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Biomedical subjects

C Ritter

Publications and source records attributed to C Ritter.

At least 73 records · Page 4Linked to original sources
PubMed1989

Combined effects of dexamethasone and 1,25-dihydroxyvitamin D3 on parathyroid hormone secretion in cultured bovine parathyroid cells.

The present studies investigate the effects of glucocorticoids on the function of the parathyroid glands using primary cultures of bovine parathyroid cells. Treatment of parathyroid cell cultures with dexamethasone for 48 h caused a dose-dependent stimulation of PTH secretion. The minimal concentration of dexamethasone required for a significant stimulation of PTH secretion was 0.1 nM. The stimulatory effect of dexamethasone on the secretion of PTH was found within 12 h of treatment with 100 nM dexamethasone. The steroids deoxycorticosterone and cortexolone, which do not have glucocorticoid activity were without effect of PTH secretion. Since glucocorticoids may modulate the effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] in other tissues, additional studies were performed to evaluate the interactions of glucocorticoids and 1,25-(OH)2D3. Addition of 1,25-(OH)2D3 to parathyroid cell cultures for 48 h significantly suppressed PTH secretion. In the presence of dexamethasone, however, 1,25-(OH)2D3 also significantly decreased PTH secretion, although it did not reduce PTH secretion to control levels. The treatment of parathyroid cell cultures with 100 nM dexamethasone did not affect the parathyroid cell content of 1,25-(OH)2D3 receptors. In summary, these studies indicate that glucocorticoids significantly increase the secretion of PTH in vitro. This stimulatory effect can be inhibited by 1,25-(OH)2D3. The parathyroid gland is an additional site of physiological antagonism of glucocorticoids and 1,25-(OH)2D3.

Animals↗
PubMed1989

In vitro inhibition of nitrogen mustard efficacy by postincubation of treated cells in serum protein.

Lettre-Ehrlich cells were loaded with sufficient HN2 to produce about a 98% cell kill. Postincubation of the HN2-loaded cells in PBS resulted in the loss of about 40% of their HN2 without changing the cytolytic effect, supporting the proposal that only bound drug was effective. Postincubation of the HN2-loaded cells in PBS which contained 2% bovine serum albumin or in cell-free mouse ascitic fluid (1.8% protein) resulted in the same relative cellular HN2 loss as well as a 79% decrease in the cell kill. The cytolytic effect of HN2 is believed to be dependent on the degree to which the drug crosslinks DNA in 2 sequential reactions. It seems likely that such crosslinking occurred in nearly all of the PBS-postincubated cells, as they were nearly all killed. By analogy, albumin postincubation apparently blocked the competition of such crosslinking.

Animals↗
PubMed1989

Choline uptake is increased by Ca++ and liposomes+ Ca++ in ascites tumor cells.

Steady-state uptake of choline by Lettre-Ehrlich tumor cells in vitro, resulting in cell-to-medium ratios of 10 or more, is significantly increased by 0.2-1.0 mM Ca++ as well as by dipalmitoyl phosphatidyl choline multilamellar liposomes + Ca++. The increases occur in spite of a decrease in carrier affinity, as indicated by the Km, and therefore result either from increased carrier velocity or utilization of new carriers. About half of the labelled choline which is taken up is firmly bound to cells. That label which freely leaves cells is phosphocholine, thus, these cells utilize choline mainly in phospholipid synthesis. Choline and nitrogen mustard (HN2) share a plasma membrane carrier but the intracellular distribution of HN2 into DNA, RNA and protein, contrasts with that of choline, into phospholipid.

Animals↗
PubMed1988

[Incidence and forensic value of liver cell hydrops in external asphyxia and sudden infant death].

A histological examination was carried out in 108 cases of asphyxia, 28 cases of SIDS, and 33 cases with other causes of death to assess the occurrence of liver-cell hydrops. In almost all cases of violent suffocation of newborns and children up to 10 years of age hydrops of the hepatocytes were found, whereas these results could be verified only exceptionally after violent suffocation of adults. Eighteen cases or 64.3% of SIDS showed a diffuse distribution of liver-cell hydrops over each liver lobule. Liver-cell hydrops seems to represent a frequent morphological equivalent of acute oxygen deficiency in asphyxia in childhood and is a common finding in SIDS.

Adult↗
PubMed1988

Distinguishing anxiety and depression with field survey data.

Data on self-reported symptoms collected in the East Baltimore site of the Epidemiologic Catchment Area Program are analysed in parallel fashion for the two syndromes of anxiety and depression. Patterns of relationships of anxiety and depression to sociodemographic factors, prior psychopathology, and life events fail markedly to distinguish the two syndromes.

Adolescent↗
PubMed1988

Effect of 1,25-dihydroxyvitamin D3 on cytosolic calcium in dispersed parathyroid cells.

We examined the effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on cytosolic calcium ([Ca]i) of dispersed bovine parathyroid cells, using the fluorescent dye indo-1. The addition of 10(-8) M 1,25-(OH)2D3 caused an increase in [Ca]i by 23.4 +/- 2.7% over a 10 minute period. There was a significant increase in [Ca]i within two minutes of the addition of 1,25-(OH)2D3. 1,25-(OH)2D3 increased [Ca]i in a dose-dependent manner and this occurred with as little as 10(-10) M. Neither 10(-7) M 25-(OH)D3 nor 10(-7) M 24, 25-(OH)2D3 caused a significant increase in [Ca]i. Chelation of extracellular calcium with EGTA blocked the 1,25-(OH)2D3-induced increase in [Ca]i, suggesting that the increase was mainly from extracellular calcium. Neither 10(-5) M verapamil nor 10(-4) M diltiazem blocked the 1,25-(OH)2D3-induced increase in [Ca]i. The present data suggest that 1,25-(OH)2D3 might modify membrane permeability to calcium independent of voltage-dependent calcium channels sensitive to verapamil or diltiazem. The rapid effect of 1,25-(OH)2D3 raises the possibility that its mechanism is independent of genome activation, perhaps attributable to direct interaction with components of the parathyroid cell plasma membrane.

Animals↗
PubMed1988

Effect of 1,25-dihydroxyvitamin D3 on phospholipid metabolism in cultured bovine parathyroid cells.

There is evidence that 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] affects phospholipid metabolism of intestine, kidney, and bone. There are no such studies concerning the parathyroid gland, which is also a target tissue for 1,25-(OH)2D3. In this investigation we examined the effect of 1,25-(OH)2D3 on the incorporation of radiolabeled choline, inositol, serine, and ethanolamine into the phospholipids of cultured bovine parathyroid cells. Treatment with 10(-8) M 1,25-(OH)2D3 for 48 h caused a significant decrease in [14C]choline incorporation, although there were no differences in the incorporation of radiolabeled inositol, serine, or ethanolamine. Time-course and dose-response evaluations of the 1,25-(OH)2D3 effect revealed that the decrease in [14C]choline incorporation was seen within 12 h of incubation and occurred with as little as 10(-9) M, respectively. In contrast, neither 10(-7) M 25-hydroxyvitamin D3 nor 10(-7) M 24,25-(OH)2D3 caused significant changes in [14C]choline incorporation. When 5 X 10(-6) M cycloheximide was added to the medium, the inhibitory effect of 1,25-(OH)2D3 on [14C]choline incorporation was completely abolished. A significant decrease in phosphatidylcholine content was observed after treatment with 10(-8) M 1,25-(OH)2D3 for 96 h. 1,25-(OH)2D3 did not cause a dramatic change in the fatty acid composition of the phosphatidylcholine. The present studies demonstrate that in parathyroid cells 1,25-(OH)2D3 causes a decrease in [14C]choline incorporation, which could be due to a decrease in the synthesis of phosphatidylcholine or increased degradation. This effect is specific for 1,25-(OH)2D3 and requires new protein synthesis.

Animals↗
PubMed1988

Myocardial infarct extension: occurrence, outcome, and risk factors in the Multicenter Investigation of Limitation of Infarct Size.

The occurrence, outcome, and predictors of myocardial infarct extension were determined in 848 patients with acute myocardial infarction. An increase in the level of plasma MB creatine kinase activity was used to detect extension, which occurred in 71 of 848 patients (8.4%). For these patients, hospital mortality was more than four times higher than for those without extension (30% versus 7%, P less than 0.01). However, for patients surviving the initial hospitalization, there was no significant difference in mortality during the following year (12% compared with 9%). Multivariable analyses indicated that extension was more likely to occur in patients with recurrent ischemic pain during the second hospital day, a history of previous myocardial infarction, and ST segment depression on the admission electrocardiogram. The occurrence of extension in patients with two of these risk factors was more than twice that of patients without any of the risk factors (15.1% compared with 5.8%). Patients with these risk factors should be considered for early coronary angiography and possible intervention to prevent infarct extension and its sequellae.

Analysis of Variance↗
PubMed1987

Modulation of the cellular toxicity of nitrogen mustard in murine cells.

A linear increase in cell uptake of nitrogen mustard, methyl-bis(beta-chloroethyl)amine (HN2), between 1 and 5 min, was observed after in vitro incubation of Ehrlich ascites tumor cells at 37 degrees C in phosphate-buffered saline containing HN2 followed by washing in 0 degrees C phosphate-buffered saline. After a second incubation in 37 degrees C phosphate-buffered saline without HN2, the cells lost about one-half of the drug which had been taken up, that which had not been covalently bound to macromolecules. The basal cytotoxic effect of HN2 on the cells was determined using a standard in vivo test for cell viability. Host survival was measured after 10(5) HN2-treated cells were injected i.p. into recipient mice, compared with injection of 10(5) untreated cells into paired control mice. Five min incubation of cells in vitro with multilamellar liposome vesicles (MLV) composed of L(alpha)dipalmitoyl-phosphatidyl choline in the presence of HN2, significantly increased tumor cell kill and mouse survival over HN2 alone. In contrast, added Ca2+ plus HN2 decreased cytotoxicity and survival. Significant increases in host survival following MLV treatment occurred without significant increase in total HN2 uptake and could be highly correlated with increased amounts of HN2 bound to DNA. Addition of vincristine (an inhibitor of microtubule polymerization) in the presence of HN2 also decreased the cytotoxic effect of HN2. The vincristine inhibition occurred, without altering total cell HN2 uptake, whether L(alpha)dipalmitoyl-phosphatidyl choline MLV were present or not. It is proposed that both Ca2+ and MLV act at membrane sites so as to alter the subcellular distribution and localization of HN2 and its accessibility to critical targets. This has been confirmed for MLV by demonstrating increased alkylation of DNA.

Animals↗
PubMed1986

[Stab injuries of the skull and brain].

A few cases of skull and brain stab wounds are described and the clinicodiagnostic problems discussed. The injuries often remain unrecognized because the external wound often appears harmless, there are no neurological symptoms, or the clinical picture is interpreted as drunkenness, blunt injury or as another disease. The importance of a precise physical examination of the whole patient's head is pointed out. The refined methods used in modern radiodiagnostics of the skull are the most helpful in correctly recognizing these injuries; there are reports of patients with severe injuries who recovered when the correct diagnosis had been established.

Adolescent↗
PubMed1986

Protection of mitochondrial genetic system against aflatoxin B1 binding in animals resistant to aflatoxicosis.

Administration of a single dose of aflatoxin B1 (AFB1) (6 mg/kg) to Sprague-Dawley rats results in a high level of modification of hepatic mitochondrial DNA (2.1 nmol of AFB1 adducts per mumol DNA-phosphate) and long-term inhibition of mitochondrial transcription and translation activities (N. Bhat et al., Cancer Res., 42: 1876-1880, 1982). Similar doses of AFB1 given to ICR mice and Syrian golden hamsters result in negligible to very low levels (0-06 nmol) of adducts in hepatic mitochondrial DNA. Intact mitochondria from rat liver can metabolize significant amounts of AFB1 (0.29 nmol/mg of protein) without externally added reduced nicotinamide adenine dinucleotide phosphate, and the metabolic activity is stimulated nearly 3-fold by Kreb's cycle intermediates (glutamate and malate), which support intramitochondrial reduced nicotinamide adenine dinucleotide phosphate production. Intact mitochondria from mice and hamsters, on the other hand, metabolize negligible or very low levels of AFB1 (0-0.1 nmol of AFB1 per mg of protein) even when intramitochondrial reduced nicotinamide adenine dinucleotide phosphate production is stimulated by the addition of Kreb's acids. Detergent-solubilized mitoplasts containing less than 1% microsome contamination from all three sources can catalyze the metabolic activation of AFB1 to electrophilic reactive forms as determined in an in vitro DNA binding assay at comparable levels (1.2-2.2 nmol of AFB1 bound per mumol of cytochrome P-450), suggesting that the low levels of AFB1 metabolism by intact mouse and hamster mitochondria and the relative resistance of macromolecular synthesis in these particles to added AFB1 may be due to mitochondrial membrane impermeability. In support of this possibility, AFB1 transported into mouse liver mitochondria through a liposome delivery system causes about 80% inhibition of protein synthesis.

Aflatoxin B1↗
PubMed1985

[Histomorphologic lung findings in long-term artificial respiration with special reference to extreme continuous artificial respiration using pure oxygen].

The respirator lung is characterized histologically in the first exudative phase by capillary congestion, intra-alveolary edema, hyaline membranes and in most cases by concomitant inflammatory alterations. In the following irreversible phase, fibrous organization processes dominate and show a variable tendency towards pulmonary fibrosis. In 27 cases with long-term artificial respiration from 4 days to 12 weeks, mainly the proliferative alterations were investigated. In 18 cases, the histopathological findings indicated fibrosis of the alveolar septa with disseminated distribution. In 9 cases, focal fibrosis with obliterations of alveoli prevailed. The extent of pathological results in the lungs does not correlate with the duration of artificial respiration. In cases of artificial respiration with pure oxygen, there is a special toxic component, which is illustrated by a young woman with polytraumatism who was administered artificial respiration for 5 weeks with pure oxygen. She died from respiratory insufficiency with severe pulmonary fibrosis. As different pathogenetic factors may cause irreversible pulmonary fibrosis, histomorphological classification is difficult later and, moreover, forensic problems result.

Adolescent↗
PubMed1985

Vietnam military service and marijuana use.

The effect of military service in Vietnam on drug use among veterans is examined on the basis of data obtained from a nationwide random sample of 2,510 young men. It is generally believed that illicit drug use was more extensive in Vietnam in the 1970s than in earlier years of the conflict. Therefore variables were constructed to reflect location of service (United States; overseas, but not Vietnam; and Vietnam) and the time of service (before 1970; 1970 or later). The results of the analysis indicate that: military service in Vietnam had no significant effect on marijuana use while on active duty, service in 1970 or later had a significant positive effect on during service use while in the service, and location of military service and time of service had a significant interactive effect on rates of marijuana use after discharge from military service. The interaction of service in Vietnam and military service after 1970 has the strongest effect on the veteran's marijuana use in civilian life.

Adult↗
PubMed1985

Technetium-99m DADS complexes as renal function and imaging agents: II. Biological comparison with iodine-131 hippuran.

To find a 99mTc agent with a high renal extraction efficiency similar to [131]hippuran, 21 analogs of DADS were labeled and evaluated. Preliminary screening by serial gamma camera imaging in rabbits showed that most analogs had a higher liver uptake and/or slower renal clearance, than hippuran. Three agents (P-DADS, AP-DADS, and CAP-DADS), exhibiting a relatively rapid blood clearance and lower liver uptake in the rabbit, were studied in greater detail in comparison with hippuran and CO2-DADS-A, the best analog to date. In the rat, the plasma clearance of the four DADS analogs was slower than that of hippuran. In rats with tubular damage induced by cisplatin, the difference in renal retention at 1 hr compared to controls was much greater with hippuran than with the DADS compounds. In the dog, there was marked hepatic retention of the four DADS compounds. In volunteers, serial posterior images obtained with these [99mTc]DADS complexes showed significant hepatic as well as renal activity. The 1-hr plasma clearance and urinary excretion were much lower than with simultaneously injected hippuran. Although these 99mTc agents are satisfactory for imaging the kidneys, they closely mimic the biodistribution of hippuran only in the rabbit, and not in the rat, dog, or man.

Animals↗
PubMed1984

Unmasking artifactual increases in creatine kinase isoenzymes in patients with renal failure.

Previous reports have suggested that creatine kinase isoenzymes are elevated in patients with chronic renal failure and thus are less useful in the evaluation of chest pain in such patients. Our data in 88 patients with chronic renal failure receiving maintenance dialysis confirm this observation for total plasma creatine kinase. However, elevations in MB and BB creatine kinase, although statistically significant, were biologically unimpressive (5.9 +/- 0.05 [SEM] IU/L compared with 4.8 +/- 0.04 IU/L for MB creatine kinase [p less than 0.02], and 5.5 +/- 0.08 ng/ml compared with 3.2 +/- 0.05 ng/ml for BB creatine kinase [p less than 0.0002] ), and were unlikely to cause diagnostic confusion. In 92% of patients with chronic renal failure, plasma MB creatine kinase activity was within the normal range (less than 13 IU/L). Eight percent of patients manifested abnormal MB creatine kinase values; the highest was 20 IU/L. The glass bead method for measuring MB creatine kinase was used to avoid the potential confusion induced by non-creatine kinase-mediated fluorescence, which occurs in the region of MB and BB creatine kinase on electrophoresis. The infrequent and modest increases in plasma MB creatine kinase observed in patients with chronic renal failure should be appreciated, but it should not cause diagnostic confusion, because acute myocardial infarction usually results in more substantial elevations of MB creatine kinase.

Clinical Enzyme Tests↗