Mast cell activation involves plasma membrane potential- and thapsigargin-sensitive intracellular calcium pools

Summary— The regulation and role of the intracellular Ca²⁺ pools were studied in rat peritoneal mast cells. Cytosolic free calcium concentration ([Ca²⁺]i) was monitored in fura-2 loaded mast cells. In the presence of Ca²⁺ and K+, compound 48/80 induced a biphasic increase in [Ca²⁺]i composed of a fast transient phase and an apparent sustained phase. The sustained phase was partially inhibited by the addition of Mn²⁺. DTPA, a cell-impermeant chelator of Mn²⁺, reversed this inhibition, suggesting that a quenching of fura-2 fluorescence occurs in the extracellular medium. In the absence of extracellular Ca²⁺, the transient phase, but not the sustained one, could be preserved, provided that mast cells were depolarized. The transient phase was completely abolished by thapsigargin, a microsomal Ca²⁺-ATPase inhibitor. Maximum histamine release induced by either compound 48/80 or antigen was obtained in the absence of added Ca²⁺ only when mast cells were depolarized. These histamine releases were inhibited by low doses (< 30 nM) of thapsigargin. Thapsigargin at higher doses induced histamine release which was unaffected by changing the plasma membrane potential, but was completely dependent on extracellular Ca²⁺, showing that a Ca²⁺ influx is required for thapsigargin-induced exocytosis. Together, these results suggest that the mobilization of Ca²⁺ from thapsigargin sensitive-intracellular pools induced by compound 48/80 or antigen is sufficient to trigger histamine release. The modulation of these pools by the plasma membrane potential suggest their localization is close to the plasma membrane.     

Bone and calcium homeostasis.

The principal repository of calcium is bone. Calcium enters bone largely via the trabeculae, with the rate of calcium clearance by bone approximating 50 percent. Calcium enters bone as an ion in solution, but undergoes a phase change to a solid as soon as in contact with the bone surfaces. Calcium removal from and redistribution in bone is mediated by the bone cells, principally osteoblasts and osteoclasts. Calcium enters the body via intestinal absorption, a transport process that is the vectorial result of a saturable and an non-saturable step. Calcium leaves the body in the urine and stool, with a circulating calcium ion having one chance in about four of being lost via excretion. Ions like lead can compete with calcium at the sites of calcium deposition and transport. Their rate in the body should therefore parallel that of calcium, but may be modified by differing binding affinities or interactions with specific sites and molecules.     

CURRENT CONCEPTS IN INFANT NUTRITION

Nutritional needs vary during the first year of life according to the infant's individualized pattern of growth and amount of physical activity. After delivery, the infant must make many physiologic adjustments, develop immunologic defenses, and take in adequate nutrients for survival. The type and consistency of foods change as the gastrointestinal system matures and becomes able to metabolize the components and excrete the needed metabolites of increasingly complex foods. The recommended dietary allowance for infancy is based on the amount of nutrients provided to healthy infants in human milk during the first six months of life and on the consumption of formula and increasing amounts of solid food during the second six months. The introduction of solid foods should parallel the developmental changes that occur within the central nervous system throughout the first year; these provide a level of readiness for the infant to manage foods of various textures from full liquid to soft. Even though significant technologic advances have led to changes in the way infants can be fed, human milk is still the optimal choice. Most women can be encouraged to breast-feed regardless of their own nutritional status or dietary intake. Contraindications can be managed on an individual basis. If women do not elect to breast-feed, suitable commercial formulas are available. The important issue in feeding is that of providing a variety of appropriately prepared foods offered in a nonjudgmental atmosphere so that the foundation is laid for the development of good food habits.     

Frequent ongoing T-cell receptor rearrangements in childhood B- precursor acute lymphoblastic leukemia: implications for monitoring minimal residual disease

Crosslineage T-cell receptor delta (TCR delta) rearrangements are widely used as tumor markers for the follow up of minimal residual disease in childhood B-precursor acute lymphoblastic leukemia (ALL) by polymerase chain reaction (PCR). The major drawback of this approach is the risk of false-negative results due to clonal evolution. We investigated the stability of V delta 2D delta 3 rearrangements in a group of 56 childhood B-precursor ALL patients by PCR and Southern blot analysis. At the PCR level, V delta 2D delta 3-to-J alpha rearranged subclones (one pathway for secondary TCR delta recombination) were demonstrated in 85.2% of V delta 2D delta 3-positive patients tested, which showed that small subclones are present in the large majority of patients despite apparently monoclonal TCR delta Southern blot patterns. Sequence analysis of V delta 2D delta 3J alpha rearrangements showed a biased J alpha gene usage, with HAPO5 and J alpha F in 26 of 32 and 6 of 32 clones, respectively. Comparison of V delta 2D delta 3 rearrangement status between diagnosis and first relapse showed differences in seven of eight patients studied. In contrast, from first relapse onward, no clonal changes were observed in six patients studied. To investigate the occurrence of crosslineage TCR delta rearrangements in normal B and T cells, fluorescence-activated cell sorter-sorted peripheral blood CD19+/CD3- and CD19-/CD3+ cell populations from three healthy donors were analyzed. V delta 2D delta 3 rearrangements were detected at low frequencies in both B and T cells, which suggests that V delta 2-to-D delta 3 joining also occurs during normal B-cell differentiation. A model for crosslineage TCR delta rearrangements in B-precursor ALL is deduced that explains the observed clonal changes between diagnosis and relapse and is compatible with multistep leukemogenesis of B-precursor ALL.     

Births of normal daughters after MicroSort sperm separation and intrauterine insemination, in-vitro fertilization, or intracytoplasmic sperm injection

The world's first deliveries of normal babies after use of flow cytometric separated human sperm cells (MicroSort) for preconception gender selection are reported. Offspring were of the desired female gender in 92.9% of the pregnancies. Most of these pregnancies and births were achieved after simple intrauterine insemination.      

Detecting pre-ovulatory luteinizing hormone surges in urine

The study objectives were to determine (i) if pre-ovulatory luteinizing hormone (LH) surges, undetected in urine by two immunoradiometric assays (IRMA), were detectable by an ultrasensitive immunofluorometric assay (IFMA) and (ii) the influence of creatinine adjustment on the detection and timing of the urinary LH surges. Daily urine specimens were contributed by healthy 25-36 year old volunteers during 14 ovulatory menstrual cycles for an epidemiological study conducted in 1983-1985. Specimens were selected as having been previously assayed by two IRMA without consistently detecting LH surges. These urine specimens were remeasured using an IFMA and adjusted for creatinine concentration. IFMA measurements revealed unambiguous LH surges in all cycles. Adjusting IRMA urinary LH values for creatinine concentrations revealed previously undetected LH surges in four of eight cycles. Creatinine adjustment also altered the timing of IRMA and IFMA LH surges by 1-5 days. These results demonstrate an IFMA that detects pre- ovulatory LH surges in unpreserved, frozen urine from cycles where such surges were previously undetectable. Further, creatinine adjustment can markedly affect detection and timing of the onset and peak of the urinary LH surge. While our analysis suggests that this adjustment improves the validity of the LH measure, this requires further investigation.      

Granulomatous appendicitis and the appendix in idiopathic inflammatory bowel disease

Granulomatous appendicitis is a rare condition, accounting for less than 2% of all cases of appendicitis. The initial belief that it represented a manifestation of Crohn's disease is incorrect in the great majority of cases, as only 5-10% of patients with granulomatous appendicitis develop Crohn's disease elsewhere in their gastrointestinal tract. The remaining etiologies are diverse. Unusual causes include sarcoidosis, foreign body reaction, and infection by mycobacteria, fungi, or parasites. These conditions combined explain less than 10% of cases. More recently, two etiologies have been recognized that potentially account for most of the previous "idiopathic" cases of granulomatous appendicitis. The first is infection by pathogenic Yersinia species, now demonstrated in approximately 25% of cases. The second cause may be the most common of all, namely subacute/recurrent appendicitis with interval appendectomy. This condition likely produces a granulomatous reaction in relation to a protracted secondary inflammatory response to appendicitis and temporizing measures to delay appendectomy, such as antibiotic therapy. Thus, granulomatous appendicitis only rarely represents a manifestation of Crohn's disease. Rather, the overwhelming majority of patients with this condition are cured by appendectomy alone. The appendix, however, can be involved by idiopathic inflammatory bowel disease, both Crohn's disease and ulcerative colitis. It can be involved by ulcerative colitis in patients with distal colonic involvement and sparing of the intervening colonic segment, a phenomenon known as the appendiceal "skip lesion" or "cecal patch" and this pattern of involvement does not necessarily indicate Crohn's disease. Interestingly, appendectomy has been shown to provide some protection against developing inflammatory bowel disease and in reducing its severity if performed before the onset of disease.     

Inhibition of mast cell histamine release by flavonoids and biflavonoids

The effect of 11 flavonoids and 4 biflavonoids on the release of histamine from peritoneal rat mast cells induced by compound 48/80 and calcium ionophore A23187 was studied. Dihydroflavonoids (flavanones) and (+)-catechin did not modify histamine release induced by both secretagogues. Flavone, apigenin and cromoglycate inhibited the secretion elicited by compound 48/80 but did not modify the A23187-induced secretion. The effect of kaempferol on the compound 48/80-induced histamine release was biphasic. Low doses (10 (-6) to 10 (-5)M) of the compound potentiated secretion whereas higher doses inhibited histamine secretion. Some of the drugs tested revealed a higher potency as referred to quercetin. Luteolin, a tetrahydroxyflavone and amentoflavone, a biapigenin, exhibited the highest inhibitory effects of mast cell histamine secretion.