The biomechanical and morphological changes in the medial collateral ligament of the rabbit after immobilization and remobilization

The effects of immobilization and remobilization on the biomechanical and morphological properties of the femur-medial collateral ligament-tibia complex and each of its components were investigated in the rabbit. Specimens that had been obtained after periods of unilateral immobilization of the knee and remobilization were evaluated for structural properties. In addition, the mechanical properties of the substance of the medial collateral ligament and the histological characteristics of both the substance of the ligament and its sites of insertion were evaluated. After immobilization, there were significant reductions in the ultimate load and energy-absorbing capabilities of the bone-ligament complex, and an increased number of failures occurred by tibial avulsion. The tissue of the medial collateral ligament also became less stiff as a result of immobilization. Histologically, the femoral and tibial insertion sites showed increased osteoclastic activity, resorption of bone, and disruption of the normal attachment of the bone to the ligament. With remobilization, the ultimate load and energy-absorbing capabilities of the bone-ligament complex improved but did not return to normal. Failure by tibial avulsion became less frequent, and the stress-strain characteristics of the medial collateral ligament returned to normal. Histologically, the sites of insertion of the ligament also showed evidence of recovery.     

Andrology: Analysis of sperm movement in relation to the oxidative stress created by leukocytes in washed sperm preparations and seminal plasma

The addition of luminol to unprocessed semen samples resultedin the generation of chemiluminescent signals, the intensityof which was highly correlated with the level of leukocyte contamination.Despite the spontaneous oxidant-generating capacity of seminalleukocytes, no correlations were observed between leukocytecontamination and the fertility status of the subjects or anyaspect of the semen profile, including the motility of the spermatozoaor their performance in a hyaluronate penetration assay. Luminol-dependentchemiluminescence and leukocyte contamination were also correlatedin washed sperm suspensions prepared either by repeated centrifugationor on discontinuous Percoll gradients. However, in such spermsuspensions, the spontaneous generation of oxidants by contaminatingleukocytes (>2x10⁴ leukocytes/ml) was invariably associatedwith a decreased capacity for movement. Moreover, causativeassociations between leukocyte contamination, reactive oxygenspecies generation, lipid peroxidation and impaired sperm motilitywere revealed by experiments involving the selective additionor removal of activated leukocytes. From these observationswe can conclude that low concentrations of leukocytes are acommon feature of the human ejaculate and can impair sperm function,particularly in the absence of seminal plasma. These findingshave implications for our understanding of the importance ofleukocytospermia in defining the fertility of human spermatozoain vivo and in vitro.     

Altered sensorium, confusion, and vertical gaze paresis: the top of the basilar syndrome

The term "top of the basilar" has been used in reference to a group of signs and symptoms of midbrain, diencephalic, and posteroinferior hemispheric dysfunction. It has been attributed to ischemia in the territory of second- and third-order vessels that arise from the uppermost portion of the basilar artery. We report our experience with four patients who had alteration of consciousness, confusion, and vertical gaze paresis accompanied by other physical abnormalities. Extensive evaluation did not help in documenting the lesions or in understanding their pathogenesis. The top of the basilar syndrome is a not uncommon form of stroke and carries a variable prognosis. Treatment by anticoagulation may prevent further infarction in selected patients who are seen early.     

Admission stool guaiac test: use and impact on patient management.

PURPOSE: A stool guaiac test is often performed on newly hospitalized patients as part of the admission evaluation. However, little is known regarding the value of testing stool obtained by digital rectal examination. We sought to document the use of the admission stool guaiac test in a teaching hospital, to determine its diagnostic yield, and to assess its potential benefit to patients. MATERIALS AND METHODS: We performed a retrospective review of the medical records for 264 consecutive patients admitted to internal medicine services during a single month, of whom 202 received a stool guaiac test on admission. Information was collected on the frequency of guaiac testing, indications for testing, test results, and diagnoses established. RESULTS: Criteria were established to distinguish "clinically indicated" from "routine" use of the admission stool guaiac test. Indicated tests were positive more often than routinely performed tests (35% versus 11%, p less than 0.001). Most patients with positive tests received further testing for gastrointestinal disease, whether or not the test was indicated. Of 104 patients with indications, 25 were ultimately found to have gastrointestinal lesions, most of which were clinically important. Of 98 patients tested routinely, only four had diagnoses established, of whom three had benign conditions. Four of five patients with cancer had clinical indications for testing. The fifth was diagnosed only after he experienced gross rectal bleeding several days after admission. CONCLUSIONS: Like other commonly applied diagnostic tests, the stool guaiac test obtained during the admission physical examination is best reserved for patients whose clinical presentation provides a reason for testing. In patients without clinical indications, the test is of uncertain value and only infrequently leads to important diagnoses.     

Identification of secreted proteins of Mycobacterium tuberculosis by a bioinformatic approach

Proteins secreted by Mycobacterium tuberculosis are usually targets of immune responses in the infected host. Here we describe a search for secreted proteins that combined the use of bioinformatics and phoA' fusion technology. The 3,924 proteins deduced from the M. tuberculosis genome were analyzed with several computer programs. We identified 52 proteins carrying an NH(2)-terminal secretory signal peptide but lacking additional membrane-anchoring moieties. Of these 52 proteins-the TM1 subgroup-only 7 had been previously reported to be secreted proteins. Our predictions were confirmed in 9 of 10 TM1 genes that were fused to Escherichia coli phoA', a marker of subcellular localization. These findings demonstrate that the systematic computer search described in this work identified secreted proteins of M. tuberculosis with high efficiency and 90% accuracy.     

The GAA triplet-repeat sequence in Friedreich ataxia shows a high level of somatic instability in vivo,with a significant predilection for large contractions

Friedreich ataxia is commonly caused by large expansions of a GAA triplet-repeat (GAA-TR) sequence in the first intron of the FRDA gene. We used small-pool PCR to analyze somatic variability among 7190 individual FRDA molecules from peripheral blood DNA of subjects carrying 12 different expanded alleles, ranging in size from 241 to 1105 triplets. Expanded alleles showed a length-dependent increase in somatic variability, with mutation loads ranging from 47% to 78%. We noted a strong contraction bias among long alleles (>500 triplets), which showed a 4-fold higher frequency of large contractions versus expansions. Some contractions were very large; of all somatic mutations scored, approximately 5% involved contractions of >50% of the original allele length, and 0.29% involved complete reversion to the normal/premutation length (< or =60 triplets). These observations contrast sharply with the strong expansion bias seen in expanded CTG triplet repeats in myotonic dystrophy. No somatic variability was detected in >6000 individual FRDA molecules analyzed from 15 normal alleles (8-25 triplets). A premutation allele with 44 uninterrupted GAA repeats was found to be unstable, ranging in size from 6 to 113 triplets, thus establishing the threshold for somatic instability between 26 and 44 GAA triplets. Analysis of an additional 7850 FRDA molecules from serially passaged lymphoblastoid cell lines carrying nine expanded alleles (132-933 triplets) showed very low mutation loads, ranging from 0% to 6.2%. Our data indicate that expanded GAA-TR alleles in Friedreich ataxia are highly mutable and have a natural tendency to contract in vivo, and that these properties depend on multiple factors, including DNA sequence, triplet-repeat length and unknown cell-type-specific factors.     

Functional consequences of ROMK mutants linked to antenatal Bartter's syndrome and implications for treatment

The antenatal variant of Bartter's syndrome is an autosomal recessive kidney disease characterized by polyhydramnios, premature delivery, hypokalemic alkalosis and hypercalciuria. It is genetically heterogeneous, having been linked recently to mutations in an ATP- sensitive, renal outer medullary K+channel, ROMK, and earlier to mutations in the Na-K-2Cl co-transporter, NKCC2. We characterized four of the mutations reported in three heterozygous ROMK variants of antenatal Bartter's and found that each expressed a distinct phenotype in Sf9 cells. One mutation expressed normal function and appears to be an allelic polymorphism. The other three mutations produced channels with significantly reduced K+fluxes. However, the mechanisms in each case were different and reflected abnormalities in phosphorylation, proteolytic processing or protein trafficking. The different mechanisms may be important in the design of appropriate therapy for patients with this disease.      

Intestinal immune response of volunteers ingesting a strain of enteroadherent (HEp-2 cell-adherent) Escherichia coli.

Enteroadherent Escherichia coli (EAEC) strains identified by adherence to HEp-2 tissue culture cells have been incriminated epidemiologically as important etiologic agents of diarrheal disease in both adult travelers and children in developing countries. One strain, JM 221, with no recognized E. coli virulence characteristics other than adherence to HEp-2 cells, caused diarrhea in 5 of 16 volunteers ingesting it. We studied the secretory immunoglobulin A (sIgA) responses to EAEC JM 221 of five volunteers with diarrhea and five volunteers who remained healthy after challenge. sIgA was extracted from stools obtained prechallenge and 7 days postchallenge. Total sIgA was standardized for all specimens. Specific sIgA titers were determined by dot blotting with the following JM 221 antigens: water-extractable surface antigens, whole cells, lipopolysaccharides, and outer membrane proteins. All five subjects who became ill had fourfold or greater rises in titers against each of the four antigens. The five subjects who remained healthy following challenge did not exhibit significant rises in titers to any JM 221 antigens, but their mean titers were significantly higher than the mean prechallenge titers of the volunteers with diarrhea, suggesting that high intestinal sIgA titers may be protective. The significant increases in intestinal antibody against JM 221 in the subjects who became ill is further evidence of the enteropathogenicity of EAEC strains.