The life of Rudolf Nissen: advancing surgery through science and principle.

Rudolf Nissen (1896-1981) was a surgeon whose career began in Germany during the first third of the 20th century, a period of rapid progress in biomedical technology, during which neurosurgery, anesthesiology, and other specialties emerged. A protégé and later close colleague of thoracic surgery pioneer Ferdinand Sauerbruch (1875-1951), Nissen resigned from the Berlin Charité Clinic and left Germany in 1933, in response to the rise of Nazi fascism. Throughout his subsequent career in Istanbul, Turkey, the American cities of Boston and New York, and finally Basel, Switzerland, Nissen developed innovative surgical techniques, advocated for patient-centered medical education, and promoted surgical subspecialization. A lifelong proponent of clear scientific writing, Nissen expressed, in extensively published work, his philosophy that progress in surgery depends critically on rigorously applying the scientific method, upholding professional integrity, and respecting human dignity.

Sporadic medulloblastomas contain PTCH mutations.

Nevoid basal cell carcinoma syndrome (NBCCS), or Gorlin's syndrome, is an autosomal dominant disorder that predisposes to developmental defects and various forms of cancer. PTCH was recently proposed as a candidate gene for NBCCS due to its frequent mutation in basal cell carcinomas, the cancer most often associated with this syndrome. Another NBCCS-associated cancer is medulloblastoma, a common central nervous system tumor in children. Most medulloblastomas, however, occur without indication of an inherited predisposition. We have examined 24 sporadic medulloblastomas for loss of heterozygosity (LOH) at loci flanking as well as within PTCH. In cases with LOH, single-strand conformational polymorphism and sequencing analysis were performed to determine the status of the remaining PTCH allele. Microsatellite analysis indicated LOH of PTCH in 5 of 24 tumors, and in three of these cases a mutation of the remaining allele was identified. Two of the mutations were duplication insertions, and the third consisted of a single base deletion. It is interesting that all three mutations occur in exon 17 of the PTCH gene. These data suggest that inactivation of PTCH function is involved in the development of at least a subset of sporadic medulloblastomas.

Astrocytoma and pineoblastoma arising sequentially in the fourth ventricle of the same patient. Case report and molecular analysis.

The sequential appearance of two different brain tumors in the same patient without intervening radiation or chemotherapy is a rare event, most often seen in hereditary cancer syndromes. We present one such case of sequential tumors, along with their molecular analysis. A 17-year-old male presented with a pilocytic astrocytoma arising in the fourth ventricle at the pontomedullary junction. Six and one half years later, a pineoblastoma was discovered in the fourth ventricle, rostral to the first tumor site. Both tumors were treated by gross-total surgical resection. Following resection of the pineoblastoma, the patient underwent craniospinal irradiation and systemic chemotherapy. Single-strand conformation polymorphism analysis showed that the patient had neither a germ-line mutation nor a somatic tumor mutation in the p53 tumor suppressor gene. Coupled with the lack of a family history of cancer, these data suggest that these were not manifestations of Li-Fraumeni syndrome, but rather two sporadic tumors which arose via a p53-independent mechanism.

Rek, a gene expressed in retina and brain, encodes a receptor tyrosine kinase of the Axl/Tyro3 family.

Rek (retina-expressed kinase) has been identified as a putative novel receptor-type tyrosine kinase of the Axl/Tyro3 family with a potential role in neural cell development. rek clones were isolated from a chick embryonic brain cDNA library with a DNA probe obtained by reverse transcriptase-polymerase chain reaction of mRNA from Müller glia-like cells cultured from chick embryonic retina. Sequence analysis indicated that Rek is a protein of 873 amino acids with an extracellular region composed of two immunoglobulin-like domains followed by two fibronectin type III domains with eight predicted N-glycosylation sites. Two consensus src homology 2 domain binding sites are present in the cytoplasmic domain, suggesting that Rek activates several signal transduction pathways. Northern analysis of rek mRNA revealed a 5.5-kilobase transcript in chick brain, retina, and kidney and in primary cultures of retinal Müller glia-like cells. Rek protein was identified by immunoprecipitation and immunoblotting as a 140-kDa protein expressed in the chick retina at embryonic days 6-13, which corresponded to the major period of neuronal and glial differentiation. Transfection of rek cDNA into COS cells resulted in transient expression of a putative precursor of 106 kDa that autophosphorylated in immune complex protein kinase assays. Overexpression of rek cDNA in mouse NIH3T3 fibroblasts resulted in activation of the 140-kDa rek kinase and induction of morphologically transformed foci. These properties indicated that Rek has oncogenic potential when overexpressed, but its normal function is likely to be related to cell-cell recognition events governing the differentiation or proliferation of neural cells.

Loss of heterozygosity on chromosome 10 in human glioblastoma multiforme.

Recessive mutations, revealed by loss of the wild-type allele, have been associated with the development of a variety of cancers in children and adults. Polymorphic chromosome 10 markers were used to screen paired tumor and lymphocyte DNA samples in 13 patients with glioblastoma multiforme. Ten patients showed loss of constitutional heterozygosity in the tumor samples. This finding suggests that a recessive gene involved in the development of glioblastoma multiforme is present on chromosome 10.

c-src and other proto-oncogenes implicated in neuronal differentiation.

The proto-oncogene c-src has been implicated in the development and mature function of the nervous system. pp60c-src, the protein product of the c-src gene, is a tyrosine protein kinase that is highly enriched in fetal neural tissue. pp60c-src appears in two phases of neuronal development. Neuroectodermal cells of gastrulating embryos first express pp60c-src around the time of commitment to neuronal or glial pathways. Later, committed neuroepithelial cells express pp60c-src near the onset of terminal neuronal differentiation. Immunocytochemical analyses of pp60c-src in developing chick retina, telencephalon, and cerebellum show immunoreactivity concentrated in regions rich in growth cones and neurites. Moreover, pp60c-src is concentrated approximately 10-fold in a biochemical fraction from fetal rat brain that is enriched in nerve growth cone membranes. These results point toward a function for pp60c-src in neurite outgrowth. A functional role for other proto-oncogenes in the development of the nervous system was indicated from a study of the expression of a battery of proto-oncogenes during the retinoic acid-induced differentiation of the mouse embryonal carcinoma cell line P19 to a neuronal phenotype. Nuclear runoff transcription of the proto-oncogenes c-src, c-fms, c-sis, N-ras, c-myc, and c-fos was observed in proliferating and retinoic acid-treated cells.

An early developmental phase of pp60c-src expression in the neural ectoderm.

The expression of the normal cellular src protein (pp60c-src) was investigated in the early chick embryo during gastrulation and neurulation by immunoperoxidase staining using antisera, raised against bacterially expressed pp60v-src, that recognizes pp60c-src specifically in normal cells. During gastrulation pp60c-src immunoreactivity appeared primarily in the neural ectoderm and was much less prominent in the mesoderm, endoderm, and nonneural ectoderm. During neurulation pp60c-src immunoreactivity began to disappear from the wall of the closing neural tube so that by the completion of neural tube closure no specific pp60c-src immunoreactivity appeared in any of the neuroepithelial cells composing the neural tube. These studies reveal a developmental phase of pp60c-src expression even earlier than reported previously, when neuroepithelial cells of later embryos undergo terminal neuronal differentiation. These findings raise the possibility that pp60c-src may mediate two different differentiation signals in the neuronal lineage.

pp60c-src in the developing cerebellum.

pp60c-src was localized in the cerebellum of developing chicken embryos by immunoperoxidase staining with antisera raised against bacterially expressed pp60v-src. Immunoreactivity (IR) appeared in the cerebellum of the chicken embryos at the time of neuronal differentiation. pp60c-src IR was detected in regions of the developing cerebellum where processes of developing neurons and glia are located. In the early embryo (stage 17), pp60c-src IR was localized in the marginal zone of the cerebellar plate. By stage 40, pp60c-src IR was localized in the process-rich molecular layer of the cerebellum and between the cells of the developing internal granular layer. Cell bodies of cerebellar neurons did not show pp60c-src IR at any stage of development. Mitotically active neuroepithelial cells of the metencephalon did not express pp60c-src before the onset of differentiation in the early embryo, nor did proliferating cells of the external granular layer express pp60c-src at later stages. Although it is not possible to ascertain whether pp60c-src is localized in developing neurons or glia at the light microscope level, the time of its appearance and pattern of distribution in the molecular layer is suggestive of a localization within the developing neuronal processes which compose the bulk of this layer. Biochemical analyses of pp60c-src in the developing cerebellum by the immune complex protein kinase activity and sensitivity of the kinase to inhibition by P1,P4-di(adenosine-5')tetraphosphate confirmed that the expression of pp60c-src coincided with the time of neuronal differentiation. We conclude from these results that in the central nervous systems, pp60c-src may be more important in an aspect of cell differentiation or a mature neuronal function than in the proliferation of neuronal or glial precursors.