Impact of logging on aboveground biomass stocks in lowland rain forest, Papua New Guinea.

Greenhouse-gas emissions resulting from logging are poorly quantified across the tropics. There is a need for robust measurement of rain forest biomass and the impacts of logging from which carbon losses can be reliably estimated at regional and global scales. We used a modified Bitterlich plotless technique to measure aboveground live biomass at six unlogged and six logged rain forest areas (coupes) across two approximately 3000-ha regions at the Makapa concession in lowland Papua New Guinea. "Reduced-impact logging" is practiced at Makapa. We found the mean unlogged aboveground biomass in the two regions to be 192.96 +/- 4.44 Mg/ha and 252.92 +/- 7.00 Mg/ha (mean +/- SE), which was reduced by logging to 146.92 +/- 4.58 Mg/ha and 158.84 +/- 4.16, respectively. Killed biomass was not a fixed proportion, but varied with unlogged biomass, with 24% killed in the lower-biomass region, and 37% in the higher-biomass region. Across the two regions logging resulted in a mean aboveground carbon loss of 35 +/- 2.8 Mg/ha. The plotless technique proved efficient at estimating mean aboveground biomass and logging damage. We conclude that substantial bias is likely to occur within biomass estimates derived from single unreplicated plots.

Estimating rainforest biomass stocks and carbon loss from deforestation and degradation in Papua New Guinea 1972-2002: Best estimates, uncertainties and research needs.

Reduction of carbon emissions from tropical deforestation and forest degradation is being considered a cost-effective way of mitigating the impacts of global warming. If such reductions are to be implemented, accurate and repeatable measurements of forest cover change and biomass will be required. In Papua New Guinea (PNG), which has one of the world's largest remaining areas of tropical forest, we used the best available data to estimate rainforest carbon stocks, and emissions from deforestation and degradation. We collated all available PNG field measurements which could be used to estimate carbon stocks in logged and unlogged forest. We extrapolated these plot-level estimates across the forested landscape using high-resolution forest mapping. We found the best estimate of forest carbon stocks contained in logged and unlogged forest in 2002 to be 4770 Mt (+/-13%). Our best estimate of gross forest carbon released through deforestation and degradation between 1972 and 2002 was 1178 Mt (+/-18%). By applying a long-term forest change model, we estimated that the carbon loss resulting from deforestation and degradation in 2001 was 53 Mt (+/-18%), rising from 24 Mt (+/-15%) in 1972. Forty-one percent of 2001 emissions resulted from logging, rising from 21% in 1972. Reducing emissions from logging is therefore a priority for PNG. The large uncertainty in our estimates of carbon stocks and fluxes is primarily due to the dearth of field measurements in both logged and unlogged forest, and the lack of PNG logging damage studies. Research priorities for PNG to increase the accuracy of forest carbon stock assessments are the collection of field measurements in unlogged forest and more spatially explicit logging damage studies.

Purification of intact microtubules from brain.

Hundred-fold purification of intact microtubules from homogenates of rat brain is reported. The success of purification depends on stabilizing the microtubule structure by the combined effects of hexylene glycol, acidic Ph, and low temperature. A practical, negative stain, electron microscopic assay is used to study purity and stability of microtubule fractions. The purified fractions show a major band which migrates like purified tubulin in the SDS gel electrophoresis system.

Microtubules in brain homogenates.

Microtubules from neurons are preserved in homogenates of mammalian brain by medium containing organic solvents at acidic pH. By means of negative staining and electron microscopy, the relative concentration of microtubules in suspensions can be assayed. Microtubules from brain have a filamentous and substructure.

Ecosystem engineering by digging mammals: effects on soil fertility and condition in Tasmanian temperate woodland.

Many small- and medium-sized mammals dig for their food. This activity potentially affects soil condition and fertility. Digging is well developed especially in Australian mammals, many of which have recently become rare or extinct. We measured the effects of digging by mammals on soil in a Tasmanian temperate dry sclerophyll forest with an intact mammal community. The density of diggings was 5812 ha-1, affecting 11% of the forest floor. Diggings were created at a rate of around 3113 diggings ha-1 yr-1, disturbing 6.5% of the forest floor and displacing 7.1 m3 ha-1 of soil annually. Most diggings were made by eastern bettongs (Bettongia gaimardi) and short-beaked echidnas (Tachyglossus aculeatus). Many (approx. 30%) fresh diggings consisted of re-excavations of old diggings. Novel diggings displaced 5 m3 ha yr-1 of soil. Diggings acted as traps for organic matter and sites for the formation of new soil, which had higher fertility and moisture content and lower hardness than undisturbed topsoil. These effects on soil fertility and structure were strongest in habitats with dry and poor soil. Creation of fine-scaled heterogeneity by mammals, and amelioration of dry and infertile soil, is a valuable ecosystem service that could be restored by reintroduction of digging mammals to habitats from which they have declined or gone extinct.

Broad-scale impacts of salmon farms on temperate macroalgal assemblages on rocky reefs.

Intensive fish culture in open sea pens delivers large amounts of nutrients to coastal environments. Relative to particulate waste impacts, the ecological impacts of dissolved wastes are poorly known despite their potential to substantially affect nutrient-assimilating components of surrounding ecosystems. Broad-scale enrichment effects of salmonid farms on Tasmanian reef communities were assessed by comparing macroalgal cover at four fixed distances from active fish farm leases across 44 sites. Macroalgal assemblages differed significantly between sites immediately adjacent (100m) to fish farms and reference sites at 5km distance, while sites at 400m and 1km exhibited intermediate characteristics. Epiphyte cover varied consistently with fish farm impacts in both sheltered and exposed locations. The green algae Chaetomorpha spp. predominated near fish farms at swell-exposed sites, whereas filamentous green algae showed elevated densities near sheltered farms. Cover of canopy-forming perennial algae appeared unaffected by fish farm impacts.

Topography of the human corpus callosum.

This study was undertaken to determine the topographical organization of fibers coursing through the human corpus callosum. We correlated the distribution of Wallerian degeneration in the corpus callosum with the anatomical sites of focal cortical lesions due to ischemic infarctions or circumscribed contusions. Fibers from the inferior frontal and anterior inferior parietal regions course through the rostrum and genu of the corpus callosum. Callosal connections from the temporo-parieto-occipital junctional region course through the splenium and caudal portion of the body of the corpus callosum. Both the superior parietal lobule and the occipital cortex give rise to interhemispheric fibers that course exclusively through the splenium of the corpus callosum. No callosal degeneration was associated with a cortical lesion in the anterior superior frontal region. The topographical organization of fibers in the human corpus callosum appears to be fairly similar to that found in the rhesus monkey (Macaca mulatta).

In vitro simulation of neural trauma by laser.

A serious lack of knowledge about central nervous system trauma is encountered on the cellular level where the inability to create precise experimental lesions of known magnitude has limited our understanding of the reactions of single cells to injury. We used a laser cell surgery technique developed in this laboratory to manipulate neurons in a controlled environment, in order to observe pathologic reactions during and immediately after the injury. This technique is especially suited for axonal and dendritic amputations close to the perikaryon. The laser provided three different physical modes of injury to neurites: direct vaporization of cytoplasm, pressure wave damage from external vaporization of substrate material, and photobiologically-induced localized cytoskeletal destruction leading to the slow pinching of processes followed by transection. Our data indicated a great similarity between laser impact damage and the cellular damage produced by physical trauma to the central nervous system.

Multiple system atrophy: the putative causative role of environmental toxins.

BACKGROUND: Whereas a number of studies have investigated the putative role of environmental toxins in the pathogenesis of idiopathic Parkinson disease, the possibility of such a role in multiple system atrophy has received little attention. DESIGN AND SETTING: Review of records of patients examined in the Parkinson's Disease Center and Movement Disorder Clinic, Baylor College of Medicine, Houston, Tex, from July 1, 1977, to February 4, 1998. PATIENTS: We reviewed 100 consecutive medical records of patients who satisfied the diagnostic criteria for multiple system atrophy formulated by the Consensus Committee of the American Autonomic Society and the American Academy of Neurology. INTERVENTION: The type and amount of toxin exposure were verified by history and examination of records whenever possible. Severity of parkinsonism was assessed by clinical rating scales. MAIN OUTCOME MEASURE: Development of multiple system atrophy after environmental toxin exposure. RESULTS: Eleven patients had a notable history of heavy exposure to environmental toxins. One patient with multiple system atrophy confirmed by postmortem evaluation was exposed to high concentrations of malathion, diazinon, and formaldehyde, while the other patients with multiple system atrophy had well-documented high exposures to agents including n-hexane, benzene, methyl isobutyl ketone, and pesticides. The case studied pathologically demonstrated extensive advanced glial changes, including glial cytoplasmic inclusions in deep cerebellar white matter, brainstem, cortex (superior frontal, insula) and putamen, with notable cell loss and depigmentation of the substantia nigra and locus ceruleus. CONCLUSION: While many studies report a possible role of environmental toxins in Parkinson disease, such a role is even more likely in multiple system atrophy, as this is a sporadic disease.

Late-onset Hallervorden-Spatz disease presenting as familial parkinsonism.

We studied a 68-year-old man who died after 13 years of progressive dementia, rigidity, bradykinesia, mild tremor, stooped posture, slow and shuffling gait, dystonia, blepharospasm, apraxia of eyelid opening, anarthria, aphonia, and incontinence. At autopsy, he had generalized brain atrophy with large deposits of iron pigment in the globus pallidus, caudate, and substantia nigra. Axonal spheroids were found in the globus pallidus, substantia nigra, medulla, and spinal cord. The neurochemical analysis of the brain revealed marked loss of dopamine in the nigral-striatal areas, with relative preservation of dopamine in the limbic areas. This is the oldest case of familial Hallervorden-Spatz disease reported and the first with neurochemical analysis of the brain.

Syndromes with lissencephaly. II: Walker-Warburg and cerebro-oculo-muscular syndromes and a new syndrome with type II lissencephaly.

Lissencephaly (smooth brain) is an abnormality of brain development characterized by incomplete neuronal migration and a smooth cerebral surface. At least two distinct pathological types occur, each associated with several recognized syndromes. In this paper, we report on the clinical and pathologic manifestations of four additional patients and classify and delineate three separate disorders with type II lissencephaly. We also report on a previously undescribed abnormality in one of the four patients--dilated rough endoplasmic reticulum cisternae containing an unknown osmiophilic secretory product, probably a glycoprotein.

Demonstration of Epstein-Barr virus in primary central nervous system lymphomas by the polymerase chain reaction and in situ hybridization.

Primary lymphomas of the central nervous system (CNS) account for 0.3% to 1.5% of all intracranial neoplasms. Several reports have noted a coincidence between this neoplasm and serologic evidence of Epstein-Barr virus (EBV) infection, but in only a few instances has the EBV genome been demonstrated in these tumors. To further evaluate the frequency of this occurrence, we analyzed primary CNS lymphomas using nucleic acid hybridization methods and the polymerase chain reaction (PCR). In situ hybridization was used in selected cases. Sequences of EBV were found in two of nine cases by PCR and in situ hybridization. Southern blot hybridization of genomic DNA from these samples was negative for EBV. Both tumors arose in patients with conditions shown to produce secondary immunodeficiency, namely, chronic alcohol abuse and diabetes mellitus. We conclude that the association of EBV and CNS lymphoma is not restricted to patients with severe primary immune deficiency, and that PCR can be applied successfully to paraffin-embedded tissue for the detection of low-abundance viral sequences.

Fatal cerebral injury in the elderly.

A medical examiner's series of 71 elderly patients with fatal internal cerebral injuries demonstrated age differences with respect to the type of cerebral lesion and the causal incident. The elderly showed relatively fewer severe cerebral contusions than did a young group, but a higher incidence of subdural and intraparenchymal hematomas. Falls, the most common cause of injury in the elderly, were often precipitated by physical illness or ingestion of alcohol. Consumption of alcohol was also a prominent factor in the fatal assault cases.

Senile plaques stimulate microglia to release a neurotoxin found in Alzheimer brain.

Senile plaques found in the brains of patients with Alzheimer's disease (AD) are surrounded by clusters of reactive microglia. Isolated human microglia placed in contact with plaques in vitro are activated to release a factor which is toxic to neurons. This same neurotoxin is found in AD brain tissue and causes damage to pyramidal neurons in vivo when infused into rat hippocampus. Highest concentrations of the neurotoxin are in those brain structures most burdened by reactive microglia, suggesting that plaque-activated cells contribute to the neuronal damage and impaired cognition seen in patients with Alzheimer's dementia.

A photoetched cell relocation matrix for long-term, quantitative observations of selected individual neurons in culture.

A photoetched matrix of indium tin oxide (ITO) on glass has been developed and tested as a tool to assist in the relocation and identification of individual neuronal cells in culture. The matrix is formed by 10-15 micron wide and 300 A thick ITO lines which subdivide a 1-cm2 area into 625 smaller squares. Each of the smaller squares measures 400 micron on a side and contains a photoetched two-letter "address". The address code allows precise relocation of specific regions of a culture as well as verification of the identities of individual neurons selected for repeated observation. Marks at 50 micron intervals along the sides of the address squares permit quantitative analysis of morphological changes, cell migration, reaggregation, etc. The ITO is transparent and does not interfere with visualization of even fine details of cells with high power microscopy.

Cytoarchitectonic distribution of zinc in the hippocampus of man and the rat.

Zinc was measured in whole hippocampus and in hippocampal sub-regions by stable-isotope dilution mass spectrometry. In both man and the rat, the most zinc (102-145 ppm, dry weight) was found in the hilar region, the least (27-35) in the fimbria. The amount of zinc directly associated with mossy-fiber axons was estimated to be approximately 8% of the total zinc in the hippocampus, and the concentration of mossy-fiber zinc was estimated at 220-300 microM. Methodological and theoretical implications of the quantitative findings were discussed.

MR appearance of an orbital leiomyoma.

The authors describe the MR appearance of an intraconal orbital vascular leiomyoma that probably arose from smooth muscle in the wall of a vein. Cavernous hemangiomas, schwannomas, neurofibromas, and other well-encapsulated masses can have a similar appearance.

Metastatic adenocarcinoma to the brain: MR with pathologic correlation.

PURPOSE: To describe the appearance on T2-weighted scans of metastatic adenocarcinoma to the brain and to show that the hypointensity frequently associated with these lesions is not related to the presence of mucin, blood products, iron, or calcium. METHODS: The MR scans of 14 patients with metastatic adenocarcinoma to the brain were reviewed retrospectively. The signal intensity on T2-weighted scans of the solid enhancing portion of the tumors was compared with white matter. Histologic examination of the surgical specimens included special stains to search for calcium, mucin, and iron. RESULTS: Eight of nine surgical and all six nonsurgical lesions were either iso- or hypointense to white matter on T2-weighted scans. There was no correlation with tumor histology or the presence of mucin, blood products, iron, or calcium. CONCLUSIONS: The presence of a hypointense intraaxial mass on T2-weighted scans strongly suggests the possibility of metastatic adenocarcinoma. The MR appearance is not explained by the presence of mucin, blood products, iron, or calcium. This phenomenon most likely reflects the relaxation parameters of the tissue from which the metastasis arose.

MR imaging of hyperacute intracranial hemorrhage in the cat.

Hyperacute intracerebral hematomas were successfully created in five cats by injecting a prepared blood sample in which the oxygen (O2) saturation ranged from 0-80%. T1- and T2-weighted spin-echo sequences and T2-weighted gradient refocused scans were obtained 2.5-10 hr after injection on a 1.5-T imaging system. Detailed histology or electron microscopy was performed on each brain to confirm the presence of intact red blood cells in a retracted clot matrix. Areas of the hematoma were hypointense relative to brain in all five cats on the gradient refocused scans. The hematoma was isointense relative to brain on the T1- and T2-weighted spin-echo scans in all cats except one, which suffered a seizure/respiratory arrest and died during the scanning procedure. Portions of the hematoma in this animal had a hypointense T2-weighted signal and a hyperintense T1-weighted signal, which corresponded to the predicted MR properties of intracellular methemoglobin. We hypothesize that acute (less than 10 hr old) hematomas that contain virtually 100% intracellular deoxyhemoglobin may not appear hypointense relative to brain on T2-weighted scan sequences at 1.5 T unless surrounding tissue hypoxia and/or anoxia promote additional changes, one of which may be the formation of intracellular methemoglobin.