Neurogenic pulmonary edema in fatal and nonfatal head injuries

Impaired pulmonary function is a frequent but poorly understood complication of acute head injury (HI). A potential early contributor to the pulmonary dysfunction seen in HI patients is neurogenic pulmonary edema (NPE). We hypothesized that NPE would occur early after HI and that it would have a continuum of clinical severity depending on the severity of the HI and associated intracranial hypertension. A large autopsy data base and inpatient HI data base were used to search for cases of NPE. Patients in the autopsy data base were stratified according to injury type and whether they died at the scene or within 96 hours of injury. There were significant (p < 0.0001, analysis of variance) elevations in lung weights in patients dying at the scene and within 96 hours from HI, compared with those dying from other noncentral nervous system injuries. No other organs studied showed significant weight increases. The incidence of NPE in isolated HI patients dying at the scene was 32%. In patients with isolated HI dying within 96 hours, the incidence of NPE was 50%. We found an inverse correlation (r = 0.62; p < 0.0014) between the initial cerebral perfusion pressure and the PaO2/FIO2 ratio despite a normal-appearing chest x-ray film. We conclude that NPE occurs frequently in HI patients. The process of edema formation begins early in the clinical course and is isolated to the lung.(ABSTRACT TRUNCATED AT 250 WORDS)     

Delayed protection by MK-801 and tetrodotoxin in a rat organotypic hippocampal culture model of ischemia

BACKGROUND AND PURPOSE: The hippocampus demonstrates a regional pattern of vulnerability to ischemic injury that depends on its characteristic differentiation and intrinsic connections. We now describe a model of ischemic injury using organotypic hippocampal culture, which preserves the anatomic differentiation of the hippocampus in long-term tissue culture. METHODS: Ischemic conditions were modeled by metabolic inhibition. Cultures were briefly exposed to potassium cyanide to block oxidative phosphorylation and 2-deoxyglucose to block glycolysis. The fluorescent dye propidium iodide was used to observe membrane damage in living cultures during recovery. RESULTS: 2-Deoxyglucose/potassium cyanide incubation resulted in dose-dependent, regionally selective neuronal injury in CA1 and the dentate hilus, which began slowly after 2 to 6 hours of recovery. Subsequent histological examination of cultures after 1 to 7 days of recovery demonstrated neuronal pyknosis that was correlated with the early, direct observation of membrane damage with propidium. Both propidium staining and histological degeneration were prevented by the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 when administered 30 minutes after the end of the exposure to 2-deoxyglucose and potassium cyanide. Tetrodotoxin, which blocks voltage-dependent sodium channels, had protective effects that were greatest during the period of 2-deoxyglucose and potassium cyanide incubation but also produced protection against the mildest conditions of metabolic inhibition when administered after 30 minutes of recovery. CONCLUSIONS: This in vitro model reproduced elements of the time course, regional vulnerability, and pharmacologic sensitivities of in vivo ischemic hippocampal injury. Inhibition of metabolism in organotypic culture provides a rapid, easily controlled injury and reproduces the in vitro pattern of hippocampal regional vulnerability to ischemia. It is the first in vitro model of ischemia to exhibit complete protection by delayed administration of an NMDA receptor antagonist during recovery from a brief insult. The protective effects of tetrodotoxin suggest that an early period of sodium entry into cells during and after ATP depletion may be responsible for the more prolonged period of toxic NMDA receptor activation.     

Gi-mediated stimulation of type II adenylyl cyclase is augmented by Gq-coupled receptor activation and phorbol ester treatment

Synergism between Gs- and Gi- or Gq-dependent signaling pathways has been demonstrated in the stimulation of type II adenylyl cyclase (AC-II). Provision of activated alpha s is known to allow numerous Gi-coupled receptors to stimulate AC-II and to potentiate the responses to Gq-coupled receptors. To explore possible interactions between Gi- and Gq-coupled receptors that are independent of alpha s, the activity of AC-II was determined after the activation of Gi- and Gq-regulated pathways. Human embryonic kidney 293 cells were transiently cotransfected with cDNAs encoding AC-II and various G-protein-coupled receptors. Agonist-bound Gi-coupled receptors (including the formyl peptide, dopamine-D2, and delta-opioid receptors) stimulated AC-II activity in the absence of activated alpha s, provided that the cells were treated with 100 nM phorbol 12-myristate 13-acetate. Activation of protein kinase C (PKC) thus appears to relieve the requirement for the presence of activated alpha s. Stimulation of PKC via Gq-coupled receptors also allowed Gi-coupled receptors to activate AC-II. Coexpression of the m1 muscarinic receptor with the dopamine-D2 receptor permitted dopamine to stimulate AC-II in the presence of carbachol. The phorbol ester-permissive and alpha s-independent stimulation was mediated by G-protein beta gamma subunits because it was blocked by the beta gamma scavengers alpha t and beta-adrenergic receptor kinase. These results show that AC-II can efficiently integrate signals generated by Gq- and Gi-coupled receptors via a mechanism that is independent of Gs.     

Morphological and molecular characterization of Giardia isolated from the straw-necked ibis (Threskiornis spinicollis) in Western Australia

Following the first report of avian Giardia infection in Australia, isolates of the parasite recovered from naturally infected straw-necked ibis (Theskiornis spinicollis) were characterized using median body morphology, scanning electron microscopy, multilocus enzyme electrophoresis, random amplified polymorphic DNA (RAPD), and small subunit ribosomal RNA (SSU-rRNA) analyses. Results were compared with Giardia from other birds and mammals, and the extent of genetic diversity between a range of ibis isolates collected in Western Australia was determined. The ibis isolates of Giardia were genetically relatively homogeneous, which is in contrast to the extensive genetic heterogeneity often displayed by mammalian Giardia isolates. Morphologically, Giardia from ibis were similar to Giardia ardeae although they differed genetically and by the fact that the ibis isolates could not be established in in vitro culture. Sequence data of the DNA coding for the SSU-rRNA found a 96% homology between the ibis isolates from Western Australia and G. ardeae, suggesting that they represent distinct strains of the same species. In contrast, the ibis isolates were genetically and morphologically very different than Giardia duodenalis and Giardia muris from mammals.     

Synaptic organization of the human striatum: a postmortem ultrastructural study

Converging with psycho-social research findings, animal and human laboratory studies indicate that behavioral alternatives are important determinants of drug-taking. To investigate associations between how early adolescents spend their time, i.e. their behavioral repertoire and drug use (use of marijuana, crack/cocaine or inhalants), we analyzed data from an epidemiological sample of 1516 urban middle-school students who had completed private interviews in spring 1993. The interview included a 36-item questionnaire to assess how frequently the youth engaged in different activities; history of drug-taking was assessed separately. Multiple logistic regression was used to estimate associations between drug use and each of seven behavioral domains as well as sex, age and racial-ethnic status. Youths spending a great deal of time working for pay and assuming other adult-like roles were more likely to have initiated drug use (estimated odds ratio, OR = 3.49; p = 0.002). Those who spent much time in religious activities were less likely (OR = 0.2, p <0.001). An exploratory search for interactions disclosed other associations that merit attention in future research. These results corroborate evidence on the potential etiological significance of behavioral repertoire in relation to risk of drug use.     

Vincristine disturbs spontaneous firing of the afferent nerve fibre in ampullary electroreceptor organs

Ampullary electroreceptor organs of the catfish were apically exposed to 0.3 mM vincristine in order to investigate the part played by the microtubular system in stimulus transduction. The main effects were repetitive firing of the afferent fibre, a reduction of the mean spontaneous activity and a reduction of the spike amplitude two to four days after exposure to vincristine. The mean sensitivity was less susceptible to vincristine than the spontaneous activity. Since the shape of the frequency curves remained unchanged and similar effects as described above were also observed after denervation, we conclude that vincristine most likely does not affect electroreceptor cell functioning, but causes degeneration of the afferent fibre.     

Multiplicity of fibronectin-binding alpha V integrin receptors in colorectal cancer

Current data from in vitro and in vivo animal models indicate that fibronectin-binding integrin receptors expressed by colon cancer cells may regulate tumour growth. While individual members of the beta 1 subfamily of integrins have now been clearly identified in colorectal cancer, little information exists with respect to the alpha V subfamily. In the present study we show that alpha V can associate with multiple and different beta subunits capable of binding fibronectin in this tumour type. This is likely to have functional implications for growth and spread of colorectal cancer.     

Heat-induced elevation of ceramide in Saccharomyces cerevisiae via de novo synthesis

Sphingolipid-related metabolites have been implicated as potential signaling molecules in many studies with mammalian cells as well as in some studies with yeast. Our previous work showed that sphingolipid-deficient strains of Saccharomyces cerevisiae are unable to resist a heat shock, indicating that sphingolipids are necessary for surviving heat stress. Recent evidence suggests that one role for the sphingolipid intermediate ceramide may be to act as a second messenger to signal accumulation of the thermoprotectant trehalose. We examine here the mechanism for generating the severalfold increase in ceramide observed during heat shock. As judged by compositional analysis and mass spectrometry, the major ceramides produced during heat shock are similar to those found in complex sphingolipids, a mixture of N-hydroxyhexacosanoyl C18 and C20 phytosphingosines. Since the most studied mechanism for ceramide generation in animal cells is via a phospholipase C-type sphingomyelin hydrolysis, we examined S. cerevisiae for an analogous enzyme. Using [3H]phytosphingosine and [3H]inositol-labeled yeast sphingolipids, a novel membrane-associated phospholipase C-type activity that generated ceramide from inositol-P-ceramide, mannosylinositol-P-ceramide, and mannose(inositol-P)2-ceramide was demonstrated. The sphingolipid head groups were concomitantly liberated with the expected stoichiometry. However, other data demonstrate that the ceramide generated during heat shock is not likely to be derived by breakdown of complex sphingolipids. For example, the water-soluble fraction of heat-shocked cells showed no increase in any of the sphingolipid head groups, which is inconsistent with complex sphingolipid hydrolysis. Rather, we find that de novo ceramide synthesis involving ceramide synthase appears to be responsible for heat-induced ceramide elevation. In support of this hypothesis, we find that the potent ceramide synthase inhibitor, australifungin, completely inhibits both the heat-induced increase in incorporation of [3H]sphinganine into ceramide as well as the heat-induced increase in ceramide as measured by mass. Thus, heat-induced ceramide most likely arises by temperature activation of the enzymes that generate ceramide precursors, activation of ceramide synthase itself, or both.     

Assessment of weighting methodology for the National Comorbidity Survey

The authors studied weighting adjustments for the National Comorbidity Survey (1990-1992), a large-scale national epidemiologic investigation of the prevalence, risk factors, and consequences of psychiatric morbidity and comorbidity in the United States. Weighting adjustments for differential selection within households, new construction, unit nonresponse, and poststratification were examined separately and in combination. Specific issues addressed included the magnitude of the bias incurred from ignoring the weights, the added variance from weighting and how well this was predicted by simple formulae, and the performance of methods for trimming the weights. Weights had quite modest effects on point estimates of prevalences but resulted in major increases in variance unless trimmed. The weights after trimming and poststratification appeared to work well. It is suggested that the added variance from weighting be carefully monitored in similar surveys. Alternatives to the use of trimming for controlling variance are worth exploring.     

Combined saphenous vein with free flap reconstruction in the treatment of carotid stenosis

Revascularization for arterial stenosis in varied anatomic sites exposed to therapeutic radiation has been well described. In most circumstances, symptomatic end organ ischemia has been the indication for surgical intervention. We report the case of a patient who had symptomatic carotid stenosis 40 years after having ipsilateral neck dissection with radiation therapy. We did a saphenous vein graft interposition and free flap reconstruction of the overlying damaged skin.