Early human impacts and ecosystem reorganization in southern-central Africa.

Modern Homo sapiens engage in substantial ecosystem modification, but it is difficult to detect the origins or early consequences of these behaviors. Archaeological, geochronological, geomorphological, and paleoenvironmental data from northern Malawi document a changing relationship between forager presence, ecosystem organization, and alluvial fan formation in the Late Pleistocene. Dense concentrations of Middle Stone Age artifacts and alluvial fan systems formed after ca. 92 thousand years ago, within a paleoecological context with no analog in the preceding half-million-year record. Archaeological data and principal coordinates analysis indicate that early anthropogenic fire relaxed seasonal constraints on ignitions, influencing vegetation composition and erosion. This operated in tandem with climate-driven changes in precipitation to culminate in an ecological transition to an early, pre-agricultural anthropogenic landscape.

PDGFR-ß-Positive Perivascular Adventitial Cells Expressing Nestin Contribute to Fibrotic Scar Formation in the Striatum of 3-NP Intoxicated Rats.

Perivascular cells expressing platelet-derived growth factor receptor beta (PDGFR-ß) have recently been implicated in fibrotic scar formation after acute brain injury, but their precise identity and detailed morphological characteristics remain elusive. This study sought to characterize and define the cellular phenotype of vascular-associated cells expressing PDGFR-ß in the striatum of rats treated with the mitochondrial toxin 3-nitropropionic acid (3-NP). In the control striatum, PDGFR-ß-positive cells were invariably localized on the abluminal side of smooth muscle cells of larger caliber vessels, and demonstrated morphological features typical of perivascular fibroblasts. PDGFR-ß expression increased and expanded to almost all vessels, including microvessels in the lesion core, at 7 days after 3-NP injection. The cells expressing PDGFR-ß had ultrastructural features of fibroblasts undergoing active collagen synthesis: large euchromatic nuclei with a prominent nucleolus, well-developed rough endoplasmic reticulum (rER) with dilated cisterns and extracellular collagen fibrils. By 14 days, PDGFR-ß-positive cells had somata located at a distance from the vasculature, and their highly ramified, slender processes overlapped with those from other cells, thus forming a plexus of processes in the extravascular space of the lesion core. In addition, their ultrastructural morphology and spatial correlation with activated microglia/macrophages were elaborated by three-dimensional reconstruction. Using a correlative light- and electron-microscopy technique, we found that the intermediate filament proteins nestin and vimentin were induced in PDGFRß-positive fibroblasts in the lesion core. Collectively, our data suggest that perivascular PDGFR-ß-positive fibroblasts are distinct from other vascular cell types, including pericytes and contribute to fibrotic scar formation in the lesion core after acute brain injury. Nestin and vimentin play critical roles in the structural dynamics of these reactive fibroblasts.

Morphological characterization of NG2 glia and their association with neuroglial cells in the 3-nitropropionic acid-lesioned striatum of rat.

Our aim was to examine the spatiotemporal profiles and phenotypic characteristics of neuron-glia antigen 2 (NG2) glia and their associations with neuroglial cells in striatal lesions due to the mitochondrial toxin 3-nitropropionic acid (3-NP). In control striatum, weak NG2 immunoreactivity was restricted to resting NG2 glia with thin processes, but prominent NG2 expression was noted on activated microglia/macrophages, and reactive NG2 glia in the lesion core after 3-NP injection. Activation of NG2 glia, including enhanced proliferation and morphological changes, had a close spatiotemporal relationship with infiltration of activated microglia into the lesion core. Thick and highly branched processes of reactive NG2 glia formed a cellular network in the astrocyte-free lesion core and primarily surrounded developing cavities 2-4 weeks post-lesion. NG2 glia became associated with astrocytes in the lesion core and the border of cavities over the chronic interval of 4-8 weeks. Immunoelectron microscopy indicated that reactive NG2 glia had large euchromatic nuclei with prominent nucleoli and thick and branched processes that ramified distally. Thus, our data provide detailed information regarding the morphologies of NG2 glia in the lesion core, and support the link between transformation of NG2 glia to the reactive form and microglial activation/recruitment in response to brain insults.

Desmin expression profile in reactive astrocytes in the 3-nitropropionic acid-lesioned striatum of rat: Characterization and comparison with glial fibrillary acidic protein and nestin.

Desmin, a muscle-specific, type-III intermediate-filament protein, is reportedly expressed in astrocytes in the central nervous system. These cells become reactive astrocytes in response to brain injuries. To elucidate whether desmin is involved in this process, we examined the spatiotemporal expression profiles of desmin and their relationship with two astroglial intermediate filaments, glial fibrillary acidic protein (GFAP) and nestin, in the striatum of rats treated with the mitochondrial toxin 3-nitropropionic acid (3-NP). Weak, constitutive immunoreactivity for desmin was observed in astrocytes generally, and in reactive astrocytes in the peri-lesional area, its expression increased in parallel with that of GFAP over 3 d post-lesion and was maintained until at least day 28. Desmin, GFAP, and nestin showed characteristic time-dependent expression patterns in reactive astrocytes forming the astroglial scar; delayed and long-lasting induction of desmin and GFAP, and rapid but transient induction of nestin. In the lesion core, desmin was expressed in two categories of perivascular cells: nestin-negative and nestin-positive. These findings show that desmin, together with GFAP and nestin, is a dynamic component of intermediate filaments in activated astroglia, which may account for the dynamic structural changes seen in these cells in response to brain injuries.

Progressive accumulation of autofluorescent granules in macrophages in rat striatum after systemic 3-nitropropionic acid: a correlative light- and electron-microscopic study.

A variety of tissue biomolecules and intracellular structures are known to be autofluorescent. However, autofluorescent signals in brain tissues often confound analysis of the fluorescent markers used for immunohistochemistry. While investigating tissue and cellular pathologies induced by 3-nitropropionic acid, a mitochondrial toxin selective for striatal neurons, we encountered many autofluorescent signals confined to the lesion core. These structures were excited by blue (wavelength = 488 nm) and yellow-orange (555 nm), but not by red (639 nm) or violet (405 nm) lasers, indicating that this autofluorescence overlaps with the emission spectra of commonly used fluorophores. Almost all of the autofluorescence was localized in activated microglia/macrophages, while reactive astrocytes emitted no detectable autofluorescence. Amoeboid brain macrophages filled with autofluorescent granules revealed very weak expression of the microglial marker, ionized calcium-binding adaptor molecule 1 (Iba1), while activated microglia with evident processes and intense Iba1 immunoreactivity contained scant autofluorescent granules. In addition, immunolabeling with two lysosomal markers, ED1/CD68 and lysosomal-associated membrane protein 1, showed a pattern complementary with autofluorescent signals in activated microglia/macrophages, implying that the autofluorescent structures reside within cytoplasm free of intact lysosomes. A correlative light- and electron-microscopic approach finally revealed the ultrastructural identity of the fluorescent granules, most of which matched to clusters of lipofuscin-like inclusions with varying morphology. Thus, autofluorescence in the damaged brain may reflect the presence of lipofuscin-laden brain macrophages, which should be taken into account when verifying any fluorescent signals that are likely to be correlated with activated microglia/macrophages after brain insults.

Spatiotemporal expression of osteopontin in the striatum of rats subjected to the mitochondrial toxin 3-nitropropionic acid correlates with microcalcification.

Our aim was to elucidate whether osteopontin (OPN) is involved in the onset of mineralisation and progression of extracellular calcification in striatal lesions due to mitochondrial toxin 3-nitropropionic acid exposure. OPN expression had two different patterns when observed using light microscopy. It was either localised to the Golgi complex in brain macrophages or had a small granular pattern scattered in the affected striatum. OPN labelling tended to increase in number and size over a 2-week period following the lesion. Ultrastructural investigations revealed that OPN is initially localised to degenerating mitochondria within distal dendrites, which were then progressively surrounded by profuse OPN on days 7-14. Electron probe microanalysis of OPN-positive and calcium-fixated neurites indicated that OPN accumulates selectively on the surfaces of degenerating calcifying dendrites, possibly via interactions between OPN and calcium. In addition, 3-dimensional reconstruction of OPN-positive neurites revealed that they are in direct contact with larger OPN-negative degenerating dendrites rather than with fragmented cell debris. Our overall results indicate that OPN expression is likely to correlate with the spatiotemporal progression of calcification in the affected striatum, and raise the possibility that OPN may play an important role in the initiation and progression of microcalcification in response to brain insults.

Increased Expression of Slit2 and its Robo Receptors During Astroglial Scar Formation After Transient Focal Cerebral Ischemia in Rats.

Slit2, a secreted glycoprotein, has recently been implicated in the post-ischemic astroglial reaction. The objective of this study was to investigate the temporal changes and cellular localization of Slit2 and its receptors, Robo1, Robo2, and Robo4, in a rat transient focal ischemia model induced by middle cerebral artery occlusion. We used double- and triple-immunolabeling to determine the cell-specific changes in Slit2 and its receptors during a 10-week post-ischemia period. The expression profiles of Slit2 and the Robo receptors shared overlapping expression patterns in sham-operated and ischemic striatum. Constitutive expression of Slit2 and Robo receptors was observed in striatal neurons with weak intensity, whereas in rats reperfused after ischemic insults, these immunoreactivities were increased in reactive astrocytes. Astroglial induction of Slit2 and Robo in the peri-infarct region was distinct on days 7-14 after reperfusion and thereafter increased progressively throughout the 10-week experimental period. Slit2 and Robo were prominently expressed in the perinuclear cytoplasm and main processes of reactive astrocytes forming the astroglial scar. This observation was confirmed by quantification of the mean fluorescence intensity of Slit2 and Robo receptors over reactive astrocytes localized at the edge of the infarct area. However, activated microglia/macrophages in the peri-infarct area were devoid of any specific labeling for Slit2 and Robo. Thus, our data revealed a selective and sustained induction of Slit2 and Robo in astrocytes localized throughout the astroglial scar after ischemic stroke, suggesting that Slit2/Robo signaling participates in glial scar formation and brain remodeling following ischemic injury.

Increased expression of suppressor of cytokine signaling 2 in the subventricular zone after transient focal cerebral ischemia in adult rats.

Suppressor of cytokine signaling 2 (SOCS2) is a well-established negative regulator of growth hormone signaling that acts on adult hippocampal neurogenesis during ischemic insults. To explore whether SCOS2 is involved in poststroke neurogenesis, we studied the temporal expression of SOCS2 mRNA in the subventricular zone (SVZ) of rats after transient focal cerebral ischemia. We found that SOCS2 expression was upregulated in the SVZ of the infarcted hemisphere. The number of SOCS2-expressing cells was significantly increased in the ipsilateral SVZ compared with that on the contralateral side on days 7-10 after reperfusion, and SOCS2-expressing cells were highly proliferative, coinciding both spatially and temporally with stroke-induced neurogenesis. Almost all SOCS2-expressing cells in the SVZ were colabeled with the neural stem cell markers nestin and musashi1 and the neural/glial progenitor transcription factor Sox-2. In addition, SOCS2 was highly expressed in newly generated neurons that were immunoreactive for polysialic acid-neural cell adhesion molecule, indicating that SOCS2 expression may be persistent during neuronal differentiation. Thus, our data demonstrated that SOCS2 mRNA was highly expressed in proliferating neural stem/precursor cells and postmitotic migratory neuroblasts in the SVZ niche after focal cerebral ischemia, suggesting that SOCS2 may be actively involved in regulating adult neurogenesis induced by ischemic stroke.

Enhanced expression of the calcium-sensing receptor in reactive astrocytes following ischemic injury in vivo and in vitro.

We recently demonstrated that the G protein-coupled calcium-sensing receptor (CaSR) is associated with the pathogenesis of ischemic stroke and may be involved in vascular remodeling and astrogliosis. To further substantiate the involvement of CaSR in the astroglial reaction common to ischemic insults, we investigated the temporal and cell type-specific expression patterns of CaSR in the hippocampus after transient forebrain ischemia. CaSR was constitutively expressed in neurons of the pyramidal and granule cell layers, whereas increased CaSR immunoreactivity was observed in reactive astrocytes, but not in activated microglia or macrophages, in the CA1 region of the post-ischemic hippocampus. Astroglial induction of CaSR expression was evident on days 3-7 after reperfusion and appeared to increase progressively through day 28, at which time CaSR expression was prominent in astrocytes with a highly reactive hypertrophic phenotype and elevated levels of glial fibrillary acidic protein. This expression pattern was supported by results of immunoblot analyses. Furthermore, CaSR expression was upregulated in rat primary cortical astrocytes exposed to oxygen-glucose deprivation, which undergo reactive gliosis-like changes. Thus, our results demonstrate that selective and long-lasting astroglial induction of CaSR expression is a common characteristic of ischemic injury and suggest its involvement in the ischemia-induced astroglial reaction.

Absence of Benefit of Transcatheter Arterial Chemoembolization (TACE) in Patients with Resectable Solitary Hepatocellular Carcinoma.

BACKGROUND: This study aimed to assess the prognostic impact of preoperative transcatheter arterial chemoembolization (TACE) on long-term survival outcomes in patients undergoing resection of small solitary hepatocellular carcinoma (HCC). METHODS: Enrolled patients had undergone macroscopic curative resection of solitary 2-5 cm HCC with (n = 105) or without (n = 830; control group) preoperative TACE. RESULTS: TACE group was divided into subgroups A (n = 68, 1-2 TACEs within 12 months), B (n = 23, ≥ 3 TACEs within 12 months), and C (n = 14, TACE prior to 12 months). The number of TACE sessions was 1.8 ± 1.6. In TACE A-C subgroups, pathological response of tumor necrosis >50 % at median post-TACE period after final TACE was observed in 41 (60.3 %) at 1.9 months, 10 (43.5 %) at 2.1 months, and 2 (14.3 %) at 18.9 months, respectively. The 5-year tumor recurrence and patient survival rates were 62.8 and 70.4 % in TACE group and 51.4 and 83.4 % in control group, respectively (p ≤ 0.003). Median periods of postoperative tumor recurrence in TACE A-C subgroups and control group were 35, 13, 14, and 55 months, respectively (p < 0.001); and postoperative survival periods at 75 % survival rate were 51, 38, 51, and 98 months, respectively (p = 0.003). TACE-induced extensive tumor necrosis did not improve postoperative prognosis in TACE A subgroup (p ≥ 0.053). Postoperative prognosis after preoperative sequential TACE and portal vein embolization was comparable to that of the control group (p ≥ 0.052). CONCLUSIONS: Preoperative TACE for small solitary HCCs may adversely affect post-resection prognosis, irrespective of pathological responses. Preoperative TACE should be avoided for patients with resectable small HCCs.

Prognostic effect of preoperative sequential transcatheter arterial chemoembolization and portal vein embolization for right hepatectomy in patients with solitary hepatocellular carcinoma.

BACKGROUNDS/AIMS: Both preoperative transcatheter arterial chemoembolization (TACE) alone and portal vein embolization (PVE) alone have a detrimental prognostic effect on the post-resection outcomes in patients with hepatocellular carcinoma (HCC). The main objective of this study was to assess the prognostic impact of preoperative TACE on the long-term survival outcomes in patients undergoing preoperative PVE and right liver resection for solitary HCC. METHODS: Patients who underwent macroscopic curative right liver resection of solitary HCC that lied between 3.0 and 7.0 cm (n=113) with or without preoperative TACE and PVE were selected for the study, making these subjects were divided into three groups; the TACE-PVE group (n=27), the PVE-alone group (n=13), and the control group (n=73). The subjects in the three groups were followed up for ≥36 months or until death. RESULTS: The 1-, 3-, 5-, and 10-year overall patient survival rates of all 113 patients were 96.5%, 88.2%, 81.3% and 65.0%, respectively. The 1-, 3-, 5-, and 10-year overall patient survival rates were 96.3%, 83.4%, 83.4% and 47.6% respectively in the TACE-PVE group; 84.6%, 76.9%, 57.7% and 19.2% respectively in the PVE-alone group; and 98.6%, 91.7%, 85.1% and 81.7% respectively in the control group (p=0.047). Patients were also sub-grouped according to tumor size, and those with a tumor of up to cutoff at 5 cm showed no prognostic difference (p=0.774), but tumor size >5 cm was associated with inferior patient survival only in the TACE-PVE group (p=0.018). CONCLUSIONS: Preoperative sequential TACE and PVE appear to be compliant to the conventional oncological concept in addition to induction of the future remnant liver regeneration. Therefore, we suggest that preoperative TACE should be come first whenever preoperative PVE for major hepatectomy is planned, especially in patients with hypervascular HCC tumors.