Effects of Intermittent Training on Anaerobic Performance and MCT Transporters in Athletes

This study examined the effects of intermittent hypoxic training (IHT) on skeletal muscle monocarboxylate lactate transporter (MCT) expression and anaerobic performance in trained athletes. Cyclists were assigned to two interventions, either normoxic (N; n = 8; 150 mmHg P_IO₂) or hypoxic (H; n = 10; ∼3000 m, 100 mmHg P_IO₂) over a three week training (5×1 h-1h30.week⁻¹) period. Prior to and after training, an incremental exercise test to exhaustion (EXT) was performed in normoxia together with a 2 min time trial (TT). Biopsy samples from the vastus lateralis were analyzed for MCT1 and MCT4 using immuno-blotting techniques. The peak power output (PPO) increased (p<0.05) after training (7.2% and 6.6% for N and H, respectively), but VO₂max showed no significant change. The average power output in the TT improved significantly (7.3% and 6.4% for N and H, respectively). No differences were found in MCT1 and MCT4 protein content, before and after the training in either the N or H group. These results indicate there are no additional benefits of IHT when compared to similar normoxic training. Hence, the addition of the hypoxic stimulus on anaerobic performance or MCT expression after a three-week training period is ineffective.     

Characterization of the methotrexate transport defect in a resistant L1210 lymphoma cell line

L1210/R81 lymphoma cells are resistant to methotrexate (MTX) by virtue of a 35-fold elevation in dihydrofolate reductase and an inability to transport the folate antagonist drug effectively. In a phosphate-containing buffer there was little or no influx into the resistant cells at either 1 or 50 μm MTX. Replacement of this buffer with a 4-(2-hydroxyethyl)-1-piperazine-N′-2-ethanesulfonic acid-Mg²⁺ system resulted in an apparent influx of MTX into the resistant cells. Under these conditions, L1210/R81 cells achieved an apparent steady state at an extracellular MTX concentration of 50 μm. The apparent steady-state level of 5 nmol $\text{[}{}^3\text{H]MTX}\text{10}{}^9$ cells was well below the intracellular level of dihydrofolate reductase (45 nmol/10⁹ cells). Efflux experiments at the apparent steady state indicated that 60% of the MTX was very rapidly removed from the cells by washing. Over the range of the experiment a further 20% of the MTX effluxed more slowly ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 12}\text{min}$). The apparent influx into the resistant cells at 5 μm MTX was inhibited 13% by sodium azide (100 μm) and initially stimulated, then inhibited, by p-chloromercuriphenylsulfonic acid (100 μm). 5-Methyltetrahydrofolate (100 μm) had little effect on the process while aminopterin (100 μm) was inhibitory (68%). K_t and V values of 2 × 10^?5m and 0.31 nmol $\text{[}{}^3\text{H]MTX}\text{10}{}^9$ cells/min, respectively, were determined for the apparent influx in $\text{L}\text{1210}\text{R}\text{81}$ cells. Comparison of apparent MTX influx in the resistant cells with MTX transport in the sensitive cells indicates profound differences in the two processes. The evidence suggests that the apparent influx in the former cell line may consist of MTX binding to the cell membrane together with a small degree of MTX influx into the intracellular compartment.     

Genetic activity of allyl chloride

Allyl chloride (3-chloroprene) is mutagenic for Salmonella typhimurium and it induces gene conversions in Saccharomyces cereuisiae. It also displays DNA-modifying activity for E. coli. This is in contrast to a recent study which reported its lack of genetic activity for Salmonella typhimurium.     

Allogromia laticollaris: A Foraminiferan with an Unusual Apogamic Metagenic Life Cycle*

SYNOPSIS. The life cycles of 3 strains of Allogromia laticollaris, a monothalamous foraminiferan, have been studied. Each of the strains had a different, nonclassical, and basically apogamic, life cycle. The Cold Spring Harbor (CSH) strain regularly alternated between 2 agamontic forms: agamont I (uninucleate and diploid) and agamont II (multinucleate and diploid). The complete life cycle took 26 days. Sexual reproduction was rare (0.01%) and autogamous. Small numbers of organisms also underwent budding, binary fission, and cytotomy. The life cycles of the Towd Point (TPA) and Sippewissett (SIP) strains were comparatively abbreviated. Agamont II dominated their typical life cycles, which were completed in 16-18 days. The life cycle of SIP was basically a continuous cycling of the agamont II phase. Approximately 75% of the schizozoites of the TPA strain developed into agamont II. The other 25% alternated between agamont II and agamont I phase. In the CSH strain schizozoites with ～ 8 (range 5-15) nuclei characterized newly formed agamonts II. More nuclei (～ 25) were found in the other 2 strains. The nuclei in young agamonts II underwent rapid morphologic changes leading to a “mushroom-like” chromosome appearance and extensive RNA synthesis. Nucleolar material accumulated at the nuclear periphery and eventually was discharged to the cytoplasm. Karyokinesis took place without the breakdown of the nuclear membrane. The single nucleus of young agamont I forms was proportionally quite large. The S₁ phase occurred quite early (2-5 days) in this part of the life cycle. RNA in the CSH strain formed a compact, subcortical, coarsely granular ring, while in the TPA it was cortical and differentiated into finely granular matrix with randomly distributed coarse granules. During the G₂ phase the nucleus became further enlarged and eventually amoeba-form. Intermediate stages in nuclear breakdown were not found.     

Foetal Rat Pancreas in Organ Culture

Foetal rat pancreas (20-day postcoitum) was grown in organ culture using a natural media (serum and chick embryo extract). The media was supplemented with several adrenal and gonadal steroids; precursors, glucocorticoids, mineralocorticoids, estrogens, androgens and progesterone. The effects of the steroids on the pancreatic explants were quantitated biochemically by analysis of amylase and insulin in the incubated culture media and in the explanted pancreatic tissue, and morphologically by quantitative morphometric analysis. Corticosterone, hydrocortisone, aldosterone and dexamethasone fully preserved the acinar cell component. The effect was concentration-dependent. Deoxycorticoste-rone and cortexolone had intermediate effects even at the highest concentration. Gonadal steroids had no effect on the acinar or islet component in this culture system. Some of the steroids inhibited the selective islet growth seen in the control explants as well as inhibiting insulin secretion. The relationship between these data and other work in this area is summarised. In addition, the possible implications of these data relating to normal in vivo pancreatic development are discussed.     

Replication ofAutographa californica nuclear polyhedrosis virus in a thymidine kinse deficientSpodoptera exigua cell line (SE-UCR-1A)

Summary Cultivation of aSpodoptera exigua cloned cell line (SE-UCR-1A) for 8 to 9 mo. in a medium containing increasing amounts of bromodeoxyuridine (BUdr) resulted in the selection of a BUdr-resistant subline unable to grow in TNMFH medium supplemented with HAT (hypoxanthine, 10⁻⁴ M; aminopterin, 10⁻⁷ M; thymidine, 10⁻³ M). Subsequent assay of this subline revealed an absence of thymidine kinase (TK) activity. The specific activity of the wild-type (wt) cells was 878±192 counts per min (cpm)/μg supernatant protein compared to 9 cpm/μg for the BUdr-resistant, HAT-sensitive subline. In addition the wt activity was inhibited >90% by addition of BUdr to the assay, indicating that the activity is predominantly due to TK and not to a nonspecific nucleoside phosphotransferase. The morphology of the TK-deficient (−) cells was indistinguishable from that of wt cells. The doubling time for wt cells in TNMFH was 16 h; however, in TNMFH-HAT it was 36 h. In comparison the TK(−) cells in TNMFH had a doubling time of 61 h. Cultivation of TK(−) cells in nonselective TNMFH for 14 mo. to date has not changed the TK(−) characteristic of the subline. The host-cell TK was not required for development of progeny virus fromAutographa californica NPV inoculum. Although similar numbers of cells were infected (80 to 90%) in the wt and TK(−) lines and extracellular virus was generated at similar rates to similar titers in both media, the initial appearance of virus in the medium of TK(−) cell was delayed 10 to 20 h compared to wt cells. In addition, polyhedra appearance was similarly delayed in TK(−) cells and only 20 to 25% of the cells contained >10 polyhedra per cell compared to 75 to 90% for wt cells. Also, during infection of wt cells, specific activity of TK increased twofold peaking at 20 to 30 h postinfection, yet there was no stimulation of TK activity in infected TK(−) cells.