Do subplate neurons comprise a transient population of cells in developing neocortex of rats?

Studies were undertaken to determine whether neurons of the subplate layer represent a transient or stable population of cells in developing neocortex of rat. The first set of studies sought to determine the fraction of subplate neurons that is lost during early postnatal development. The optical dissector method was used to analyze fluorescently stained material in animals the age of postnatal day 0 (P0) to P40. These results demonstrate a reduction of slightly less than half of the total number of subplate neurons from P0 to P40. Counts of labeled cells in littermates at varied ages after [(3)H]thymidine or BRDU treatment on gestational day 14 (G14 - birthdate of occipital subplate neurons) or G18 (birthdate of layers III-IV neurons) demonstrate loss of approximately 50% of neurons in the subplate layer between P0 and P40, somewhat greater than the loss of neurons from cortical layers III-IV. The second set of studies investigated whether subplate neurons display cellular atrophy during postnatal development. Analysis of subplate neurons injected intracellularly with Lucifer yellow in fixed slice preparations indicates no reduction in soma size, number of dendrites, or extent of dendritic fields of subplate neurons taken from animals age P0 to P60. The third set of studies investigated whether functional markers of subplate neurons are reduced during postnatal development. Analysis of tissue stained histochemically for cytochrome oxidase or acetylcholinesterase, or stained immunocytochemically for GABA, somatostatin, or neuropeptide Y, demonstrate a remarkable loss of expression of staining patterns from late gestational ages to P20. These data demonstrate that, although subplate neurons seem not to be a transient population of cells in the usual sense of being eliminated by cell death or structural atrophy, the loss of histochemical and immunocytochemical markers indicates that they may be a functionally transient population of cells.

Emergency physician use of ultrasonography in blunt abdominal trauma.

OBJECTIVE: To evaluate the diagnostic utility of abdominal diagnostic ultrasonography (DUS) performed by emergency physicians for intraperitoneal fluid caused by blunt abdominal trauma (BAT). METHODS: The design was a prospective, blind, observational study. During a 15-month period, a convenience sample of patients presenting to the ED with BAT necessitating CT scan of the abdomen, diagnostic peritoneal lavage (DPL), or laparotomy was studied. Scans were performed by an emergency medicine (EM) attending, or a resident supervised by an attending, using a real-time sector ultrasound scanner with a 3.5-MHz probe. Training in DUS included a 1-hour didactic session and 1 hour of practice on human volunteers. Free intraperitoneal fluid was defined as an anechoic stripe in the hepatorenal, bladder-rectal, or splenorenal space, and constituted a positive DUS study. Free intraperitoneal fluid detected on abdominal CT scan, DPL, and/or laparotomy was the criterion standard. RESULTS: Of 110 patients scanned, 13 were excluded secondary to technical difficulty or lack of diagnostic follow-up modalities. Of the remaining 97 patients, there were 24 females and 73 males, ranging from ages 2 to 78 years. DUS detected intraperitoneal fluid in 21 subjects, including 3 false positives. There were 6 false-negative DUS examinations. DUS had a sensitivity of 75% (95% CI 53-90%), a specificity 96% of (95% CI 89-99%), and an accuracy of 91% (95% CI 83-96%). No false-positive or false-negative DUS study occurred after the first 67 cases. The mean interval for a DUS scan was 4.9 +/- 2.9 minutes, ranging from 0.5 to 16 minutes, and the mean intervals were not different between the positive and the negative studies. The accuracies of DUS were similar in the pediatric patients, 97% (95% CI 83-100%), and in the adults, 88% (95% CI 78-95%). The hepatorenal view provided the highest sensitivity as well as the least number of uninterpretable scans of the 3 DUS views. CONCLUSION: Emergency physicians with minimal training can use DUS with fair sensitivity and good specificity and accuracy to detect free intraperitoneal fluid in both pediatric and adult BAT victims. The hepatorenal view provides the highest sensitivity for intraperitoneal fluid, although the 3-view series (with hepatorenal, bladder-rectal, and splenorenal spaces) can typically be performed within 5 minutes and may increase the specificity and accuracy.

The role of mononuclear phagocytes in wound healing after traumatic injury to adult mammalian brain.

We monitor cellular responses to a penetrating wound in the cerebral cortex of adult rat during the first weeks after injury. Two classes of activated mononuclear phagocytes containing acetylated low-density lipoprotein (ac-LDL) receptors appear within hours at the wound site. One type of cell surrounding the lesion edge had thin, delicate processes and is identical in appearance to ramified microglia found in developing brain. Within the lesion, round cells are recognized as blood-borne macrophages when labeled by intravenous injection of carbon particles. Thus, both process-bearing reactive microglia and invading macrophages respond to brain trauma. The greatest number of ac-LDL(+) or nonspecific esterase(+) mononuclear phagocytes appears 2 days after injury within the wound site and are associated with a peak production of the cytokine interleukin-1 (IL-1). Because intracerebral infusion of IL-1 is known to stimulate astrogliosis and neovascularization (Giulian et al., 1988), we examine the time course of injury-induced reactive astrogliosis and angiogenesis. A 5-fold increase in the number of reactive astroglia is found at 3 d and a marked neovascularization at 5 d after injury. During the first week, mononuclear phagocytes engulf particles and clear them from the wound site either by migrating to the brain surface or by entering newly formed brain vasculature. To investigate further the role of reactive brain mononuclear phagocytes in CNS injury, we use drugs to inhibit trauma-induced inflammation. When applied in vivo, chloroquine or colchicine reduce the number of mononuclear phagocytes in damaged brain, help to block reactive astrogliosis and neovascularization, and slow the rate of debris clearance from sites of traumatic injury. In contrast, the glucocorticoid dexamethasone neither reduces the number of brain inflammatory cells nor hampers such responses as phagocytosis, astrogliosis, neovascularization, or debris clearance in vivo. Our observations show that mononuclear phagocytes play a major role in wound healing after CNS trauma with some events controlled by secretion of cytokines. Moreover, certain classes of immunosuppressive drugs may be useful in the treatment of acute brain injury.

Colony-stimulating factors as promoters of ameboid microglia.

Immunomodulators were tested for their ability to stimulate proliferation and biologic activity of ameboid microglia. Only the colony-stimulating factors (CSFs), multipotential-CSF (multi-CSF) and granulocyte/macrophage-CSF (GM-CSF), were potent mitogens for microglia. Other immunomodulators, including interleukin-1, interleukin-2, interferon gamma, tumor necrosis factor, or granulocyte-CSF (G-CSF), had no effect upon microglial growth in vitro. Multi-CSF or GM-CSF were also observed to induce more rapid phagocytosis of polystyrene microspheres by cultured ameboid cells. In order to determine which immunomodulators alter brain inflammatory responses in vivo, we infused recombinant forms of GM-CSF, multi-CSF, macrophage-CSF, or G-CSF into the cerebral cortex of rats. Within 48 hr after infusion multi-CSF or GM-CSF stimulated the appearance of large numbers of mononuclear phagocytes at the site of injection. These same factors also accelerated the clearance of polystyrene microspheres from the brain. Our observations indicate that certain classes of immunomodulators which are mitogens and activators of ameboid microglia in vitro amplify the inflammatory response of the CNS in vivo by action upon intrinsic brain mononuclear phagocytes.