated by intracranial retinal transplants.

We have adapted a pupillometry measurement system to test the functional efficacy of retinae previously transplanted over the midbrain of neonatal rats in mediating a pupillary light reflex in the host eye. This has permitted us to examine factors influencing various parameters of the response, and to study transplant-mediated responses in comparison with responses mediated by way of the normal consensual pathway. Despite the unusual location of these transplanted retinae and the absence of supportive tissues normally associated with retinae in situ, it is clear that pupilloconstriction in the host eye can be elicited by transplant illumination. Under the optimal conditions here defined, response parameters for individual animals were stable with repeated testing over extended periods. When considered as individual cases, response amplitude, constriction rate and response latency were intensity dependent, although responses elicited by transplant illumination were less sensitive than normal, typically by 2-3 log units. Large-amplitude transplant-mediated pupillary responses could, however, be elicited repeatedly throughout long trains of stimuli, unlike normal responses, which rapidly failed to recover to baseline under similar test conditions. Finally, even though some cellular elements of the visual cycle are absent in transplanted retinae, pupilloconstriction in the host eye could be elicited repeatedly by transplant illumination as long as two years after transplantation took place. These observations indicate the applicability of this preparation as an assay for the effects of experimental manipulations on information processing and response plasticity in the visual system, and as a tool for examining, in general, the necessary conditions for optimal function of grafts that work by synthesizing and relaying neural signals.