Proliferation and migration kinetics of stem cells in the rat fundic gland

The proliferation and migration of stem cells in the developing and adult rat fundic gland have been studied using BrdU immunohistochemistry and BrdU-GSA II (Griffonia-simplicifolia agglutinin-II) double staining. In the developing rat fundic gland, stem cells were first scattered throughout all levels of the epithelia and then concentrated in the depth of the pits. With the elongation and maturation of the fundic glands, stem cells left the gland base and moved upward. By 4 weeks after birth, the development of the fundic gland was completed and stem cells were confined to a narrow proliferative zone in the isthmus, reaching the adult distribution pattern. In the adult rat fundic gland, stem cells in the isthmus differentiated and migrated upward and downward, replacing the surface mucous cells and glandular cells respectively. For upward migration, it took about one week for stem cells to migrate from the isthmus to the surface. For downward migration, it took about two weeks for stem cells to migrate from the isthmus to the neck, and it took 30-36 weeks to reach the gland unit's blind end. Finally stem cells were lost at the deepest level of the glands. The results obtained by simple topographical distribution in the present experiment agreed well with those obtained by quantitative analysis, suggesting the usefulness of BrdU immunohistochemistry for cell kinetic studies.     

Fludarabine. An update of its pharmacology and use in the treatment of haematological malignancies

Fludarabine is an antineoplastic agent which has been studied in patients with a variety of lymphoproliferative malignancies. Clinical evidence from comparative studies in chronic lymphocytic leukaemia (CLL) suggests that fludarabine is at least as effective as CAP (cyclophosphamide, doxorubicin and prednisone) or CHOP (cyclophosphamide, vincristine, doxorubicin and prednisone) in previously treated or chemotherapy-naive patients and significantly more effective than chlorambucil in terms of response rate and duration and survival in chemotherapy-naive patients. Promising results have also been reported with fludarabine-based combination therapy in the treatment of patients with CLL. In addition, sequential therapy with fludarabine and cytarabine has demonstrated good efficacy in the treatment of acute leukaemias, as has fludarabine monotherapy and combination therapy in low grade non-Hodgkin's lymphoma. A favourable cytoreductive response has been reported in patients with lymphoplasmacytoid lymphoma and in a smaller number of patients with cutaneous T cell lymphomas, CLL of T cell origin or prolymphocytic leukaemia. Recent data also support the use of fludarabine, either as a component of a nonmyeloablative conditioning regimen or in the attainment of minimal residual disease, in patients undergoing peripheral blood stem cell or bone marrow transplantation. The tolerability profile of fludarabine is similar to that of CAP, with the most common adverse events being granulocytopenia, thrombocytopenia, anaemia and infection. Alopecia and nausea/vomiting appear to be less frequent with fludarabine therapy than with CAP although the development of immune cytopenias is more frequent with fludarabine. Severe neurotoxicity has been reported with fludarabine but this is mostly confined to the use of high doses. Clinical experience therefore indicates that fludarabine is an effective and generally well-tolerated antineoplastic agent for the second-line treatment of advanced CLL. Recent data from comparative studies also support the earlier use of fludarabine in the treatment of chemotherapy-naive patients with CLL. Furthermore, results of available studies are increasingly highlighting an important future role for fludarabine in the treatment of acute leukaemias and low grade NHL and possibly other lymphoproliferative disorders, particularly when used as a component of combination chemotherapy.     

Impact of stenting on coronary angioplasty procedures

The efficacy and toxicity of chronic administration of oral etoposide was evaluated in 61 patients with inoperable non-small-cell lung cancer (NSCLC). Ten patients received previous chemotherapy, 15 received radiotherapy, and one received both treatments. Twenty-four patients had concurrent cardiac and/or pulmonary impairment, which precluded more intensive treatment. Etoposide was given orally, 100 mg daily for 7 consecutive days and consequently 100 mg every other day for 14 more days in a 28-day schedule. Partial response was observed in 17 patients (28%; 95% confidence interval, 17-39%) and stable disease in 21 (34%). The median duration of response was 6 months (range, 2-34 months). The median survival for responders was 22 months and that of nonresponders was 7 months (p < 0.001). The median survival for all patients was 9 months (range, 1-35 months; 95% confidence interval, 5.69-12.31%). Toxicity was acceptable. Other than alopecia, which was observed in all patients, myelotoxicity was the most common toxicity--particularly leukopenia, which was severe in nine patients. Other less common toxicities included nausea and vomiting, stomatitis, anorexia, and neurotoxicity and were mild. No treatment-related deaths were observed. In conclusion, the regimen was effective and well tolerated with significant survival benefit for the responders. It represents an interesting therapeutic approach, especially in the elderly.     

The molecular basis of isolated 17,20 lyase deficiency

Human P450c17 catalyzes the 17alpha-hydroxylation of pregnenolone to 17OH pregnenolone and of progesterone to 17alpha-OH progesterone; the same P450c17 enzyme also catalyzes 17,20 lyase activity on the same active site, converting 17OH-pregnenolone to DHEA. Rodent and porcine P450c17 also catalyze 17,20 lyase activity with delta4 substrates, converting 17OH-progesterone to delta4 androstenedione, but human P450c17 catalyzes this reaction very inefficiently, so that virtually all human C19 sex steroids are made via 17OH pregnenolone and DHEA. P450c17 is encoded by a single gene and a single species of mRNA. Many mutations of this gene have been described, but until recently all of these either entirely eliminated both 17alpha-hydroxylase and 17,20 lyase activity, or affected each activity equivalently. We have identified and characterized the first patients with P450c17 mutations that selectively ablate 17,20 lyase activity while retaining 17alpha-hydroxylase activity. Through a combination of enyzmologic experiments in transfected mammalian cells and in genetically manipulated yeast, plus a computer model of human P450c17, we have proven that the responsible mutations, R347H and R358Q lie in the redox-partner binding site of P450c17. This site, through which P450c17 interacts with P450 oxidoreductase to receive the electrons needed for catalysis, can be allosterically influenced by cytochrome b5. These two mutations have contributed substantially to our understanding of the mechanisms by which 17alpha-hydroxylase and 17,20 lyase activities are regulated independently, and thus have contributed to the study of regulated 17,20 lyase activity in adrenarche, aging, and the polycystic ovary syndrome.     

Novel beta-thalassemia mutation in patients of Jewish descent: [beta 30(B12)Arg-->Gly or IVS-I(-2)(A-->G)]

Classical congenital adrenal hyperplasia (CAH) results from an inherited enzymatic defect in cortisol synthesis and more than 90 per cent of cases are due to 21-hydroxylase deficiency. The androgen excess associated with this condition typically results in ambiguous external genitalia in affected females. It has been shown that prenatal treatment with dexamethasone is successful in preventing or reducing genital ambiguity in affected females. Rather than treating with dexamethasone, some couples choose to terminate the pregnancy when an affected fetus is prenatally diagnosed. We report a female with classical CAH who was born with normal external genitalia, although maternal treatment with dexamethasone did not begin until 16 weeks' gestation.     

Functional evaluation of invariant arginines situated in the mobile lid domain of phosphoribulokinase

Rhodobacter sphaeroides phosphoribulokinase contains four invariant arginines (R49, R168, R173, and R187). The high-resolution structure of this enzyme [Harrison, D. H. T., Runquist, J. A., Holub, A., and Miziorko, H. M. (1998) Biochemistry (submitted for publication)] reveals that it folds in a manner similar to that of adenylate kinase. Three invariant arginines (R168, R173, and R187) as well as arginine-186, which is conserved in prokaryotic phosphoribulokinases, have not been previously functionally evaluated. These arginine residues map within the mobile lid domain that is a distinctive feature of the adenylate kinase family of proteins. Precedent for the significant function of arginines in phosphotransferase reactions prompted substitution of glutamine for each of these three invariant arginines. Solution state characterization of the isolated mutant proteins indicated that they retained a high degree of structural integrity, as indicated by their stoichiometric binding of an alternative nucleotide substrate (trinitrophenyl-ATP) as well as the allosteric effector (NADH). Kinetic characterization indicated > 10(4)-fold diminution in V/KRu5P for R168Q, attributable to a > 300-fold decrease in catalytic efficiency and an increase (approximately 50-fold) in Km Ru5P. For R173Q, a 15-fold diminution in Vmax and a 100-fold increase in Km Ru5P were observed. These observations implicate new components of the ribulose 5-phosphate binding site. Additionally, they confirm assignment of the mobile lid domain as part of the phosphoribulokinase active site, even though this region is well separated from other active site elements in the structure of the open form of the protein. Characterization of R186Q and R187Q mutants suggests that they influence the cooperativity of substrate binding.     

Double-evoked otoacoustic emissions. II. Intermittent noise rejection, calibration and ear-canal measurements

Measurements of double-click-evoked otoacoustics emissions (2CEOAEs) and double-chirp distortion products (2ChDPs) are reported for normal-hearing adults based upon theory presented in an earlier report [Keefe, J. Acoust, Soc. Am. 103, 3489-3498 (1998)]. The nonlinear acoustic response of a probe assembly used in ear-canal measurements in tested in a calibration cavity to compare the double-evoked (2E) technique with existing OAE techniques. The 2E technique reduces the peak distortion by approximately 30 dB relative to existing click-evoked techniques. The 2E subtraction of click responses is partially analogous to current techniques in that the linear response is eliminated, but differs in that high-frequency measurements are improved by eliminating time gating of the cochlear response, and low-frequency measurements are improved by reducing probe distortion, especially when two acoustic sources are used. Because time gating is eliminated, it is straightforward to measure the onset of a click-evoked OAE. The nonlinear coherence function is used to measure the nonlinear distortion signal-to-noise ratio (DNR) for the 2ChDPs and 2CEOAEs. The DNR is typically 20-30 dB. An intermittent noise rejection technique is implemented in real time that compares a currently acquired ear-canal response with a stored response. Dissimilar responses indicate the presence of intermittent noise, and the noise-contaminated responses are thereby discarded before ensemble averaging.     

Identification of a quantitative trait locus influencing plasma insulin levels after 70% pancreatectomy using the OLETF rat

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat has poor capacity for proliferation of pancreatic beta-cells after partial pancreatectomy, which may be the critical pathogenetic event in NIDDM development. The poor pancreatic beta-cell proliferation in this model is characterized by reduction in beta-cell mass and decrease in insulin content in the remnant pancreas. Our investigation was designed to identify quantitative trait loci (QTLs) responsible for beta-cell mass and plasma insulin levels after partial pancreatectomy by performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and the Fischer-344 (F344) rats. We have identified a suggestive QTL for the plasma insulin levels, near D20Mgh5 on rat chromosome 20, with a maximum lod score of 3.75 which accounts for 20% of the total variance, while no QTLs were detected for beta-cell mass. This chromosome 20 QTL, whose OLETF allele is associated with low plasma insulin levels through acting in an incompletely recessive manner, may affect insulin secretion itself rather than beta-cell proliferation.     

Correlation of pseudoexfoliative material and optic nerve damage in pseudoexfoliation syndrome

PURPOSE: To determine whether the severity of glaucomatous damage in eyes with pseudoexfoliative (PEX) glaucoma is related to the amount of PEX material in the trabecular meshwork. METHODS: Trabecular meshwork and optic nerves from 19 eyes (11 donors) with PEX syndrome were studied. Eyes were chosen to represent all stages of severity of disease. Sections from each quadrant around the circumference of each eye were studied with light and transmission electron microscopy. Morphometric measurements were made of Schlemm's canal (SC) and of the components of the cribriform region and were statistically correlated with axonal counts of the optic nerves. Correlations between clinical and histologic data were determined. RESULTS: Pseudoexfoliative material was frequently found in isolated aggregates beneath the inner-wall endothelium of SC. The cribriform region was otherwise normal in structure; disorganization of this region was found only in focal regions of a few eyes. The amount of PEX material was correlated with the maximal intraocular pressure (IOP) and the IOP on treatment and was inversely correlated with the number of axons in the optic nerve. The number of axons was inversely correlated with the maximal IOP and the IOP on treatment, but not with duration of disease. CONCLUSIONS: The severity of glaucoma in PEX is related to the amount of PEX material present in the cribriform region. Elevation of IOP occurs before disorganization of the cribriform region and may be related to the location of the PEX material near the inner wall of SC. Comparison of clinical and histologic findings revealed that the results of visual field examinations fit more closely with the axonal counts than did the clinical assessment of the cup-to-disc ratio.     

Organochlorine pesticides and polychlorinated biphenyls (PCBs) in sediments and biota from four US Arctic lakes

Organochlorine (OC) concentrations in surface sediment, snails (Lymnea sp.), and two freshwater fish species (grayling, Thymallus arcticus; and lake trout, Salvelinus namaycush) from four lakes in the US Arctic were determined. In surface sediment, chlorinated benzenes (including hexachlorobenzene, HCB), and p,p'-DDT were the primary analytes detected (max = 0.7 ng/g dry wt), while individual polychlorinated biphenyl (PCB) congeners were always below 0.1 ng/g. A wider range of compounds and higher concentrations were found in lake trout, the top predatory fish species in the same lakes. The concentration ranges for hexachlorocyclohexanes (HCHs), chlordane-related compounds (CHLORs), DDTs, and PCBs in lake trout and grayling were similar to those reported for other arctic freshwater fish (1-100 ng/g wet wt), but one to two orders of magnitude lower than Great Lakes salmonids. Nitrogen isotope analysis confirmed that differences in OC concentrations between grayling and lake trout are explained partly by differences in food web position.