DNA double-strand break repair and development.

Normal development of an organism requires the ability to respond to DNA damage. A particularly deleterious lesion is a DNA double-strand break (DSB). The cellular response to DNA DSBs occurs via an integrated sensing and signaling network that maintains genomic stability. The outcomes of defective DNA DSB repair are related to the developmental stage of an organism, and often show striking tissue specificity. Many human diseases are associated with deficiencies in DNA DSB repair and can be characterized by neuropathology, immune deficiency, growth retardation or predisposition to cancer. This review will focus on the requirements of the DNA DSB response that function to maintain homeostasis during mammalian development.

Randomized trial of parathyroidectomy in mild asymptomatic primary hyperparathyroidism: patient description and effects on the SF-36 health survey.

BACKGROUND: The treatment of patients with asymptomatic primary hyperparathyroidism remains controversial despite a National Institutes of Health consensus statement. This statement also recommended a randomized clinical trial because none exists to address this issue. METHODS: Informed consent was obtained from 53 asymptomatic patients with confirmed asymptomatic primary hyperparathyroidism who participated in this randomized trial of parathyroidectomy versus observation. Patients completed the SF-36 Health Survey, an instrument that measures wellness, every 6 months for 2 years. Average annual changes were compared. RESULTS: Fifty-three patients (42 female, 11 male) with asymptomatic, mild (serum calcium level, 10.1-11.5 mg/dL) asymptomatic primary hyperparathyroidism who agreed to participate were randomized into either a surgical group or an observation group. The mean calcium level was 10.31 mg/dL. The only demographic difference between groups was age, with the operative group being older (66.7 vs 62.6 years; P <.03). The scores on 2 of the 9 domains of the SF-36 were significantly different (P <.007 and <.012, respectively); both favored the operative group. CONCLUSIONS: Improved function is seen after parathyroidectomy when compared with patients who did not undergo operation. This study supports surgical management of mild primary hyperparathyroidism at the time of diagnosis because many patients have reversible nonclassic symptoms of the disease.

Reduced vitamin D receptor expression in parathyroid adenomas: implications for pathogenesis.

BACKGROUND AND OBJECTIVES: Parathyroid adenomas discovered fortuitously grow very slowly and their cell birth rate greatly declines, features explicable by an initial increase in secretory set-point. In the nodules of severe uraemic parathyroid hyperplasia, there is an increased set-point and decreased expression of both the calcium sensing receptor (CaSR) and the vitamin D receptor (VDR). Accordingly, we examined VDR and CaSR expression in parathyroid adenomas. PATIENTS AND DESIGN: We studied 24 patients with primary hyperparathyroidism with a wide range of vitamin D nutritional status (plasma 25-hydroxyvitamin D range 10-107 nmol/l). Eighteen patients discovered by biochemical screening were enrolled in a natural history or treatment option study, and six additional US patients matched a group studied concurrently in India with low plasma 25-hydroxyvitamin D level (< 37 nmol/l). MEASUREMENTS: Receptor expression was determined by immunocytochemistry in each tumour and in 11 cases also in adjacent nonadenomatous tissue. VDR expression was reported as the proportion of positive cells (strongly rather than weakly stained) determined by systematic random sampling and CaSR expression as grey scale values of staining intensity in arbitrary units determined by image analysis. RESULTS: The mean (SD) proportion of cells positive for VDR was 2.93 (2.17)% in the parathyroid adenomas and 95.7 (5.10)% in the nonadenomatous tissue. In about two-thirds of the cases VDR positive cells could have been remnants of a normal gland, but in the remaining one-third they were too numerous to be accounted for by this explanation. The mean (SD) intensity of CaSR expression was 151 (4.71) units in parathyroid adenomas and 218 (5.0) units in nonadenomatous tissue (P<0.001). The frequency of VDR loss and the changes in CaSR immunohistochemistry were unrelated to race, sex, or disease severity, except that the reduction in CaSR was significantly greater in patients with normal vitamin D nutrition (32.1% vs. 29.0%). CONCLUSIONS: (1) There is reduction of vitamin D receptor expression in almost all cells in parathyroid adenomas. This defect was probably present in the founder cell of the tumour clone in the majority of cases. Since mutations in the vitamin D receptor gene have been sought but not found, possible explanations include inhibition of vitamin D receptor gene transcription, decreased amount of the corresponding mRNA, or failure of normal translation. (2) Reduction in calcium sensing receptor could be either the primary defect or (more commonly) secondary to loss of vitamin D receptor and is of sufficient magnitude to account for the increase in secretory set-point and consequent asymptotic growth and stable clinical course.

Effect of vitamin D nutrition on parathyroid adenoma weight: pathogenetic and clinical implications.

In primary hyperparathyroidism, adenoma size is a major determinant of disease severity and manner of presentation, but the reason for the large variation in size (>100-fold) is unknown. One factor could be the level of vitamin D nutrition, because in India, where vitamin D deficiency is endemic, adenomas are larger and the disease more severe than in the U.S. Accordingly, we determined the relationship between vitamin D nutrition, as measured by serum levels of 25-hydroxyvitamin D (25OHD), and parathyroid gland weight, expressed on a logarithmic scale, in 148 U.S. patients with primary hyperparathyroidism. A significant inverse relationship was found between log gland weight as dependent variable and serum 25OHD as independent variable (r = -0.365; P < 0.0001). The only other influence on gland weight was a weak inverse correlation with age. Log gland weight as an independent variable was significantly related to adjusted calcium, PTH, and alkaline phosphatase (AP) as dependent variables. In 51 patients with serum 25OHD levels less than 15 ng/mL, gland weight, PTH, AP, and adjusted calcium were each significantly higher than in 97 patients with 25OHD levels of 15 ng/mL or more, but 1,25-dihydroxyvitamin D levels were similarly increased in both groups. In the former group the response of adjusted calcium to PTH was blunted, and the response of AP was enhanced, based on significant differences in regression slopes (P = 0.0004 and 0.0022, respectively). Suboptimal vitamin D nutrition stimulates parathyroid adenoma growth by a mechanism unrelated to hypocalcemia or 1,25-dihydroxyvitamin D deficiency and reduces the calcemic response to PTH, so that a higher PTH level and more parathyroid cells are needed to raise the patient's serum calcium to the level corresponding to the increased set-point that is characteristic of the disease. Improved vitamin D nutrition in the population is partly, perhaps largely, responsible for the historical changes in disease severity and manner of presentation that have occurred over the last 50 yr.

The gene expression index c-myc x E2F-1/p21 is highly predictive of malignant phenotype in human bronchial epithelial cells.

Recent methodological developments allow expression measurement of many genes simultaneously, thereby revealing patterns of gene expression that can be related to phenotype. We hypothesized that through the use of such methods we could identify patterns of gene expression associated with the malignant phenotype in human bronchial epithelial cells (BEC). To test this hypothesis, a recently developed quantitative reverse transcriptase polymerase chain reaction method was used to assess simultaneously expression of 15 genes mechanistically associated with cell-cycle control (c-myc, E2F-1, p21, rb, PCNA, cyclin D2, cyclin D3, cyclin E, cdc2, CDK2, CDK4, mad, max p21, max p22, and p53) in normal cell cultures from five individuals and in nine different malignant BEC lines. Relative to the mean expression levels in cultured normal cell populations, expression of c-myc, E2F-1, PCNA, cyclin E, and CDK4 messenger RNA (mRNA) were significantly increased and expression of p21 and p53 mRNA were significantly decreased in one or two, but not all three subtypes (squamous, adenocarcinoma and small cell) of carcinoma cell lines evaluated. No single cell-cycle control gene discriminated all three subtypes from normal cell populations. In contrast, the gene expression index c-myc x E2F-1/p21 separated all carcinoma cell lines from all normal cell populations initially evaluated. This malignancy index was validated in an additional three cultured normal BEC and three carcinoma cell lines, as well as three pairs of matched primary normal bronchial epithelial and primary bronchogenic carcinoma samples, and three pairs of matched primary normal lung parenchyma and primary bronchogenic carcinoma tissue. Again, the c-myc x E2F-1/ p21 index successfully discriminated all cultured and primary normal from malignant samples and thereby had a predictive value of 1 (no false positives and no false negatives). We hypothesize that because of functional mutations in cell-cycle regulatory genes (e.g., p53 and/or rb), cells lose the ability to maintain a pattern of gene expression mechanistically associated with normal, division-limited homeostatic equilibrium. Because the c-myc x E2F-1/p21 gene expression index has high specificity for malignant tissue, it will allow confirmation that there is a significant amount of tumor tissue present in small (e.g., fine-needle) biopsy specimens prior to evaluating them for expression of other genes, such as those involved in chemoresistance or radioresistance. In addition, the goal of most gene therapy efforts is to alter levels of gene expression quantitatively. This index and others derived in a similar manner may better define potential gene therapy targets as well as response of targeted genes to therapy.

Temporal production of streptococcal erythrogenic toxin B (streptococcal cysteine proteinase) in response to nutrient depletion.

The effects of various growth conditions on the production of streptococcal erythrogenic toxin B (streptococcal pyrogenic exotoxin B [SPE B]) by Streptococcus pyogenes were analyzed. SPE B was detected in broth culture supernatant fluid only during the stationary phase of growth when glucose and other potential carbon sources were depleted from the medium. Additionally, SPE B production was inhibited when the concentration of glucose in the medium was maintained. These results suggest that SPE B is secreted under conditions of starvation and may be involved in nutrient acquisition.

Adrenocortical oncocytoma: two case reports and review of literature.

Oncocytomas of the adrenal gland are rare; only 9 cases are reported in the world literature. We report 2 new cases in which benign adrenal masses were detected during evaluation for microhematuria or flank pain. Subsequent to extirpation of the mass, pathologic examination established the diagnosis of adrenocortical oncocytoma.

Local tissue of the lumbar spine response to titanium plate--screw system. Case reports.

STUDY DESIGN: This study reported the histopathologic findings of peri-implant tissue harvested from two patients with titanium plate-screw fixation in the lumbar spine. OBJECTIVES: To describe and discuss the histopathologic findings with regard to local tissue response to the titanium plate-screw system in the lumbar spine. SUMMARY OF BACKGROUND DATA: There are no reports about local tissue of the lumbar spine response to titanium plate-screw system in the literature. METHODS: Two patients who underwent titanium plate-screw fixation in the lumbar spine were evaluated for this study. Histopathologic evaluation of the specimens from these cases included soft tissue, bone, and cartilage from the areas around the screws and plates. RESULTS: The primary histopathologic changes of the two cases included fibrous scarring, accumulation of metallic debris, both free in the fibrous tissue and within macrophages, and mild histiocytic and epithelioid changes. CONCLUSIONS: The histopathologic findings of the two cases presented resulted in local tissue response of the lumbar spine to titanium similar to tissue response in other previously reported cases.

Intraoperative imprint cytology: its significance as a diagnostic adjunct.

We retrospectively evaluated 664 specimens submitted for intraoperative frozen-section analysis for which cytologic imprints or smears were also prepared; 238 (36%) were malignant neoplasms. These preparations were retrospectively evaluated independently by three reviewers of varied experience in the detection of malignancy. The number of false-positive and false-negative results were recorded, and various assessment parameters (sensitivity, specificity, efficiency, and predictive value) were calculated. The imprint was of chief value as an adjunct to the frozen section, particularly in avoiding false-positive and, to a lesser extent, false-negative interpretations. Experience with the use of intraoperative cytology demonstrated the technique to be of value in providing abbreviated preparation time (3-5 min); supportive diagnostic information when frozen section was equivocal; diagnostic information when frozen-section evaluation could not be done (e.g., excessively small sample); contributory information for final diagnosis on difficult cases; and excellent teaching material for cytopathology.

A nonviral, virus strain-specific antigen expressed on rat cells transformed by avian sarcoma virus.

Five of six rat sarcomas, induced by the Schmidt-Ruppin (SR) strain of avian tumor virus, expressed a Mr 60,000 tumor cell surface antigen (TSA), immunoprecipitable from non-ionic detergent extracts. Expression of the antigen was exclusive to rat cells transformed by the SR virus strain. Moreover, expression of TSA appeared restricted by cell type. The five TSA-positive SR-transformed rat cell lines tested were apparently of fibroblastic origin, but cultured rat cerebral endothelial cells (RCE-T1), transformed by SR virus, showed no expression of TSA. However, the antigen emerged on cultured tumors obtained after histoincompatible transplantation of these cells into newborn rats of another strain (tumor digest cells). Investigation of TSA for immunological relationship to viral structural antigens and the src gene product indicated that the TSA is distinct from any of these and more probably derives from a virus-directed alteration in a host molecule.

Sleep apnea in cluster headache.

The impetus to study sleep changes in a cluster population arose from a recent hypothesis that predicted the finding of sleep apnea in this disorder. It holds that cluster attacks may occur in response to oxygen desaturation. Proposed mechanisms involve impairment of carotid body activity secondary to hypothalamic-vasomotor regulatory dysfunction. Five chronic and five episodic cluster patients underwent nocturnal polysomnography, utilizing standard equipment for monitoring sleep status, cardiac activity, nasal and buccal air flow change, chest and abdominal breathing, muscle activity and oxygen saturation. All episodic patients and one of five chronic patients were found to have sleep apnea (60%). Mean apneas per hour during NREM sleep were similar to that of REM sleep; 26.7 and 28.2, respectively. Six patients with sleep apnea experienced 14 cluster headache attacks during the study period. Eight attacks (57%) followed episodes of oxygen desaturation ranging from 65% to 85%. In the sleep apnea group, 8 out of 14 attacks (57%) were associated with REM; three without, and five following oxygen desaturation. Of the non-apnea group, all of whom had chronic cluster headache, none of 5 attacks were associated with oxygen desaturation, and only 2/5 attacks occurred in relation to REM. Thus, our study showed that sleep apnea was a common finding in a randomly selected group of episodic cluster patients; and most nocturnal attacks were preceded by oxyhemoglobin desaturation and REM-related. These findings were uncommon in the chronic cluster group.

Failure to confirm evidence for a nonvirion tumor-specific surface antigen in avian retrovirus-transformed cells.

Triton X-100 or Nonidet P40-deoxycholate extracts of [3H]fucose-labeled Rous sarcoma virus-transformed chick embryo fibroblasts were examined by indirect immunoprecipitation for the presence of a tumor-specific neoantigen of 100,000 daltons. Extracts were incubated with immune IgG from Rous tumor-sensitized chickens, and the resultant antigen-antibody complexes were precipitated with rabbit antichicken IgG and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Radioactivity appeared between the migration positions of proteins having molecular weights of 65,000 and 95,000 daltons and at about 30,000 daltons. These antigens were group-specific, and thei precipitation could be inhibited by competition with extracts from cultured fibroblasts that had been infected with a nontransforming avian leukosis virus. They were not precipitated with IgG from unimmunized chickens or chickens immunized with the culture supernatants of uninfected chick embryo fibroblasts. In contrast to results reported recently, the present results could not confirm by immunoprecipitation, the existence of a tumor neoantigen different from that associated with viral components. However, the tumor-specific antigen possibly existed on the cell surface but was not preserved in these detergent extracts.

Immunologic identification of fetal calf serum-derived proteins on the surfaces of cultured transformed and untransformed rat cells.

The antigens of rat embryo fibroblasts (REF) and of rat Rous sarcoma cells (derived by in vivo passage of oncogenically transformed REF) were studied using the technique of non-ionic detergent solubilization of radiolabelled cells. Solubilized antigens were complexed with rat immune IgG, and precipitation of the complexes was accomplished with rabbit anti-rat IgG. The precipitated radiolabelled antigens were then dissolved in sodium dodecyl sulfate and separated by polyacrylamide gel electrophoresis. This investigation disclosed the existence of cell surface antigenic proteins which are derived from the fetal calf serum (FCS) used in the cell-culture medium. These FCS-dependent antigens include at least three molecular species of approximate molecular weights 95,000, 80,000 and 98,000 daltons. They are probably derived from simple adsorption of FCS proteins to the cell surface, although more complex interactions are possible. One of these proteins (95,000 daltons) is of particular interest. It tenaciously adheres to the cell surface so that a trace amount remains even after subculture in the absence of FCS. Rat Rous sarcomas which are morphologically highly transformed appear to bind very little or none of this protein to their surfaces, whereas untransformed rat embryo fibroblasts bind large quantities. A rat Rous sarcoma line which is intermediate in morphological transformation binds an intermediate amount of this antigen. These findings invite speculation that the interaction of certain serum components with the cell surface may be related to plasma membrane properties which distinguish untransformed and transformed cells.