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Biomedical subjects

R Carmel

Publications and source records attributed to R Carmel.

At least 55 records · Page 3Linked to original sources
PubMed1990

Human umbilical vein endothelial cells secrete transcobalamin II.

Transcobalamin II (TC II) is essential for cellular uptake of cobalamin. However, the origin of this transport protein is controversial and many organ sources have been suggested. We studied human umbilical vein endothelial cells cultured in vitro. The cells contained TC II (2.3 pmol/10(8) cells) and released progressively increasing amounts of the protein into the surrounding medium during the 3-day incubation period. This release exceeded the starting intracellular content of TC II. In contrast, endothelial cells did not contain or elaborate R binder, the other major circulating binding protein for cobalamin, Cycloheximide inhibited the elaboration of TC II, suggesting that the endothelial cells synthesize the protein. Thrombin, which stimulates tissue plasminogen activator release, did not enhance TC II release, and neither did endotoxin or mellitin. However, thrombin did appear to partially protect TC II release from inhibition by cycloheximide. Among other cells studied, human fibroblasts also released TC II into the incubation medium, while K562 human leukemia cells, ARH-77 and HS Sultan human plasma cell lines, and Raji strain lymphoblasts did not. The data suggest that endothelial cells are an important source of the metabolically crucial TC II.

Cycloheximide↗
PubMed1990

Neurologic and evoked potential abnormalities in subtle cobalamin deficiency states, including deficiency without anemia and with normal absorption of free cobalamin.

The meaning of a low serum cobalamin level when the classic findings of pernicious anemia are lacking is undergoing reevaluation. We therefore studied the neurologic status of 11 patients who had low cobalamin levels without definite hematologic evidence of deficiency. Neurologic evaluation included pattern-shift visual and median and posterior tibial nerve somatosensory evoked potentials. None of the patients had megaloblastic changes in the blood or bone marrow, although 7 of the 11 had subtle cellular cobalamin disturbances demonstrated by an abnormal deoxyuridine suppression test result. Seven patients had normal Schilling test results and 2 had borderline results; however, 2 of the 5 patients tested further had food-cobalamin malabsorption, while a third had prepernicious anemia. The patients displayed a variety of neurologic problems, including dementia, depression, myelopathy, neuropathy, and seizure disorder; 1 patient was neurologically normal by clinical criteria. Evoked potential abnormalities were demonstrable in 8 of the 9 patients with subtle cobalamin deficiency, and in at least 5 cases the disturbance was central. In contrast, both patients whose low serum cobalamin levels were found on evaluation to be spurious had normal evoked potentials. Evoked potential abnormalities improved in the one patient retested after cobalamin therapy. These findings demonstrate that neurologic deficits occur not only in classic cobalamin deficiency but also in subtle or atypical cobalamin deficiency states in which anemia is absent and Schilling test results are normal. Electrophysiologic evidence of neurologic impairment is often present, even in patients without obvious clinical neurologic abnormalities.

Absorption↗
PubMed1990

Subtle and atypical cobalamin deficiency states.

Evidence for cobalamin (vitamin B12) deficiency usually involves some combination of low serum cobalamin levels, clinical abnormalities (classically, megaloblastic anemia and neurologic defects), metabolic abnormalities, and response to therapy. However, cobalamin deficiency may often display few of the expected clinical findings. Identification of the underlying cause is also important in the diagnosis of deficiency, and its value may be particularly great when the expression of deficiency is subtle. The cause of cobalamin deficiency is usually malabsorptive, but may sometimes be limited to malabsorption of food cobalamin while free cobalamin is absorbed normally. Nongastroenterologic entities may sometimes also be found. All of these considerations allow the proposal of four patterns of cobalamin deficiency. The first type is classical deficiency; typical megaloblastic anemia with or without neurologic dysfunction occurs because of classical cobalamin malabsorption such as lack of intrinsic factor (pernicious anemia). The second type consists of classical cobalamin malabsorption in which the cobalamin deficiency is expressed subtly rather than in classical fashion. There is no megaloblastic anemia and sometimes the only evidence of deficiency may be metabolic. In the third type, cobalamin deficiency is expressed classically but is attributable to a subtle or atypical cause, such as food-cobalamin malabsorption. In the fourth type, deficiency is both expressed subtly and arises from subtle or atypical causes. Such presentations require further investigation but are a challenging expansion of our understanding and recognition of cobalamin deficiency.

Diagnosis, Differential↗
PubMed1990

Transfer of cobalamin from the cobalamin-binding protein of egg yolk to R binder of human saliva and gastric juice.

Patients may fail to absorb cobalamin (vitamin B12) bound to food even when they have adequate intrinsic factor to absorb free cobalamin normally. We studied cobalamin transfer from egg yolk cobalamin-binding protein to human saliva and gastric juice as a model of this important first step in cobalamin assimilation. The cobalamin-binding protein of egg yolk eluted with human R binder on Sephadex gel chromatography and bound cobalamin with a comparable affinity, but it did not cross-react with R binder immunologically. Transfer of cobalamin from egg yolk to saliva or gastric juice R binder did not occur at neutral pH. Slight transfer (8%-12% of the 57Co-cobalamin bound to egg yolk) occurred when the saliva was acidified to pH 1.5. This minor transfer by acid was not inhibited by pepstatin A, a pepsin inhibitor. Acidification caused variable transfer to gastric juice R binder (12%-40%) that appeared to be partially due to residual gastric pepsin activity. Adding 1200 U of pepsin per milliliter enhanced cobalamin transfer to saliva or gastric juice R binders (39%-58% transfer). At no time was cobalamin transferred directly to intrinsic factor; R binder-deficient gastric juice failed to accept cobalamin from egg yolk. The transfer of cobalamin from egg yolk to human R binder requires both an acid pH and pepsin activity. While as little as 30 U of pepsin added per milliliter of saliva promoted transfer of cobalamin, the requirement for an acid pH was very strict. Virtually no transfer occurred when pH exceeded 2.0, regardless of the amount of pepsin present. Acid provided an optimal pH for pepsin activity and, to a lesser extent, affected transfer by a mechanism unrelated to pepsin. Our data suggest that compromised pepsin secretion and, probably even more importantly, compromised acid secretion interfere with transfer of food cobalamin to R binder.

Anemia, Pernicious↗
PubMed1990

Autoimmune cytopenias in pernicious anemia: a report of four cases and review of the literature.

Pernicious anemia appears to be autoimmune in origin and is associated with immune disorders of several organ systems. We report 4 patients with pernicious anemia and immune cytopenias, an association that may sometimes pose diagnostic problems unless specifically considered. Pernicious anemia coexisted with or was closely followed by idiopathic thrombocytopenic purpura in 3 patients and by autoimmune hemolytic anemia in a 4th patient. In addition to cobalamin therapy, all patients required corticosteroids (2 also received danazol), while 1 also required splenectomy. All 4 patients were women. The 3 patients with idiopathic thrombocytopenic purpura were also blood group O and were iron-deficient. Autoimmune cytopenias may occur in patients with treated or untreated pernicious anemia and require specific therapy.

Adult↗
PubMed1989

Platelet-derived growth factor concentrations in platelet-poor plasma and urine from patients with myeloproliferative disorders.

Our enzyme-linked immunosorbent assay (ELISA) for measuring human platelet-derived growth factor (PDGF) detects nanogram quantities (ranging from 0.007 to 16 ng/100 microL) in purified PDGF standards. This assay is sensitive enough for studying plasma and urine. The range in normal volunteers was 0.6 to 2.3 micrograms/L for platelet-poor plasma and 1.4 to 3.3 micrograms/L for urine. We determined PDGF levels in the circulation (outside platelets) in patients with myeloproliferative diseases. Platelet-poor plasma and urine PDGF were significantly elevated in patients with myelofibrosis (6.2 +/- 2.0 micrograms/L for plasma; 7.8 +/- 2.4 micrograms/L for urine) and essential thrombocythemia (5.5 +/- 1.5 micrograms/L for plasma; 11.4 +/- 2.2 micrograms/L for urine), but not in patients with chronic myelogenous leukemia (2.1 +/- 0.4 micrograms/L for plasma; 2.8 +/- 1.2 micrograms/L for urine). Polycythemia vera produced an intermediate pattern: although plasma PDGF was within the normal range (2.1 +/- 0.2 micrograms/L), urine levels were increased (3.7 +/- 0.6 micrograms/L). These results show that PDGF is increased in the circulation in some but not all myeloproliferative diseases, and suggest that this is due to abnormal in vivo release from either megakaryocytes in the bone marrow or circulating platelets.

Enzyme-Linked Immunosorbent Assay↗
PubMed1989

Blood transfusion in medically treatable chronic anemia. Pernicious anemia as a model for transfusion overuse.

Transfusion practice in patients with treatable, readily recognizable, chronic anemia was reviewed because such patients only infrequently need to be transfused. Pernicious anemia with hemoglobin concentration below 100 g/L was chosen as the model for this assessment. Sixty-two (51%) of 122 patients received blood transfusion, although most patients had chronic, low-grade symptoms despite their low hemoglobin levels and could have been satisfactorily managed without transfusion. Only 34 of the 122 had findings suggesting an urgent need to raise the blood cell count, but their transfusion rate (44%) was no different from that in patients without such findings. These observations in pernicious anemia indicate that transfusion of patients with medically reversible anemia is a common problem. They further suggest that current transfusion usage overemphasizes laboratory results (ie, hemoglobin levels) at the expense of clinical assessment of severity of symptoms. Improvement of current practice is needed, particularly in view of valid concerns about the serious side effects of transfusion, shortages of available blood resources, and health care costs.

Adolescent↗
PubMed1988

Cobalamin and osteoblast-specific proteins.

Cobalamin deficiency has well-known hematologic and neurologic effects, but little is known about its other effects. We therefore studied the effect of cobalamin on osteoblast-related proteins. We found that mean (+/- 1 SD) levels of skeletal alkaline phosphatase in the blood were lower in 12 cobalamin-deficient patients (3.89 +/- 2.19 units per liter) than in 5 nondeficient and 5 iron-deficient control subjects (7.55 +/- 3.99 units per liter). The degree of the megaloblastic anemia correlated with the reduction in skeletal alkaline phosphatase levels (r = 0.67, P less than 0.01). With cobalamin therapy, levels of skeletal alkaline phosphatase rose in 11 of the 12 cobalamin-deficient subjects but not in the controls. The cobalamin-deficient patients also had significantly lower osteocalcin levels than the control subjects (1.11 +/- 0.77 vs. 1.84 +/- 0.49 nmol per liter). During cobalamin therapy, these levels rose in the cobalamin-deficient patients but not in the controls. In contrast to the levels of osteoblast-related proteins, hepatic alkaline phosphatase levels were similar in the patients and controls and were usually unaffected by cobalamin therapy. In vitro studies of calvarial cells from chicken embryos showed that their alkaline phosphatase content was cobalamin-dependent, thus supporting our in vivo observations in humans. Our findings suggest that osteoblast activity depends on cobalamin and that bone metabolism is affected by cobalamin deficiency, but we do not yet know whether cobalamin deficiency produces clinically important bone disease.

Adult↗
PubMed1988

Pernicious anemia. The expected findings of very low serum cobalamin levels, anemia, and macrocytosis are often lacking.

When patients are examined for possible cobalamin deficiency, great stress is often placed on the presence or absence of macrocytosis and anemia and on how low the serum cobalamin level is. The present study, however, shows that only 45 (64%) of 70 consecutively diagnosed patients with pernicious anemia, the most common cause of cobalamin deficiency, had very low cobalamin levels (less than 74 pmol/L [or less than 100 ng/L]). Anemia was absent in 13 (19%) of the patients, and macrocytosis was absent in 23 (33%) of the patients; such absence was particularly common when cobalamin levels were only slightly or moderately low (74 to 184 pmol/L). Coexisting iron deficiency was responsible for the absence of macrocytosis in nine patients. Of the ten patients with neither anemia nor macrocytosis, neurological disturbance was prominent in six, including four whose only noticeable abnormality was cerebral. These observations indicate that macrocytosis and anemia, two classic features of pernicious anemia, may be overstressed in our diagnostic approach. All subnormal serum cobalamin results are best viewed as pathological until proved otherwise. Emphasis on only very low cobalamin levels risks delaying the diagnosis of pernicious anemia in a substantial proportion of cases, particularly in those without anemia or macrocytosis.

Adult↗
PubMed1988

Treatment of severe pernicious anemia: no association with sudden death.

An increased risk of early, sudden death after treatment of megaloblastic anemia has been reported. This was particularly true for severe anemia, with a mortality rate of 14%. Because no other investigations of this phenomenon have been done since these alarming findings, the experience at our medical center was reviewed. Of 219 patients with pernicious anemia, 101 had severe anemia (hemoglobin less than or equal to 80 g/L). None of the severely anemic patients died during hospitalization. Only one death occurred among all 219 patients and this death was not unexpected but attributable to coexisting diseases. Pernicious anemia, even when severe, is not associated with increased mortality after therapy.

Adolescent↗
PubMed1988

Red blood cell distribution width in untreated pernicious anemia.

The red blood cell distribution width (RDW) was studied in 26 unselected patients with untreated pernicious anemia. RDW changes were also sequentially followed after therapy in 12 patients. The mean (+/- 1 SD) RDW values were significantly higher in pernicious anemia patients than in controls (21.7 +/- 9.1% vs. 13.2 +/- 1.1%, P less than 0.0001). Nevertheless, 31% of the patients had normal RDWs. There were no consistent findings among those who had normal RDW. Most of them were in the early stages of deficiency, but some had advanced deficiency. Over half of those with normal RDW also had normal mean corpuscular volume (MCV). Overall, 9 of the 26 patients (35%) had normal MCV. Of eight patients whose RDW fell with therapy, some showed a steady fall while others had a transient rise followed by a progressive drop. Despite current advocacy that a high RDW is a sensitive and consistent finding in vitamin B12 deficiency, our findings show that a large proportion of untreated pernicious anemia patients have normal RDWs and that in contrast to iron deficiency, elevation of RDW is not necessarily the earliest indicator of vitamin B12 deficiency.

Adolescent↗
PubMed1988

Pepsinogens and other serum markers in pernicious anemia.

Pepsinogen (PG) I and PG II levels were determined in sera from 147 patients with pernicious anemia. Race, sex, age, gastrin level, and antibody status did not influence pepsinogen levels. PG I values less than 30 micrograms/L were found in 92% of cases and PG I to PG II ratios less than 3.0 in 82% of cases. At least one of these two results was abnormal in 97% of all patients with pernicious anemia. In comparison, results of other blood tests used in the investigation of pernicious anemia were less often abnormal. Serum gastrin level exceeded 200 ng/L in 90% of patients with pernicious anemia and was second to pepsinogen abnormality in diagnostic sensitivity. Results for anti-intrinsic factor antibody were positive in 73% of cases and anti-parietal cell antibody in only 52%. Although its specificity is limited, the presence of low PG I level and/or low PG I-PG II ratio is currently the most sensitive serum indicator for pernicious anemia, and absence of both can be taken as a strong argument against the diagnosis. This highly sensitive test can be combined further with the highly specific serum anti-intrinsic factor antibody test for the presumptive diagnosis of pernicious anemia when definitive tests (the Schilling test or gastric analysis for intrinsic factor) cannot be done or results are inconclusive.

Adolescent↗
PubMed1988

Monoclonal antibodies to different sites on human transcobalamin II.

Two IgG1K monoclonal antibodies to human transcobalamin II (TC II) were generated. These antibodies, 16.1 and 16.6, did not cross-react with the other two types of human cobalamin-binding proteins, intrinsic factor and R binder (TC I). Both antibodies cross-reacted with orangutan and simiang TC II but not with TC II from cynomolgus and howler monkeys, who are less closely related to humans. This finding suggests close structural similarity of human to ape TC II. The antibodies also did not react with TC II of lower mammals which included the horse, dog, guinea pig, and mouse; in particular, reaction did not occur with rabbit TC II, which has been considered structurally close to human TC II. Neither of the two antibodies was directed at the cobalamin-binding site of TC II. However, antibody 16.6 hindered TC II binding to cell receptor. This reactivity with the receptor-binding site should prove particularly useful in studies of that region of the TC II molecule.

Animals↗
PubMed1988

Combined congenital deficiencies of intrinsic factor and R binder.

Coexisting deficiencies of both intrinsic factor (IF) and R binder were identified in an Algerian boy who presented with severe megaloblastic anemia, growth retardation, and neurologic dysfunction with typical features of subacute combined degeneration of the spinal cord. The anemia responded completely to cyanocobalamin and folic acid. IF was absent from gastric juice, but acid secretion and gastric mucosa were normal. R binders were absent from gastric juices as well as from serum, saliva, and polymorphonuclear leukocytes. The patient's father exhibited absence of R binder in his serum with a low serum vitamin B12 level and was asymptomatic. This unique case of simultaneous IF and R binder deficiencies suggests a genetic association between these two functionally and immunologically dissimilar, but structurally close vitamin B12-binding proteins.

Adolescent↗
PubMed1988

Neurologic abnormalities in cobalamin deficiency are associated with higher cobalamin "analogue" values than are hematologic abnormalities.

Serum cobalamin "analogue" levels were estimated by the discrepancy in cobalamin results with radioassays done with pure intrinsic factor and R binder in 364 patients with low cobalamin levels. No differences were found among the various causes of low cobalamin levels, except for the lower "analogue" levels among pregnant women. However, 76 patients with low cobalamin levels and primarily neurologic (spinal cord, neuropathic, cerebral, or a combination of these) symptoms had significantly higher "analogue" levels than 19 patients with primarily hematologic abnormalities. Moreover, the "analogue" levels correlated with hemoglobin values and were significantly higher in patients without megaloblastic changes in their bone marrow than in patients with megaloblastosis. An analysis limited to 47 patients with pernicious anemia yielded similar findings. The seven patients with only neurologic abnormalities had higher "analogue" levels than did the nine patients with only hematologic abnormalities. Because of the higher "analogue" levels, the assay done with R binder failed to register low cobalamin levels in 33 of 76 patients with low cobalamin levels and primarily neurologic abnormality (compared with only two of 19 with hematologic abnormality) and in 10 of 20 patients with pernicious anemia who had neurologic abnormalities (compared with only two of 12 without such abnormalities). These differences between patients with hematologic disturbances and patients with neurologic disturbances, and the inverse relationship of "analogue" level with severity of anemia, suggest that the disproportionate accumulation of analogues may explain why some patients with cobalamin deficiency display neurologic abnormalities while others do not.

Adult↗