Molecular cloning of infectious ecotropic murine leukemia virus AK7 from an emv-14-positive AKXL-5 mouse and the resistance of AK7 to recognition by cytotoxic T lymphocytes.

The AKXL-5 recombinant inbred mouse strain is positive for the endogenous ecotropic murine leukemia virus emv-14, the only emv present in its germ line. emv-14 is of particular interest because spleen cells expressing emv-14 virus escape recognition by anti-AKR/Gross virus-specific cytotoxic T lymphocytes. We report here the isolation and characterization of a replication-competent emv clone, pAK7, derived from an AKXL-5 mouse. This clone is novel in that it encodes a variant ecotropic murine leukemia virus that, when expressed in SC.Kb target cells, fails to be recognized efficiently by anti-AKR/Gross virus cytotoxic T lymphocytes. The pAK7 clone can therefore be used to further probe mechanisms of escape from cell-mediated immunity.     

Expression analysis of the mixed function oxidase system in rat brain by the polymerase chain reaction

Metabolism of therapeutic drugs in the body by the mixed function oxidase system is an important consideration in the analysis of a drug's effectiveness. P450-dependent metabolism within the brain of a neuro-specific drug may affect the drug's course of action. To determine whether cytochrome P450 was expressed in brain, RNA was isolated from the whole brains of rats treated with a variety of known hepatic P450 inducers, including amitriptyline, imipramine, isosafrole, phenobarbital, and -naphthoflavone. The RNA was analyzed for the presence of P450 isozymes by the PCR technique. Differential expression of P450IA1, P450IIB1, P450IIB2, P450IID, and P450IIE1 was detected in the brain samples, depending on the treatment. Cytochrome P450 reductase expression was also detected in the brain samples, giving strong evidence that the brain contains a competent mixed function oxidase system under all conditions studied. (Mol Cell Biochem120: 171–179, 1993)Thesis student of the Graduate School of Biomedical Sciences, the University of Texas Health Science Center at Houston     

Randomised controlled trial of graded exercise in patients with the chronic fatigue syndrome.

OBJECTIVE: To test the efficacy of a graded aerobic exercise programme in the chronic fatigue syndrome. DESIGN: Randomised controlled trial with control treatment crossover after the first follow up examination. SETTING: Chronic fatigue clinic in a general hospital department of psychiatry. SUBJECTS: 66 patients with the chronic fatigue syndrome who had neither a psychiatric disorder nor appreciable sleep disturbance. INTERVENTIONS: Random allocation to 12 weeks of either graded aerobic exercise or flexibility exercises and relaxation therapy. Patients who completed the flexibility programme were invited to cross over to the exercise programme afterwards. MAIN OUTCOME MEASURE: The self rated clinical global impression change score, "very much better" or "much better" being considered as clinically important. RESULTS: Four patients receiving exercise and three receiving flexibility treatment dropped out before completion. 15 of 29 patients rated themselves as better after completing exercise treatment compared with eight of 30 patients who completed flexibility treatment. Analysis by intention to treat gave similar results (17/33 v 9/33 patients better). Fatigue, functional capacity, and fitness were significantly better after exercise than after flexibility treatment. 12 of 22 patients who crossed over to exercise after flexibility treatment rated themselves as better after completing exercise treatment 32 of 47 patients rated themselves as better three months after completing supervised exercise treatment 35 of 47 patients rated themselves as better one year after completing supervised exercise treatment. CONCLUSION: These findings support the use of appropriately prescribed graded aerobic exercise in the management of patients with the chronic fatigue syndrome.     

Electrical consequences of spine dimensions in a model of a cortical spiny stellate cell completely reconstructed from serial thin sections

We built a passive compartmental model of a cortical spiny stellate cell from the barrel cortex of the mouse that had been reconstructed in its entirety from electron microscopic analysis of serial thin sections (White and Rock, 1980). Morphological data included dimensions of soma and all five dendrites, neck lengths and head diameters of all 380 spines (a uniform neck diameter of 0.1 m was assumed), locations of all symmetrical and asymmetrical (axo-spinous) synapses, and locations of all 43 thalamocortical (TC) synapses (as identified from the consequences of a prior thalamic lesion). In the model, unitary excitatory synaptic inputs had a peak conductance change of 0.5 nS at 0.2 msec; conclusions were robust over a wide range of assumed passive-membrane parameters. When recorded at the soma, all unitary EPSPs, which were initiated at the spine heads, were relatively iso-efficient; each produced about 1 mV somatic depolarization regardless of spine location or geometry. However, in the spine heads there was a twentyfold variation in EPSP amplitudes, largely reflecting the variation in spine neck lengths. Synchronous activation of the TC synapses produced a somatic depolarization probably sufficient to fire the neuron; doubling or halving the TC spine neck diameters had only minimal effect on the amplitude of the composite TC-EPSP. As have others, we also conclude that from a somato-centric viewpoint, changes in spine geometry would have relatively little direct influence on amplitudes of EPSPs recorded at the soma, especially for a distributed, synchronously activated input such as the TC pathway. However, consideration of the detailed morphology of an entire neuron indicates that, from a dendro-centric point of view, changes in spine dimension can have a very significant electrical impact on local processing near the sites of input.     

Seasonal ectomycorrhizal fungal biomass development on loblolly pine (Pinus taeda L.) seedlings

Ergosterol, a membrane sterol found in fungi but not in plants, was used to estimate live mycelial biomass in ectomycorrhizae. Loblolly pine (Pinus taeda L.) seeds were sown in April 1993 and grown with standard nursery culture practices. Correlations between total seedling ergosterol and visual assessment of mycorrhizal colonization were high during July and August but low as ectomycorrhizal development continued into the growing season. Percentages of mycelial dry weight over lateral roots decreased from 9% in July to 2.5% in November because seedling lateral root dry weight accumulated faster than mycelial dry weight. Total ergosterol per seedling increased from July through February. As lateral root dry weight ceased to increase during winter months, ectomycorrhizal mycelia became the major carbohydrate sink of pine seedlings. No distinctive seasonal pattern of soil ergosterol content was observed. The impact of ectomycorrhizal fungi on plant carbohydrate source-sink dynamics can be quantitatively estimated with ergosterol analysis but not with conventional visual determination.     

Post-thawing survival of motile ram sperm after isolation by layering on protein columns

Post-thawing survival of ram sperm was examined after semen which had been layered on top of isolation columns containing solutions of bovine serum albumin (BSA) in Tris diluent was processed for freezing by the pellet method. Sperm isolated from the bottom of the BSA column had better post-thawing survival than sperm from the top of the column. The efficiency of sperm isolation was affected by the concentration of BSA in the column, the holding time of semen on the column and the concentration of sperm in the layered semen. The best post-thawing survival of sperm occurred when semen diluted to a concentration of 200 x 10(6) sperm/ml was layered on a column of 6% BSA in Tris diluent and the bottom layer of the column was isolated for freezing after two hours' holding time.     

The effect of alpha, alpha'-bis[3-(N,N-diethylcarbamoyl)piperidino]-p-xylene on human blood platelet structural physiology

alpha, alpha'-Bis[3-(N,N-diethylcarbamoyl)piperidino]-p-xylene enhances human blood platelet membrane integrity by exerting a stabilizing action at the level of the dense tubular system in surface membrane complexes known to sequester platelet calcium.     

Production of an insulin-like growth factor by osteosarcoma

To test the possibility that osteosarcoma cells produce their own growth factors, we measured levels of insulin and somatomedin C (SMC), an insulin-like growth factor, in culture media of two cell lines derived from patients with that disease. SMC but not insulin levels increased three- to ten-fold over a period of 7 days paralleling the increases in cell number. Production of SMC was inhibited by cycloheximide.