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The implantation of a deep brain stimulator (DBS) is often a staged procedure that involves stereotactic placement of the neurostimulator electrode, followed by connection of the electrode to a pulse generator during a separate operation. The authors describe a practical technique for the retrograde tunneling of the stimulator lead during the initial electrode implantation procedure. After DBS electrode placement and securing of the lead, the lead is covered with a protective cap and boot, which are then folded back to tunnel a redundant loop of the lead in a retrograde fashion into a subgaleal pocket. This technique facilitates connection of the lead to the pulse generator connecting wire at the subsequent operation and may reduce lead damage.

Object.In this study the authors describe secular trends in the incidence of three glial tumors—glioblastoma multiforme (GBM), astrocytoma not otherwise specified (ANOS), and anaplastic astrocytoma (AA)—in New York state from 1976 through 1995. They also describe the effect of age and sex on the relative risk (RR) for these tumors, specifically GBM.

Methods.Crude, age-, and sex-specific incidence rates were calculated for each tumor type from 1976 to 1995 by using data from the New York State Cancer Registry. Age-adjusted incidence rates were calculated by the direct standardization procedure, in which the 1970 United States Census Population Standard Million is used. The RR of GBM for the female population was calculated and plotted. Statistical comparisons were made using Pearson's correlation coefficient and regression analysis with the coefficient of variation.

Conclusions.The age-adjusted incidence of these three glial tumors increased during the study period. Increases in age-specific incidence of GBM were primarily limited to patients 60 years of age or older. The reasons for these increases cannot be fully explained with the data. Those in the female population had a lower risk of developing these tumors than those in the male. For GBM, the protective effect of sex was first evident at the approximate age of menarche, was greatest at the approximate age of menopause, and decreased in postmenopausal age strata. The overall protective effect of female sex and the described trend in RR for GBM in the female population suggests that sex hormones and/or genetic differences between males and females may play a role in the pathogenesis of this tumor.

✓ The application of several recent advances in cell biology, brain implantation, and cell-mediated tumor immunotherapy requires successful and reproducible placement of viable cell suspensions into brain. Stereotaxic implantation is being used to inject cytotoxic lymphocytes into gliomas and to replace dopaminergic cells in parkinsonian models. Systematic assessment of the factors that influence success in implantation of cell suspensions into solid tissues is needed.

A model was developed for investigation of stereotaxic implantation using radiolabeled rat lymphokine-activated killer (LAK) cells. Anesthetized rats received microliter injections of cell suspension into the right caudate nucleus. The injection volume, cell concentration, infusion rate, and needle size were varied systematically. The animals were sacrificed 1 hour after injection; the brain was removed and sectioned, and the radioactivity was counted. Three aliquots of the suspension were injected into counting tubes for control analysis. Recovery of radioactivity was expressed as the percent of mean counts per minute (cpm) in the right frontal lobe/mean cpm in the three control tubes. To assess the viability of implanted cells, the right frontal region was mechanically dissociated in media and centrifuged, and the pellet and supernatant were counted. By using small needles and slow infusion of volumes of 10µl or less, 85% to 90% of the radioactivity was recovered in the caudate nucleus. At least half of the implanted cells were viable. Consistent, accurate implantation of dispersed cells into brain over a range of volumes, cell concentrations, infusion rates, and needle sizes was achieved.

✓Intrastriatal与多巴胺或植入nondopaminergic tissue can elicit behavioral recovery in parkinsonian animals. Because in these animals, especially in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned monkeys, there are still considerable numbers of dopaminergic neurons left in the mesencephalon, implantation-induced trophic effects on host residual dopaminergic neurons have been suggested as a mechanism underlying the behavioral recovery. Gliosis around the graft is a universal finding in any implantation procedure and is probably mediated by interleukin-1 (IL-1); in addition, activated astrocytes secrete several neurotrophic factorsin vitro. Therefore, the authors postulated that trophic effects from IL-1-induced gliosis may be a “final common pathway” for recovery in parkinsonian animals after implantation.

Hemiparkinsonism was induced in rats by injection of 6-hydroxydopamine either directly into the substantia nigra or into the median forebrain bundle. The substantia nigra-lesioned rats showed complete depletion of dopaminergic neurons in the substantia nigra but sparing of those in the ventral tegmental area, whereas the median forebrain bundle-lesioned animals had depletion of dopaminergic cells in the substantia nigra and the ventral tegmental area. Polymer pellets containing either slow-released IL-1 alpha and beta or placebo pellets were implanted in the caudate nucleus on the lesioned side in both groups. The rats' rotational response to amphetamine was tested weekly for 8 weeks. Selective substantia nigra-lesioned rats with implantation of IL-1 pellets had a 45% reduction in amphetamine-induced rotation, whereas placebo-implanted substantia nigra-lesioned rats had a 14% reduction in rotation. In the median forebrain bundle-lesioned group, neither IL-1 nor placebo implantation elicited any effect on turning. Immunohistochemical staining for glial fibrillary acidic protein was markedly increased surrounding the IL-1 pellets compared to the placebo pellets. In the selective substantia nigra-lesioned rats with IL-1 pellets implanted in the caudate nucleus, a considerable number of tyrosine hydroxylase immunoreactive (TH-IR) fibers were observed in the medial and middle portions of the caudate nucleus. Fewer TH-IR fibers were seen in the rats with placebo-bearing pellets.

这些结果表明,神经营养的活动mediated by IL-1 and reactive astrocytes might be a common path through which tissue trauma and some tissue transplants exert their beneficial effects in parkinsonian animals. Furthermore, most of the sprouted dopaminergic fibers induced by IL-1 in the caudate nucleus come from dopaminergic neurons in the ventral tegmental area.

✓ Autografts of adrenal medulla were implanted into preformed cavities in the caudate nuclei of four rhesus monkeys with hemiparkinsonism induced by l-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Five other hemiparkinsonian monkeys underwent caudate cavitation, but received no tissue implant. All of the animals had marked bradykinesia of the affected arm and stable apomorphine-induced turning before cavitation or implantation.

Moderate behavioral recovery was seen in all five monkeys with cavitation and two of the three monkeys with long-term adrenal autografts (the fourth adrenal recipient was sacrificed 10 days after grafting). The improvement occurred months after the procedure and was not as early or as complete as that seen after fetal dopaminergic grafts. Surviving adrenal tissue was found only in the animal that showed no behavioral recovery. The other two adrenal autograft recipients (with no surviving adrenal medulla) and all of the animals with cavitation had ingrowth of dopaminergic fibers from the area olfactoria and nucleus accumbens into the caudate, oriented toward the cavity.

这些发现表明improvem机制ent after adrenal medullary implants for parkinsonism is not dopamine secretion by chromaffin cells, but may be related to the sprouted host fibers. The results also indicate that the limited recovery after adrenal implants in parkinsonian patients may be a result of the cavitation, and not necessarily the result of tissue implantation.

✓ Implantation of fetal dopamine-containing tissue into preformed cavities in the caudate nucleus of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonian monkeys leads to behavioral recovery. Recovery may be related to two sources of dopamine: the grafted cells and/or the sprouted fibers from host dopaminergic neurons. The authors undertook this study to determine whether behavioral recovery requires release of dopamine by the implanted tissue, and to establish if nondopaminergic fetal central nervous system implants can induce sprouting of dopamine fibers in the primate brain and cause behavioral recovery.

Rhesus monkeys with MPTP-induced hemiparkinsonism or full parkinsonism and a stable neurological deficit were used for this study. Cavities were created in the caudate nuclei anterior to the foramen of Monro via an open microsurgical approach. Fetal cerebellum or spinal cord was implanted into the preformed cavities of three monkeys. Control parkinsonian monkeys showed no recovery. However, implant-induced improvement was stable for up to 6 months after implantation. Sprouted dopaminergic fibers oriented from the ventral striatum and nucleus accumbens were found in the area of the tissue implant in the animals that received fetal grafts but were not present in the control monkeys.

It is concluded that brain implants do not need to contain dopamine to induce functional recovery in MPTP-induced parkinsonian primates. Implant-induced and trophic factor-mediated dopaminergic sprouting by the host brain plays a role in the behavioral recovery and may well be responsible for the clinical improvement seen in parkinsonian patients after brain implants.

Object.The authors studied the effect of gender and hormonal status on survival in nude rats implanted with human glioblastoma multiforme (GBM) cell lines.

Methods.Nude rats received intracerebral implants of either wild-type U87MG cells or U87MG cells transfected with the gene for endothelin-1 (U87/ET-1). In the initial study, survival was compared in males and females for each of the two cell lines. The six second-phase study groups were composed of: 1) males; 2) females; 3) ovariectomized females; 4) sham ovariectomized females; 5) ovariectomized rats given 10 µg/day estradiol benzoate for 21 days; and 6) ovariectomized rats given 20 mg/kg/day progesterone for 21 days. All rats in the second phase were implanted with U87/ET-1 cells. Animals were killed when they exhibited initial signs of neurological deterioration. Female nude rats survived longer than male rats implanted with either U87 or U87/ET-1 cells. In the second phase, ovariectomized, male, and progesterone-treated rats died at approximately 19 days, whereas the female, sham-treated, and estrogen-treated animals died 23 to 25 days after tumor cell implantation.

Conclusions.The authors demonstrate that female nude rats implanted with human GBM cells have a survival advantage over male rats and that estrogen provides the advantage.

✓ Although several experimental therapies such as dopaminergic cell implantation in parkinsonian models and intratumoral placement of lymphokine-activated killer cells require intracerebral deposition of dispersed cell suspensions, a successful technique of needle implantation of cells into primate brain has not been demonstrated. The authors have sought to establish a stereotaxic technique to predictably deposit dispersed cells in primate brain. Human lymphocytes were cultured in recombinant interleukin-2, labeled with sodium 51 chromate (⁵¹Cr), and stereotaxically injected into the frontal white matter of six anesthetized rhesus monkeys. A 10-µl aliquot of cell suspension (2 × 10⁷cells/ml) was deposited 16 mm deep to the dura at 5µl/min via Hamilton No. 22s or 26s needles. Five control aliquots were counted for each injection. Reflux out of the needle track was absorbed on gauze, and the recovered cells were counted. The animals were sacrificed 1 hour after implantation and the brain was removed and sectioned such that the cortex and white matter along the needle track were separate. The tissue sections were then counted. Recovery was expressed as the percentage of total injected radioactivity (cpm) that was present in each brain section. Two additional injected hemispheres were processed for autoradiography and histological study.

Cell recovery in the brain (mean ± standard deviation) was 87.2% ± 13.9% (3.3% ± 4.9% in cortex and 83.9% ± 15.9% in white matter). The autoradiograms and histological examination showed a dense accumulation of radioactivity (cells) at the target site and minimal radioactivity (cells) in the needle track. Accurate intracerebral deposition of dispersed cells in primates was achieved with the technique described. This knowledge permits reliable stereotaxic implantation of cells into the brains of nonhuman primates and humans for investigation and therapy.

✓ Ischemia is the pathophysiological mechanism in many types of spinal cord injury. In the present study, the infrarenal segment of the aorta was occluded for 25 minutes to produce spinal cord infarction in rabbits. Paraplegia occurred in 100% of control animals. Thiopental administered before aortic occlusion resulted in paraplegia in only 40% of animals so treated (p < 0.01). Histological study of the spinal cord demonstrated infarction of the gray matter in all paraplegic animals, whereas the microscopic appearance was normal in animals without neurological deficit. The protective influence of thiopental therapy in spinal cord ischemia was demonstrated.

✓ Although recent animal and human experiments suggest that tissue implantation can ameliorate parkinsonism, there is controversy about what mechanism underlies recovery. Secretion of dopamine from the graft seems unlikely to be the sole restorative factor. Regenerative sprouting by the host brain may also underlie behavioral recovery. Fetal amnion and term amnion, which were shown to produce and secrete a factor that supports the outgrowth of neurite processesin vitro, were implanted in hemiparkinsonian monkeys. Fetal amnion implants induced sprouting of dopaminergic fibers from the host brain and behavioral improvement, despite failure of the grafts to survive. Animals implanted with term amnion also had some sprouted dopaminergic fibers and behavioral improvement, but these were limited and were similar to the recovery, in prior experiments using the same primate model of parkinsonism, of animals that received surgical cavitation only.

Recovery after central nervous system grafting with fetal amnion, a fetal accessory tissue, does not require secretion of a deficient neurotransmitter(s) from the graft and occurs despite the failure of graft survival. Recovery after cerebral implantation of fetal tissues appears to depend more on the regenerative and recuperative processes of the host brain than on graft replacement of deficient neurotransmitters or development of functional synaptic connections between the graft and the host brain.