Calcitriol for congenital osteopetrosis.
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Calcitriol↗
Biomedical subjects
D M Brown
Publications and source records attributed to D M Brown.
Bilin attachment sites in the alpha and beta subunits of B-phycoerythrin. Amino acid sequence studies.
The amino acid sequence about the sites of attachment of all of the bilin prosthetic groups of the alpha and beta subunits of Porphyridium cruentum B-phycoerythrin has been determined. The sequences of five unique tryptic peptides, each carrying one phycoerythrobilin, are as follows: alpha-1 Ile-Asx-Lys-Cys*-Tyr-Arg alpha-2 Asx-Arg-Leu-Cys*-Val-Pro-Arg beta-1 Met-Ala-Ala-Cys*-Leu-Arg beta-2 Met-Ser-Phe-Ala-Ala-Gly-Asp-Cys*-Thr-Ser-Leu-Ala-Ser-Glu-Val-Ala-Gln-Tyr - Phe-Asp-Arg beta-3 Leu-Asp-Ala-Val-Asn-Ser-Ile-Val-Ser-Asn-Ala-Ser-Cys*-Met-Val-Ser-Asp-Ala - Val-Ser-Gly-Met-Ile-Cys*-Glu-Asn-Pro-Gly-Leu-Ile-Ser-Pro-Gly-Gly-Asn-Cys -Tyr- Thr-Asn-Arg where the designations alpha and beta refer to the subunit from which the peptide was derived. Cysteinyl residues involved in bilin attachment are indicated with an asterisk. The bilins in peptides alpha-1, alpha-2, beta-1, and beta-2 are attached to the peptide through a single thioether linkage to a cysteinyl residue. In contrast, the phycoerythrobilin on peptide beta-3 is attached through two thioether linkages to cysteinyl residues 10 residues apart. This appears to be the first report of a prosthetic group covalently bound to a polypeptide through two linkages separated by such a considerable distance in the linear sequence. The visible absorption spectrum of peptide beta-3 is red-shifted by about 10 nm relative to the spectra of the other four bilin peptides. Comparison of the sequences from B-phycoerythrin to sequences of several other biliproteins has revealed the presence of a number of invariant tyrosyl and arginyl residues near bilin attachment sites.
Amino Acid Sequence↗
Alterations in immunological function in streptozotocin-induced murine diabetes mellitus: correction by islet cell transplantation.
Cell-mediated and humoral immune responses of streptozotocin-induced diabetic mice were evaluated using in vivo and in vitro immunological assays. C57BL/6 mice were rendered diabetic by a single intraperitoneal injection of 125-200 mg/kg of streptozotocin. Immunological studies were performed after the mice were diabetic (mean +/- SEM serum glucose 537 +/- 14 mg/dl) for a minimum of 4 weeks. Spleen cells from streptozotocin-induced diabetic mice exhibited significantly diminished direct IgM plaque-forming cell (PFC) responses following either in vivo or in vitro immunization with sheep erythrocytes, markedly impaired cytotoxic cell responses following in vivo or in vitro allogeneic stimulation, and diminished blastogenic response to the T-cell mitogens phytohemagglutinin and concanavalin A. In contrast the blastogenic response of diabetic spleen cells to lipopolysaccharide, a B-cell mitogen, was normal. The defects in in vivo PFC responses and in vivo cytotoxic cell responses were corrected by islet cell transplantation, suggesting that the abnormalities in immunological function of streptozotocin-induced diabetic mice are a consequence of the diabetic state and not of direct streptozotocin toxicity to lymphoid cells.
Animals↗
Response of an experimental mammary carcinoma to fractionated X-irradiation with misonidazole and microwave hyperthermia.
X/Gf mice bearing the MT2 mammary adenocarcinoma were subjected to 4,000 rad of X rays given either as a single dose, or five daily fractions of 800 rad. Additional experimental groups were treated with either short term localized microwave hyperthermia (LMH) (42.5 degrees C for 25 min.), or the hypoxic cell radiosensitizer misonidazole (MISO) (0.67 mg/g bw), or both hyperthermia plus MISO with X rays. The combined use of MISO plus 42.5 degrees C with X rays was superior to the other treatment regimens as assessed by tumor regrowth delay and mean survival time. However, for the five fraction schedule, the addition of MISO plus hyperthermia was not as effective as observed for the single dose treatment. This may be attributed to reoxygenation of the hypoxic tumor cells between treatment fractions. MISO retention in tumor tissue under ambient and hyperthermic conditions was studied. The application of heat locally to the tumors caused a significant increase in MISO tumor concentration. However, after four X ray fractions the influence on MISO concentration by hyperthermia in the tumors could not be demonstrated. This may be related to the stromal damage by X rays in the tumor tissue that was observed histologically.
Adenocarcinoma↗
The effect of vitamin B6 on the neurotoxicity and pharmacology of desmethylmisonidazole and misonidazole: clinical and laboratory studies.
The clinical usefulness of misonidazole (MISO) and desmethylmisonidazole (DMM) is severely limited by neurotoxicity. Based on theoretical considerations and on laboratory data suggesting that pyridoxine (PN) decreased MISO toxicity in mice, we attempted to ameliorate the clinical neuropathy of DMM using oral PN. Pharmacokinetic analysis suggested interaction of PN and DMM but no protection against neuropathy was observed. Serial experiments with C3H and BALB/c mice were done using various forms of vitamin B6 (PN, pyridoxal, pyridoxal phosphate) administered orally and i.p. and the nonspecific adsorbing agent activated charcoal. No consistent protection was observed. A slower rate of drug delivery (dose/day) allowed a larger cumulative dose of MISO to be given, a result paradoxical to that seen in the clinic. Dexamethasone did not alter MISO toxicity in mice, contrary to the clinical findings. We conclude that vitamin B6 is not useful in preventing clinical neurotoxicity of MISO or DMM. Furthermore, this mouse model of neurotoxicity assessment has produced results inconsistent with those seen clinically.
Animals↗
Enhancement of melphalan cytotoxicity in vivo and in vitro by inhibitors of poly (ADP-ribose) polymerase.
In these preliminary experiments, we have found enhanced cell killing by the bifunctional alkylating agent L-phenylalanine mustard (L-PAM) in the presence of inhibitors of poly (ADP-ribose) polymerase (ADPRP) in vitro. In vivo enhancement of the tumoricidal effects of L-PAM was observed with the ADPRP inhibitor nicotinamide (1000 mg/kg), although enhanced myelosuppression was also demonstrated. Nicotinamide also increased the plasma elimination half-life of L-PAM by a factor of at least 2. This alteration of L-PAm pharmacokinetics makes it difficult to assess the role that ADPRP inhibition plays in the enhancement of L-PAM tumor cell killing in vivo.
Animals↗
Modification of alkylating agent cytotoxicity by cisplatin.
The effect of cisplatin on the cytotoxicity of alkylating agents in the RIF-1 tumor both in vivo and in vitro was investigated. A single dose of cisplatin (1 mg/kg) enhanced the in vivo tumor killing by melphalan (L-PAM; 8 mg/kg). The effect was maximal when cisplatin was given between 3 hours before and 1 hour after injecting L-PAM; the enhancement was lost as the time interval increased. Similar results were obtained with cyclophosphamide (CYT; 75 mg/kg) and CCNU (50 mg/kg) although the enhancement was much less than that seen with L-PAM. The enhancement by cisplatin was constant at all L-PAM doses as measured by both cloning assay and regrowth delay. Measurements of white blood cell counts four days after drug administration suggests that a therapeutic gain can be achieved. Exponential and plateau phase RIF-1 cells grown in monolayer culture were also exposed to various L-PAM doses. A 1 hour pre-exposure to cisplatin (0.5 micrograms/ml) under aerobic conditions increased the cell killing by L-PAM. The results are discussed with reference to the possible reasons for the therapeutic gain.
Alkylating Agents↗
Structural-functional relationships in diabetic nephropathy.
Renal biopsies in 45 patients with insulin-dependent diabetes mellitus (IDDM) were examined by semiquantitative light microscopy and quantitative electron microscopic stereologic morphometry. In these 14 males and 31 females, aged 13-52 yr, who had had IDDM for 2.5-29 yr there was no strong relationship between either glomerular basement membrane (GBM) thickness or mesangial expansion and duration of IDDM. There was only a weak relationship between the thickness of the GBM and expansion of the mesangium. Thus, GBM thickening and mesangial expansion in IDDM occur at rates that often differ from one another and that vary greatly among patients. The clinical manifestations of diabetic nephropathy, albuminuria, hypertension, and decreased glomerular filtration rate related poorly or not at all to GBM thickening. In contrast, all light and electron microscopic measures of mesangial expansion were strongly related to the clinical manifestations of diabetic nephropathy, although in the absence of these clinical findings, it was not possible to predict the severity of any of the diabetic glomerular lesions. Mesangial expansion had strong inverse correlations with capillary filtering surface area density. It is hypothesized that mesangial expansion could lead to glomerular functional deterioration in IDDM by restricting the glomerular capillary vasculature and its filtering surface. However, capillary closure, glomerular sclerosis, and interstitial fibrosis could also contribute to the clinical manifestations of this disorder.
Adolescent↗
Effect of prenatal dexamethasone on immunoreactive 6-ketoprostaglandin F1 alpha levels in fetal rat lungs.
The effect of prenatal glucocorticoid treatment on levels of immunoreactive 6-ketoprostaglandin F1 alpha (PGF1 alpha) (the stable metabolite of prostacyclin) was studied in fetal rat lungs. During late gestation (20-22 days), levels of 6-keto-PGF1 alpha peaked at 21 days in offspring of control mothers. At a maternal dose of 0.2 mg/kg dexamethasone, maximal enhancement of fetal 6-keto-PGF1 alpha levels occurred at 20 days gestation. At a treatment dose of 0.4 mg/kg, however, dexamethasone increased fetal lung 6-keto-PGF1 alpha concentrations throughout late gestation. Because maturation of fetal lung is known to be delayed in males relative to females, we also studied the impact of sex of the fetus on levels of 6-keto-PGF1 alpha. Our results showed no statistically significant differences between females and males in any of the treatment groups at any of the gestational ages studied. These results suggest that prenatal dexamethasone enhances endogenous levels of 6-keto-PGF1 alpha in fetal rat lungs. Since prostacyclin may play important roles in fetal lung maturation and neonatal lung function, the effectiveness of prenatal glucocorticoid therapy for accelerating functional maturity of the fetal lung may in part be due to stimulation of prostacyclin synthesis.
6-Ketoprostaglandin F1 alpha↗
The effects of chronic renal failure and hemodialysis on human red and white cell calmodulin levels.
Red blood cell (RBC) and polymorphonuclear white blood cell (WBC) calmodulin levels were measured in 25 uremic patients on regular hemodialysis. Uremic patients had significantly higher RBC [11.45 +/- 0.66 (+/-SE) fg/cell] and WBC (590.5 +/- 110 fg/cell) calmodulin levels than normal subjects (8.62 +/- 0.37 and 130 +/- 30 fg/cell; P less than 0.05). An extremely high RBC calmodulin level (20.58 fg/cell) was found in a patient with sickle cell anemia. Uremic patients on dialysis for 2 yr or more had lower RBC (10.99 +/- 0.58 fg/cell) and WBC (390 +/- 50 fg/cell) calmodulin levels than those who were on dialysis for less than 2 yr (RBC, 12.30 +/- 1.56 fg/cell; WBC, 943 +/- 256 fg/cell; P less than 0.05). There were no statistically significant differences in calmodulin levels when different subgroups of uremic patients were compared, e.g. patients with diabetes mellitus or those receiving supplemental vitamin D, anabolic steroids, or antihypertensive medications. We conclude that calmodulin levels are elevated in uremic patients on regular hemodialysis.
Adult↗
The effects of aging and diabetes mellitus on human red and white cell calmodulin levels (chemotaxis/phagocytosis/calcium).
Both the calcium ion and calmodulin have been proposed to play a role in producing the intracellular effects of insulin. Abnormalities in calmodulin levels have previously been reported in tissues from diabetic animals. Thus, using a sensitive and specific radioimmunoassay, we measured calmodulin levels in red cells and polymorphonuclear leukocytes from humans with diabetes mellitus. Diabetic patients have significantly lower white cell calmodulin levels than age-matched controls. There were no significant differences in red cell calmodulin levels in diabetics compared with controls. Red cell calmodulin levels in normal subjects were decreased with advancing age. We conclude that the alteration in calmodulin levels in leukocytes from diabetics may be associated with the decreased neutrophil function that has been observed in diabetics.
Adolescent↗
In vivo chloroquine-induced inhibition of insulin degradation in a diabetic patient with severe insulin resistance.
We report on a 26-yr-old patient with an 11-yr history of insulin-dependent diabetes mellitus who exhibited insulin resistance with a requirement of up to 15,000 U of intravenous (i.v.) insulin/day. Attempts to diminish her insulin requirement by administration of sulfated insulin or Trasylol were unsuccessful, with the patient remaining resistant to subcutaneous (s.c.) and i.v. administration of pure pork insulin. Chloroquine phosphate therapy (500 mg twice a day) resulted in a decreased requirement for i.v. insulin (700 U/day as compared with the pretreatment requirement of 8400 U/day). Accelerated insulin degradation in s.c. fat tissue of the patient before treatment with chloroquine was demonstrated. This activity was decreased by 64% during chloroquine therapy. Inhibition of insulin degrading activity (IDA) during chloroquine therapy was associated with reductions in the leukocyte lysosomal enzymes alpha-galactosidase and hexosaminidase-A but not hexosaminidase-B and beta-glucuronidase. This study constitutes the first reported use of chloroquine for treatment of insulin resistance as a result of accelerated insulin degradation, and it provides evidence of the effectiveness of this agent in this rare condition.
Adipose Tissue↗
Inhibition of X-ray-induced potentially lethal damage (PLD) repair in aerobic plateau-phase Chinese hamster cells by misonidazole.
The effect of the 2-nitroimidazole radiosensitizer misonidazole (MISO) and the hydrophilic analog SR-2508 on the repair of X-ray-induced potentially lethal damage (PLD) was studied in plateau-phase Chinese hamster ovary (HA-1) cells. It was found that although MISO does not radiosensitize aerobic cells, it inhibits the repair of PLD. However, under hypoxic conditions, MISO has no effect on PLD repair. The major portion of the inhibition of PLD repair in aerobic cells requires the presence of MISO only during irradiation; little or no additional inhibition occurs when MISO is present during the postirradiation repair period. Also, treatment of aerobic cells with 5 mM MISO for either 5 or 30 min prior to irradiation is equally inhibitory. This suggests that the presence of MISO in some way modifies the initial lesion under aerobic conditions since it does not increase cell killing as determined by immediate plating but inhibits subsequent repair. The inhibition is concentration dependent; 0.5 mM MISO inhibits PLD repair by one-half while 5-10 mM totally inhibits the repair measured 6 hr postirradiation. This phenomenon suggests that radiosensitization of tissue in vivo by MISO and other 2-nitroimidazoles may not be unequivocal proof of the presence of hypoxic cells.
Aerobiosis↗
Alterations in proteoglycan metabolism in the nephrotic syndrome induced by the aminonucleoside of puromycin.
The synthesis of intact proteoglycans and their glycosaminoglycan (GAG) side chains by isolated rat glomeruli in vitro were studied both at the onset (5 days) and at the point of maximal proteinuria (7 days) of the nephrotic syndrome induced with the aminonucleoside of puromycin. Glomeruli from nephrotic animals incorporated 1.5-fold and 3.0-fold more 35SO4 label into GAG than glomeruli from control animals at 5 and 7 days, respectively, with heparan-35SO4 GAG being responsible for the majority of the increment. Both nephrotic and control incubations contained 60% of the label in the incubation medium, 40% in the glomerular fractions, and less than 1% in the glomerular basement membrane. Glomerular basement membrane from nephrotic rats had no change in their total heparan-35SO4 GAG content. The majority of intact proteoglycan(s) from the glomerular matrix and from the incubation medium of nephrotic and control animals was found in the most buoyantly dense fraction of CsCl gradients (fraction 1). 35S-labeled material isolated from glomeruli of nephrotic animals showed a consistent shift toward lower density gradient fractions, indicating a decrease in their overall carbohydrate to protein ratio. Diethylaminoethyl chromatography of fraction 1 proteoglycan showed a single biphasic peak with the nephrotic rat having an increase in the proportion contributed by the earlier component of the peak. Fraction 1 proteoglycan(s) from the nephrotic experiment was found to have a smaller average hydrodynamic size by Sepharose CL-2B chromatography without a significant change in the corresponding 35S-GAG chain sizes (molecular weight 14,000) by Sepharose CL-6B chromatography. 35S-macromolecules from glomeruli of nephrotic and control rats that appeared in the middle of the CsCl gradients (fraction 3) had similar Sepharose CL-2B elution volumes, whereas the corresponding 35S-GAG chains from incubations of glomeruli from nephrotic animals were smaller. Increased synthesis of heparan sulfate proteoglycan by glomeruli from puromycin aminonucleoside-induced nephrotic rats may be compensatory to loss of another component of the glomerular filtration barrier or may result from abnormal interaction of proteoglycan(s) from nephrotic animals with other glomerular matrix constituents.
Animals↗
The influence of inhibitors of poly (ADP-ribose) polymerase on X-ray-induced potentially lethal damage repair.
Inhibition of repair of X-ray-induced potentially lethal damage (PLD) could enhance the curability of radioresistant tumours. We have studied the effect of inhibitors of the enzyme poly (ADP-ribose) polymerase on X-ray PLD repair. Four classes of inhibitors are known: aromatic amides (e.g., 3-aminobenzamide), thymidine, nicotinamides and methyl xanthines (e.g., caffeine). Plateau-phase Chinese hamster ovary (HA-1) cultures were exposed to 10mM concentrations of thymidine, nicotinamide, 3-aminobenzamide (3-ABA) and caffeine prior to irradiation to 12 Gy in air, and then incubated with drug at 37 degrees C for varying times (0-6 h) prior to subculture. Irradiated cells without drug exhibited a 5-6 fold increase in survival over the 6 h period compared to cultures plated immediately after irradiation. Although none of the compounds proved cytotoxic to unirradiated controls over the 6.5 h exposure, all of the compounds except thymidine reduced the capacity of the cells to repair PLD. The order of the inhibitory effect was caffeine greater than 3-ABA greater than nicotinamide, and the inhibition was concentration dependent for nicotinamide and 3-ABA. We also studied the effect of 3-ABA on the radiation response of exponentially growing cells. 5mM 3-ABA for 2 h post-irradiation resulted in a dose-multiplicative sensitization reducing the D0 from 0.88 Gy to 0.69 Gy, indicating an involvement of poly (ADP-ribose) polymerase in the radiosensitivity of exponentially growing as well as plateau-phase cells.
Animals↗
Separate influences of insulin and hyperglycemia on hepatic drug metabolism in mice with genetic and chemically induced diabetes mellitus.
Numerous investigators have reported abnormalities of hepatic drug metabolism in hypoinsulinemic animal models with chemically induced diabetes mellitus, but there has been little assessment of hepatic drug metabolism in recently described animal models with genetic diabetes mellitus characterized by hyperinsulinemia and insulin resistance rather than insulin deficiency. Hepatic microsomal cytochrome P-450 content and drug metabolizing activity in obese, diabetic C57BL/KsJ mice homozygous for the diabetes gene mutation (db/db) have been compared with levels found in livers of 1) lean, nondiabetic control mice with the same C57BL/KsJ genetic background and 2) lean C57BL/6J animals made diabetic by streptozotocin treatment. No changes in specific enzyme content or activity were seen in young db/db mice, but microsomal protein and total hepatic cytochrome P-450 content and meperidine demethylation and pentobarbital hydroxylation activity were markedly increased compared to controls. In hyperglycemic, hypoinsulinemic mice with streptozotocin-induced diabetes mellitus, the amount of microsomal protein did not change, but hepatic cytochrome P-450 content and enzyme activity were significantly increased whether expressed per milligram of microsomal protein or as totals per liver. In old db/db animals, hyperglycemia persisted but plasma insulin levels fell into the normal range so that the insulin-glucose profile of these animals resembled that seen in the streptozotocin treatment group. In association with these changes, hepatic enzyme specific activities in the old db/db mice approximated values found in the streptozotocin group rather than in the young db/db animals. These differences in hepatic microsomal enzymes between hyperinsulinemic and hypoinsulinemic mice with diabetes mellitus suggest that both hyperglycemia and insulin separately and significantly influence cytochrome P-450 turnover and mixed function oxidase activity.
Animals↗
Biliary scintigraphy. The "hot rim" sign.
A new cholescintigraphic finding, the "hot rim" sign, is reported in a case of acute cholecystitis. Local inflammation in the gallbladder fossa may be the cause of this phenomenon.
Acute Disease↗
Hypophosphatasia: clinicopathologic comparison of the infantile, childhood, and adult forms.
Histochemical and direct enzyme analysis of osseous tissue from 23 patients with hypophosphatasia revealed that all clinical forms of this inherited metabolic bone disease are characterized by deficiency of alkaline phosphatase (ALP) activity in bone. The severe infantile form has the most profound deficiency, infantile form has the most profound deficiency, yet the cellular source of this enzyme--osteoblasts and their matrix vesicles--are normal by routine light and electron microscopy. Despite radiographic changes in bone metaphyses consistent with rickets, iliac crest biopsy of one affected child revealed no abnormalities; the other had evidence of a mineralization defect, but not as severe as that in affected infants. In this child and several affected adults with osteomalacia, osteoblasts appeared flat and metabolically inactive. Although these histological changes suggested a different pathogenetic mechanism for adult and childhood hypophosphatasia, these changes are most likely secondary to the underlying osteomalacia. Our findings are most consistent with evidence that childhood and adult hypophosphatasia often represent clinical expression of the heterozygous state for ALP deficiency which, when homozygous, results in the clinically severe, recessive, infantile form. Histochemical and direct analysis of bone tissue from controls and patients with hypophosphatasia demonstrated that the severe infantile form is associated with the most severe ALP deficiency. In the milder clinical forms, ALP deficiency in bone is not as profound. In general, the severity of the clinical expression of hypophosphatasia reflects the magnitude of the deficiency of ALP in bone. This is the expected finding for this inborn error of metabolism, which illustrates the major role bone ALP activity has in the process of normal skeletal mineralization.
Adolescent↗