Chronic fatigue syndrome, the immune system and viral infection.

The chronic fatigue syndrome (CFS), as defined by recent criteria, is a heterogeneous disorder with a common set of symptoms that often either follows a viral infection or a period of stress. Despite many years of intense investigation there is little consensus on the presence, nature and degree of immune dysfunction in this condition. However, slightly increased parameters of inflammation and pro-inflammatory cytokines such as interleukin (IL) 1, IL6 and tumour necrosis factor (TNF) α are likely present. Additionally, impaired natural killer cell function appears evident. Alterations in T cell numbers have been described by some and not others. While the prevalence of positive serology for the common herpes viruses appears no different from healthy controls, there is some evidence of viral persistence and inadequate containment of viral replication. The ability of certain herpes viruses to impair the development of T cell memory may explain this viral persistence and the continuation of symptoms. New therapies based on this understanding are more likely to produce benefit than current methods.

The effect of eccentric strength training at various speeds on concentric strength of the quadriceps and hamstring muscles.

This study investigated the effect of eccentric training on concentric strength of the quadriceps and hamstring muscles. The dominant legs of 43 college-age males were pretested concentrically using the KIN-COM(R) at speeds of 60 and 180 degrees /sec. Twenty-eight treatment subjects trained eccentrically at one of the testing speeds for a period of eight weeks; the remainder served as the control group. Prior to each training session, the subjects gave a subjective evaluation of muscle soreness. Delayed muscle soreness did not affect the subjects' ability to train eccentrically. A concentric posttest was taken to determine any treatment effects. The quadriceps muscle did not show any significant change after eccentric training. Eccentric training at 60 and 180 degrees /sec significantly increased the concentric strength of the hamstrings. Eccentric training does appear to be effective in developing concentric strength in the hamstrings. The speed of eccentric training was not a factor in concentric conditioning. J Orthop Sports Phys Ther 1991;13(5):226-230.

Identification of the regions of Fv1 necessary for murine leukemia virus restriction.

The Fv1 gene restricts murine leukemia virus replication via an interaction with the viral capsid protein. To study this interaction, a number of mutations, including a series of N-terminal and C-terminal deletions, internal deletions, and a number of single-amino-acid substitutions, were introduced into the n and b alleles of the Fv1 gene and the effects of these changes on virus restriction were measured. A significant fraction of the Fv1 protein was not required for restriction; however, retention of an intact major homology region as well as of domains toward the N and C termini was essential. Binding specificity appeared to be a combinatorial property of a number of residues within the C-terminal portion of Fv1.

Use of a transient assay for studying the genetic determinants of Fv1 restriction.

To probe the genetic determinants controlling the interaction between the retroviral restriction gene Fv1 and its murine leukemia virus target, we set out to develop rapid, transient assays for Fv1 function. Cells were transfected or transduced with Fv1 expression plasmids which can produce green fluorescent protein via an internal ribosome entry site positioned between the Fv1 and green fluorescent protein coding sequences. Fv1 function was then assessed by comparing virus replication in green fluorescent protein-positive and -negative cells, using retroviral vectors encoding a second fluorescent marker, yellow fluorescent protein, or beta-galactosidase. Using this assay, we could show that Fv1 specificities were not as absolute as previously thought, since the Fv1(b) allele was capable of interacting with "nonrestricted" B- and NB-tropic viruses and by shuffling the n- and b-alleles of Fv1, it was possible to generate a Fv1 molecule capable of restricting N-, B-, and NB-tropic viruses equally efficiently. Further, we could show that the presence of nonrestricting Fv1 in the same cell as restrictive Fv1 abrogates restriction, implying competition for binding to the retroviral target.