Biomedical subjects
C Frank
Publications and source records attributed to C Frank.
Water content alters viscoelastic behaviour of the normal adolescent rabbit medial collateral ligament.
Testing environment is an important factor in the outcome of mechanical tests on connective tissue. The purpose of this investigation was to determine the effect of ligament water content on ligament mechanical behaviour by altering the test environment. Water content of medial collateral ligament (MCLs) from 19 three-month-old New Zealand White rabbits was varied in subsets of ligaments pairs by means of immersion in 2, 10 or 25% sucrose or 0.9% phosphate-buffered saline (PBS) solutions for 1 h. One knee joint was cycled 50 times in the designated solution (experimental), while the contralateral knee (uncycled control) was simultaneously soaked in the same tank. Following cycling, the water contents of both test and control ligaments were determined. Water contents of 22 normal MCLs were determined immediately post-sacrifice and served as 'normal water content' controls. Normalized peak cyclic load changes were used as a measure of the viscoelastic behaviour of each MCL. Results demonstrated that only ligaments soaked (but not cycled) in a 10% sucrose solution had water contents (60.5 +/- 2.5%) which were statistically similar to the 22 fresh normal MCLs (63.9 +/- 6.0%). Ligaments soaked in PBS (74.0 +/- 1.3%) or 2% sucrose (69.2 +/- 2.3%) had significantly higher water contents compared to fresh normal MCLs. Ligaments with higher water contents (e.g. soaked in PBS or 2% sucrose) demonstrated greater cyclic load relaxation compared to ligaments with lower contents (e.g. soaked in 25 or 10% sucrose). Different fluid test environments can significantly alter ligament water content and, in turn, significantly affect ligament viscoelastic behaviour.
Effects of adenosinergic drugs on hypoxia-induced electrophysiological changes in rat hippocampal slices.
The effects of adenosinergic antagonists caffeine and DPCPX, and of the adenosinergic agonists L-PIA, CPA and CGS 21680 were investigated on fully and partially reversible hypoxia-induced electrophysiological changes in rat hippocampal slices. The influence of a high potassium solution and of the N-methyl-D-aspartate antagonist dizocilpine (MK 801) was also tested. The latency to obtain a 50% decrease in the amplitude of the CA1 population spike (CA1 PS) during a short- (5-10 min) lasting hypoxic period was significantly increased (P less than 0.01) by slice perfusion with caffeine (50 microM), DPCPX (0.2 microM), and by increasing (from 3 to 4 mM) the potassium concentration in the medium bathing the hippocampal slices. The latency was significantly decreased (P less than 0.01) by slice perfusion with L-PIA (0.2 microM) and CPA (0.05 microM). It was not significantly modified by CGS 21680 (5 microM). The incidence of reappearance of the CA1 PS during reoxygenation after long- (45 min) lasting hypoxia was significantly increased (P less than 0.05) by slice perfusion with MK 801 (50 microM), while it was not significantly affected by slice perfusion with caffeine (50 microM) or DPCPX (0.2 microM) or L-PIA (0.2 microM) or CPA (0.05 microM) or CGS 21680 (5 microM). The results indicate a prevalent involvement of the A1 adenosine receptors in the early mechanisms underlying hypoxia-induced reversible changes. Adenosine seems to have a limited role in the late mechanisms occurring after a long-lasting hypoxic period.
Hippocampal long-term potentiation in nucleus basalis magnocellularis-lesioned rats.
The probability of hippocampal long-term potentiation induction in the mossy fiber CA3 and commissural/associational CA3 responses and the cortical levels of choline acetyltransferase (ChAT) activity were compared in right nucleus basalis magnocellularis (NBM)-lesioned rats. A 50% reduction in the right cortical ChAT activity was demonstrated 4 weeks after an ibotenic acid lesion of the NBM. No significative differences were found in the probability of LTP induction of right hippocampal slices in sham-operated rats from 10 to 40 days after the injection into the right NBM. On the contrary, a progressive and significative increase in the probability of LTP induction was shown in right hippocampal slices of NBM-lesioned rats from 10 to 40 days after the injection of ibotenic acid into the right NBM. The results demonstrated the appearance of a paradoxical increase of hippocampal synaptic plasticity when the cortical cholinergic biochemical alterations are still present. This finding might be responsible for a behavioural recovery, in NBM-lesioned rats.
Collagen fibril diameters in the healing adult rabbit medial collateral ligament.
This study was carried out to test the hypothesis that improvements in ligament scar mechanical behavior during healing may be related, in part, to increases in collagen fibril diameters. Forty-eight adult female New Zealand White rabbits had standardized midsubstance gap injuries created in their right medial collateral ligaments (MCLs) and were allowed normal cage activity until sacrifice in groups of 12 at 3, 6, 14 or 40 weeks post-injury. Eight animals in each group had both MCLs tested biomechanically while 4 animals had transmission EM investigation of midsubstance collagen fibril diameters by a standardized protocol. Results of mechanical tests showed a three- to fourfold increase in scar strength and stiffness over the intervals of healing studied while there was no change in collagen mean fibril minimum diameters. These results demonstrate no correlation between material or structural properties of scar and collagen fibril diameters in this model of healing and suggest that other mechanisms for scar mechanical improvement under these conditions must be investigated.
New drugs on the horizon.
The agents covered in this article are useful in a wide range of illnesses, including infections, cancers, cardiovascular and gastrointestinal diseases, and others. One of the major forces driving the development of new drugs is the use of biotechnology. Biotechnology encompasses the techniques of recombinant DNA and monoclonal antibody technologies to produce protein drugs that have not been previously available in sufficiently pure form or in adequate quantities. As new drugs are developed, the authors hope that intensified efforts will be geared towards the development of unique drugs that offer important therapeutic gains.
Immobilization alters cell metabolism in an immature ligament.
This investigation examined the metabolic and cellular effects of immobilization on immature rabbit medial collateral ligaments (MCLs). Thirty-two three-month-old rabbits had their right knee pinned in flexion for intervals of two weeks, one month, two months, or three months before being killed for comparison with MCLs from nonpinned contralateral controls and MCLs from 16 normal age-matched controls. Twelve animals were studied by gait analysis after either one month or three months of immobilization and were killed with the others for in vitro analysis of ligament mass, collagen synthesis, plasminogen activator secretion, or DNA content. Immobilized hindlimbs carried less weight than did contralaterals, and MCLs from those hindlimbs synthesized less collagen and secreted less plasminogen activator than did controls at all intervals. Contralaterals also showed some signs of altered cell metabolism compared with normal controls, suggesting that they are not normal by these assessment criteria. With increasing periods of knee immobilization, immobilized MCLs switched progressively from an anabolic to a more catabolic state, apparently contributing to the failure of immobilized ligaments to increase normally in mass. Knee immobilization alters the metabolic behavior of MCLs in both knees in growing rabbits, and, based on these results, either knee joint motion or hindlimb load bearing could be necessary for normal rabbit medial collateral ligament growth and maturation.
Synovial fluid stimulates the proliferation of rabbit ligament. Fibroblasts in vitro.
This study was designed to test the hypothesis that synovial fluid may be inhibitory to cell proliferation. The effects of bovine synovial fluid (SF) and hyaluronic acid (HA) on the proliferation of normal rabbit medial collateral ligament (MCL), anterior cruciate ligament (ACL), and MCL scar cells were therefore investigated. Cell lines established from rabbit tissues were plated, incubated, and allowed to attach before treatment with varying concentrations of SF, HA, and a balanced salt solution (BSS). The BSS group was added as a control to observe the effects of media dilution alone on cell proliferation. Cell numbers from each group were quantified at 24, 48, 72, and 96 hours. Results showed that for all cell types, cell proliferation during the log phase of growth was significantly stimulated by SF. Maximum stimulation occurred in 20% SF with stimulation decreasing at higher concentrations of SF. HA had virtually no effect on scar and ACL cells, and only a slight stimulatory effect on MCL cells. Media dilution had no effect on scar cells and began to inhibit cell proliferation of ACL and MCL cells only at high dilutions. These findings suggest that low concentrations of bovine SF stimulate proliferation of rabbit ligament and scar fibroblasts in vitro by a mechanism that appears not to involve HA. Even in high concentrations, SF was not inhibitory to proliferation. The implications of these findings to ligament healing and normal ligament physiology require further investigation.
The effects of initial end contact on medial collateral ligament healing: a morphological and biomechanical study in a rabbit model.
In this investigation, the effect of initial end contact on medial collateral ligament (MCL) healing was studied in the rabbit model. Sixty-eight 1-year-old New Zealand white rabbits were separated into two groups. In one group, a 4 mm saggital Z-plasty was performed in the right MCL midsubstance (contact group), and in the other group, an analogous 4 mm midsubstance segment was removed (gap group). Left knees were unoperated to serve as internal contralateral MCL controls. Animals had unrestricted cage activity until sacrifice in groups of eight at 3, 6, 14, and 40 weeks postoperatively. Early results demonstrated that contact and gap injuries healed with what appeared to be scar tissue both morphologically and biomechanically. In both groups, laxities recovered to their contralateral values within 6 weeks and biomechanical viscoelastic behaviors recovered to 68-92% of contralaterals by 14-40 weeks. Despite these similarities, contacts showed morphological and biomechanical evidence of improved healing over gaps. Contact scars remodeled more quickly, recovered laxity more quickly, and were generally closer to contralaterals than gaps in terms of their structural strength, stiffness, and material behaviors, after 40 weeks of healing. With the exception of appearances and failure stress, all measured properties of contact healing MCLs were statistically indistinguishable from contralateral MCLs at 40 weeks of healing. These advantages of contact healing in this model support speculations that there are differences in the early rate and possibly in the later quality of ligament healing when cut rabbit MCL ends are in proximity. Longer-term studies to define end points and mechanisms of healing are required.
A quantitative analysis of matrix alignment in ligament scars: a comparison of movement versus immobilization in an immature rabbit model.
This investigation quantified the alignment of fibrillar matrix in normal rabbit medial collateral ligaments (MCLs) and in healing MCLs from animals treated with or without knee immobilization. Twenty-four immature female rabbits were given complete midsubstance injuries to their right MCLs. Fifteen of them had that knee pin immobilized in flexion, while the remaining nine were allowed unrestricted cage activity. Animals were sacrificed in groups of three at intervals of 3, 6, or 14 weeks after injury, and both healing MCLs and unoperated contralateral controls were fixed in situ for subsequent removal, freeze-fracture, and preparation for scanning electron microscopy (SEM). A random sampling of SEM photographs followed by automated, statistically validated image processing was used to quantify alignment of matrix in all samples. Results showed that nonimmobilized MCL scars in this model do remodel over 14 weeks of healing, returning to normal alignment values in that time. Surprisingly, MCL scars in immobilized knees were even better, with mean matrix alignments falling statistically within normal MCL limits at all healing intervals studied. If not due to an unknown sampling or fixation artifact, these results suggest that gross knee flexion and extension is not a prerequisite for scar matrix alignment in this immature model of ligament healing.
Aminoglycoside antibiotics affect hippocampal LTP: a comparative study with the N-type calcium antagonist omega-conotoxin-GVIA.
The in vitro activity of N-type calcium antagonists such as omega-conotoxin-GVIA and the aminoglycoside antibiotics neomycin and streptomycin was studied in rat hippocampal slices. The effects of the drugs were tested on basal CA1 synaptic transmission and on the hippocampal long-term potentiation (LTP) induced by tetanic electrical stimulation and by increasing (4mM) the calcium concentration. Omega-conotoxin-GVIA, neomycin and streptomycin were able to significantly reduce the amplitude of the CA1 population spike at 1 microM, 0.5 mM and 1 mM, respectively. In addition, the drugs affected the induction and maintenance of the CA1 tetanic and calcium-induced LTP at concentrations which did not modify the magnitude of the control CA1 population spike. Omega-conotoxin-GVIA (0.5 microM), neomycin (0.3 mM) and streptomycin (0.7 mM) perfused for 60 min, before inducing LTP, prevented the subsequent increase of the CA1 population spike in all the experiments. The same concentrations of these drugs perfused for 60-min after a previously established LTP significantly reduced the amplitude of the CA1 population spike. The results promote a role for the N-type calcium channels and for the release of neurotransmitters in both the induction and the maintenance of hippocampal LTP.
In vitro depressant effects of U-54494A, an anticonvulsant related to kappa opioids, in the hippocampus.
The effects of cis-3,4 dichloro-N-2-(1-pyrrolidinyl)cyclo-hexyl-benzamide (U-54494A), an anticonvulsant related to kappa opioids, were studied in vitro on the extracellular electrical activity of the CA1 region of slices of hippocampus in the rat. The effects of U-54494A were compared to those of the kappa opioid agonist trans-3,4 dichloro-N-2-(1-pyrrolidinyl)cyclo-hexyl benzeneacetamide methane sulphonate (U-50488H). Both U-54494A and U-50488H, in concentrations of 50 and 100 microM, respectively, reduced the magnitude of the orthodromically evoked CA1 population spikes after electrical stimulation of the stratum radiatum (100-200 microA, 70 microseconds, 0.1 Hz). Naltrexone (25 microM), or the selective kappa opiate receptor antagonist, 1-cyclopenthyl-5-(1,2,3,4,5,6-hexahydroxy-3,6,11-trimethyl-2 -6-methano-3- benzazocin)-3-pentatone methane sulphonate (WIN 44441-3) (25 microM), prevented the depressant activity of U-54494A (200 microM) on the CA1 population spikes. High calcium (+3mM) solutions prevented the depressant activity of increasing concentrations of both U-54494A and U-50488H on the amplitude of CA1 population spikes. Up to 200 microM, both drugs were ineffective in depressing the epileptiform bursting in CA1, due to 1 mM penicillin or to perfusion of the slice in absence of magnesium ions. The results demonstrate: (1) the inability of U-54494A to show antagonistic activity in two in vitro models of interictal epilepsy; (2) a depressant effect of U-54494A on basal synaptic transmission in the CA1 region of the hippocampus, which may be related to an influence on transneuronal calcium currents and which may be involved in the reported antagonism of ictal epileptic seizures by drugs.
An in vitro study on the hippocampal electrophysiological properties of enkephalinase inhibitors in rats.
The effects of two enkephalinase inhibitors were studied on the CA1 and dentate hippocampal extracellular field potentials (FPs). The enkephalinase inhibitors thiorphan and SCH 32615, at a concentration of 1-500 microM, failed to significantly affect CA1 and dentate FPs. Thiorphan and SCH 32615, at a concentration of 150 microM, were able to potentiate the enkephalin-induced epileptiform bursting, inducing an increase in the bursting duration and in the number of spikes per burst due to 3.5 microM DAEAM or 0.20 microM DAGO. The results suggest: 1) the potentiation of an electrophysiological opiate receptor-mediated response by enkephalinase inhibitors; 2) the inability to show a direct effect on the basal CA1FP as a result of the inhibition of the endogenous enkephalinase.
An in vitro study on the hippocampal epileptogenic properties of enkephalins and enkephalinase inhibitors in rats.
1. The effects of enkephalins and enkephalinase inhibitors were studied in CA1 area in rat hippocampal slices. 2. The data demonstrate a prevalent involvement of mu opiate receptors in the epileptogenic properties of enkephalins. 3. A potentiation of the mu opiate receptor-mediated epileptogenic response by enkephalinase inhibitors has been shown. 4. The results also show an inability to affect basal CA1 field potentials by inhibition of endogenous endopeptidase.
Effects of some calcium antagonists and of calcium concentration changes on CA1 paired pulse inhibition in rat hippocampal slices.
1. In rat hippocampal slices, the lowering of the calcium concentration (from 2 to 1 mM) or diltiazem (200 microM) or CdCl2 (50 microM) significantly (P less than 0.01) increased the amplitude and shifted the stimulus-response curve of the secondary population spikes, due to paired pulse CA1 stimulation to the left. 2. The amplitude of the primary population spikes was not significantly affected. 3. The data demonstrated that the role of the concentration of calcium ions is critical in control of local inhibitory hippocampal circuitry at the base of paired pulse inhibition.
Diversified electrophysiological properties of morphinan drugs in rats.
1. In in vivo and in vitro studies in rats, the effects of dextromethorphan (DM), dextrorphan (DX), and levorphanol (LV) were compared with those induced by kappa and sigma opiate agonists. 2. In rat hippocampal slices all the morphinans were able to pertubate the CAI hippocampal synaptic transmission, while only DX and LV affected the N-methyl-D-aspartate excitability through a possible interaction at sigma opiate receptors. 3. On the other hand EEG studies show that only DX appears to act as a full agonist at sigma opiate receptors. 4. Present data demonstrate diversified electrophysiological properties of morphinans both in in vitro and in vivo studies.
Effects of calcium and potassium extracellular ionic concentration changes on the hippocampal CA1 activity of purinergic drugs.
1. The influence of the change of potassium and calcium concentrations in the medium bathing hippocampal slices has been tested on the purinergic drug effects. 2. The depressive effect of purinergic agonists were antagonized by 50% by doubling the potassium concentration, while they were not affected by doubling calcium concentrations. 3. The data demonstrate a direct intrinsic activity of potassium ions, and suggest a possible direct interaction between adenosine receptors and potassium transneuronal fluxes.
Racial differences in social support and mental health in men with HIV infection: a pilot study.
The mediating role of social support in the mental health and behaviours of persons coping with life-threatening chronic illness is of potentially great importance in determining the quality of life of persons with HIV infection (PWHs). As part of a biracial pilot study of the ways black and white men manage the stresses of sexually acquired HIV infection, we have examined the relationship between social support and mental health and behaviours. Forty homosexual/bisexual men (20 white and 20 black) attending a Detroit hospital-based HIV outpatient clinic were recruited for the study and underwent physical and mental health (HSCL-59 and NIMH DIS interview), behavioural and psychosocial evaluations, and a neuropsychologic screening test battery. The black and white men did not differ in terms of age, education, sexual behaviours, physical or mental health status. However, the black men were less likely to be open about their sexuality to their primary social support network, and to report that their social support was less affirmative than did the white men. When correlations between the six-dimensional social support measures (Wortman & O'Brien, 1987) and HSC-L distress scores were examined, both availability of material social support and affirmation were correlated negatively with distress among the white men but positively among the black men. Similarly, the previously observed positive relationship between perceived adequacy of social support and adoption of safer sexual practices was observed among white but not black participants.(ABSTRACT TRUNCATED AT 250 WORDS)