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Biomedical subjects

C Frank

Publications and source records attributed to C Frank.

At least 145 records · Page 8Linked to original sources
PubMed1991

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.

4-Aminopyridine↗
PubMed1991

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)

Adaptation, Psychological↗
PubMed1990

Transplantation of the rabbit medial collateral ligament. I. Biomechanical evaluation of fresh autografts.

This investigation was designed to study the biomechanical recovery of a free bone-ligament-bone graft that was returned to its normal extra-articular position, with as little disturbance to its mechanical and biological environments as possible. Twenty-five adult New Zealand white rabbits had their right bone-medial collateral ligament (MCL)-bone complex removed completely and replaced immediately using internal fixation. Animals were allowed unrestricted cage activity before sacrifice in groups of five at intervals of 3, 6, 12, 24, and 48 weeks posttransplantation. Contralateral legs served as internal controls and a separate series of normal animals served as external controls. All MCLs were tested biomechanically using a detailed testing protocol. Results showed early deterioration of 20-35% in autograft complex structural behavior, with weakening of both ligament substance and insertions. Viscoelastic behavior of these ligaments was also affected, showing increases in the amount of both cyclic load-relaxation and static load-relaxation at early healing intervals. These properties were statistically indistinguishable, however, from controls at 48 weeks. Failure behavior of autografts was even better preserved, reaching a low of 65% of control values at 24 weeks and recovering to within 10% of controls at 48 weeks. These results, plus the major changes in failure modes that occurred over that duration, suggest that autograft incorporation is a slow but dynamic process. These results further suggest that at least some connective tissue autografts, when placed under, as yet undefined, "proper biological and mechanical conditions," can retain and recover a number of biomechanical properties over a period of 1 year. The longer-term fate of these autografts and the exact nature of their similarities or differences from other graft alternatives (e.g., tendon for ligament), however, is unknown.

Animals↗
PubMed1990

Transplantation of the rabbit medial collateral ligament. II. Biomechanical evaluation of frozen/thawed allografts.

This study was designed to test the mechanical behavior of a frozen/thawed bone-medial collateral ligament (MCL)-bone allograft in a rabbit model and to compare allograft behavior with contralateral unoperated ligaments as well as a group of normal bone-ligament-bone preparations prior to freezing. Twenty-five mature rabbits received similarly frozen bone-MCL-bone allografts and were subsequently allowed to heal without immobilization in groups of five for 3, 6, 12, 24, or 48 weeks after transplantation. A series of biomechanical tests was performed on each allograft, contralateral, and external normal control ligament. Results demonstrated that allografts were significantly tighter than controls at 3 weeks and they remained tight over time. All allografts, however, had inferior structural and material behaviors as compared with controls. Allograft insertional bone and substance deteriorated to about 60% of contralateral strength at 12 and 48 weeks. Bony insertions became the most common site of graft weakness. Both stress at failure and the elastic modulus of allograft substance similarly reached a plateau at those intervals, but at about 30% of contralateral controls. Cyclic and load relaxation properties of allografts, on the other hand, did not deteriorate and were, in fact, indistinguishable from contralateral and normal values at 48 weeks. Comparison with a series of fresh autografts suggests that, with the exception of this viscoelastic recovery, allografts were mechanically inferior to autografts in their healing at the intervals tested. Collectively, these results suggest that allograft MCL healing in this composite model is dynamic but slow, featuring changes in bone and soft tissue over the first year after transplantation. Although "viable" and vascular, allografts have not normalized mechanically and, in fact, appear to have reached a new equilibrium whereby properties are neither improving nor deteriorating. Despite this apparent equilibrium, the trend for some viscoelastic recovery provides hope that allografts may have further potential for improvement. Longer-term studies of MCL allograft mechanical behaviors are clearly required.

Animals↗
PubMed1990

Inhibitory influence of excitatory amino acid antagonists on penicillin-induced epileptiform bursting in rat hippocampal slices.

The inhibitory influence of excitatory amino acid (E.A.A.) antagonists such as kynurenic acid, 2-amino-5-phosphonopentanoic acid (AP5), cis-2,3-piperidine dicarboxylic acid (cis-2,3 PDA) and (+)-5-methyl-10,11,-dihydro-5H-dibenzo(a,d)cyclo-hepten-5,10-imine maleate (MK 801), has been studied on the epileptiform activity elicited in rat hippocampal slices, bathed in penicillin (1 mM). The rank of the inhibitory potency was: MK 801 greater than kynurenic acid greater than cis 2,3 PDA greater than AP5. Moreover, only MK 801 was able to block the last population spike of the penicillin-induced epileptiform bursting in 100% of the experiments. The data indicate that the antiepileptic activity of E.A.A. antagonists on the penicillin epileptiform bursting in CA1 pyramidal cells is low and limited, indicating that the hippocampal area is not the primary site of the anticonvulsant activity of E.A.A. antagonists.

Amino Acids↗
PubMed1990

High calcium solutions prevent the depressant effects of aminoglycoside antibiotics on central synaptic transmission in rat hippocampal slices.

1. The aminoglycoside antibiotics neomycin and streptomycin were tested on the synaptic activity of the CA1 pyramidal neuron-Schaffer collateral interconnections in rat hippocampal slices. 2. Neomycin (0.5 mM) decreased the magnitude and shifted to the right the stimulus-response curve of the somatic and dendritic excitatory postsynaptic potential (EPSP) and the somatic population spike (PS). 3. Streptomycin (1 mM) decreased the magnitude and shifted to the right the stimulus-response curve of the somatic and dendritic EPSP and the somatic PS. 4. High (+2 mM) calcium solutions were able to prevent the effects induced by the antibiotics and to shift to the left the stimulus-response curve of the 0.5 mM neomycin and 1 mM streptomycin treated hippocampal slices. 5. The data demonstrate an effect of aminoglycoside antibiotics on a central mammalian hippocampal synapses, that may depend on an interference of the drugs on calcium conductances.

Animals↗
PubMed1990

Stress and the heart: biobehavioral aspects of sudden cardiac death.

Stress has been implicated as a developmental factor in atherosclerotic heart disease, essential hypertension, and sudden cardiac death. This article reviews the mechanisms and biobehavioral effects of stress on the heart, focusing on its relation to sudden cardiac death. Epidemiologic evidence, cultural studies, animal experiments, and human research are reviewed to better understand the biobehavioral aspects of stress on the heart. Emphasis is placed on understanding the interaction of the central nervous system's frontal cortex and hypothalamus with cardiovascular control areas. With today's understanding of the frontal cortex and the interaction of hormones and neurotransmitters with the cardiovascular system, clinical interventions utilizing psychotherapy and psychopharmacology are needed, particularly since both approaches are underutilized in combating arrhythmias.

Animals↗
PubMed1990

Synovial fluid does not inhibit collagen synthesis. Bovine cruciate ligament studied in vitro.

An organ culture model of four bovine anterior cruciate ligaments was used to compare synovial fluid with bovine serum, lactated Ringer's solution, and Basal Medium Eagle's (BME) to determine their relative abilities to support in vitro conversion of proline into hydroxyproline. There was no difference between serum and synovial fluid in their ability to support collagen synthesis. These results suggest that bovine synovial fluid is not inhibitory in that it is similar to bovine serum in supporting ligament collagen synthesis under the conditions described.

Animals↗
PubMed1989

An electrophysiological study on the common antitussive drug dextromethorphan in hippocampal slices in the rat.

Dextromethorphan, a common antitussive drug derived from the opioid class of morphinans, has been reported to have antiepileptic properties in some experimental tests. The effects of dextromethorphan were tested on the synaptic responses of the interconnections between Schaffer collaterals and CA1 pyramidal cells in hippocampal slices of the rat. Dextromethorphan, up to 100-200 microM, did not affect the basal field potentials resulting from electrical stimulation of the radiatum (0.1 Hz, 100-200 microA, 75 mu sec) of CA1 pyramidal cells. Larger concentrations of the drug (300-400 microM) depressed the amplitude and increased the duration of the CA1 basal population spikes. Dextromethorphan, up to 200-300 microM, affected neither the duration nor the incidence of the additional population spikes of the epileptiform bursting, resulting from perfusion of the slice with 1 mM penicillin or in the absence of magnesium ions. The data indicate that: (1) dextromethorphan has an influence on CA1 pyramidal cells, different from that of other opioids; (2) the reported antiepileptic effects of dextromethorphan do not involve the hippocampal area.

Animals↗
PubMed1989

Pharmacology of calcium-induced long-term potentiation in rat hippocampal slices.

A transient increase (10 min) in extracellular calcium concentration (4 mM) causes a long-lasting (greater than 2 hr) enhancement of population spike responses evoked by radiatum fibers to CA1 pyramidal neurons in rat hippocampal slices. This phenomenon is similar to tetanic long-term potentiation (LTP), and is also related to memory processes. The influence of various drugs was investigated on calcium-induced LTP. The NMDA antagonist 2 amino-5-phosphonopentanoic acid (AP5; 100 microM) was able to prevent the calcium-induced LTP, while atropine sulphate (10 microM), propranolol hydrochloride (10 microM) and verapamil hydrochloride (100 microM) were ineffective. The results suggest an involvement of the NMDA receptor in the development of calcium-induced LTP.

2-Amino-5-phosphonovalerate↗
PubMed1989

[Neurologic complications in mid-face fractures].

The aim of this study was to discuss the various neurological complications after middle face fractures. The study is based on 186 patients with injuries of the middle face region, admitted to the ENT Department for clinical diagnosis and treatment. Only patients with apparently minor head injury (SHT I. degree) were included in this study. The neurological complications are divided into extracranial and intracranial neurological impairments. It was evident that extracranial neurological complications are frequent and that they decisively influence the surgical treatment (decompression of the N. infraorbitalis or N. opticus). The intracranial neurological complications, however, are rare, but most important for the prognosis quoad vitam, because a small number of patients with middle face fractures can develop a life-threatening intracranial haematoma that must be rapidly detected and removed.

Adolescent↗
PubMed1989

Electron microscopic quantification of collagen fibril diameters in the rabbit medial collateral ligament: a baseline for comparison.

To establish a normal baseline for comparison, thirty-one thousand collagen fibril diameters were measured in calibrated transmission electron (TEM) photomicrographs of normal rabbit medial collateral ligaments (MCL's). A new automated method of quantitation was used to compare statistically fibril minimum diameter distributions in one midsubstance location in both MCL's from six animals at 3 months of age (immature) and three animals at 10 months of age (mature). Pooled results demonstrate that rabbit MCL's have statistically different (p less than 0.001) mean minimum diameters at these two ages. Interanimal differences in mean fibril minimum diameters were also significant (p less than 0.001) and varied by 20% to 25% in both mature and immature animals. Finally, there were significant differences (p less than 0.001) in mean diameters and distributions from side-to-side in all animals. These mean left-to-right differences were less than 10% in all mature animals but as much as 62% in some immature animals. Statistical analysis of these data demonstrate that animal-to-animal comparisons using these protocols require a large number of animals with appropriate numbers of fibrils being measured to detect small intergroup differences. With experiments which compare left to right ligaments, far fewer animals are required to detect similarly small differences. These results demonstrate the necessity for rigorous control of sampling, an extensive normal baseline and statistically confirmed experimental designs in any TEM comparisons of collagen fibril diameters.

Animals↗
PubMed1989

Isolated posterior cruciate ligament injury in a child: literature review and a case report.

The authors describe the sixth reported case of a child with a truly isolated posterior cruciate ligament (PCL) injury and the first in which the deficiency was not repaired immediately. Review of this case emphasizes a number of points: the need for awareness of PCL injuries in children; the inability of x-ray films to detect cartilaginous avulsions in such circumstances; and the fact that missed PCL avulsions can cause locking and may also result in abnormal ligament length in the growing child, preventing reattachment. Finally, it is noteworthy that despite ongoing PCL laxity in this child, functional results were excellent at 3.5-year follow-up, supporting at least short-term conservative management of such injuries in children.

Athletic Injuries↗
PubMed1988

Comparative influence of calcium blocker and purinergic drugs on epileptiform bursting in rat hippocampal slices.

Caffeine (50 microM) increases the amplitude of the basal field potential (BFP) due to orthodromic stimulation of CA1 pyramidal neurons in rat hippocampal slices. This effect is absent if (1) the adenosine agonist L-phenyl-isopropyladenosine (L-PIA) (0.5 microM) is added to the perfusion with caffeine, and (2) low calcium (0.1 mM)-high magnesium (5mM) solutions are used. The calcium blocker verapamil (0.05-0.2 mM) does not modify the caffeine-induced effects. Higher concentrations of caffeine (0.2-0.5 mM) elicit the appearance of an epileptiform bursting, whose duration is inhibited at almost the 50% by 0.5 microM of L-PIA and unaffected by verapamil (0.2 mM) and nifedipine (0.05-0.10 mM). 5 microM of L-PIA, low calcium (0.1 mM)-high magnesium (5 mM) solution and verapamil (0.2 mM) are able to inhibit at almost the 50% the epileptiform bursting duration due to the potassium blocker 4-aminopyridine (4-AP). Nifedipine (0.05-0.1 mM) does not affect the 4-AP effects. L-PIA (0.5-2 microM) but not verapamil (0.2 mM) and nifedipine (0.1 mM) inhibits at almost the 50% the penicillin (1 mM) epileptiform bursting duration. The data indicate a different antagonistic influence of purinergic drugs and verapamil, on different models of epilepsy in rat hippocampal slices. In addition, the lack of antagonism between purinergic drugs and verapamil suggests different sites of action of the drugs.

Adenosine↗
PubMed1988

Viability of ligaments after freezing: an experimental study in a rabbit model.

Our purpose in this study was to assess ligament fibroblast viability after freezing by quantifying the subsequent ability of fibroblasts to synthesize collagen in vitro. Both medial collateral ligament (MCL) complexes from 40 adolescent rabbits were studied. Collagen production was determined by in vitro incubation of ligaments in 3H-proline (a collagen precursor) and subsequent analysis of 3H-hydroxyproline (a marker of newly synthesized collagen). Autoradiographs determined the distributions of ligament cell activity. All right MCL complexes served as fresh controls, providing a baseline of collagen production. Each left MCL was assigned to an experimental group and was either incubated fresh (10 animals); "killed" by drying, multiple freeze thawing, or cycloheximide (six animals); or slowly frozen at -70 degrees C without cryoprotection (24 animals). Collagen production of rapidly thawed ligaments was studied by proline incubation at 1 day, 9 days, or 6 weeks after freezing and was compared with that of contralateral fresh controls. Results demonstrate that some cells in the substance of these rabbit ligaments retained the ability to synthesize collagen in vitro after being frozen for up to 6 weeks. Mean collagen production of frozen ligaments was decreased, but tests of mean and median values as well as ratios were statistically similar to fresh contralateral ligaments in all animals. This postfreezing ligament cell survival and collagen production after -70 degrees C storage may have implications for ligament transplantation.

Animals↗
PubMed1988

Two methods of ligament injury: a morphological comparison in a rabbit model.

Our purpose in this study was to compare morphologically the reproducibility and control of two common methods of ligament injury. Polarized light and scanning electron microscopy were used to quantify the injury patterns and the extent of ligament damage caused by scalpel division and wire rupture of rabbit medial collateral ligaments. Results demonstrate that the scalpel cut and wire rupture methods of ligament injury are each controllable and reproducible in location, pattern, and extent of ligament damage. The wire rupture technique, however, produced consistently more extensive midsubstance ligament damage than the scalpel cut and thus created an injury pattern that better simulated the extent of damage seen in clinical injuries. Although neither technique was an ideal simulation of clinical injuries, results suggest that the wire rupture technique is a more relevant technique to study ligament injury and healing in this model.

Animals↗