Assessment of quadriceps/hamstring strength, knee ligament stability, functional and sports activity levels five years after anterior cruciate ligament reconstruction

The purpose of this study was to examine individuals 5 years after ACL reconstruction and analyze changes involving strength, stability, function, and sports activities. Nineteen males and six females, mean age = 31.4 +/- 7.31 years, participated in this study. Fifteen subjects had received extraarticular and ten subjects had received intraarticular ACL reconstructions. Subjects completed a 100 point subjective functional activity questionnaire and a sports participation survey. Knee ligament stability was assessed during an objective knee examination. Isokinetic quadriceps and hamstring muscle strength were tested at 240 and 120 deg/sec using the Cybex II dynamometer. Anterolateral rotatory instability and positive Lachman were elicited on the operated leg for 80% of the subjects. No significant relationship was found between objective instability and the functional activity score. For the intraarticular group, a significant correlation (P less than 0.05) was found between increased quadriceps and hamstring strength on the operated leg and return to functional activities. Subjects' functional activity score was positively correlated (P less than 0.001) with their ability to participate in sports. Subjects participating in sports involving cutting and twisting motions were less successful in returning to their preinjury participation levels and reported more subjective complaints of pain, swelling, and/or instability. These results indicate that long-term progressive rehabilitation emphasizing increased quadriceps and hamstring strength to approximate the nonoperated leg may enhance successful return to functional and sports activities after ACL reconstruction.     

Postprandial acid reflux is reduced by delayed gastric emptying.

The aim of this study was to investigate influence of delayed gastric emptying on postprandial reflux in esophageal pH. Sixty-nine consecutive patients underwent 24 hour (h) esophageal pH monitoring and gastric emptying. In 24 h esophageal pH monitoring, % postprandial reflux pH<4 for 2 h after each meal (% PRT) was extracted from the 24 h pH profile. After solid test meal (1 mCi, Tc99m) was given, gastric emptying was measured with a gamma detector placed transnasally 5 cm below lower esophageal sphincter. % PRT was similar among the 34 normal, 26 delayed and 9 rapid gastric emptying rate patients. Thirty-five with a positive pH study and 34 with a negative had a similar prevalence of gastric emptying disorder. In the positive pH study group, patients with normal gastric emptying had significantly higher % PRT than those with delayed gastric emptying (22.0 vs 12.1%, P<0.05). In the same population, patients with a normal %PRT had a significantly higher prevalence of delayed gastric emptying compared with those with a positive % PRT (6/8 vs 9/27, P<0.05). In patient with abnormal acid exposure but normal % PRT on 24 h esophageal pH monitoring, gastric emptying may be delayed.     

Indium-111 labelled pooled human immunoglobulin imaging to monitor the efficacy of specific therapy for Pneumocystis carinii pneumonia

Functional imaging is ideally suited to monitoring the effect of specific therapy on disease processes. In this pilot study five patients with AIDS and Pneumocystis carinii pneumonia (PCP) were imaged with Indium-111 labelled pooled human immunoglobulin (111In-HIG) during infection and after therapy for PCP. The lung activity of t t tln-HIG, measured as a lung/heart ratio, was calculated in a study performed during infection with PCP and after therapy. In all five patients the lung/heart ratio of t t 1ln-HIG was reduced after treatment. The mean reduction in heart/lung ratio was 27% (range 12%-53%). If these results are confirmed by a larger study, ¹¹In-HIG will be useful in monitoring the response of PCP to therapy in patients with AIDS.     

Correlation between the induction of an immediate early gene, zif/268, and long-term potentiation in the dentate gyrus.

Expression of the immediate early gene zif/268 (also termed NGFI-A, Krox 24, TIS8 and Egr-1) was investigated in awake rats following various long-term potentiation (LTP) induction protocols.zif/268 mRNA (Northern blots) and protein (immunohistochemistry) levels sharply increased following LTP, and followed a time course characteristic of other immediate early genes. When measured across 3 tetanization protocols known to produce differing degrees of LTP persistence,zif/268 induction was found to be more highly correlated with LTP duration than with the magnitude of initial LTP. These data support the hypothesis that the immediate early gene zif/268 plays a role as a third messenger in the cascade of cellular and nuclear events that govern the persistence of LTP.     

Regional myocardial oxygen tension: 19F MRI of sequestered perfluorocarbon

A novel noninvasive method of measuring local myocardial oxygen tension (pO₂) In the perfused rat heart using ¹⁹F MRI is demonstrated. Tissue pO₂ was determined on the basis of the ¹⁹F spin-lattice relaxation rate (R1) of perflubron (perfluorooctyl bromide) sequestered in the heart after IV infusion of an emulsion. Spectroscopic measurement of R1 was previously used to measure a global weighted average of oxygen status. ¹⁹F MRI now provides 3D spatial resolution indicating local cardiac pO₂ under normally perfused, globally ischemic, and regionally ischemic conditions.     

Cytology and neuron-glial apposition of migrating cerebellar granule cells in vitro

In developing mammalian brain, many neurons migrate to their final position by moving in direct apposition to radially oriented glial cells. Glial-guided migration can be visualized in microcultures of mouse cerebellar cells by the combined use of cellular antigen markers and high resolution time-lapse video microscopy (Hatten et al., 1984; Edmondson and Hatten, 1987). Such studies have demonstrated the behavior of migrating cells and revealed a motile leading process on the migrating neuron that resembles an axonal growth cone and grows along extended glial fibers. To study the fine structural details of the migrating neuron and its neuron-glial apposition, we identified and monitored neurons in microcultures with video microscopy and examined the cytology and cellular contacts of the same cells with transmission electron microscopy. The cytology of the soma and leading process of migrating cells closely matches that described for granule cells in intact brain (Rakic, 1971). Newly observed structures include the presence of longitudinally oriented microtubules extending from a basal body in the soma into the leading process, and microfilament-rich filopodia arising from the soma and leading process. The most striking feature of actively migrating neurons is a specialized junction between the neuronal cell soma and apposing glial fibers. At this junction, here termed "interstitial density," the extracellular space is dilated to 20 nm and filamentous material in the intracellular cleft either spans the cleft or runs parallel to the cell membranes. Some interstitial fibrils are contiguous with, or are transmembranous extensions of, submembranous cytoskeletal elements that attach to microtubules. Interstitial junctions were not found between neurons that did not translocate in the observation period before fixation. Instead, stationary cells formed desmosomes (puncta and macula adhaerentia) at appositions with glial processes.     

Cerebellar target neurons provide a stop signal for afferent neurite extension in vitro.

The contributions of cell-cell interactions to the establishment of specific patterns of innervation within target brain regions are not known. To provide an experimental analysis of the regulation of afferent axonal growth, we have developed an in vitro assay system, based on the developing mouse cerebellum, in which afferent axons from a brainstem source of mossy fiber afferents, the basilar pontine nuclei, were cocultured with astroglia or granule neurons purified from the cerebellum. In the absence of cells from the cerebellum, pontine explants produced axons that fasciculated and extended rapidly on a culture surface treated with poly-lysine or laminin. When pontine neurites grew onto cerebellar astroglial cells, outgrowth was more abundant than on substrates alone, suggesting that glial cells provide a positive signal for axon extension. Time-lapse video microscopy indicated that the rate of neurite extension increased from less than 50 microns/hr to more than 100 microns/hr when axonal growth cones moved from the culture substratum onto an astroglial-cell surface. Acceleration of neurite extension was also observed as pontine neurites grew onto other pontine neurites. By contrast, when pontine neurites grew on granule neurons, the appropriate targets of mossy fibers, the length of pontine neurites was greatly reduced. As growing axons terminated on granule neurons, the target cells appeared to provide a "stop-growing signal" for axon extension. The length of pontine neurites decreased with increasing granule neuron density. Two lines of evidence suggested that the stop signal was contact mediated. First, video microscopy showed that pontine growth cones stopped extending after contacting a granule neuron. Second, the length of afferent axons was not reduced when pontine neurites grew at a distance from granule neurons. Competition experiments where both astroglia and granule neurons were plated together suggested that the growth arrest signal provided by granule neurons could override the growth-promoting signal provided by astroglial cells. These results suggest that specific cell-cell interactions regulate the growth of pontine afferent axons within their cerebellar target, with axoaxonal and axoglial interactions promoting axon extension and axon-target cell interactions interrupting axon extension.