Cryogenic Lesion Research Articles

The NCAM‐derived P2 peptide facilitates recovery of cognitive and motor function and ameliorates neuropathology following traumatic brain injury

The neural cell adhesion molecule (NCAM) plays a crucial role during development and regeneration of the nervous system, mediating neuronal differentiation, survival and plasticity. Moreover, NCAM regulates learning and memory. A peptide termed P2, corresponding to a 12-amino-acid sequence in the second immunoglobulin (Ig)-like module of NCAM, represents the natural cis-binding site for the first NCAM Ig module. The P2 peptide targets NCAM, thereby inducing a number of intracellular signaling events leading to the stimulation of neurite outgrowth and promotion of neuronal survival in vitro. The present study evaluated the effect of the P2 peptide on functional and histological outcomes following traumatic brain injury inflicted by a cortical cryogenic lesion. Lesioned rats were injected subcutaneously with P2 peptide, 5 mg/kg daily for 15 days beginning 2 h after injury. This treatment significantly improved postlesion recovery of motor and cognitive function, reduced neuronal degeneration, protected cells against oxidative stress, and increased reactive astrogliosis and neuronal plasticity in the sublesional area. P2 appeared rapidly in blood and cerebrospinal fluid after subcutaneous administration and remained detectable in blood for up to 5 h. The results suggest that P2 has therapeutic potential for the treatment of traumatic brain injury.

148. Characterization of cell death and survival within cryogenic lesions using a tissue engineered human prostate cancer model

148. Characterization of cell death and survival within cryogenic lesions using a tissue engineered human prostate cancer model

Ultrashort intracorporeally maneuverable cryoprobes for laparoscopic renal cryoablation in the porcine model

To determine the feasibility and efficacy of laparoscopic renal cryosurgery using a novel ultrathin ultrashort intracorporeal cryoprobe in a porcine model. Novel cryoprobes 4 cm in length and 1.5 mm in diameter were manipulated intracorporeally after insertion via a designated 15 mm laparoscopic port. Renal cryoablative lesions were induced laparoscopically in four 40 kg female piglets. We correlated between intraoperative temperature, ice ball geometry, intraoperative ultrasonographic properties, and histology. Laparoscopic manipulation of the cryoprobes was straightforward. No port site bleeding occurred during insertion, freezing, thawing or upon removal of the probes. The 0 degrees C, -20 degrees C, and -40 degrees C isotherms were measured at 6, 8, and 12 mm from the probe circumferentially. Ice-ball volume stabilization as determined by ultrasound occurred after 10 min of activation. Lower temperatures were reached after 10 min of probe activation as compared with 5 min (ice ball diameter 30 mm, DeltaT = 13-21 degrees C). Using a second 10-min-long freeze cycle resulted in a 14-22 degrees C lower temperature within the ice ball compared to a single cycle. Full coagulative necrosis was noted in the areas between the inserted probes with an additional 1-2 mm circumferential rim of severe tubular damage and apoptosis. Our novel cryoprobe can be used effectively and conveniently in laparoscopic renal cryosurgery. Considering the size of the cryogenic lesion, using a cluster of probes may be advisable.

Issues Critical to the Successful Application of Cryosurgical Ablation of the Prostate

The techniques of present-day cryosurgery performed with multiprobe freezing apparatus and advanced imaging techniques yield predictable and encouraging results in the treatment of prostatic and renal cancers. Nevertheless, and not unique to cryosurgical treatment, the rates of persistent disease demonstrate the need for improvement in technique and emphasize the need for proper management of the therapeutic margin. The causes of persistent disease often relate to a range of factors including selection of patients, understanding of the extent of the tumor, limitations of the imaging techniques, and failure to freeze the tumor periphery in an efficacious manner. Of these diverse factors, the one most readily managed, but subject to therapeutic error, is the technique of freezing the tumor and appropriate margin to a lethal temperature [Baust, J. G., Gage, A. A. The Molecular Basis of Cryosurgery. BJU Int 95, 1187-1191 (2005)]. This article describes the recent experiments that examine the molecular basis of cryosurgery, clarifies the actions of the components of the freeze-thaw cycle, and defines the resultant effect on the cryogenic lesion from a clinical perspective. Further, this review addresses the important issue of management of the margin of the tumor through adjunctive therapy. Accordingly, a goal of this review is to identify the technical and future adjunctive therapeutic practices that should improve the efficacy of cryoablative techniques for the treatment of malignant lesions.

Cryosurgery: Ultrastructural Changes in Pancreas Tissue after Low Temperature Exposure

A number of theoretical and experimental studies, both in vitro and in vivo, have been performed to explain the action of low temperatures on tissue. It is now evident that the thermal parameters used in the past for freezing during cryosurgery were not precise; this may have resulted in the failure of treatment. For the first time, this report describes the early ultrastructural features of pancreatic parenchyma after low temperature exposure, i.e., cryosurgery, in vivo. We demonstrate the effect of freeze-thawing processes using temperatures of various intensities. The cryosurgical response of pancreas parenchyma, i.e., ultrastructural cellular changes in pancreas tissue, was investigated. The electronic microscopic analysis showed that, after local cryodestruction at temperatures of -80 degrees C and -180 degrees C, similar processes occurred within the pancreas tissue in the early postcryosurgical phase -- immediately and up to 24 hours after low temperature exposure on tissue. The exocrine pancreatic cells in the center of the cryozone changed upon thawing. Ultrastructural changes in the exocrine pancreatic cells, where the first signs of dystrophic processes had been noticed, were increased. These ultrastructural changes in the pancreatic cells provide a platform to better understand the mechanisms of damage and the pathogenesis of frostbite after cryosurgery. The properties of the pancreas parenchyma response after low temperature exposure provide important insights into the mechanisms of damage and the cryogenic lesion immediately after thawing in cryosurgery. Our new insights prove on the cell level that suddenly and progressively damaged pancreatic cells in the postcryosurgical zone lead to aseptic cryonecrosis and then to aseptic cryoapoptosis of vital normal tissue. The vascular capillary changes and circulatory stagnation demonstrate the anti-angiogenesis mechanism, which, together with cryoaponecrosis and cryoapoptosis, are some of the main mechanisms of biological tissue injury following the low temperature exposure.

Experimental models for cardiac regeneration

Simple ex vivo or in vitro models are most useful for testing putative cell therapy protocols, as they allow quick and controlled screening of variants and possible improvements. We discuss here three different models: coculture of precursors of human bone marrow cells (BMCs) with mouse heart slices bearing a cryogenic lesion; coculture of human BMCs and rat cardiomyocytes separated by a porous membrane that allows passage of soluble substances but prevents migration of nuclear material; and injection of human BMCs in developing chick heart bearing burn lesions. Our results indicate that the damaged areas express specific genes such as MPC1 and SDF1, and that some human BMCs migrate and graft near the lesion, where they can originate cells with a cardiac phenotype that produce human cardiac proteins. The frequency of this transformation is, however, very low. Understanding the factors that determine and regulate nuclear reprogramming and transdifferentiation would be crucial to appraising the contribution of these phenomena to cardiac regeneration and, eventually, to modulating them with therapeutic intent.

Inhibition of neuronal nitric oxide synthase-mediated activation of poly(ADP-ribose) polymerase in traumatic brain injury: neuroprotection by 3-aminobenzamide

Focal traumatic injury to the cerebral cortex is associated with early activation of the neuronal isoform of nitric oxide synthase (nNOS), where high concentrations of nitric oxide-derived free radicals elicit extensive DNA damage. Subsequent activation of the nuclear repair enzyme poly(ADP-ribose) polymerase (PARP) causes a severe energy deficit leading to the ultimate demise of affected neurons. Little is known about the temporal relationship of nNOS and PARP activation and the neuroprotective efficacy of their selective blockade in traumatic brain injury. To determine the relationship of nNOS and PARP activation, brain injury was induced by cryogenic lesion to the somatosensory cortex applying a pre-cooled cylinder after trephination for 6 s to the intact dura mater. Pre-treatment with 3-bromo-7-nitroindazole (BrNI; 25 mg/kg, i.p.), and pre- or combined pre- and post-treatment with 3-aminobenzamide (AB; 10 mg/kg (i.c.v.) or 10 mg/kg/h (i.p.)) were used to inhibit nNOS and PARP, respectively. Cold lesion-induced changes in the somatosensory cortex and neuroprotection by BrNI and AB were determined using immunocytochemistry and immunodot-blot for detection of poly(ADP-ribose; PAR), the end-product of PARP activation, and the triphenyltetrazolium-chloride assay to assess lesion volume. PAR immunoreactivity reached its peak 30 min post-lesion and was followed by gradual reduction of PAR immunolabeling. BrNI pre-treatment significantly decreased the lesion-induced PAR concentration in damaged cerebral cortex. Pre-treatment by i.c.v. infusion of AB markedly diminished cortical PAR immunoreactivity and significantly reduced the lesion volume 24 h post-injury. In contrast, i.p. AB treatment remained largely ineffective. In conclusion, our data indicate early activation of PARP after cold lesion that is, at least in part, related to nNOS induction and supports the relevance of nNOS and/or PARP inhibition to therapeutic approaches of traumatic brain injury.

Differential glial and vascular expression of endothelins and their receptors in rat brain after neurotrauma.

We characterized the time-course, intensity of expression and cellular origin of components of the endothelin (ET) system in the rat brain after a standardized neurotrauma (cryogenic lesion of the parietal cortex). ET mRNAs were expressed at sham level after neurotrauma, whereas immunoreactivity for ET-1 was enhanced in glia and endothelium of the lesioned hemisphere and both hippocampi. The number of ET-3 positive mononuclear cells in the lesion perimeter increased starting at 24h after injury. At 48h after neurotrauma, ET-receptor immunoreactivity was increased in astrocytes. In basilar artery endothelium, ETB-immunoreactivity was reduced at 48h to 72h recovering at 7 days whereas ETA-receptor and ET-peptide immunoreactivities were not altered. In summary, neurotrauma leads to a multicellular stimulation of endothelins in the brain along with a delayed selective loss of vascular ETB-receptors. These changes seem to be posttranscriptional and cell type specific. They favor vasoconstriction increasing the risk of late vasospasm and ischemia.

The effect of riluzole and mannitol on cerebral oedema after cryogenic injury in the mouse

A cryogenic lesion was produced under halothane anaesthesia in the mouse by placing a cotton swab soaked in liquid nitrogen onto the surface of the cranium. This provoked an oedematous lesion which developed within the hour after the insult and evolved over the following week. Treatment with mannitol at 3 g/kg i.v. caused a significant 22% reduction in oedema 1 h later, when administered immediately after lesion, but not when administered 23-h post lesion. Likewise riluzole (16 mg/kg, i.v.) significantly reduced oedema by 17% when administered immediately after lesion, or 13% ( P<0.05) when administered 23 h after lesion. Repeated doses (2×16 mg/kg, i.p.) of riluzole were also able to reduce oedema significantly (24%, P<0.05) at 24 h post lesion. Riluzole, in four repeated doses of 8 mg/kg i.p. was also able to reduce lesion surface size by 16% ( P<0.05) 48 h after lesion.

Temporal profile of expression and cellular localization of inducible nitric oxide synthase, interleukin-1β and interleukin converting enzyme after cryogenic lesion of the rat parietal cortex

We used in situ hybridization, RT PCR and immunohistochemistry to study the time course of expression and the cellular localization of inducible nitric oxide synthase (iNOS) and interleukin-1β (IL-1β) during the first 7 days after induction of a standardized cryogenic lesion on the right parietal cortex in male rats. Cryogenic lesion induced iNOS mRNA in the lesioned hemisphere after 6 to 72 h with a maximum (15±2 cells/mm 2, n=4, p<0.01 vs. sham) at 24 h. Microglia, invading monocytes and granulocytes in and around the lesion expressed iNOS immunoreactivity starting at 12 h and peaking (29±10 cells/mm 2, n=4, p<0.05 vs. sham) at 24 h after lesion. Induction of IL-1β mRNA expression was immediate with a peak (9±1 cells/mm 2, n=4, p<0.01 vs. sham) at 24 h after cryogenic lesion. The number of round cells with IL-1β immunoreactivity around the lesion was maximal (8±2 cells/0.1 mm 2, n=3, p<0.01 vs. sham) at 24 h. A weak astrocytic expression of IL-1β-immunoreactivity was seen in sham animal brains. Astrocytic IL-1β-expression was significantly increased in the lesion hemisphere and both hippocampi. Interleukin converting enzyme (ICE) was expressed in astrocytes and microglia around the lesion 6 h after injury. The number of ICE immunoreactive cells (8±2 cells/0.1 mm 2, n=3, p<0.05 vs. sham) peaked at 72 h after lesion. Neuronal expression of ICE and IL-1β was seen in the lesion periphery 72 h and 7 days after injury. At this time, morphological features of apoptosis were evident in cells in the lesion periphery. The data indicate an early activation of microglia and monocyte invasion into the lesion hemisphere leading to multicellular expression of iNOS, ICE, and IL-1β. These events may contribute to the expansion of neuronal damage after brain injury.

A Comparative Study of Cryogenic Lesions in Organ-Cultured Human Skin and in Reconstituted Human Skin Equivalent

Cryosurgery is a technique that is widely used in the treatment of cutaneous tumors. However, there are still features of healing in cryosurgery wounds that are incompletely understood and necessitate further study. In the present paper, we describe twoin vitromodels that were developed to study the initial stages of development of the cryolesion: reconstituted human skin and organ-cultured human skin. Cryolesions were generated in both models by applying a 2-mm-diameter cryoprobe at −196°C for 35 s. Histological features were analyzed at days 0, 3, 5, and 14 following cryotreatment and showed epidermal detachment and keratinocyte necrosis very close to the findings reportedin vivo.Results were similar in the two models. Gross alteration of the dermal architecture was noticed beneath the cryolesion, particularly in the reconstituted skin model. Cell proliferation was investigated at days 0, 3, and 5 by [3H]thymidine incorporation and Ki-67 antigen immunolabeling. In the case of organ-cultured skin, a significant increase in keratinocyte and fibroblast proliferation was observed at day 3, compared to the controls. At day 5, a return to the basic level was noticed. This was not observed in the reconstituted skin model at either day 3 or day 5. These data led us to propose that organ-cultured skin may be a useful model for evaluating the response of human skin to freezing; reconstituted skin was not adequate for this purpose.

Expression of monocyte chemoattractant protein (MCP-1) and nitric oxide synthase-2 following cerebral trauma.

Traumatic injury to the brain initiates multiple interrelated processes that involve parenchymal, vascular, and infiltrating inflammatory cells. Nitric oxide (NO) and chemokines have been implicated as regulators of the central nervous system injury response. Following a cryogenic lesion of the cerebral cortex in mice, mRNA for NO synthase (NOS)-2 was detected by reverse transcriptase polymerase chain reaction ipsilaterally 12 h after injury and persisted for 2 weeks. While mRNA was also detected contralaterally, the time course of expression was shorter (1 week). By immunohistochemistry, NOS-2 protein was initially detected ipsilaterally 12 h after injury in infiltrating inflammatory cells. Astroglial cells expressed NOS-2 from 24 to 72 h after injury. The expression of monocyte chemoattractant protein (MCP-1) mRNA peaked at 6 h on the lesion side, remained for 24 h and then declined by 48 h. On the unlesioned side, MCP-1 mRNA was expressed to a much lesser extent and had declined by 24 h. The up-regulation of MCP-1 was relatively specific as a closely related mRNA encoding IP-10 was not significantly increased. These findings implicate a role for NOS-2 and MCP-1 as potential regulators of cellular events following cryogenic cerebral trauma.

Cryoablation of hepatic neoplasia

SummaryCryotherapy can destroy localised hepatic tumours while sparing normal liver tissue if some elementary rules are followed. Due to advances in instrumentation, cryogenic lesions can now be reliably produced. For the safe placement of cryoprobes, intraoperative ultrasound (US) is indispensable. Synergistic freezing with several probes is recommended for tumours > 2–3 cm. The ice-front should exceed the diameter of the lesion by a minimum of 1 cm. Tissue temperatures of −50d`C are required.The results from our first 18 patients (8/93–7/96) with unresectable liver metastases are encouraging. 55% of the patients treated with open cryosurgery were alive at a follow-up of 24 months. In contrast to the open approach, five of 13 lesions in patients treated percutaneously could not be completely destroyed. Due to the high probability of extrahepatic disease in liver metastases, it seems unlikely that a percutaneous or laparoscopic approach will be standard in the future. Nevertheless, cryoablation of unresectable hepatic neoplasia widens the treatment options for these patients.

Intraoperative Phrenic Nerve Monitoring in Cardiac Surgery

Left hemidiaphragmatic paralysis due to phrenic nerve lesion is a frequent complication of hypothermic cardiopulmonary bypass. Although this is believed to be caused by cold injury to the phrenic nerve, its exact cause is still not clear. To assess feasibility, safety, and usefulness of intraoperative phrenic nerve function monitoring. Elective cardiac surgery in a university hospital. Consenting patients scheduled for myocardial revascularization surgery with the use of the left internal mammary artery. Intraoperative monitoring of compound diaphragmatic action potentials (CDAPs) through transcutaneous stimulation of phrenic nerves. Patients were divided in two groups. Group 1 received intracoronary cold St. Thomas's solution as the only cardioplegic method. Group 2 received topical cardiac cooling with ice-cold solutions in addition to intracoronary cardioplegia. In all group 1 patients, function of phrenic nerves was maintained throughout the surgical procedure. Group 2: in two patients, bilateral, and in one patient, left phrenic nerve conduction was abolished after submersion of the heart in ice-cold solution. In two of them, the action potential of the left hemidiaphragm was absent by the end of surgery. In one, nerve conduction recovered with rewarming of the patient. Intraoperative monitoring of CDAP was safe and easily obtained in the intraoperative setting. It allowed us to observe changes in phrenic nerve conduction occurring during surgery and as a result of cold cardioplegia. Cryogenic lesion of phrenic nerve might explain our findings. However, nerve ischemia cannot be ruled out and it may worsen axonal damage or delay its recovery. This monitoring method allowed us to predict postoperative diaphragmatic dysfunction. Also, surgeons can be warned of the damaging effects of excessive cooling of the pericardium and surrounding structures; thus, preventive measures can be taken.

Influence of Anesthetics on Formation of Brain Edema

To the Editor: We read with interest the article by Murr et al. [1] regarding the influence of various anesthetics on the formation of brain edema resulting from a focal cryogenic lesion in rabbits. Although they demonstrated that isoflurane anesthesia attenuates cerebral edema when compared to fentanyl, thiopental, or alpha-chloralose, in their discussion they did not discuss the obvious differences in blood glucose levels. It is, however, a well known clinical and laboratory phenomenon that increases in brain glucose may worsen cerebral injury [2]. The high variance in some groups indicates that blood glucose levels in some animals greatly exceeded normal. We would be interested in knowing why blood glucose levels were not determined in the control group, how the authors explain the different blood glucose levels in the experimental groups, and whether differences in blood glucose might have contributed to the difference in the extent of cerebral edema. Ch. Kolbitsch, MD A. Benzer, MD Department of Anesthesia University of Innsbruck A-6020 Innsbruck, Austria

Influence of isoflurane, fentanyl, thiopental, and alpha-chloralose on formation of brain edema resulting from a focal cryogenic lesion.

The objective of this study was to analyze the effects of various anesthetics on the formation of brain edema resulting from a focal cryogenic lesion. Thirty rabbits (six per group) were anesthetized with isoflurane (1 minimum alveolar anesthetic concentration [MAC] 2.1 vol%), fentanyl (bolus 5 micrograms/kg; infusion rate 1.0-0.5 micrograms.kg-1.min-1), thiopental (32.5 mg.kg-1.h-1), or alpha-chloralose (50 mg/kg). Control animals (sham operation, no lesion) received alpha-chloralose (50 mg/kg). Regional cerebral blood flow (rCBF) in perifocal brain tissue was measured by H2-clearance. Animals anesthetized with isoflurane required support of arterial pressure by angiotensin II (0.15 micrograms.kg-1.min-1). Six hours after trauma the animals were killed. Formation of brain edema was studied by specific gravity of cortical gray matter, white matter, hippocampus, caudate nucleus, putamen, and thalamus. Brain tissue samples were collected at multiple sites close to and distant from the lesion. Mean arterial pressure, arterial PCO2 and PO2, hematocrit, body temperature, and blood glucose were not different between groups during the posttraumatic course (except for an increased arterial pressure with alpha-chloralose compared to thiopental 4-6 h after trauma). The specific gravity of cortical gray matter was significantly reduced up to a distance of 6 mm from the center of the lesion in animals anesthetized with isoflurane, thiopental, or alpha-chloralose and up to 9 mm in animals given fentanyl.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Isoflurane, Fentanyl, Thiopental, and alpha-Chloralose on Formation of Brain Edema Resulting from a Focal Cryogenic Lesion

The objective of this study was to analyze the effects of various anesthetics on the formation of brain edema resulting from a focal cryogenic lesion.Thirty rabbits (six per group) were anesthetized with isoflurane (1 minimum alveolar anesthetic concentration [MAC] 2.1 vol%), fentanyl (bolus 5 micro gram/kg; infusion rate 1.0-0.5 micro gram centered dot kg-1 centered dot min-1), thiopental (32.5 mg centered dot kg-1 centered dot h-1), or alpha-chloralose (50 mg/kg). Control animals (sham operation, no lesion) received alpha-chloralose (50 mg/kg). Regional cerebral blood flow (rCBF) in perifocal brain tissue was measured by H2-clearance. Animals anesthetized with isoflurane required support of arterial pressure by angiotensin II (0.15 micro gram centered dot kg-1 centered dot min-1). Six hours after trauma the animals were killed. Formation of brain edema was studied by specific gravity of cortical gray matter, white matter, hippocampus, caudate nucleus, putamen, and thalamus. Brain tissue samples were collected at multiple sites close to and distant from the lesion. Mean arterial pressure, arterial PCO2 and PO2, hematocrit, body temperature, and blood glucose were not different between groups during the posttraumatic course (except for an increased arterial pressure with alpha-chloralose compared to thiopental 4-6 h after trauma). The specific gravity of cortical gray matter was significantly reduced up to a distance of 6 mm from the center of the lesion in animals anesthetized with isoflurane, thiopental, or alpha-chloralose and up to 9 mm in animals given fentanyl. In white matter, vasogenic edema extended up to 12 mm from the lesion focus in animals anesthetized with fentanyl, thiopental, or alpha-chloralose. In isoflurane-anesthetized animals, white matter samples in all regions were similar to control. The specific gravity in hippocampus, caudate nucleus, putamen, or thalamus was not altered as compared to the controls. rCBF studied before cryogenic injury had a range of 37-44 mL centered dot 100 g-1 centered dot min-1, except in animals given fentanyl (i.e., 59.9 mL centered dot 100 g-1 centered dot min-1). During the first 3 h after trauma, animals given fentanyl had significantly higher rCBF values than animals with thiopental or the controls. At 4-6 h after trauma, rCBF was decreased in animals with fentanyl or thiopental as compared to the baseline level, although differences were not observed between groups. Regression analyses of data from all experimental groups do not reveal a relationship between the formation of posttraumatic brain edema and mean arterial pressure or rCBF. We conclude that isoflurane anesthesia attenuates cerebral edema from a standard cerebral lesion as compared to fentanyl, thiopental, or alpha-chloralose. (Anesth Analg 1995;80:1108-15)

THE EFFECT OF HYPERTONIC FLUID RESUSCITATION ON BRAIN EDEMA IN RABBITS SUBJECTED TO BRAIN INJURY AND HEMORRHAGIC SHOCK

Small-volume resuscitation with 7.2% NaCl/10% dextran 60 (HHS) restores cardiovascular stability faster than all other therapeutic modalities currently known. This study was undertaken to elucidate the effects of HHS on the brain, specifically on the formation of posttraumatic brain edema. HHS was administered to anesthetized albino rabbits with or without a focal cryogenic brain lesion and hemorrhagic shock. Specific gravity of small tissue samples was determined 4 h after injury and values were topographically assembled to form a color-coded map of both hemispheres, allowing for a high resolution mapping of brain edema. Cerebral blood flow on the side of the lesion, as assessed by the H2 clearance method, increased transiently after injury but remained unchanged from baseline during shock and after infusion of HHS, indicating intact cerebrovascular autoregulation. The cryogenic lesion without subsequent HHS infusion resulted in significant brain edema formation in grey and white matter of the exposed hemisphere. In injured animals, resuscitation with HHS led to a global reduction of brain water content in both hemispheres. We conclude that small-volume resuscitation with HHS does not worsen posttraumatic brain edema. To the contrary, our results show that it decreases cerebral water content even in regions close to the injury. This makes it worthwhile to investigate the benefits of HHS for the treatment of intracranial hypertension.

Cryogenic spinal cord injury induces astrocytic gene expression of insulin-like growth factor I and insulin-like growth factor binding protein 2 during myelin regeneration.

To study injury-induced astrocytic responses associated with regrowth of axons and regeneration of myelin, the method of Collins and colleagues was used to make focal cryogenic lesions in spinal cords of adult rats (Collins et al.: J Neuropathol Exp Neurol 45: 742-757, 1986). The duration of cryogenic injury (CI), the size of the cryode, and its temperature were chosen to destroy all myelin sheaths and axons without producing cavities or hemorrhages. Messenger RNA and peptide distributions of insulin-like growth factor I (IGF-I), IGF-I receptor (IGFR-I), IGF binding protein 2 (IGFBP-2), glial fibrillary acidic protein (GFAP), and myelin basic protein (MBP) were studied 3-56 days after CI by in situ hybridization and immunocytochemistry. At 3 days, vimentin-positive, GFAP-negative astrocyte-like cells in the lesion expressed IGF-I mRNA and peptide and 7 days after CI, both were expressed by typical GFAP-positive, hypertrophic astrocytes, many of which also were vimentin-positive. Levels of IGF-I, IGFBP-2, and GFAP mRNA and peptide were higher in lesion astrocytes after 14 days. They attained maximum levels at 21-28 days before declining to near control levels at 56 days. Decreasing relative levels of oligodendroglial MBP mRNA were found in and around lesions 7-14 days after CI; subsequently, rising levels accompanied remyelination. At 28 and 56 days after CI, some transferrin-positive, oligodendroglia-like cells also were immunostained by anti-IGFR-I. Our findings suggest that early astrocytic production of IGF-I and IGFBP-2 may be involved in the myelin regeneration which occurs in this model of spinal cord injury.

Sevoflurane Versus Halothane Anesthesia After Acute Cryogenic Brain Injury in Rabbits: Relationship Between Arterial and Intracranial Pressure

The relationship between intracranial pressure and arterial blood pressure during sevoflurane or halothane anesthesia was evaluated in New Zealand white rabbits after cryogenic brain injury. Fourteen rabbits were randomized to be anesthetized with 1.5 MAC of sevoflurane or halothane in oxygen. All animals were paralyzed with pancuronium, and mechanically ventilated. A cryogenic lesion was created over the left hemisphere. Thirty minutes later, the intracranial pressure had risen to a mean value of 15 mm Hg. The inhaled concentration of anesthetic drugs was then increased to achieve a blood pressure of 35 mm Hg. Baseline measurements were made of monitored variables including mean arterial pressure, intracranial pressure, esophageal temperature, end-tidal CO2, and arterial blood gases. Neosynephrine was then infused to raise the blood pressure from 35 to 100 mm Hg during 20 min. The PaCO2 was maintained between 38 and 42 mm Hg. At baseline, there were no significant differences in mean arterial pressure, intracranial pressure, and blood gas values between the two groups. The intracranial pressure in the sevoflurane anesthesia group increased from 11 +/- 1 to 44 +/- 4 mm Hg as mean arterial pressure increased from 35 to 100 mm Hg. Intracranial pressure in the halothane anesthesia group increased from 9 +/- 1 to 32 +/- 3 mm Hg during the same range of blood pressure. Linear regressions of intracranial pressure on mean arterial pressure were performed for each of the two anesthetic groups. The slope of the regression line for the sevoflurane animals (0.491) was significantly greater than that for the halothane animals (0.323, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)