Differences in protein synthesized in vivo and in vitro by cells associated with the cerebral microvasculature. A protein synthesized in response to trauma?

Effects of heat shock, stannous chloride, and gallium nitrate on the rat inflammatory response

Heat and a variety of other stressors cause mammalian cells and tissues to acquire cytoprotection. This transient state of altered cellular physiology is nonproliferative and antiapoptotic. In this study, male Wistar rats were stress conditioned with either stannous chloride or gallium nitrate, which have immunosuppressive effects in vivo and in vitro, or heat shock, the most intensively studied inducer of cytoprotection. The early stages of inflammation in response to topical suffusion of mesentery tissue with formyl-methionyl-leucyl-phenylalanine (FMLP) were monitored using intravital microscopy. Microvascular hemodynamics (venular diameter, red blood cell velocity [Vrbc], white blood cell [WBC] flux, and leukocyte-endothelial adhesion [LEA]) were used as indicators of inflammation, and tissue levels of inducible Hsp70, determined using immunoblot assays, provided a marker of cytoprotection. None of the experimental treatments blocked decreases in WBC flux during FMLP suffusion, an indicator of increased low-affinity interactions between leukocytes and vascular endothelium known as rolling adhesion. During FMLP suffusion LEA, an indicator of firm attachment between leukocytes and vascular endothelial cells increased in placebo and gallium nitrate-treated animals but not in heat- and stannous chloride-treated animals, an anti-inflammatory effect. Hsp70 was not detected in aortic tissue from placebo and gallium nitrate-treated animals, indicating that Hsp70-dependent cytoprotection was not present. In contrast, Hsp70 was detected in aortic tissues from heat- and stannous chloride-treated animals, indicating that these tissues were in a cytoprotected state that was also an anti-inflammatory state.

Tissue-level cytoprotection

In vitro and ex vivo tissue models provide a useful level of biological organization for cytoprotection studies positioned between cultured cells and intact animals. We have used 2 such models, primary tissue cultures of winter flounder renal secretory epithelium and ex vivo preparations of rat intestinal tissues, the latter to access the microcirculation of exposed mesentery tissues. Herein we discuss studies indicating that differentiated functions are altered in thermotolerant or cytoprotected tissues. These functions include transepithelial transport in renal epithelium and attachment and transmigration of leukocytes across vascular endothelium in response to mediators of inflammation. Evidence pointing to inflammation as a major venue for the heat shock response in vertebrates continues to mount. One such venue is wound healing. Heat shock proteins are induced early in wound responses, and some are released into the extracellular wound fluid where they appear to function as proinflammatory cytokines. However, within responding cells in the wound, heat shock proteins contribute to the acquisition of a state of cytoprotection that protects cells from the hostile environment of the wound, an environment created to destroy pathogens and essentially sterilize the wound. We propose that the cytoprotected state is an anti-inflammatory state that contributes to limiting the inflammatory response; that is, it serves as a brake on inflammation.

Tissue-level cytoprotection

In vitro and ex vivo tissue models provide a useful level of biological organization for cytoprotection studies positioned between cultured cells and intact animals. We have used 2 such models, primary tissue cultures of winter flounder renal secretory epithelium and ex vivo preparations of rat intestinal tissues, the latter to access the microcirculation of exposed mesentery tissues. Herein we discuss studies indicating that differentiated functions are altered in thermotolerant or cytoprotected tissues. These functions include transepithelial transport in renal epithelium and attachment and transmigration of leukocytes across vascular endothelium in response to mediators of inflammation. Evidence pointing to inflammation as a major venue for the heat shock response in vertebrates continues to mount. One such venue is wound healing. Heat shock proteins are induced early in wound responses, and some are released into the extracellular wound fluid where they appear to function as proinflammatory cytokines. However, within responding cells in the wound, heat shock proteins contribute to the acquisition of a state of cytoprotection that protects cells from the hostile environment of the wound, an environment created to destroy pathogens and essentially sterilize the wound. We propose that the cytoprotected state is an anti-inflammatory state that contributes to limiting the inflammatory response; that is, it serves as a brake on inflammation.

Differential distribution of 70-kD heat shock protein in atherosclerosis. Its potential role in arterial SMC survival

Smooth muscle cell death may contribute to necrotic plaque rupture and subsequent thromboembolus. Stress-induced synthesis of heat-shock proteins (HSPs) normally protects cells from death, but vascular HSPs may become insufficient as cytotoxicity increases in advanced plaques. To determine whether vascular HSP content is altered near necrosis, we compared 70-kD HSP (HSP70) distribution between fibrotic and necrotic plagues in immunostained carotid endarterectomy specimens. Average levels of HSP70 immunoreactivity were compared by video densitometry between fibrotic and necrotic plaques or between their underlying media. Both necrotic plaques and their underlying media contained significantly more HSP70 staining than did fibrotic tissues. To test whether cellular HSP70 correlated with resistance to toxicity in vitro, aortic smooth muscle cells (aSMCs) were heat shocked to induce endogenous HSPs or given 2 to 50 micrograms/mL purified HSP70. Cells were then serum deprived or exposed to 12 to 96 mumol/L cholestanetriol (C3ol) or 25-hydroxycholesterol, and survival was determined. Cellular HSP70 content was assayed by immunoblotting, and protein synthesis was monitored by 35S radiolabeling. Serum deprivation inhibited general protein synthesis but induced HSP70; C3ol exposure inhibited both overall protein and HSP70 synthesis, including post-heat shock. Induction of endogenous HSPs or 10 micrograms/mL exogenous HSP70 improved viability of serum-deprived cells (P < .05 and P < .01, respectively), while only exogenous HSP70 protected against C3ol (P < .002). The results suggest that insufficient HSP70 accumulates in aSMCs residing near necrosis to protect against plaque toxicity; aSMC death might then occur, allowing resident macrophages to degrade and destabilize the matrix, leading to rupture.

Effects of electroconvulsive shock on the levels of hsp70 and hsc73 mRNA in the rat brain

We evaluated the effects of electroconvulsive shock (ECS) on the expression of two genes encoding 70 kDa stress proteins, in the rat brain. The study was carried out by in situ hybridization using oligonucleotide probes specific for either the constitutively expressed hsc73, or the strictly inducible hsp70 gene. Rats were submitted to single or repeated (7 days, one session for each day) sessions of Electroconvulsive Shock. Animals were sacrificed at various time after treatment. ECS enhanced the basal expression of hsc73 in limbic areas, such as dentate gyrus, CA3, and median habenular nucleus. ECS induced hsp70 mRNA, which was not detectable in control animals, specifically in the Dentate Gyrus. The effect was present 2 h following treatment. Both single and repeated ECS were similarly effective. The finding likely reflects neuroadaptive local changes associated with a generalized seizure activity.

Immunocytochemical localization of glucocorticoid receptors in the spinal cord: effects of adrenalectomy, glucocorticoid treatment, and spinal cord transection

1. Studies were performed to determine the changes in immunoreactive (IR) type II glucocorticoid receptors of the ventral horn of the spinal cord produced by adrenalectomy (ADX), dexamethasone (DEX) treatment, and spinal cord transection in rats. 2. These treatments did not significantly affect the number of IR neurons of the ventral horn; however, staining intensity was enhanced after ADX and decreased following 4 days of DEX. A similar response pattern was observed for glial-type cells. 3. In control rats, about half of the ventral horn motoneurons were surrounded by immunoreactive glial perineuronal cells. These perineuronal cells increased after ADX (77% of counted neurons) and decreased following DEX treatment (32%; P < 0.05). 4. Two days after transection, staining was intensified in ventral horn motoneurons and glial cells located in the spinal cord below the lesion. Immunoreactive perineuronal cells increased to 85% of counted neurons, from a value of 66% in sham-operated rats (P < 0.05). 5. These findings suggest considerable plasticity of the spinal cord GCR in response to changes in hormonal levels and experimental lesions. It is possible that factors involved in cell to cell communication with transfer of hypothetical regulatory molecules may play roles in GCR regulation and the increased immunoreaction of glia associated with neurons following transection and ADX.

Induction of 70-kDa heat shock protein and hsp70 mRNA following transient focal cerebral ischemia in the rat

Induction of the 70-kDa heat shock protein (HSP70) was demonstrated immunocytochemically in adult rats 4 h to 7 days following temporary middle cerebral artery (MCA) occlusions lasting 30, 60, or 90 min. Maximal HSP70 induction occurred approximately 24 h following ischemia. Thirty minutes of ischemia induced HSP70 in neurons throughout the cortex in the MCA distribution, whereas 90 min of ischemia induced HSP70 in neurons in the penumbra. HSP70 protein was induced in endothelial cells in infarcted neocortex following 60-90 min of MCA occlusion, and HSP70 was induced in endothelial cells in infarcted regions of lateral striatum following 30-90 min of MCA occlusion. hsp70 mRNA was induced in the MCA distribution in cortex and to a lesser extent in striatum at 2 h to 3 days following 60 min of ischemia. It is proposed that brief ischemia induces hsp70 mRNA and HSP70 protein in the cells most vulnerable to ischemia--the neurons. HSP70 protein is not induced in most neurons and glia following 60-90 min of ischemia in areas destined to infarct, whereas it is induced in vascular endothelial cells.

T-lymphocyte reactivity to the recombinant mycobacterial 65- and 70-kDa heat shock proteins in multiple sclerosis

Owing to their conservation and immunogenicity, heat shock proteins (hsps) represent a class of potential autoantigens. Moreover, they could be targets for gamma delta T lymphocytes, which are prominent in various immune disorders. We studied the T cell proliferative primary responses to recombinant M. bovis 65 kDa hsp (hsp65) and M. tuberculosis 70 kDa hsp (hsp70) in 31 patients with multiple sclerosis (MS), 19 patients with other neurological diseases (OND) and 19 healthy individuals. Positive responses to hsp70, but not to hsp65 were significantly more frequent in patients with MS than in patients with OND or in healthy individuals. In order to verify and refine these results and to characterize the hsp reactive T lymphocytes, we screened 147 PPD-specific long-term T cell lines (76 from 10 patients with MS and 71 from 12 healthy donors) for their proliferative response to hsp65 and hsp70. hsp70-reactive T lines were significantly more common in patients with MS than in healthy controls. The number of T lines responding to hsp65 increased in the MS group only slightly. In 19 T lymphocyte lines from patients with MS and healthy donors, a cytofluorometric analysis was performed with special attention paid to distinct T cell receptor gamma delta determinants. With one exception, in each line the population of gamma delta T cells remained a minority. We conclude that an increased T cell response to mycobacterial hsp70 may be present in patients with multiple sclerosis.

Neuronal injury and expression of 72-kDa heat-shock protein after forebrain ischemia in the rat

We evaluated the relationship between the induction of the 72-kDa heat-shock protein (hsp 72) and the presence of necrotic neurons in the rat hippocampus, 48 h after an 8-min episode of forebrain ischemia in eight rates. Hsp 72 was detected using the monoclonal antibody C92 on vibratome brain tissue sections. Hematoxylin and eosin (H&E) staining on adjacent paraffin-embedded sections was used to determine histopathological features. All morphologically intact CA1/2 neurons, 70% of which are destined to become necrotic 7 days after ischemia, exhibited intense hsp 72 staining, while necrotic or damaged neurons were devoid or low in hsp 72. Hsp 72 was also detected in CA3 neurons destined to survive 7 days after ischemia. Blood vessels positive for hsp 72 were detected in focal brain regions, in which severely damaged neurons were either devoid or low in hsp 72 staining. Occasional glial cells expressed hsp 72 in both normal and damaged brain regions. Hsp 72 response to a transient forebrain ischemia seemingly reflects differences in the selective ischemic vulnerability of CA1/2 and CA3 neurons. Further, the presence of hsp 72 within a neuron is likely only a marker of stress and is not necessarily indicative of eventual neuronal survival.

Expression of heat shock protein 70 and heat shock cognate 70 messenger RNAs in rat cortex and cerebellum after heat shock or amphetamine treatment

The expression of strictly inducible hsp70 mRNAs and constitutively expressed hsc70 mRNAs was compared in cerebellum and cerebral cortex of control rats, heat-shocked rats, and rats made hyperthermic with amphetamine. An hsc70-specific oligonucleotide probe identified a 2.55-kb mRNA in cerebellum and cerebral cortex of all rats. An hsp70-specific oligonucleotide probe identified a 3.05-kb mRNA and a 3.53-kb mRNA in cerebellum and cerebral cortex of heat-shocked and amphetamine-treated rats, but not in control rats. Quantitation demonstrated that both hsp70 and hsc70 mRNA levels, relative to 18S rRNA levels, were increased following each treatment. The relative levels of both mRNAs were higher in cerebellum than in cerebral cortex. In amphetamine-treated rats, hsc70 mRNA relative levels increased at body temperatures greater than 39 degrees C, whereas hsp70 mRNA synthesis was induced at temperatures greater than 40 degrees C. Total thermal response values and relative levels of both mRNAs were compared. The results suggested that both the transcription and turnover of hsp70 mRNAs differed between cerebellum and cerebral cortex. At equivalent total thermal response values, amphetamine-treated rats had higher relative levels of hsp70 mRNAs than heat-shocked rats, suggesting that amphetamine enhanced the induction of hsp70 mRNAs.

Induction of heat shock protein 72-like immunoreactivity in the hippocampal formation following transient global ischemia

Global ischemia was produced in adult rats by combining bilateral carotid artery occlusions with systemic hypotension for 5 or 10 minutes. Induction of the 72 kD heat shock protein (HSP72) in the hippocampus was examined immunocytochemically 18-24 hours later. Several patterns of HSP72-like immunoreactivity (HSP72LI) were observed. Five minutes of ischemia induced HSP72 in isolated columns of CA1a pyramidal neurons, or throughout CA1 pyramidal neurons and dentate hilar neurons. Ten minutes of ischemia induced marked HSP72LI in CA3 pyramidal neurons, moderate HSP72LI in dentate granule cells, and minimal HSP72LI in CA1 pyramidal, dentate hilar neurons, and hippocampal glia. Two hippocampi subjected to 10 minutes of ischemia exhibited marked HSP72LI in capillary endothelial cells but no neuronal or glial HSP72LI. It is proposed that (a) the induction of HSP72 in hippocampal sectors correlates with their vulnerability to global ischemia (CA1 greater than hilus greater than CA3 greater than dentate gyrus); (b) the induction of HSP72 in hippocampal cells correlates with their vulnerability to global ischemia in that mild ischemia induced HSP72 only in neurons, moderate ischemia in neurons and glia, and severe ischemia only in capillary endothelial cells; (c) the failure to induce HSP72 in hippocampal neurons in 2 cases of 10 min ischemia may be related to severe injury causing disruption of protein synthesis in these cells.

Effect of heat shock proteins on survival of isolated aortic cells from normal and atherosclerotic cynomolgus macaques

Alterations in the level and distribution of arterial heat shock proteins (HSPs) have been demonstrated during atherogenesis. The significance of these changes within the developing and dying plaque, however, is not understood. To examine a potential protective effect of HSPs on arterial cells, enzymatically isolated cells from normal and diet-induced atherosclerotic aortas of cynomolgus macaques were stressed for 20 h with and without added 72/73 kDa heat shock proteins (HSP-72/73), over a range of temperatures and dosages. Cells were analyzed for changes in viability and lysosomal membrane integrity. The responses of cells from normal and diseased aortas for all test regimens were similar. Viability and lysosomal membrane integrity of untreated cells were correlated (r = 0.85), and both factors declined with increasing thermal stress (P less than 0.0005 and P less than 0.004, respectively). Exogenous HSP-72/73 increased cell viability after stress at a minimum concentration of 10 micrograms/ml (P less than 0.05) but was not concentration dependent. Response to different temperatures showed exogenous HSP-72/73 increased cell survival at all temperatures, with the greatest effect at 37 degrees C (P less than 0.01). In contrast, HSP-72/73 did not have an effect on lysosomal membrane integrity for the test period studied. The results demonstrate exogenous HSP-72/73 increases arterial cell survival, suggesting these proteins are associated with a protective mechanism in normal and diseased arteries.

The induction of the major heat-stress protein in purified rat glial cells

Cultured purified oligodendroglia and astroglia exposed to heat stress (45 degrees C, 10 or 20 min) synthesized a 68-kDa heat-stress protein, which migrates on two-dimensional gel electrophoresis and reacts with a specific monoclonal antibody suggesting it is similar to a major 72-kDa heat-shock protein previously reported in other cell types. This protein was not detected in control glial cultures. Actinomycin D prevented synthesis of this protein demonstrating an absolute requirement for newly synthesized mRNA. The response was prolonged by increasing the period of heat stress from 10 to 20 min. In addition to the 68-kDa HSP protein, the incorporation of radioactivity into 70-, 89-, and 97-kDa proteins was also increased after heating, but in contrast to the 68 kDa protein these proteins appeared to be made in control glial cultures.

Rat mammary adenocarcinoma heat-stress proteins in vivo

Rat 13762NF mammary adenocarcinoma cells (clone MTC) were heated to 42 degrees C either in vivo as a subcutaneous tumour in the rat mammary fat pad or in vitro as attached cells. Labelling in vivo or in vitro detected very similar heat-stress proteins (hsp) at 160, 112, 90, 70 and 56 kDa. Syngeneic rat endothelial and macrophage cells synthesized several cellular proteins in vitro differently than did the tumour cells in vitro, but both types of normal cells were similar to tumour cells in the hsp synthesized. Although the quantitative aspects of induction and repression of hsp may depend on cell type and microenvironment, the major tumour hsp being studied for function in vitro were qualitatively similar to those produced and labelled in vivo in response to a similar heat dose. Hsp were similar in both normal cells and tumour cells from the same host. These observations support the concept that hsp function in fundamental processes in the different microenvironmental and metabolic conditions found in vivo and in vitro. In addition, these observations suggest that prediction of tumour thermal response by measuring hsp levels may be influenced by host cell components.

Effects of polyhydroxyl alcohols on protein synthesis in brain slices

Stressors such as tissue slicing, toxic chemicals, and heat shock applied to cultured cells, organ tissues, or whole animals in vivo induce the synthesis of a 71,000-kilodalton stress protein (SP71) that is not normally present in most organ tissues. In the present experiment, an attempt was made to inhibit selectively the synthesis of SP71 in rat brain tissue slices. Of several manipulations to the brain slice incubation medium that were examined, only addition of very high concentrations of certain polyhydroxyl alcohols, i.e., 1.0 M glycerol, selectively inhibited SP71 synthesis. Glycerol also selectively inhibited SP71 synthesis in heat-shocked cerebral microvascular cells in culture but failed to inhibit SP71 synthesis in anesthetized rats in vivo in response to heat shock. The effects of glycerol on SP71 synthesis are discussed in relationship to current hypotheses concerning the function of SP71.

Rapid expression of novel proteins in goldfish retina following optic nerve crush

Polyadenylated messenger RNA was isolated from goldfish retinas at various times following unilateral crush of the optic nerve. RNA was translated in a cell-free system and product proteins analyzed by two-dimensional gel electrophoresis and autofluorography. Poly(A)+ mRNA-directed protein synthesis revealed an 8-fold increase in the labeling of polypeptides of about 30 kd Mr and a pI of 5.5 in retinas 2 d following optic nerve crush, compared with control retina mRNA translation products. In vitro labeling of retinal proteins revealed the enhanced synthesis of comparable 30 kd proteins in 2 d post-crush retinas. Evidence presented suggests that this 30 kd protein cluster may correspond to fish 30 kd stress or heat-shock proteins (hsp-30).

Synthesis of heat shock proteins in rat brain cortex after transient ischemia

Cell-free protein synthesis and two-dimensional gel autoradiography were used to characterize early postischemic protein synthesis in rat neocortex. Severe forebrain ischemia was induced for 30 min (four-vessel occlusion model) and followed by 3 h of recirculation. Polysomes were isolated from the cerebral cortex, translated in vitro in a reticulocyte system, and analyzed by two-dimensional gel electrophoresis. The translation products of postischemic polysomes included a major new protein family (70 kDa) with multiple isoelectric variants that was found to comigrate with the 68- to 70-kDa "heat shock" protein synthesized from polysomes of hyperthermic rats. Two other stress proteins (93 and 110 kDa) also appeared to be synthesized in increased amounts after ischemia. A complement of proteins that was indistinguishable from that of controls was also synthesized after ischemia, indicating that messenger ribonucleic acid coding for most brain proteins is preserved after ischemia and is bound to polysomes.

Selective gene expression in focal cerebral ischemia

Regional patterns of protein synthesis were examined in rat cortex made ischemic by the occlusion of the right common carotid and middle cerebral arteries. At 2 h of ischemia, proteins were pulse labeled with intracortical injections of a mixture of [3H]leucine, [3H]isoleucine, and [3H]proline. Newly synthesized proteins were analyzed by two-dimensional gel fluorography, and the results correlated with local CBF, measured with [14C]iodoantipyrine as tracer. Small blood flow reductions (CBF = 50-80 ml 100 g-1 min-1) were accompanied by a modest inhibition in synthesis of many proteins and a marked increase in one protein (Mr 27,000). With further reduction in blood flow (CBF = 40 ml 100 g-1 min-1), synthesis became limited to a small group of proteins (Mr 27,000, 34,000, 73,000, 79,000, and actin) including two new polypeptides (Mr 55,000 and 70,000). Severe ischemia (CBF = 15-25 ml 100 g-1 min-1) caused the isoelectric modification of several proteins (Mr 44,000, 55,000, and 70,000) and induced synthesis of another protein (Mr 40,000). Two polypeptides (Mr 27,000 and 70,000) dominated residual protein synthesis in severe ischemia. The changes in protein synthesis induced by different grades of ischemia most likely comprise a variation of the so-called "heat shock" or "stress" response found in all eukaryotic cells subjected to adverse conditions. Since heat shock genes are known to confer partial protection against anoxia and a variety of other noxious insults, their induction may be a factor in limiting the extent of ischemic tissue damage.

Amino acid incorporation in relation to molecular weight of proteins in young and adult brain

Rates of protein synthesis were studied in immature and adult rat brain tissue. After an amino acid incorporation period, in vivo or in incubated slices from brain, the soluble protein was fractionated according to molecular weight by column chromatography. In examining soluble whole proteins, no direct correlation between molecular weights and synthesis rates could be established; the highest synthesis rates were found in fractions around 70,000 MW and below 10,000. Incorporation into the subunits after fractionation by SDS gel electrophoresis was proportional to subunit molecular weight, with rates of incorporation into the largest subunits being the highest. The results suggest a relationship between turnover rate and structure of subunits of brain proteins.

A histochemical examination of the metabolic profiles of rat ventral tegmental area and substantia nigra arterioles

To determine the metabolic profiles of arterioles of the rat ventral tegmental area and zona compacta and zona reticulata of the substantia nigra (SN), the distribution of selected enzymes, or by-products, of key metabolic pathways were examined histologically. Arterioles of all three regions expressed the enzymes required for aerobic and anaerobic metabolism. However, the relative abundance of the enzymes and byproducts suggests a lower metabolic capacity for the SN than the ventral tegmentum, while lipid catabolism in both regions appears non-operative. Moreover, the larger ventral tegmental arterioles possess a greater potential for nucleic acid and protein synthesis. Together, these results suggest the larger ventral tegmental arterioles possess a greater capacity for proliferation and repair.

Induction of a heat shock protein in the isolated mammalian retina

The effects of elevated ambient temperature and addition of the psychotropic drug LSD on protein synthesis in the isolated rabbit retina were investigated. Two dimensional gel electrophoresis followed by fluorography of proteins synthesized in vitro demonstrated that synthesis of a heat shock protein of molecular weight 74,000 (74K) was induced by the elevation of temperature and not by the addition of LSD. The appearance of this heat shock protein was shown to be dependent upon the synthesis of new RNA as shown by the addition of actinomycin-D to the incubation medium. The newly synthesized heat shock protein was associated with both nuclear and cytoplasmic fractions.

Heat shock-like protein is transferred from glia to axon

Glia-axon protein transfer was examined in the squid giant axon. Proteins synthesized by the glial sheath surrounding the axon were labeled with [3H]leucine. Raising the temperature of the incubation medium from 20 degrees C to 30 degrees C increased the synthesis of glial proteins that resembled heat-shock proteins. These proteins were among the group known to be transferred into the axon. Thus, glia provide the axon with proteins that may be involved in the reaction to trauma.

Differential expression of histone sequences in Drosophila following heat shock

The expression of the sequences encoding the four nucleosomal histone proteins was examined following heat shock of a variety of Drosophila cells and was found to be highly differential. In Drosophila melanogaster KC-O cells grown in suspension culture, there is a continuation of the synthesis of all four of the nucleosomal histone proteins following heat shock. Analysis of RNA from these cells confirms that histone messengers are transcribed and located on polysomes. This exact same pattern of histone protein synthesis occurs in KC-O cells grown to low density on plates. In contrast, KC-O cells grown to high density on plates exhibit a dramatic elevation of H2b protein synthesis relative to the synthesis of the other core histones. Organs from D melanogaster third instar larvae were examined to ascertain whether histone protein synthesis continues following heat shock in the organism. Different tissue types exhibited differential histone synthesis. Imaginal disks excised from heat-shocked larvae continue to synthesize nucleosomal histones in a variable fashion. In contrast, neither fat bodies, brains, nor salivary glands continues to synthesize core histone proteins at a significant level. D hydei plated cell cultures and larval tissues fail to synthesize histones at any detectable level following a heat shock. Based on these observations, we propose that there is a differential synthesis of nucleosomal proteins in Drosophila that is highly dependent on the state of the cells prior to the heat shock.

Synthesis of a stress protein following transient ischemia in the gerbil

In vitro translation products of gerbil brain preparations, obtained from animals killed during recirculation following transient ischemia, showed increased synthesis of a 70-kilodalton stress protein, identified by two-dimensional gel electrophoresis. Stimulation of stress protein synthesis was evident as early as 2 h after recirculation, at which time overall translation activity remained low. Expression of the 70-kilodalton protein reached a maximum at 8 h recirculation, when incorporation into other translation products had returned to essentially control levels. Increased incorporation into the stress protein was still detectable after 24 h recirculation. Although the functional consequences of increased expression of this stress protein remain unknown, these results suggest that the gerbil ischemia model may provide a useful experimental system in which to study the involvement of this phenomenon in processes related to postischemic cell damage and recovery.

A metabolic profile of the rat caudate microvasculature: a histochemical study

Arterioles of the rat caudate nucleus were examined histochemically to determine their metabolic profile. These microvessels appear capable of aerobic and anaerobic metabolism with a potential for nucleic acid and protein synthesis. Little intramural lipid storage occurs and any fatty acids utilized are provided via the blood supply. Likewise, glycogen is not seen in the arteriolar wall and may be rapidly turned over as a substrate for anaerobic metabolism.

Temporal profiles of proteins responsive to transient ischemia

The responses of long and short half-lived proteins to ischemia were measured in rat brain during 6 days of recovery from 30 min of transient forebrain ischemia produced by four-vessel occlusion. At the end of the ischemic interval, the neocortical activities of four vulnerable enzymes [ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylases, and RNA polymerases I and II] were unchanged, but within 30 min of reperfusion, their activities dropped by 25-50%. The loss of substance P in the striatum and substantia nigra was slower, reaching about 50% by 12 h. On the other hand, the activities of 5 long half-lived enzymes did not change in the neocortex at 5 and 15 h of reperfusion and regional protein concentrations were essentially unaffected over 6 days survival. The rate and extent of normalization of the amounts or activities of the vulnerable proteins varied. RNA polymerase II and ODC activities were restored within 4 h, and ODC showed a biphasic increase in activity, with peaks at 10 h and 2-3 days. RNA polymerase I and SAMDC activities were restored by 18 h and 5 days, respectively, whereas substance P concentrations did not completely recover, even at 6-15 days. The greater the regional reduction of blood flow during ischemia, the larger the net change (gain or loss) of SAMDC or ODC activity and the longer the time required to normalize the activities of these enzymes. The average rate of proteolysis, assessed by measuring the rate of clearance of 14C from protein prelabeled with [14C]bicarbonate, was abnormal during the first 2 days of reperfusion. Postischemic changes in both protein synthesis and degradation could affect the amounts of some of the proteins responsive to transient ischemia.

Axonal transport of a heat shock protein in the rabbit visual system

Intraocular injection of [35S]methionine was used to demonstrate the pronounced induction of a 74-kDa heat shock protein in the rabbit retina after a 3 degrees C increase in body temperature was generated by intravenous administration of D-lysergic acid diethylamide. Two-dimensional polyacrylamide gel electrophoresis and fluorography revealed that the induced heat shock protein underwent axonal transport from retinal ganglion cells into the optic nerve and subsequently down the contralateral optic tract to synaptic termini in the visual projection area. Since the heat shock protein took more than 8 days to move down the optic nerve to the superior colliculus, it is transported by slow rather than by fast axonal transport.

Isolated rat brain capillaries possess intact, structurally complex, interendothelial tight junctions; freeze-fracture verification of tight junction integrity

Populations of isolated brain capillaries have been proposed as useful models for in vitro studies of the blood-brain barrier. Preliminary investigations of barrier properties using such preparations of brain microvessels have suggested that the tight interendothelial junctions (zonulae occludentes) are intact and retain the impermeability to the protein tracer horseradish peroxidase, exhibited by them in vivo. The endothelial junctions of isolated capillaries are therefore assumed to be functionally "tight' in vitro. In order to determine the precise structural organization of these occluding junctions, including an estimate of their tightness (complexity), and to demonstrate a method for simple but precise assessment of junctional integrity, pellets of isolated rat brain capillaries were freeze-fractured and then replicated with platinum and carbon. The freeze-fracture images of interendothelial zonulae occludentes revealed complex arrays of intramembrane ridges and grooves characteristic of tight junctions. Longitudinal fractures of the cellular lining of capillaries exposed vast expanses of interendothelial plasma membrane interfaces and the junctional complexes situated between the cells. From such arrays, the elaborate and complex architecture of the zonulae occludentes could be readily appreciated. Situated on the PF fracture faces are 6-8 parallel ridges which display a high degree of anastomosing between adjacent strands. The EF fracture face contains grooves complementary to the PF face ridges. The zonulae occludentes of these capillary endothelial cells are similar in complexity to those reported in the literature for reptilian brain capillaries and therefore can be presumed "very tight'. This study demonstrates that freeze-fracture of pellets of brain capillaries alleviates sampling problems inherent in whole tissue preparations and, in addition, demonstrates the usefulness of freeze-fracture as a tool to monitor junction structure during in vitro investigation of the blood-brain barrier.

Glial polypeptides transferred into the squid giant axon

The proteins synthesized by the glial sheath of an isolated segment of squid giant axon and by the cell bodies of the giant axon in the isolated stellate ganglion were labeled by incubation in the presence of [3H]leucine. The axoplasm, which contained labeled proteins transferred from the glial sheath, was separated from the sheath by mechanical extrusion. The labeled proteins in the axoplasm, the empty sheath and the stellate ganglion were analyzed and compared by one- and two-dimensional polyacrylamide gel electrophoresis. Over 80 glial polypeptides were found to be selectively transferred into the axoplasm and many of these were distinct from stellate ganglion polypeptides which presumably could be supplied to the axon via axonal transport. Three of the more highly labeled transferred glial polypeptides (TGPs) were actin, a fodrin-like polypeptide and a polypeptide we have named traversin. Our observations, considered in the context of other reports, suggest that the squid axon receives a large number of polypeptides from its surrounding glia either by phagocytozing glial cell process that project into it or via cytoplasmic channels between adaxonal glia and the axon. These TGPs may help the axon survive unfavorable conditions.

Induction of brain ornithine decarboxylase during recovery from metabolic, mechanical, thermal, or chemical injury

Metabolic, mechanical, thermal, and chemical injury induced ornithine decarboxylase (ODC) activity in rat brain. A two- to sixfold increase in ODC activity was measured at 5-9 h after different modes of injury to the brain. During the early phase of recovery from transient ischemia, when average protein synthesis was less than 50% of control, ODC activity was increased nearly fivefold. The rise in activity could be blocked by anisomycin, or reduced by intracerebral injections of actinomycin D. Drilling burr holes into the skull, injection of the vehicle for actinomycin D, hyperthermia, and freezing lesions all caused increased ODC activity. Neurotoxic chemicals (ammonia, methionine sulfoximine, acrylamide, carbon tetrachloride, and anisomycin) also increased brain ODC activity, whereas other chemicals (mannitol and valine) did not. Treatments known to stimulate the synthesis of heat shock proteins (carotid occlusion, hyperthermia, Cd2+, canavanine, and ethanol) induced ODC activity in the liver, whereas only hyperthermia and ethanol caused significant increases in spleen ODC activity. All increases in ODC activity were blocked by difluoromethylornithine, an irreversible inhibitor of ODC. The cellular response to noxious or stressful stimuli includes the synthesis of a small number of proteins of unknown functions; ODC may be one of these "heat shock" or "trauma" proteins.

Heat shock protein in mammalian brain and other organs after a physiologically relevant increase in body temperature induced by D-lysergic acid diethylamide

A physiologically relevant increase in body temperature from 39.7 to 42.5 degrees C, which was generated after the intravenous injection of D-lysergic acid diethylamide (LSD), caused the induction of synthesis of a 74,000-dalton heat shock protein in the brain, heart, and kidney of the young adult rabbit. A marked increase in the relative labeling of a 74,000-dalton protein was noted after analysis of both in vivo labeled proteins and cell-free translation products of isolated polysomes. A temporal decrease in the synthesis of this protein was noted as LSD-induced hyperthermia subsided. The 74,000-dalton protein, which is induced in various organs of the intact animal at a body temperature similar to that attained during fever reactions, may play a role in homeostatic control mechanisms.

Translation of mRNA associated with monosomes and residual polysomes following disaggregation of brain polysomes by LSD and hyperthermia

Intravenous administration of LSD to young adult rabbits induces a transient disaggregation of brain polysomes and a relocalization of mRNA from polysomes to monosomes. To analyze the spectrum of mRNA molecules which were associated with either the residual polysomes or the translationally inactive monosome complex, these two fractions were isolated on sucrose gradients and translated in a reticulocyte cell-free system. Analysis of [35S]methionine labeled translation products by one and two dimensional gel electrophoresis revealed that a full spectrum of mRNA molecules was relocalized from polysomes to monosomes following drug induced polysome disaggregation. The only exception was the mRNA coding for the LSD-induced 74K protein which was associated with the residual polysome fraction and not with the monosome complex. This brain protein is similar in molecular weight to one of the major 'heat shock' proteins which are induced in tissue culture cells following elevation of ambient temperature and disaggregation of existing polysomes. The mRNA coding for the 74K brain protein was not observed in polysomes isolated following blockage of LSD-induced hyperthermia but it was noted when hyperthermia was induced by elevation of ambient temperature. The mRNA species coding for the 74K protein was polyadenylated.

Protein and RNA synthesis in cerebral microvessels: a radioautographic study

The distribution of protein and ribonucleic acid (RNA) synthesized by telencephalon slices was determined by radioautography at the light microscope level. Previous studies had shown that, in telencephalon slices, the cells associated with the cerebral microvasculature were synthesizing protein at very high rates compared to other cerebral cells such as neurons. In this study, therefore, particular emphasis was placed on the distribution of newly synthesized protein and RNA among the various cell types of the microvasculature. Rat telencephalon slices were incubated with either [3H] leucine or [3H] uridine for 1 h. The 3H-protein that was found in association with microvessels was present in endothelial cells, pericytes and smooth muscles cells. There was also extensive labeling of cellular processes adjacent to the abluminal side of the basement membrane and extending as far as 15 micrometer from the lumen. The latter processes may have been astrocyte glial projections. All [3H] RNA found associated with microvessels was, however, restricted to endothelial cells and pericytes. This data is discussed in relation to the induction of a 71,000 dalton protein which occurs within minutes of the preparation of tissue slices, and requires the synthesis of new RNA.

Trauma-induced protein in rat tissues: a physiological role for a "heat shock" protein?

Hyperthermic shock induces the synthesis of a novel protein (P71) in many rat tissues in vivo. In incubated rat tissue slices P71 is the major protein synthesized even though it is undetectable in the tissues of a normal, unstressed rat. P71 is "heat shock" protein, and it may be induced in vivo by stimuli other than hyperthermia. These results indicate that caution must be used in studies of protein synthesis in tissue explants, since the pattern of proteins synthesized by rat tissue slices is characteristic of stressed tissue.

Cellular responses to stress: comparison of a family of 71--73-kilodalton proteins rapidly synthesized in rat tissue slices and canavanine-treated cells in culture

Cultured rat embryo cells exposed to the L-arginine analogue L-canavanine rapidly accumulated a major 71 kilodalton polypeptide and several minor ones (110, 95, 88, and 78 kilodaltons). Canavanine-treated cultures contained elevated levels of translatable mRNA encoding P71, and the stimulated synthesis of this protein was blocked by actinomycin D, suggesting that P71 is inducible. Rat embryo cells maintained under routine culture conditions synthesized only trace amounts of P71; however, they accumulated an abundant 73 kilodalton protein that was closely related to P71. No kinetic evidence of a precursor-product relationship between P73 and P71 was found. The peptide map of P71 from cultured cells was identical to the map of proteins with the same electrophoretic mobility isolated from incubated slices of rat telencephalon. Previous studies (White, '80a, b, c) have shown that the latter proteins are rapidly synthesized by cells associated with cerebral microvessels in incubated brain slices, but are not detectable in vivo. Herein we present evidence that the synthesis of P71 is not unique to brain slices. Incubated slices of heart, lung, thymus, kidney, spleen, and liver all accumulated an abundant 71 kilodalton size class. The peptide maps of P71 obtained from brain, heart, lung and thymus tissue were similar. The stimulated synthesis of P71 in brain, heart, and lung slices was inhibited strongly by the addition of actinomycin D at the start of incubation. The 71-73 kilodalton proteins of canavanine-treated rat embryo cells and incubated slices from seven different organs were compared in detail on two-dimensional polyacrylamide gels. Eight charge variants were detected in extracts of lung, spleen, and thymus tissue, four in liver and heart, three in kidney, and two different pairs of variants in extracts of brain tissue and cultured cells. The possible significance of the rapid synthesis of a similar small set of proteins in tissue slices and cultured cells in response to a variety of physical, chemical, and biological stimuli is discussed in terms of cellular responses to traumatic injury and metabolic stress.