Dense granular bodies: a novel nucleoplasmic structure in hibernating dormice

Dense granular bodies (DGB) are particular structural constituents observed in cell nuclei of different tissues-liver, pancreas, brown adipose tissue, adrenal cortex-of hibernating dormice. They appear as strongly electron-dense clusters of closely packed granules, with thin fibrils spreading out at their periphery. DGB always occur in the nucleoplasm, sometimes making contact with other nuclear structural constituents typical of the hibernating state, such as coiled bodies, amorphous bodies and nucleoplasmic fibrils. DGB are present only during deep hibernation and rapidly disappear upon arousal from hibernation. Cytochemical and immunocytochemical analyses showed that DGB contain ribonucleoproteins and several nucleoplasmic RNA processing factors, suggesting that DGB can represent accumulation sites of splicing factors which are provided to splicing sites when normal metabolic activity is rapidly restored during arousal.

Localization of heat shock proteins in mouse male germ cells: an immunoelectron microscopical study

We have examined the intracellular distribution of heat shock proteins HSP27 and HSP90 by means of specific antibodies and ultrastructural immunocytochemistry in the normal mouse testis as well as after heat shock. In the unstressed testis, these heat shock proteins are present in the cytoplasm and to a lesser extent in the nucleus throughout spermatogenesis. They do not show preferential association with any specific cytoplasmic structures and are absent from mitochondria. They disappear from the cell nucleus at the stage of elongating spermatids. After heat shock (42 degrees C), both HSP90 and HSP27 increase and partly relocate to the nucleus. Similarly to the localization in unstressed cells, they are mainly associated with perichromatin fibrils and the nucleolus. Moreover, a remarkable increase in the frequency of perichromatin fibrils in Sertoli cells, spermatogonia, and primary spermatocytes is also observed upon heat shock. Finally, a sharp increase in the labeling of HSPs in chromatoid bodies of round spermatids occurs following hyperthermic treatment. Interestingly, these two HSPs are localized on nuclear structures which are actively involved in RNA synthesis and processing, suggesting that they may have protective functions in these processes in a tissue which is particularly sensitive to heat stresses.

The cell nucleus in early bovine and caprine preimplantation embryos: fine structural cytochemistry and immunoelectron microscopy

Fine structural cytochemistry and immunocytochemistry were used to study nucleic acids and nuclear proteins in nuclear bodies (NB) of pronuclear and 2-cell bovine and caprine embryos on ultrathin sections of paraformaldehyde fixed and Lowicryl K4M or LR White embedded specimens. The most striking feature detected in some of these nuclear bodies (NBs) was the presence of non-nucleolar proteins known to be involved in pre-mRNA splicing. One category of such intranuclear bodies (showing a rather dense finely fibrillar composition and named here dense body-DB) contained the Sm-antigen (an antigen common to a major group of nucleoplasmic spliceosomal snRNPs). Another, more numerous category of NBs differed morphologically from the former one by a much looser composition of fibrillogranular elements (loose body-LB). Moreover, it showed the presence of the non-snRNP splicing factor SC-35, in addition to the Sm-antigen. Both categories of these nuclear bodies were distinguished clearly from the nucleolar precursor bodies (NPBs) by an absence of immunolabeling of NPB with antibodies against nuclear proteins involved in splicing. Moreover, the former NBs are not stained with silver, while NPBs already in pronuclei exhibit strong affinity to silver. In addition to the immunolabeling in prominent (approx. 0.2-2.0 microns) NBs, regularly occurring high concentration of snRNP was revealed in very small (approx. 0.05 micron), morphologically poorly defined areas (named here small snRNP-enriched areas-SSA), harboring moreover a set of nuclear proteins similar to that of the coiled body. Numerous observations of the presence of these small areas in nuclear bodies and in their close vicinity, in nucleoplasm, in proximity of the nuclear envelope and also in ooplasm suggested that they are possible carriers of certain nuclear proteins moving between nuclear bodies, nucleoplasm and cytoplasm. A functional relationship of all these embryonic subnuclear elements has not been elucidated so far but their mutual relation is suggested, since the NPBs and other nuclear bodies usually occur in a close association. Fine structural and immunoelectron microscopic observations further suggest a similarity of the nuclear bodies in the early ruminant embryo with specific intranuclear bodies ("snurposomes") known from Xenopus laevis oocytes. A new and striking feature emerging from these observations is a possible involvement of a group of nucleoplasmic proteins in a yet unknown way in the differentiation processes concomitant with early embryonic nucleologenesis.

Fine structural cytochemical and immunocytochemical analysis of nucleic acids and ribonucleoprotein distribution in nuclei of pig oocytes and early preimplantation embryos

The fine structure of pig oocytes at the germinal vesicle (GV) stage and early preimplantation embryos (one to four blastomeres) isolated at slaughter was investigated by cytochemical and immunocytochemical methods. The distribution of nucleic acids and ribonucleoproteins (RNPs) in "compact nucleoli" [denominated nucleolus-like bodies (NLB) in oocytes and nucleolus precursor bodies (NPB) in early embryos] and in intranuclear bodies or granules was investigated by staining methods preferential for nuclear RNPs or using the osmium ammine or ethidium bromide-phosphotungstic acid (EB-PTA) reactions for nucleic acids. The distributions of the Sm antigen of nucleoplasmic small nuclear RNPs (snRNPs), the methyl-3 guanosine (m3G) cap of snRNAs and the splicing factor SC-35 were detected by immunoelectron microscopy using specific antibodies. The RNP nature of both NLBs and NPBs, and of nuclear granules in oocytes and embryos, and of fibrillar strands radially projecting from NLBs was revealed. Cytochemical evidence for RNA as a component of NLBs was further provided by EB-PTA staining in combination with the enzymatic removal of RNA, or by osmium-ammine staining without previous acid hydrolysis, while the absence of DNA in NLBs was established by Feulgen-like osmium-ammine staining. In addition, autoradiography demonstrated the absence of [6-3H]thymidine incorporation into NPBs. Other autoradiographic evidence attested the accumulation of RNA in NLBs of oocytes after a 60 min in vitro pulse of [5-3H]uridine. Immunoelectron microscopy using specific antibodies revealed the occurrence of nucleoplasmic snRNPs in both NLBs and NPBs. The presence of snRNA in NLB was confirmed by means of an antibody recognizing the m3G-cap structure. Another spliceosomal component, the protein SC-35 was also detected in NLBs. Among the numerous and variable intranuclear granules occurring mostly in aggregates, the Sm antigen was clearly detected only in the interchromatin granule-type component. Some Sm labeling was occasionally seen in other categories of larger granules. No reaction was detected over any granules when using the anti-m3G-cap antibody. The aggregates consisting of large granules and a finely fibrillar component were intensely immunolabeled by the anti-SC-35 splicing factor probe. Our observations suggest that the compact nucleoli, known to be present before and after fertilization in mammals (NLBs of oocytes and NPBs of early embryos), represent nuclear structural elements containing nonnucleolar, spliceosomal components.

Immunoelectron microscope analyses of rat germinal vesicle-stage oocyte nucleolus-like bodies

Germinal vesicle (GV) stage oocytes isolated from rat ovaries were investigated by immunoelectron microscopy for the presence of several nuclear proteins in the prominent 'compact nucleoli' (nucleolus-like bodies named here NLB). Specific spliceosomal components including the Sm antigen of the nucleoplasmic small nuclear ribonucleoproteins (snRNP) and the non-snRNP splicing factor SC-35 were clearly detected in the dense finely fibrillar mass of the NLB. Moreover, the presence of small nuclear RNA (snRNA) in the NLB was demonstrated by means of an antibody which recognized the m3G-capped snRNA. The level of immunolabelling for the nuclear proteins fibrillarin and p80-coilin was relatively lower in the NLB. p80-coilin was distinctly localized, in small, poorly morphologically defined structural constituents in the nucleoplasm. Aggregates of intranuclear granules having similar antigenic composition to the NLB were also detected. Our observations suggested that the 'compact nucleoli' of rat GV oocytes represented nuclear compartments containing significant amounts of non-nucleolar, spliceosomal components. These NLB have a molecular composition closer to the composition of certain nuclear bodies than to the functional nucleoli of somatic cells. The NLB may represent a compartment in the mammalian oocyte, akin to the sphere organelle of the amphibian oocyte (also reported to contain spliceosomal components and a p80-coilin-related protein). Both structures may serve as temporary storage organelles for different maternal macromolecules, which support early embryonic development, inter alia of that involved in the maturation of pre-mRNA to be transcribed from the embryonic genome.

Novel nuclear ribonucleoprotein structural components in the dormouse adrenal cortex during hibernation

Adrenocortical cell nuclei of the dormouse Muscardinus avellanarius were investigated by electron microscopic immunocytochemistry in hibernating, arousing and euthermic individuals. While the basic structural constituents of the cell nucleus did not significantly modify in the three groups, novel structural components were found in nuclei of hibernating dormice. Lattice-like bodies (LBs), clustered granules (CGs), fibrogranular material (FGM) and granules associated with bundles of nucleoplasmic fibrils (NF) all contained ribonucleoproteins (RNPs), as shown by labeling with anti-snRNP (small nuclear RNP), anti-m3G-capped RNA and anti-hnRNP (heterogeneous nuclear RNP) antibodies. Moreover, the FGM also showed immunoreactivity for the proliferation associated nuclear antigen (PANA) and the non-snRNP splicing factor SC-35. All these nuclear structural components disappeared early during arousal and were not found in euthermic animals. These novel RNP-containing structures, which have not been observed in other tissues investigated so far in the same animal model, could represent storage and/or processing sites for pre-mRNA during the extreme metabolic condition of hibernation, to be quickly released upon arousal. NFs, which had been sometimes found devoid of associated granules in nuclei of brown adipose tissue from hi-bernating dormice, were present in much higher amounts in adrenocortical cell nuclei; they do not contain RNPs and their role remains to be elucidated. The possible roles of these structures are discussed in the frame of current knowledge of morpho-functional relationships in the cell nucleus.

The post-transcriptional regulator Rex of the human T-cell leukemia virus type I is present as nucleolar speckles in infected cells

The rex-encoded protein (Rex) of human T-cell leukemia virus type I (HTLV-I) is responsible for the cytoplasmic accumulation of incompletely spliced mRNAs that encode the virion structural proteins. Rex is known to be located predominantly in the cell nucleoli in transient transfections or in the isolated nuclei of HTLV-I-infected cells. However, precise location of Rex under physiological conditions has not been determined unequivocally. Here we report that Rex is primarily located as intranucleolar speckles in HTLV-I-infected cells, except for a few nucleoplasmic speckles. This is in contrast to the more diffuse nucleolar distribution of the rev-encoded protein (Rev) of human immunodeficiency virus type 1 (HIV-1), the functional homologue to Rex, in HIV-1-infected cells. Accumulation of Rev is associated with disruption of nucleolar structure and cell death, whereas Rex does not have these effects. The difference in distribution of Rex and Rev within the nucleoli may reflect the difference of toxicity toward the host cells. Involvement of the nucleolus in processing of certain mRNAs is also discussed.

The cytotoxicity of human immunodeficiency virus type 1 Rev: implications for its interaction with the nucleolar protein B23

Human immunodeficiency virus type 1 (HIV-1) encodes several regulatory proteins, including two essential trans-activators for viral replication, Rev and Tat. Both Rev and Tat have a nucleolar targeting signal and are actually located predominantly in the nucleoli. Within the nucleoli, Rev is localized to the combined regions of the dense fibrillar (DFC) and the granular (GC) components. Tat does not colocalize precisely with any nucleolar component tested, but partly overlaps regions of the DFC and the GC. Regions of both Rev and Tat are overlapped by the distribution of the major nucleolar protein B23. Overexpression of Rev causes nucleolar ballooning and general structural deformity with aberrant accumulation of rRNAs, whereas Tat does not have that effect. B23 is markedly accumulated in those nucleoli deformed by Rev. Components of the nucleolar DFC, GC, and fibrillar center domains are not accumulated but dispersed in few small spots or larger patches within the enlarged nucleoli. Cytophotometric DNA determinations revealed that transient expression of Rev results in accumulation of G2, prophase, and mitotic cells which have failed cytokinesis, suggesting that Rev is capable of preventing or slowing the progression through mitosis. Tat, in contrast, does not affect the cell cycle. We speculate, based on these results, that Rev represses cell growth by inhibiting the transport of ribosomal proteins and preribosomal particles across the nuclear envelope and affecting the cell cycle, both of which may be related to proposed functions of B23.

Immunocytochemical characterization of nuclear ribonucleoprotein fibrils in cells of the central nervous system of the rat

Nucleoplasmic structural constituents observed in partially decondensed nuclei of the central nervous system of the rat were analyzed by postembedding immunoelectron microscopy using antibodies specifically recognizing heterogenous nuclear ribonucleoprotein (hnRNP) and small nuclear ribonucleoprotein (snRNP) complexes and DNA. Fibrogranular RNP structures (polyparticles) were found in close proximity to DNA containing fibrillar areas resulting from partial dispersion of compact chromatin. The polyparticle-type fibrils are labeled by antibodies recognizing hnRNP core proteins as well as snRNPs (Sm antigen or 70 kDa protein of U1snRNP) or the m3G-cap structure of snRNAs. These observations suggest that such polyparticle-type fibrils correspond to extended perichromatin fibrils. Partially decondensed perichromatin granules are rarely labeled by anti-snRNP or snRNA antibodies. When labeling occurs it is restricted to the periphery of the granules. However, anti-hnRNP antibodies frequently label these granules. Our results favor the idea, previously proposed for Balbiani ring granules, that perichromatin granules are formed by the folding of hnRNP containing perichromatin fibrils (polyparticles) in the process of splicing, and that mature perichromatin granules contain already spliced messenger RNA.

Cytochemical and immunocytochemical characterization of nuclear bodies during hibernation

Brown adipose tissue and liver of hibernating, arousing and euthermic individuals of the dormouse Muscardinus avellanarius were studies using ultrastructural cytochemistry and immunocytochemistry with the aim to investigate possible fine structural modifications of the cell nucleus during the seasonal cycle. The general morphology of brown adipocyte and hepatocyte nuclei was similar in the three experimental groups. However, three nuclear structural constituents were identified only in hibernating individuals: coiled bodies (CBs) and amorphous bodies (ABs) were observed in hepatocytes and, together with bundles of nucleoplasmic fibrils (NF), were present in brown adipocytes of hibernating dormice. In arousing animals only some structural constituents suggestive of poorly structured CBs were found. The latter showed the same immunocytochemical features as CBs of hibernating individuals, suggesting that they are disappearing CBs. A possible involvement of CBs in storing and/or processing RNA which must be rapidly and abundantly released upon arousal is discussed. ABs similarly to CBs contain RNA and nucleoplasmic ribonucleoproteins (RNPs) and could also be involved in mRNA pathways. NF do not contain nucleic acids or RNPs and seem to be composed of protein-aceous material; their functional role in the nuclear metabolism of hibernating brown adipocytes remains unclear.

Physiologically inactive nucleoli contain nucleoplasmic ribonucleoproteins: immunoelectron microscopy of mouse spermatids and early embryos

Physiologically inactivating or reactivating nucleoli represent a good model to investigate modifications of the nucleolar activity, which influence to a great extent the morphology of this organelle. We have studied the nucleoli of mouse spermatids during gradual inactivation, as well as those of early mouse preimplantation embryos, which undergo reactivation. In the 2-cell systems, inactive nucleoli are represented by homogeneously, finely fibrillar spherical bodies. With the aim of clarifying the composition of these nucleoli, we have analyzed them by means of immunoelectron microscopy using specific antibodies directed against nucleoplasmic snRNPs, hnRNPs, ribosomal proteins, or fibrillarin as well as by cytochemical methods for visualizing DNA and RNA. Our results indicate that RNA is present in zygote and 2-cell nucleolus precursor bodies (NPBs) as well as in 4- to 8-cell or more advanced embryo nucleoli, but not in inactive spermatid nucleoli. DNA is absent from inactive spermatid nucleoli and NPBs but is present within the nucleolus-associated chromatin and the nucleolonema of active nucleoli. The dense masses constituting the NPBs of the zygote and 2-cell embryos contain ribosomal proteins and fibrillarin but also hnRNPs and nucleoplasmic snRNPs. Of these, only fibrillarin is present in the spermatid residual nucleoli.

Is the coiled body involved in nucleolar functions?

Coiled bodies (CBs) are structural constituents observed in nuclei of most eukaryotic cells. They usually occur in the nucleoplasm as well as in contact with the nucleolar surface. In this work we studied the hepatocyte nuclei of hibernating dormice in order to investigate possible modifications of CBs along the seasonal cycle. CBs were abundant during hibernation and rapidly disappeared upon arousal from hibernation. Moreover, CBs were frequently found to be integrated into the nucleolar body. Immunocytochemical analyses showed that CBs contain nucleoplasmic as well as nucleolar RNA-processing factors, suggesting an "ambiguous" role for this organelle in the nuclear functions.

Glyceraldehyde-3-phosphate dehydrogenase modifier protein is associated with microtubules in kidney epithelial cells

After exposure of monkey kidney epithelial cells to a reduced concentration of K, a known mitogenic signal, the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (G3PD) is activated by a cytosolic protein whose function appears to be novel. A monospecific antibody was used as an immunoprobe to study the contribution of this G3PD modifier protein (MP) to signal transduction. Raising the extracellular Na concentration as well as lowering the K concentration of the medium increased the amount of MP in cytosol and also activated G3PD. Metabolic labeling of cells followed by preparation of detergent-soluble (cytosolic) and detergent-resistant (cytoskeletal) fractions, immunoprecipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of radiolabeled immune precipitates suggested that the protein was also associated with cytoskeleton. Depolymerization of the microtubules with colchicine or nocodazole increased cytosolic immunoreactive MP, whereas cytochalasin D had no effect. Taxol, which stabilizes microtubules, blocked the effects of colchicine or nocodazole. When tubulin, actin, and intermediate filament fractions of the cytoskeleton were prepared, blotted, and probed with specific antibodies, MP was found in the tubulin fraction. These observations suggest that MP is associated with the microtubules and can be displaced into the cytosol, wherein it could activate G3PD and thereby stimulate glycolytic production of ATP during mitogenic signal transduction.

The effect of a new ejection seat headbox and high G garments on head mobility during air combat

Full coverage anti-G trousers, a chest counter pressure garment for positive pressure breathing for G tolerance, and a smaller ejection seat headbox have been developed for future agile aircraft. The hypotheses that the new headbox might improve, and that the more restrictive high G garments might compromise, pilot head mobility were tested. The RAF institute of Aviation Medicine Hawk aircraft was equipped with a wide angle video camera facing the front seat pilot. Two experimental conditions were compared to the control air combat sortie: 1. standard garments and the smaller headbox; 2. high G garments and the smaller headbox. Data were recorded from five instructor pilots during three scheduled air combat training sorties. Their helmets were marked with 10-mm white dots in a standardized pattern. Software for recording helmet dot positions from single frame video images, and a trigonometric method for calculating head rotation and translation from changes in the helmet dot positions were devised. No differences were found between headboxes or garments at the three extremes of head movements analyzed. Observed neck rotations were similar to maximal seated norms. Optimal head and neck extension is impeded by the ejection seat headbox. Pilots' head movements are not restricted during air combat at moderate G levels.

Resolving the casualty evacuation conflict

One of the most contentious issues surrounding the prehospital management of the injured is the decision to stabilize on site or to rapidly evacuate the patient. Although there are vociferous proponents for both views, there appears to be little thought given to the rationalization of these decisions, and the subject has only merited lip-service in previous texts. Treatment choices and decisions in the prehospital environment are notoriously difficult to make. The doctor, unlike ambulance paramedics, does not necessarily work to didactic protocols and, if suitably trained, is at liberty to commence advanced resuscitation procedures at the roadside. However, these may be time consuming and, to be of greatest benefit to the patient, a fine balance between resuscitation and evacuation must be drawn. This paper aims to discuss some of the key issues which need to be considered in the prehospital scenario, such as treatment triage, evacuation priorities, mode of transportation and hospital destination. The end result must be to eliminate the medical 'bottleneck' and to afford early and appropriate definitive care to those in most need.

Immunoelectron microscope localization of snRNP, hnRNP, and ribosomal proteins in mouse spermatogenesis

We have studied the ultrastructural distribution of heterogeneous nuclear ribonucleoproteins (hnRNPs), small nuclear ribonucleoproteins (snRNPs), and ribosomal proteins during mouse spermatogenesis and spermiogenesis by means of specific antibodies and immunocytochemistry. All the above components were detectable from primary spermatocytes until the spermatid elongation phase, when the RNA synthetic activity is known to cease. Ribosomal protein (P1/P2 and L7) labeling disappeared as early as during the acrosome phase, and nucleoli were no longer labeled even during the cap phase. The nucleoplasmic structures labeled with the different anti-nucleoplasmic RNP immunoprobes corresponded, until the acrosome phase, to those previously observed as targets of the same antibodies in the nucleoplasm of somatic cell nuclei. Clusters of interchromatin granules of spermatocyte and early spermatid nuclei exhibit some labeling for hnRNP when compared with nuclei of Sertoli cells or previously analyzed liver or tissue culture cells, where these structural constituents usually remain weakly labeled or unlabeled. In spermatids in step 10, another type of nuclear granule, resembling perichromatin granules, but occurring in aggregates, can be observed. These structural constituents were labeled with antibodies recognizing nucleoplasmic snRNP antigens and therefore suggesting a non-nucleolar origin of these granules. Finally, we have observed nucleoplasmic areas of fibrogranular material, occurring only in primary spermatocytes. These components were labeled with anti-ribosomal protein antibodies but did not contain either hnRNPs or snRNPs.

Ribonucleoprotein components of root meristematic cell nuclei of the tomato characterized by application of mild loosening and immunocytochemistry

Immunocytochemistry and hypotonic-formaldehyde fixation have been used to study the extranucleolar ribonucleoprotein (RNP) constituents of the nucleus of tomato root meristematic cells. The study of the distribution of small nuclear uridine-rich RNPs (snRNP) by means of a monoclonal anti-Sm antibody recognizing a 29-kDa protein in plants, after standard fixation, shows a preferential labeling of the perichromatin region and a lower labeling of the interchromatin space. These results suggest that in the tomato there is a perichromatin region similar to that of animal cells, in which much of the nonnucleolar transcription and splicing takes place. In hypotonic-formaldehyde-detergent-fixed nuclei, fibrogranular polyparticles have been visualized reacting with anti-snRNP antibody. These structures are frequently associated with filaments of extended chromatin characterized by their reaction with an anti-DNA monoclonal antibody.

Cytokeratin reorganization induced by adenosine diphosphate in kidney epithelial cells

Exogenous adenosine diphosphate (ADP), the most potent mitogen for nontransformed African green monkey kidney epithelial cells of the BSC-1 line, rapidly alters the appearance of the cell monolayer. Examination of the cells with indirect immunofluorescence using monoclonal antibodies reveals a considerable reorganization of cytokeratin filaments without a major change in the pattern of microtubules or microfilaments. In untreated confluent cells, cytokeratin filaments are predominantly confined to a star-like spot in the perinuclear area, but these can be seen to begin to spread within 2 min after addition of ADP. The effect is particularly notable using anti-cytokeratin 8 antibodies. At 6 h this process is complete and produces a well-developed filamentous network throughout the cell. By 12 h, the network appears to collapse, so that the filaments again form a spot in the perinuclear area, a process that is complete by 24 h. Immunoblotting of total cellular proteins reveals no apparent alterations in the amounts of several species of cytokeratins, including cytokeratin 8 and 18, at 3 or 24 h after exposure to ADP. Other purine and pyrimidine nucleotides which do not stimulate DNA synthesis in these cells fail to alter cytokeratin organization, and there is no apparent alteration in the distribution of vimentin, another intermediate filament protein. The rapid ADP-induced cytokeratin reorganization appears to coincide with the induction of early growth-response gene transcription in these cells and may be correlated with the capacity of ADP to subsequently initiate DNA synthesis. This dramatic and reversible cytokeratin reorganization immediately after exposure to ADP may be an important step in the mitogenic signal transduction pathway.

Al Jubail — An Aeromedical Staging Facility during the Gulf Conflict: Discussion Paper

During the latter half of 1990 the Royal Air Force established a medical evacuation chain in support of the British First Armoured Division during Operation Granby (known as Operation Desert Storm in the USA). Medical contingency plans, formulated prior to embarkation from the UK, foresaw the need for five aeromedical staging facilities sub-deployed throughout the east of the Arabian Peninsula. The early days of the deployment found personnel busy with the construction of tented and hardened facilities and with the establishment of local operating procedures. Many problems were initially encountered, especially with supply, communications and in co-ordinating with collaborating coalition and host nation units. Nevertheless, progress was rapid and non-combatant operations were started within days of arrival. As the ground offensive became more imminent, training took on a sense of urgency. Advanced first aid techniques were taught to all non-medical staff, whereas doctors, nurses and paramedical personnel were taught ACLS and ATLS skills. All studied field hygiene, the hazards of nuclear, chemical and biological warfare, casualty handling, battle psychology and the intricacies of loading and unloading various types of aircraft. By the start of the ground phase of the war the British evacuation chain was fully operational and capable of treating and transferring hundreds of casualties per day. In the event, only about 850 patients were transported down the evacuation chain during the conflict, and less than 10% of these were battle casualties. This paper presents an overview of the British aeromedical evacuation system and discusses, in more detail, the establishment and operation of the busiest aeromedical staging facility at Al Jubail in the Eastern Province of Saudi Arabia.

Immunoelectron microscopic localization of small nuclear ribonucleoproteins during bovine early embryogenesis

Small nuclear ribonucleoproteins (snRNPs) were localized using human autoimmune or monoclonal anti-snRNP antibodies and ultrastructural immunocytochemistry in early preimplantation bovine embryos before and at transcription onset. Bovine cleavage stages up to 16-cell embryos were obtained either by culture of in vitro-fertilized ovarian oocytes or by isolation at slaughter of embryos fertilized and developed in vivo. Before transcription onset, up to the four-cell stage, diffuse labeling of nucleoplasm was detected, whereas cytoplasm labeling remained low. At the transcription onset, labeling of all eight-cell embryo nuclei was markedly concentrated at the borderline of already formed, condensed chromatin aggregates, where it was associated mainly with perichromatin fibrils. The condensed chromatin blocks revealed by several different staining methods were more prominent than is the case in most somatic cells. The degree of chromatin condensation and the pattern of its distribution differed between in vivo- and in vitro-produced eight-cell embryos: the in vitro embryos showed a higher degree of chromatin condensation and a peripheral distribution of chromatin blocks. A relation of this observation to the developmental potential of cow embryos is suggested. In two- and four-cell embryos, intensive labeling was seen in interchromatin granules, which, in their turn, were often seen in close proximity to the nucleolus precursor bodies, or in the four-cell stage were interconnected to them. No labeling was ever seen, using antibodies specific for the snRNP Sm antigen, in nucleolar precursor bodies during embryonic nucleologenesis nor in the resulting nucleoli. There was some incidental labeling of the large central vacuole appearing at the beginning of the nucleolus precursor body transformation, testifying the nucleoplasmic origin of this entity.

Nucleic acid binding characteristics of group A/B hnRNP proteins

hnRNP proteins are primarily defined by their specific sedimentational, reconstitutional, and extraction properties and are presumed to be RNA binding. However, it is not clear whether all these proteins have RNA binding capabilities. Recently, using two monoclonal antibodies, fA12 and AC88, we reported that the abundance of a subclass of the highly basic A/B hnRNP proteins was specifically down regulated during terminal differentiation of human and murine cells in vitro. In this report we have examined the nucleic acid binding characteristics of this subclass and other members of the A/B hnRNP proteins in vitro. All members of class A/B hnRNP proteins appear to have similar but not identical nucleic acid binding characteristics. However, the subclass of proteins recognized by AC88 and fA12 exhibit stronger binding affinities and are shown to be highly selective in their binding to RNA vs DNA in vitro. These proteins also preferentially bind poly(U) RNA, suggesting that in vivo they may bind effectively to uridine rich motifs critical in pre-mRNA processing.

Immunoelectron microscopic localization of estrogen receptor on pre-mRNA containing constituents of rat uterine cell nuclei

The localization and quantitative changes of estradiol receptor (ER) were studied by means of immunogold-electron microscope methods using a polyclonal antibody directed against an amino acid sequence representing the DNA binding site of ER, a monoclonal antibody against hnRNP core protein, and anti-DNA antibody. The uteri of normal rats in estrus and those of ovariectomized females were used. Ovariectomized rats were studied 21 days after surgery at different times after the injection of normal saline or estradiol-17 beta. The density of labeling was measured in interchromatin space, compact chromatin, nucleolus, cytoplasm, and background of epithelial cells, muscle cells, and fibroblasts. In the three types of cells ER was found mainly on extranucleolar ribonucleoprotein (RNP) fibrils. In epithelial and muscle cells the nucleolus was labeled but compact chromatin was not labeled. In epithelial cells there was a low but significant labeling of the cytoplasm. Fibroblasts exhibited a low labeling of the compact chromatin. Ovariectomy did not change these distributions. The estradiol injection increased labeling in all compartments of epithelial and muscle cells but decreased the labeling of compact chromatin of fibroblasts. These results show: (a) that ER is mainly nuclear but it is also present in the cytoplasm, (b) that ER binds to the nuclear particles containing newly synthesized RNA, and (c) that the binding to RNPs does not block the DNA binding domain of the ER.

Immunoelectron microscopical visualization of ribonucleoproteins in the chromatoid body of mouse spermatids

The chromatoid body (CB), a cytoplasmic organelle present only in germ cell line, was studied at the electron microscopic level in mouse spermatids using cytochemical techniques and specific antibodies directed against sn-RNPs, hnRNPs, and ribosomal proteins. We found that specific staining for DNA as well as the use of monoclonal anti-DNA antibodies show a complete absence of DNA in the CB. The CB remains stained, however, after the application of the ethidium bromide-PTA technique, suggesting the presence of RNA within this organelle. snRNP as well as hnRNP proteins are demonstrated within the CB by means of specific monoclonal or polyclonal antibodies, especially during earlier spermiogenic stages. Monoclonal antibodies directed against the large ribosomal subunit proteins P1/P2 detect these antigens on the CB essentially along the internal threads of dense fibrillar material. Our findings suggest that the CB may function as a source of mRNA and/or of its partially processed precursors during the late stages of spermiogenesis, when the spermatid nucleus becomes gradually inactive.

The Ramstein airshow disaster

In August 1988 an aircraft of the Italian aerobatic display team fell into the spectator enclosure at the Ramstein Airshow, causing over 500 casualties. The survivors were triaged, treated and evacuated from Ramstein within 96 minutes. The speed and efficiency of this evacuation was a result of prior planning, thorough training, medical reinforcement, co-operation with other agencies and the availability of an abundance of vehicles for both air and road evacuation. Not suprisingly, though, problems did occur, especially with communications, casualty identification and documentation.

Ultrastructural distribution of ribonucleoprotein complexes during mitosis. snRNP antigens are contained in mitotic granule clusters

The great majority of snRNP and hnRNP ribonucleoproteins have been shown to be confined to the nucleus except during periods of cell division. We have now determined the fine structure distribution of polypeptides associated with these RNP complexes during interphase and mitosis in mammalian tissue culture cells using immunoelectron microscopy. Many hnRNP antigens are found at the periphery of heterochromatin masses, known to be the sites of non-rRNP proteins initially surround areas of condensing chromatin and later become generally dispersed throughout the mitotic cell. The Sm protein antigens of snRNP complexes are found diffusely distributed in interphase nuclei as well as concentrated in fields of interchromatin granules (ICG). Proteins of snRNP complexes, unlike those of hnRNP, are associated with discernible cellular structures during mitosis. By prometaphase/metaphase, dense granular clusters are observed to contain a high concentration of snRNPs. These mitotic granule clusters (MGCs) are often in close proximity to chromosomal masses by late anaphase/telophase. The MGC structures are morphologically similar to interchromatin granule fields found in interphase nuclei. Furthermore, like interchromatin granules, they are sites of a high concentration of snRNP antigens and do not contain detectable hnRNP proteins or DNA.