Polarizabilities of Isolated Silicon Clusters

The static electric polarizabilities a of silicon clusters with up to 60 atoms have been measured employing a mass selective molecular beam deflection method. The polarizability per atom αN = α/N of the SiN-clusters has been investigated for Si11 and the size ranges N = 14-28, 22-34, 28-44, 34-50, 41 -58, and 42-68. The results show that the polarizability per atom decreases from N = 11 until a minimum at N≥28 is reached. The polarizability per atom increases for N > 28, passes through a maximum at N≈36 and finally converges between N≈50-70 against the value αN =1.9Å3. If the model of a homogeneous dielectric sphere is applied to the larger clusters one calculates that the value αN =1.9Å3 corresponds to a dielectric constant of ε = 3.2. This value is significantly smaller than the dielectric constant of bulk silicon εb = 11.8.

The present paper focuses on the maximum in the polarizability at N≈36. This effect is discussed with special emphasis to recent Car-Parinello calculations which have predicted cage-like silicon structures that enclose a core of several highly coordinated atoms. This structure suggests an improved dielectric sphere model where the core is represented by a smaller sphere with its own dielectric constant εc. It is shown within this model that the observed maximum in polarizability is due to a significant enhancement of the core dielectric constant to a value of εc ≈50. This enhancement is related by means of a simple model to the effect that silicon becomes metallic under high pressure

Proliferative inflammatory atrophy: a background lesion of prostate cancer?

Proliferative inflammatory atrophy (PIA) belongs to the atrophic lesions that frequently occur in the prostate. The location of PIA in the periphery of the gland near to prostate carcinoma or even showing direct transition to malignant or pre-malignant epithelia suggested a connection between PIA and prostate cancer. Further findings in PIA, such as imbalance between proliferation and apoptosis and detection of molecular-biological abnormalities specific for oxidative stress or malignancy, supported this hypothesis. Recently, epidemiological studies including large cohorts of patients have been undertaken in order to investigate the causal connection between PIA and prostate carcinoma. The current understanding of PIA allows us to consider it as a benign lesion with certain genetic instability which can degenerate into prostate intraepithelial neoplasia or carcinoma, provided that the balance between anti-carcinogens and carcinogens is perturbed. To evaluate the role of PIA as a precursor lesion of prostate cancer, further examinations of genetic or epigenetic aberrations are required.

Spectrometric measurement in laryngeal cancer

Only early diagnosis of laryngeal cancer can prevent major or mutilating treatment. Recently, autofluorescence endoscopy has been developed to enhance endoscopic information and succeeded in facilitating the detection and demarcation of precancerous lesions, carcinoma in situ and cancer of the larynx. The aim of the present study is to quantify autofluorescence imaging by spectroscopy in order to validate the above mentioned findings. In a prospective study, 42 patients with suspected one-sided precancerous or cancerous lesions of the vocal folds were investigated during microlaryngoscopy. Autofluorescence (AF) was induced by filtered blue light (375-440 nm) of a xenon short arc lamp and processed by a CCD camera system (D-light AF System, STORZ, Germany). Autofluorescence images were gathered in a contact mode. For spectrometric measurements an optical multi channel analyzer (AVS-USB 2000, Avantes, The Netherlands) was applied. The results were compared to pathohistological findings. Under blue light excitation normal mucosa presented a bright green fluorescence. Intensity increased from the ventricular folds to the subglottic area. Averaged spectra of the normal laryngeal mucosa demonstrated different fluorescence maxima at 475, 515, 550, 600 and 630 nm. Highest intensity was measured at 515 nm explaining the green appearance of the autofluorescence picture. In contrast, precancerous as well as cancerous lesions showed a significant decrease in autofluorescence intensity with a reddish-violet color. Highest loss of autofluorescence intensity was measured at 515 nm. At this wave length intensity dropped 70% on average in comparison to the regularly appearing contralateral vocal fold. In contrast to 515 nm, the loss of intensity at 630 nm amounted to 38%. Sensitivity amounted to 97% and specificity to 82%. Comparable to autofluorescence endoscopy a differentiation between precancerous and cancerous lesions could not be detected. The reason for the loss of autofluorescence may predominantly be caused by mucosal thickening but also by changes in metabolism and higher nuclei density.

Phosphoinositid-3-Kinase- (PI3-K) Expression

Phosphoinositide 3-kinase (PI3-K) is a heterodimeric enzyme involved in the regulation of mitogenesis, apoptosis, cell adhesion, and motility. PI3-K was suggested as a protooncogene in human cancer. To determine the expression of PI3-K during cancerogenesis and tumor invasion of HNSCC, we investigated normal and dysplastic epithelium of the oral cavity, squamous cell carcinoma and lymph node metastasis by immunohistochemistry. The strongest immunoreactivity for p85alpha and p110alpha was found in invasive tumors and their metastases. Carcinomas in situ showed a focal positivity. Dysplasias and normal epithelium reacted predominantly negatively. The PI3-K inhibitor LY294002 inhibited proliferation and invasion of the HNSCC cell line CAL-27 and induced apoptosis in vitro. Our data suggest PI3-K as a marker of malignancy and tumor invasion. We suggest including PI3-K in the multistep carcinogenesis model of HNSCC. In addition, PI3-K is a potential target for pharmacological intervention.

Pressure-jump small-angle x-ray scattering detected kinetics of staphylococcal nuclease folding

The kinetics of chain disruption and collapse of staphylococcal nuclease after positive or negative pressure jumps was monitored by real-time small-angle x-ray scattering under pressure. We used this method to probe the overall conformation of the protein by measuring its radius of gyration and pair-distance-distribution function p(r) which are sensitive to the spatial extent and shape of the particle. At all pressures and temperatures tested, the relaxation profiles were well described by a single exponential function. No fast collapse was observed, indicating that the rate limiting step for chain collapse is the same as that for secondary and tertiary structure formation. Whereas refolding at low pressures occurred in a few seconds, at high pressures the relaxation was quite slow, approximately 1 h, due to a large positive activation volume for the rate-limiting step for chain collapse. A large increase in the system volume upon folding implies significant dehydration of the transition state and a high degree of similarity in terms of the packing density between the native and transition states in this system. This study of the time-dependence of the tertiary structure in pressure-induced folding/unfolding reactions demonstrates that novel information about the nature of protein folding transitions and transition states can be obtained from a combination of small-angle x-ray scattering using high intensity synchrotron radiation with the high pressure perturbation technique.

Idiopathic myelofibrosis with extramedullary hematopoiesis in the kidneys

Extramedullary hematopoiesis is a common finding in idiopathic myelofibrosis and is usually found in liver and spleen. We report on a patient with biopsy-proven myeloid metaplasia and fibrosis of the renal parenchyma as a rare cause of chronic renal failure. The renal biopsy specimen showed numerous infiltrates of hematopoietic cells expressing growth factors like M-CSF, GM-CSF, IL-1beta and PDGF while TGF-beta was not elevated. These findings suggest that hematopoietic growth factors play a key role in the pathogenesis of this condition causing proliferating fibrosis and enlargement of the kidneys.

[Miliary tuberculosis and adult respiratory distress syndrome in an infant]

We report on a 7 months old infant, who was admitted to our hospital with the tentative diagnosis of interstitial pneumonia. The infant was treated with erythromycin because of a positive mycoplasma antigen test in the nasopharyngeal mucus and the radiological findings. A tension pneumothorax led to rapid respiratory deterioration and a severe ARDS developed. A sustained respiratory stabilization could not be achieved. The diagnosis miliary tuberculosis was detected on autopsy. A parenchymal focus was found subpleurally in the left lung with a massive hematogenous spread and a tuberculous meningitis. The source of infection could not be identified in the family or in persons known to have had contact to the infant. The tuberculin skin test (PPD) was negative. Clinical, radiological and pathological findings are demonstrated.

[Sacrococcygeal chordoma with malignant spindle cell components. Case report and review of the literature]

Malignant fibrous histiocytoma (MFH), arising in combination with a sacral chordoma in a 70-year-old men, is described. Intermediate spindle-shaped cells demonstrating keratin positivity, showed a gradual transition between the areas of conventional chordoma, and the spindle cell areas, lending credence to the theory of a multipotential neoplasm. We chose the descriptive term "chordoma with malignant spindle cell component" in the sense that high malignant sarcomatous components exists in conjunction with chordomas in the primary tumor and the local recurrence. A review of literature is undertaken chronicling the documented associations of chordoma and sarcoma, followed by a discussion of the various causes proposed to explain this phenomenon.

DNA cytophotometry and prognosis in typical and atypical bronchopulmonary carcinoids. A clinicomorphologic study of 100 neuroendocrine lung tumors

Surgical material obtained from 100 patients with typical carcinoids (TC) and atypical carcinoids (AC) of the lung (including 100 primary, four residual tumors, and four lymph node or distant metastases) was investigated by conventional histology and scanning DNA cytophotometry. Of the 60 TC (96%), 58 exhibited euploid DNA histograms compared with only 20 (50%) of the 40 AC. The morphologic findings were related to the patients' survival (median observation period, 9 years). Statistical analyses disclosed the histologic type of disease (TC versus AC) and the DNA content of tumors (euploid versus aneuploid) to affect prognosis significantly (p < 0.001). Deaths resulting from tumor were exclusively observed among patients with atypical (eight of 40) or DNA aneuploid carcinoids (eight of 22). Six patients were alive with persistent tumor manifestations 3 to 20 years after initial diagnosis, four with DNA diploid primary carcinoids. The presence of lymph node metastases alone was not associated with poor prognosis as long as the primary tumor or the related metastases showed a diploid DNA content. DNA cytophotometry thus might be regarded as an adjunctive prognostic criterion in individual carcinoid cases.