Integrating plant physiology into simulation of fire behavior and effects

Wildfires are a global crisis, but current fire models fail to capture vegetation response to changing climate. With drought and elevated temperature increasing the importance of vegetation dynamics to fire behavior, and the advent of next generation models capable of capturing increasingly complex physical processes, we provide a renewed focus on representation of woody vegetation in fire models. Currently, the most advanced representations of fire behavior and biophysical fire effects are found in distinct classes of fine-scale models and do not capture variation in live fuel (i.e. living plant) properties. We demonstrate that plant water and carbon dynamics, which influence combustion and heat transfer into the plant and often dictate plant survival, provide the mechanistic linkage between fire behavior and effects. Our conceptual framework linking remotely sensed estimates of plant water and carbon to fine-scale models of fire behavior and effects could be a critical first step toward improving the fidelity of the coarse scale models that are now relied upon for global fire forecasting. This process-based approach will be essential to capturing the influence of physiological responses to drought and warming on live fuel conditions, strengthening the science needed to guide fire managers in an uncertain future.

Galanin expression in adult human dorsal root ganglion neurons: initial observations

Human dorsal root ganglia (DRGs) were obtained during various procedures and processed for single and double in situ hybridisation using oligonucleotide probes complementary to three peptide mRNAs. Some postmortem ganglia were also analysed. In donor (unlesioned) DRGs 12.5% of the neuron profiles (NPs) were galanin mRNA-positive (mRNA(+)), 47.5% calcitonin gene-related peptide (CGRP) mRNA(+) and 32.7% substance P mRNA(+). The corresponding percentages for cervical/thoracic DRGs from patients suffering from severe brachial plexus injury were 32.8%, 57.4% and 34.5%, respectively. In these DRGs a high proportion of the galanin mRNA(+) NPs contained CGRP mRNA and substance P mRNA. In DRGs from a patient with migraine-like pain a comparatively small proportion expressed galanin, whereas in DRGs from a herpes zoster patient galanin mRNA(+) NPs were comparatively more frequent. The results from human postmortem DRGs revealed only weak peptide mRNA signals. The present results demonstrate that galanin is expressed in DRGs not only in a number of animal species including monkey as previously shown, but also in a considerable proportion of human DRG neurons, often together with CGRP and substance P, and mostly in small neurons. Thus, galanin may play a role in processing of sensory information, especially pain, in human DRGs and dorsal horn. However, to what extent a similarly dramatic upregulation of galanin expression can be seen after peripheral nerve lesion in man, as has been reported for rat, mouse and monkey, remains to be analysed.

GDNF and NGF family members and receptors in human fetal and adult spinal cord and dorsal root ganglia

We describe the expression of mRNA encoding ligands and receptors of members of the GDNF family and members of the neurotrophin family in the adult human spinal cord and dorsal root ganglia (DRG). Fetal human spinal cord and ganglia were investigated for the presence of ligands and receptors of the neurotrophin family. Tissues were collected from human organ donors and after routine elective abortions. Messenger RNA was found encoding RET, GFR alpha-1, BDNF, trkB, and trkC in the adult human spinal cord and BDNF, NT-3, p75, trkB, and trkC in the fetal human spinal cord. The percentage of adult human DRG cells expressing p75, trkA, trkB, or trkC was 57, 46, 29, and 24%, respectively, and that of DRG cells expressing RET, GFR alpha-1, GFR alpha-2, or GFR alpha-3 was 79, 20, 51, and 32%, respectively. GFR alpha-2 was expressed selectively in small, GFR alpha-3 principally in small and GFR alpha-1 and RET in both large and small adult human DRG neurons. p75 and trkB were expressed by a wide range of DRG neurons while trkA was expressed in most small diameter and trkC primarily in large DRG neurons. Fetal DRG cells were positive for the same probes as adult DRG cells except for NT-3, which was only found in fetal DRG cells. Messenger RNA species only expressed at detectable levels in fetal but not adult spinal cord tissues included GDNF, GFR alpha-2, NT-3, and p75. Notably, GFR alpha-2, which is expressed in the adult rat spinal cord, was not found in the adult human spinal cord.

NOGO mRNA expression in adult and fetal human and rat nervous tissue and in weight drop injury

Nogo is a myelin-associated protein known to inhibit growth of neurites. In order to understand possible physiological roles of Nogo, we performed in situ hybridization using rat and human probes complementary to a Nogo-A-specific sequence and a sequence shared by all known Nogo transcripts recognizing nogo-A, -B, and -C. We studied the cellular distribution of nogo-mRNA in fetal and adult human and rat tissues, with a focus on the spinal cord and ganglia. Rat mRNA expression was also studied in a spinal cord weight-drop model and in animals exposed to kainic acid. In human fetal tissue, nogo-A was strongly expressed in the ventral two-thirds of the spinal cord, the dorsal root ganglia, and autonomic ganglia. Similarly, nogo-A mRNA expression was observed in the adult human spinal cord and ganglia. High levels of nogo-A message were observed in neurons, such as motor neurons and sensory ganglia neurons. The distribution of nogo message in rats resembled that seen in human tissues. Thus, nogo mRNA was expressed in neurons and oligodendrocytes, but not astrocytes or Schwann cells. In addition, expression of nogo-A mRNA was observed in human and rat developing muscle tissue. High level of nogo-mRNA were also expressed in the rat trigeminal ganglion and trigeminal pontine nucleus. In fetal rats the adrenal gland and cell clusters in the liver were positive for the nogo-ABC pan-probe, but negative for the nogo-A probe. While neurons in the adult rat brain were generally positive, very prominent nogo-A mRNA and nogo-ABC mRNA signals were obtained from neurons of the hippocampus, piriform cortex, the red nucleus, and the oculomotor nucleus. Nogo-A mRNA expression was markedly reduced in the epicenter of a lesion in the spinal cord of adult rats 6 and 24 h after a weight-drop injury, while no perifocal upregulation of nogo mRNA was seen. No obvious change of nogo expression was detected in kainic acid exposed animals. In conclusion our in situ hybridization study has demonstrated widespread expression of nogo mRNA in the fetal, developing and adult nervous system of rat and man. In addition to oligodendroglial cells, high levels of nogo-A mRNA expression were found in neurons, raising important questions about the function of neuronal nogo mRNA. No obvious regulation of nogo was detected following injury.

A spinal thecal sac constriction model supports the theory that induced pressure gradients in the cord cause edema and cyst formation

OBJECTIVE

Spinal cord cysts are a devastating condition that occur secondary to obstructions of the spinal canal, which may be caused by congenital malformations, trauma, spinal canal stenosis, tumors, meningitis, or arachnoiditis. A hypothesis that could explain how spinal cord cysts form in these situations has been presented recently. Therefore, a novel spinal thecal sac constriction model was implemented to test various aspects of this hypothesis.

METHODS

Thecal sac constriction was achieved by subjecting rats to an extradural silk ligature at the T8 spinal cord level. Rats with complete spinal cord transection served as a second model for comparison. The animals underwent high-resolution magnetic resonance imaging and histological analysis.

RESULTS

Thecal sac constriction caused edema cranial and caudal to the ligation within 3 weeks, and cysts developed after 8 to 13 weeks. In contrast, cysts in rats with spinal cord transection were located predominantly in the cranial spinal cord. Histological sections of spinal cords confirmed the magnetic resonance imaging results.

CONCLUSION

Magnetic resonance imaging provided the specific advantage of enabling characterization of events as they occurred repeatedly over time in the spinal cords of individual living animals. The spinal thecal sac constriction model proved useful for investigation of features of the cerebrospinal fluid pulse pressure theory. Edema and cyst distributions were in accordance with this theory. We conclude that induced intramedullary pressure gradients originating from the cerebrospinal fluid pulse pressure may underlie cyst formation in the vicinity of spinal canal obstructions and that cysts are preceded by edema.

Functional MRI at 4.7 tesla of the rat brain during electric stimulation of forepaw, hindpaw, or tail in single- and multislice experiments

Stimulation of peripheral nerves activates corresponding regions in sensorimotor cortex. We have applied functional magnetic resonance imaging (fMRI) techniques to monitor activated brain regions by means of measuring changes of blood oxygenation level-dependent contrast during electric stimulation of the forepaw, hindpaw, or tail in rats. During alpha-chloralose anesthesia, artificial respiration, and complete muscle relaxation, stimulations were delivered at 3 Hz via subcutaneous bipolar electrodes with 500-microseconds-current pulses of 0.2-2.0 mA. Single- or multislice gradient echo images were collected during recording sessions consisting of five alternating rest and stimulation periods. Stimulation of the right and left forepaws and hindpaws repeatedly led to robust activation of the contralateral sensorimotor cortex. There was a significant correlation (P < 0.05) between current pulse strength and amount of activation of the sensory cortex during forepaw stimulation. The center of the main cortical representation of the forepaw was situated 3.4 mm lateral to the midline and 5 mm posterior to the rhinal fissure. The main representation of the hindpaw was 2.0 mm lateral to the midline and 6 mm posterior to the rhinal fissure. Tail stimulation gave rise to a strikingly extended bilateral cortical activation, localized along the midline in medial parietal and frontal cortex 4 and 5 mm posterior to the rhinal fissure. In conclusion, the experiments provide evidence that peripheral nerve stimulation induces a fMRI signal in the respective division of the somatosensory cortex in a stimulus-related manner. The marked cortical activation elicited by tail stimulation underlines the key importance of the tail.

A characteristic serpin cleavage product of thyroxine-binding globulin appears in sepsis sera

T4-binding globulin (TBG), the principal thyroid hormone-binding protein of serum, is a member of the serine protease inhibitor (serpin) superfamily. We report a characteristic serpin cleavage product of TBG in sepsis sera. At 49-50 kDa, the TBG remnant is 4-5 kDa smaller than the intact protein and is the same molecular mass as a TBG cleavage product produced by incubation with polymorphonuclear elastase. Incubation with polymorphonuclear leukocytes also produces the 49- to 50-kDa remnant, and this proteolysis is stimulated by zymosan activation. Polymorphonuclear cell cleavage of TBG increases the ratio of free/bound T4. As previously described, in vitro cleavage of TBG by elastase also increases free/bound T4. These findings are consistent with the hypothesis that serine proteases present at inflammatory sites cleave TBG, releasing its hormonal ligands.

Meeting infection control standards in the OR

Quality health care is associated with the absence of negative outcomes in patients. Institutions realize that quality cannot be assured but it can be assessed and methods can be developed to improve patient care. Many heath care institutions, therefore, have begun the conceptual transition from quality assurance model to principles of continuous quality improvement (CQI). This article describes a CQI project that was developed to enhance infection control standards in OR settings. The project involved three phases: development of a survey tool, implementation of an environmental assessment and monitoring model, and transfer of the model to OR staff members. Five months after implementation of the model, the chi-square test revealed there was a significant improvement in compliance (chi 2 = 5.0, P < .03). After 22 months of using the model, compliance to infection control standards remains high and OR staff members have taken ownership of the model by incorporating it into their departmental CQI process.

The numbers game: sample-size determination

Sample-size determination is a crucial component of study design. Estimates of sample size are influenced by the amount of change that must occur between study groups and the degree of risk that the investigator is willing to accept in evaluating the null hypothesis. A complete understanding of the impact of sample size on the interpretation of study data is therefore a prerequisite for quality, innovative, valid research.

Difficult parents. From adversaries to partners

The pediatrician's job becomes frustrating when it is necessary to deal with difficult parents. Some physicians may not have the training or inclination to engage such parents in a therapeutic partnership. This paper discusses tools available to physicians which will help them develop an effective partnership that includes uncovering the hidden meaning behind a child's illness; understanding the reciprocal nature of partnerships; and the importance of determining each party's goals, roles, and expectations. Negotiating these steps enables physicians to develop a productive relationship with difficult parents of sick children. This strategy can facilitate the child's medical care and improve the parents' and physician's satisfaction with the services rendered. This paper also discusses steps to take when these attempts are not sufficient to handle the situation.

A cluster of vancomycin-resistant Enterococcus faecium in an intensive care unit

OBJECTIVE

To describe the epidemiology of a cluster of vancomycin-resistant Enterococcus faecium (VAREC) in a cardiothoracic surgery intensive care unit.

DESIGN

A case series of patients identified through review of surveillance data on nosocomial infections, review of microbiologic records, and culture survey of patients in the unit.

RESULTS

Six patients in the cardiothoracic surgery intensive care unit had VAREC with identical antimicrobic susceptibility patterns over a 6-month period. Four patients were identified with VAREC through prospective surveillance and 2 through retrospective review. Prior vancomycin use was seen more commonly in patients with VAREC (6/6, 100%) than in those without VAREC (3/12, 25%) (Fisher's exact test, p = .01). Six of the 7 patients with prior infection developed VAREC (85.7%). A prior nosocomial infection and prior exposure to vancomycin were found to be important variables in a logistic regression analysis. VAREC also was isolated from the environment. A combination of cohorting of patients and staff, and modifications of standard contact isolation practices eliminated the presence of VAREC from the cardiothoracic surgery intensive care unit.

CONCLUSIONS

The results suggest that prior administration of vancomycin, especially in the patient who develops nosocomial infection, can influence the acquisition of vancomycin-resistant enterococci and that VAREC may be transmitted from patient to patient. Using a modification of the standard infection control practice of isolation, we were able to control the spread of this resistant strain of E faecium.

Risk-specific nosocomial infection rates

Because nosocomial infection rates vary by hospital area and service, most infection control programs calculate area-specific rates to augment the reporting of their hospital-wide data. Rate development is often limited by the availability of appropriate specific denominator data to support important comparisons. Our university hospital reports a 20 month experience in which numerator data was collected as per the National Nosocomial Infections Surveillance System criteria for hospital-wide, high-risk nursery and ICU surveillance. These data were then combined with data in our hospital's patient-specific denominator file. This has enabled the development of risk-specific infection rates based on the analytic control of important variables available in both the numerator and denominator files. We found rate differences that were length of stay cohort specific, hospital day specific, age specific, birthweight specific, and survival cohort specific when examining our data by both the cumulative incidence and incidence density methods.

Strategies for the management of varicella-susceptible healthcare workers after a known exposure

Three different sequentially applied post-varicella zoster virus (VZV) exposure management strategies were employed over a 43-month period. We began by using a standard post-exposure protocol in which 50 susceptible healthcare workers (HCW) involved in hospital exposures were furloughed from work at a loss to the hospital of 424 workdays and $46,000. Of the eight nosocomial cases of VZV infection in HCWs, four (50%) caused future HCW and patient exposure. In trial I, we substituted a post-exposure screening procedure for the standard work furlough procedure. We screened 77 exposed staff resulting in one nosocomial VZV infection that was the source of another exposure incident. No secondary cases of varicella resulted from this exposure and only 20 days of furlough time were used during trial I. As VZV resulting from a home exposure source was responsible for most hospital exposures in which HCWs were the source, our trial II protocol added the Centers for Disease Control's (CDC) off-duty procedure, but limited its use to susceptibles exposed at home. The 43-month overall attack rate of nosocomial varicella was 4.7%, while the true home exposure attack rate was 79% (p less than .00001). There was an average of 42.4 lost workdays charged to the hospital per incident under the standard protocol and three days per incident in the combined experience of trials I and II (p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between intravenous fluid contamination and the frequency of tubing replacement

Medical patients receiving IV therapy were randomly assigned to one of two IV tubing change groups. One group had a 48-hour tubing change and the other had no tubing change for the remainder of the cannula placement. A daily IV fluid specimen was processed microbiologically. To complete the study, a minimum of 3 continuous days of therapy and three fluid specimens was required. There were two contaminated specimens, one in each tubing change group. The contamination rate in the 48-hour change group was 0.87% and 0.96% in the no change group. The rate difference of 0.09% has a 95% confidence interval (-0.035 to +0.036) which includes zero. Survival analysis also revealed no significant difference in the cumulative probability of survival, however the mean duration of continuous tubing use of 4.3 days in the no change group and 1.8 days in the 48 hour change group were significantly different (p less than 0.05). The cumulative probability of surviving contamination free was 0.988 in the 48-hour group and 0.987 in the no-change group. We conclude that it is safe to change IV tubing at intervals up to but not exceeding 4 days.

An epidemiologic study of postcesarean infection

Cesarean section (CS) is associated with increased postpartum infectious morbidity, predominantly endometritis. In this prospective cohort study, endometritis was found in 28% of 229 patients who underwent consecutive CS from September 1979 to May 1980 at a university hospital. When the occurrence of bacteremia and wound infection was considered, the study found 31% of the patients were infected. Among the 20 potential epidemiologic and operative risk factors for infection that were studied, the most important were primary CS, membrane rupture, labor, and meconium staining (p = 0.0001). Failure to progress, breech presentation, and fetal distress were also significantly associated with infection (p = 0.001). Another factor correlated to the rate of infection was attendance by physician in training (p = 0.002). Discriminant function analysis was used to develop an equation that correctly classified, as infected or noninfected, 76% of a sample of CS patients (p = 0.004). This sample was not part of the original sample from which the discriminant function equation was developed. Finally toward the end of the study period, we observed a decrease in the infection rate among patients of house staff physicians. This decrease has resulted in similar infection rates for patients of attending physicians and patients of house staff physicians, which have continued to the present.

Cavitary Legionnaires' pneumonia: nosocomial infection in renal transplant recipients

Cavitation is an unusual manifestation of legionnaires' pneumonia. Mortality rates range from 24 to 58 percent with effective therapy. Antibiotic therapy is not standardized and is largely based on anecdotal reports. This report has described nosocomially acquired cavitary legionnaires' pneumonia in five renal transplant recipients. The diagnosis was made by seroconversion and immunofluorescent staining of lung tissue or transtracheal aspirates. Frequently seen associated symptoms were not present. All patients were successfully treated with 2 to 4 g of erythromycin for at least 4 weeks.

Infection complicating intrapericardial steroid instillation in uremic pericarditis

Short-term, indwelling, percutaneous pericardiocentesis for drainage with local steroid instillation has been advocated for refractive uremic pericarditis. It is reported to be almost universally successful and to cause only minor complications. We describe a patient in whom this technique lead to purulent pericarditis (Staphylococcus aureus) requiring pericardiectomy.