Assignment of the prealbumin (PALB) gene (familial amyloidotic polyneuropathy) to human chromosome region 18q11.2–q12.1

Summary The assignment of the human prealbumin (PALB) gene to chromosome region 18q11–q12.1 has been achieved using a human genomic probe in the study of human-mouse somatic cell hybrids and by in situ hybridization. Because familial amyloidotic polyneuropathy was reported previously to be due to a mutation in prealbumin, it can be inferred that the gene for this disorder also maps to 18q11.2–q12.1.     

Two ATP-activated conductances in bullfrog atrial cells

Currents activated by extracellular ATP were studied in single voltage-clamped bullfrog atrial cells. Rapid application of ATP elicited currents carried through two different conductance pathways: a rapidly desensitizing conductance reversing near -10 mV, and a maintained, inwardly rectifying conductance reversing near -85 mV. ATP activated the desensitizing component of current with a K 1/2 of approximately 50 microM and the maintained component with a K 1/2 of approximately 10 microM. Both types of current were activated by ATP but not by adenosine, AMP, or ADP. The desensitizing current was selectively inhibited by alpha, beta-methylene ATP, and the maintained, inwardly rectifying current was selectively suppressed by extracellular Cs. The desensitizing component of current was greatly reduced when extracellular Na was replaced by N-methylglucamine, but was slightly augmented when Na was replaced by Cs. GTP, ITP, and UTP were all ineffective in activating the desensitizing current, and of a variety of ATP analogues, only ATP-gamma-S was effective. Addition of EGTA or BAPTA to the intracellular solution did not obviously affect the desensitizing current. Fluctuation analysis of currents through the desensitizing conductance suggested that current is carried through ionic channels with a small (less than pS) unitary conductance.     

Cytotoxicity of Fusarium species mycotoxins and culture filtrates of Fusarium species isolated from the medicinal plant Tribulus terrestris to mammalian cells

Ayurvedic medicine, which uses decoctions made of medicinal plants, is used to cure diseases in many Asian countries including Sri Lanka. Although proper storage facilities for medicinal plants are unavailable in Sri Lanka, neither the potential for growth of toxigenic fungi nor their ability to produce mycotoxins in stored medicinal plants has been investigated. We isolated three Fusarium species, F. culmorum, F. acuminatum and F. graminearum from the medicinal plant Tribulus terrestris. Culture extracts of the 3 Fusarium spp. were cytotoxic to mammalian cell lines BHK-21 and HEP-2. Three toxic metabolites produced by Fusarium spp; T-2 toxin, zearalenone, and diacetoxyscirpenol were also cytotoxic to the same mammalian cell lines. The 3 Fusarium spp. grown on rice media produced zearalenone. Plant material destined for medicinal use should be stored under suitable conditions to prevent growth of naturally occurring toxigenic fungi prior to its use.     

Toxigenic Aspergillus flavus and aflatoxins in Sri Lankan medicinal plant material

The fungal flora of 6 Asian medicinal plants, Aerva lanata (Linn.) Juss. Alyssicarpus vaginalis D.C., Tribulus terrestris Linn. Adhatoda vasica Nees., Centella asciatica (L.) Urb., Cardiospermum halicacabum Linn. was determined. After surface disinfection Aspergillus spp. were most frequently observed. Aspergillus flavus, isolated from Alyssicarpus vaginalis and Aerva lanata produced aflatoxins in culture. Aflatoxin B₁ was also detected in a sample of Aerra lanata at a level of 0.5 g/g. Plant material destined for medicinal use should be stored carefully prior to its use to prevent growth of naturally occurring toxigenic mold fungi.     

Site recognition by protein-primed T cells shows a non-specific peptide size requirement beyond the essential residues of the site. Demonstration by defining an immunodominant T site in myoglobin.

In previous studies, six T sites within myoglobin (Mb) were localized. To define precisely the boundaries of the T sites, a new approach is introduced and applied here to the T site residing within residues 107-120 of Mb. Two sets of peptides were synthesized. One set represents a stepwise elongation by one-residue increments of the Mb sequence. The other set represents an identical stepwise addition of one-residue increments of the Mb sequence, but which were extended by additional unrelated (nonsense) residues to a uniform size of 14 residues. The longer peptides (nonsense-extended) usually gave higher proliferative responses than did their shorter counterparts having the same Mb region. Thus a minimum peptide size is required for optimal T-cell stimulation. The T site subtends, in three high-responder mouse strains, residues 109-119 or 110-120, depending on strain, and, in three low-responder strains, maps to residues 108-120. Thus, in this case, the T site coincides with the site of B-cell recognition and resides in a small discrete surface region of the protein chain.     

A comparison of the effect of three fungicides on growth and roridin E production by Myrothecium roridum

Three fungicides, chlorothalonil, dichloran and mancozeb were studied to determine the effects on growth and production of roridin E by Myrothecium roridum in vitro. With increasing concentrations of fungicides, both growth and production of roridin E were inhibited. Of the three fungicides, chlorothalonil was much more effective in the inhibition of growth and production of roridin E, than dichloran and mancozeb.     

Suppression of the responsiveness of lymphocytes from cancer patients triggered by co-culture with autologous tumor-derived cells

The question as to whether or not cancer patients have "tumor antigen"-induced suppressor T cells is of considerable interest and importance. As an approach to that question, the effect of addition of autologous irradiated tumor-derived cells (TDC) on the mixed lymphocyte response (MLR) of patients' lymphocytes (Ly) and of healthy donor Ly was tested. The rationale for these experiments was based on the fact that circulating antigen-responsive blood lymphocytes can be reactivated in vitro by exposure to the appropriate antigen. Thus, if there are circulating tumor "antigen"-reactive suppressor Ly, exposure to TDC as a source of the antigen should reactivate those cells. Reactivation of suppressor cells might result in diminished responsiveness to other stimuli such as alloantigens in the mixed leukocyte culture. We found that the addition of TDC to Ly cultures produced four distinct patterns of reaction. In 26 of the 74 different patient-tumor assays, the addition of autologous TDC to the patient cultures inhibited MLR, but the addition of the same TDC to cultures of Ly from healthy donors had no effect or increased their responsiveness (Specific Suppression). In 21 cases, the addition of autologous TDC to the patient cultures suppressed the MLR and the addition of the same TDC to control cultures suppressed the response of some but not all the healthy donors (Selective Suppression). In four cases, the addition of TDC to the cultures suppressed the MLR of the patients and all of the control donors (Nonspecific Suppression). In 23 cases, the addition of autologous TDC resulted in no suppression of the patient MLR or of any of the simultaneously tested normal donors (No Suppression). When TDC of patients with noninvasive bladder cancer were added to their own Ly cultures, only four of 11 produced specific or selective suppression compared to 11 of 12 when TDC came from patients with superficially invasive cancer. These data provide indirect evidence to support the hypothesis that human tumors induce circulating suppressor cells that may be reactivated in vitro by co-culture with TDC.     

Selective Utilization of Pyrimidine Deoxyribonucleosides for Deoxyribonucleic Acid Synthesis in Pneumococcus

When pyrimidine deoxyribonucleosides are supplied to growing cultures of Diplococcus pneumoniae, they are selectively used for incorporation into deoxyribonucleic acid (DNA). Differently labeled molecules of deoxyuridine, thymidine, and deoxycytidine were used to study the precursor pathways of this organism. Each of these preformed pyrimidine deoxynucleosides is incorporated intact (i.e., without cleavage of the glycosidic bond) and is predominantly recoverable as DNA thymidine. During the utilization of deoxycytidine and deoxyuridine by pneumococci, large proportions of the available precursor are converted to free thymidine, which is secreted back into the growth medium. The biochemical pathways for selective incorporation into DNA and the regulation of concentrations of intracellular thymidine compounds by excretion of free thymidine are discussed.     

Time-Lapse Cinemicrographic Studies of X-Irradiated HeLa S3 Cells: II. Cell Fusion

Analysis of time-lapse cinemicrographs of X-irradiated HeLa S3 cells has shown that the incidence of cell fusion was increased from 0.9% (following 1267 divisions) in control cells to an average of 22% (following 655 divisions) in cells irradiated with 500 rad doses of 220 kv X-rays. The incidence depended on the stage of the generation cycle at which the parent cells were irradiated. It was nearly constant in the first three postirradiation generations. Fusion occurred at all stages of the generation cycle, but preferentially during the first 20%. Cells undergoing fusion progressed more slowly through the generation cycle and had a higher probability of disintegrating than did irradiated cells that did not fuse. The occurrence of fusion was clonally distributed in the population. It took place only between sister (or closely related) cells. Protoplasmic bridges were often visible between sister cells prior to fusion. Giant cells arose only as a result of fusion. The incidence of multipolar divisions, though higher than in unirradiated cells, was only 5.5% in cultures irradiated with 500 rads. Fusion occurred following 85% of the multipolar divisions and was often followed by a multipolar division.