Deletion mapping of the medulloblastoma locus on chromosome 17p

Isochromosome 17q has previously been observed consistently in cytogenetic studies of medulloblastoma, the most common posterior fossa neoplasm in children. We performed a restriction fragment length polymorphism (RFLP) investigation of medulloblastoma which showed a loss of chromosome 17p sequences in 45% of these tumors. This finding was predictive of a poor clinical response to treatment. A contiguous panel of markers permitted mapping of the deletion to 17p12-p13.1, the same chromosomal region for which loss of alleles has been shown in tumor specimens from patients with colon cancer, and the same region to which the p53 gene has been mapped. This suggests that medulloblastoma is associated with a recessive oncogene on chromosome 17p that may be involved in the genesis of several embryologically unrelated neoplasms and that the absence of this gene in tumor tissue has prognostic significance.     

Guidelines for the Control of Human Immunodeficiency Virus Infection in Adolescents

Although adolescents account for only 0.4% of reported cases of the acquired immunodeficiency syndrome (AIDS) in the United States, they are sexually active and, therefore, at risk of acquiring human immunodeficiency virus (HIV) infection. To address issues of HIV control in adolescents, we developed guidelines that emphasize education and medical care and deemphasize antibody testing. For adolescents known to be infected with HIV, we recommend no restrictions on access to educational or treatment programs except when their health providers recommend such restrictions to protect them from exposure to opportunistic infections. For adolescents of unknown antibody status with a possible previous exposure to HIV, we recommend that as long as the incidence of HIV infection and clinical AIDS remains low, there should be no restrictions on residential placements and no routine antibody testing.     

Determination of the Cellular Mechanisms Regulating Thermo-Induced Stem Growth in Thlaspi arvense L

Field pennycress (Thlaspi arvense L.) is a species with a cold requirement for the initiation of reproductive development (thermoinduction). Work in this laboratory has been focused on elucidating the biochemical and molecular mechanisms underlying the bolting or rapid stem elongation response that is an intricate part of reproductive development in this species. In the present paper the cellular basis for thermo-induced stem growth was determined. Evidence is presented indicating that bolting results from the production of new cells that elongate to their original length before thermoinduction. This increase in cell division occurs in the pith and cortex approximately 0.5 to 5.0 millimeters below the stem apex. For at least the early stages of thermo-induced stem growth, enhanced cell elongation does not appear to be a factor because average lengths of pith cells from stems of thermo-induced plants were similar or less than noninduced controls. In addition, both the amount of increase in the production of new pith cells and stem growth were positively correlated with the length of the cold treatment. Two other lines of evidence are presented corroborating previous assertions (JD Metzger [1985] Plant Physiol 78: 8-13) that gibberellins mediate thermo-induced stem growth in field pennycress. First, treatment of noninduced plants with gibberellin A₃ completely mimicked the effects of a 4-week cold treatment on mitotic activity in the pith and cortex. Second, very little increase in the production of new cells was observed in the pith and cortex of thermo-induced plants of a gibberellin-deficient dwarf mutant of field pennycress. It is also shown that the influence of photoperiod on stem growth is mediated by an effect on the final length that cells ultimately attain.     

Synthesis of novel immunologically active tripalmitoyl-S-glycerylcysteinyl lipopeptides as useful intermediates for immunogen preparations

The synthesis and characterization of lipopeptides consisting of the lipoamino acid N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-[R]-cysteine (Pam3Cys-OH) and different peptide segments and/or spacer molecules is described. Pam3Cys-peptides, which are derived from the immunologically active N-terminus of bacterial lipoprotein, were obtained either by solution or solid phase peptide synthesis. In particular, the amphiphilic and water-soluble lipohexapeptides Pam3Cys-Ser-(Lys)4 and Pam3Cys-Ser-(Glu)4 proved to be potent macrophage and B-cell activators and non-toxic, non-pyrogenic immune adjuvants in combination with or covalently linked to antigens and haptens.     

Identification of Endogenous Gibberellins in the Winter Annual Weed Thlaspi arvense L

Eleven endogenous gibberellins (GAs) were identified by combined gas chromatography-mass spectrometry in purified extracts from shoots of field pennycress (Thlaspi arvense L.): GA_{1,9,12,15,19,20,24,29,44,51,53}. Traces of GA₈ and GA₂₅ were tentatively indicated by combined gas chromatography-mass spectrometry-selected ion monitoring. Comparison of the total ion current traces indicated that GA₁₉ and GA₄₄ were most abundant, while GA_{12,15,20,24,29,53} occurred in lesser amounts. Only small amounts of GA_1,9,51 were present. The levels of GA₈ and GA₂₅ were barely detectable. Consideration of hydroxylation patterns of the ent-gibberellane ring structure indicates two families of GAs: one with a C-13 hydroxyl group (GA_{1,8,19,20,29,44,53}) and another whose members are either nonhydroxylated (GA_{9,12,15,24,25}) or lack a C-13 hydroxyl group (GA₅₁). This suggests that in field pennycress there are two parallel pathways for GA metabolism with an early branch point from GA₁₂: an early C-13 hydroxylation pathway, leading ultimately to GA₁ and GA₈ and a C-13 deoxy pathway culminating in the formation of GA₉ and GA₅₁.     

Dissociation of the receptor for immunoglobulin E in mild detergents

We previously showed that, in the absence of phospholipids, exposure of the tetrameric receptor for immunoglobulin E to mild detergents dissociates the intact beta chain and two gamma chains from the alpha chains. Having developed a practical method for assaying the dissociation, we have now explored a variety of different detergents, detergent concentrations, temperatures, times, salts, pHs, and other factors that influence the detergent-induced dissociation. Our findings should be useful for optimizing the stability of the receptor and for future studies on recombination of the subunits. The data suggest the following: (1) The critical perturbant is micellar detergent. (2) Unlike solubilization of membranes, where a molar ratio of micellar detergent:lipid of 2 is adequate, dissociation of the receptor is incomplete even at molar ratios of micellar detergent:receptor of greater than 10(5) and may be limited by a reversible component. (3) Detergents that are best for solubilizing membranes are also best for dissociating the receptors. (4) The latter observation and other data implicate bound lipid as stabilizing the receptor. Our findings may be applicable to the study of interactions between membrane proteins in general.     

Phase separation of the receptor for immunoglobulin E and its subunits in Triton X-114

Above its critical micelle concentration, Triton X-114 in solution forms two phases at room temperature: a lower phase containing supramicellar aggregates and an upper phase largely depleted of detergent. This property of the detergent is potentially useful for separating under mild conditions proteins that bind detergent from those that do not (Bordier, C. (1981) J. Biol. Chem. 256, 1604-1607). We studied the distribution of the receptor for immunoglobulin E (IgE) and its subunits in the two phases. IgE and IgE complexed either with intact receptors or with the alpha chains of the receptor alone are principally partitioned into the upper phase, whereas the unliganded receptor as well as the isolated alpha, and especially the beta and gamma chains of the receptor, preferentially partition into the lower detergent phase. Chromatography of IgE and of the subunits of the receptor on a hydrophobic support showed that the beta and gamma chains have a considerably greater hydrophobic surface than the alpha chains or IgE. These results indicate that the distribution of a protein in the two phases of phase-separated Triton X-114 is not an all-or-none effect based upon whether it binds detergent or not. Rather, it reflects the overall balance between the hydrophobic and hydrophilic properties of the protein's surface.     

Role of intracellular pH in muscle fatigue

Intracellular pH of in vitro diaphragm preparations was determined following low- (5 Hz, 1.5 min) and high- (75 Hz, 1 min) frequency stimulation, using glass microelectrodes of the liquid membrane type (pHm). Results were compared with values obtained by the standard homogenate technique (pHh). High- and low-frequency stimulation reduced peak tetanic tension to 21 +/- 1 (SE) and 71 +/- 2% of initial values, respectively. Peak tetanic tension returned to resting values after 10- to 15-min recovery from high- or low-frequency stimulation. Resting pHm was 7.063 +/- 0.011 (n = 72), and after fatiguing stimulation declined to values as low as 6.33. During recovery pHm significantly increased and by 10 min had returned to prefatigue values. No difference was observed in the recovery of pHm between the low- and high-frequency stimulation groups (analysis of variance test, ANOVA), and in both groups pHm recovery was highly correlated to the recovery of peak tetanic tension (r = 0.94, P less than 0.001). Resting pHh was 7.219 +/- 0.023 (n = 13), which was significantly higher than the pHm value. In contrast to pHm, intracellular pHh was significantly higher during recovery from 75- vs. 5-Hz stimulation (P less than 0.05). For both groups pHh increased significantly with time and by 10 min returned to prestimulation values. The ANOVA test demonstrated that pHh values were significantly higher than pHm values during recovery from fatigue. The results from this study support our hypothesis that fatigue from both high- and low-frequency stimulation is at least partially due to the deleterious effects of intracellular acidosis on excitation-contraction coupling.     

A New Plating Medium for the Isolation of Enteric Pathogens: II. Comparison of Hektoen Enteric Agar with S S and E M B Agar

During this study, 2,855 stool specimens from patients at Cook County Hospital were cultured for enteric pathogens. Hektoen Enteric Agar (HE) was compared with E M B and S S Agars by replicate samplings with both direct and indirect methods. Shigella species were recovered more than twice as often on HE Agar as on S S Agar by both methods. With the direct method only, out of 98 Shigella isolated, 97 were isolated from HE Agar, 74 were recovered from E M B Agar, and 40 were found on S S Agar. In addition, HE yielded better isolation of Salmonella strains than did S S or E M B by either direct or indirect methods. The greater efficiency of HE medium is discussed with respect to colonial recognition of enteric pathogens.