Protective effects of extracellular acidosis and blockade of sodium/hydrogen ion exchange during recovery from metabolic inhibition in neuronal tissue culture

Acidosis is a universal response of tissue to ischemia. In the brain, severe acidosis has been linked to worsening of cerebral infarction. However, milder acidosis can have protective effects. As part of our investigations of the therapeutic window in our neuronal tissue culture model of ischemia, we investigated the effects of acidosis during recovery from brief simulated ischemia. Ischemic conditions were simulated in dissociated cortical cultures by metabolic inhibition with potassium cyanide to block oxidative metabolism and 2-deoxyglucose to block glycolysis. Lowering the extracellular pH (pH0) to 6.2 during metabolic inhibition had no effect on injury, as measured by lactate dehydrogenase release from cultures after 24 h of recovery. Lowering the pH0 during the first hour of recovery, in contrast, had profound protective effects. When the duration of metabolic inhibition was lengthened to 30 min, most of the protective effects of the NMDA receptor antagonist MK-801 were lost. However, the protective effects of acidosis were unchanged. This suggested that the protective effects of extracellular acidosis could be due to more than blockade of NMDA receptors. Intracellular acidosis might be responsible. To test this, recovery of intracellular pH (pH1) was slowed by incubation with blockers of Na+/H+ exchangers at normal pH0. The two compounds tested, dimethylamiloride and harmaline, had protective effects when present during recovery from metabolic inhibition. Measurements of pH1 confirmed that the blockers slowed recovery from intracellular acidosis; more rapid pH1 recovery was correlated with injury. The protective effects of acidosis could be reversed by brief incubation with the protonophore monensin, which rapidly normalized pH1. These results are the first demonstration of the protective effects of blocking Na+/H+ exchange in a model of cerebral ischemia. The protective effects of acidosis appear to arise either from suppressing pH-sensitive mechanisms of injury or from blocking sodium entry due to Na+/H+ exchange.

Solubility of Sulfur and Dithiocarbamates in Natural Rubber

Knowledge of equilibrium solubilities of sulfur and accelerators in rubbers at various temperatures allows prediction of whether blooming is possible in particular compounds or products. Reliable data of this nature for natural rubber appeared not to exist in the literature. Immersion of 1 mm thick sheets of peroxide-vulcanized natural rubber in both liquid and, more surprisingly, powdered solid curatives was found to be an adequate method for measuring solubilities. The same experimental method also enabled some diffusion data to be obtained. Solubilities of sulfur, zinc diethyldithiocarbamate (ZDEC) and zinc di-n-butyl dithiocarbamate (ZDBC) were determined at various temperatures between 23° and 135°C. The experimental results did not agree well with the theory which had previously been found to describe the solubility of waxes in natural rubber. This theory, which is a combination of the Flory-Huggins Equation with an expression for the latent heat of fusion, was modified to take into account the dependence of the interaction parameter on temperature and on degree of swelling. The new expression gave much better agreement with the experimental results for all three substances.

Resonant photoemission from complex cuprates and nickelates

Synchrotron-excited resonant-photoemission measurements at rare-earth 4d --> 4f and transition-metal 3p --> 3d thresholds have been carried out using a variety of complex cuprates and nickelates on stations 6.1 (grazing-incidence monochromator) and 6.2 (toroidal-grating monochromator) at the SRS CLRC Daresbury Laboratory. The systems studied are Nd(2)Ni(1 - x)Cu(x)O(4), La(2 - x)Sr(x)Ni(1- y)Fe(y)O(4 + delta) and Bi(2)Sr(2)Ca(1 - x)Y(x)Cu(2)O(8 + delta). A combination of EDC and constant-initial-state data is used to examine the 4f and 3d contributions to the valence-band density of states and their binding-energy positions relative to the Fermi energy. This allows the study of the valence states of the transition-metal ions and their modulation on doping. For La(2 - x)Sr(x)Ni(1 - y)Fe(y)O(4 + delta), this approach is used to infer a valence state of >/= 3.0 for Fe. In the case of Bi(2)Sr(2)Ca(1 - x)Y(x)Cu(2)O(8 + delta), the effect of Cu valence modulation on the 3p resonance is observed as x is varied. This is discussed in the light of controversy surrounding shifts in core-level photoemission with doping for this system.

Manchester procedure vs. vaginal hysterectomy for uterine prolapse. A comparison

The Manchester procedure (MP) was compared with vaginal hysterectomy (VH) to determine whether any differences regarding patient demographics or operative or postoperative outcome could be found between the two techniques. A retrospective chart analysis was done comparing data from 88 consecutive MP to 105 randomly selected VH patients. All the operations were performed for uterine prolapse at Mount Sinai Hospital between 1984 and 1988. MP patients, when compared to VH patients, were more likely to be older and postmenopausal at the time of surgery and to have a private physician. MP patients were less likely to have significant medical illnesses than were VH patients. Statistically significant differences between MP and VH were found for operative time (100 vs 130 minutes, respectively) and blood loss (200 vs. 300 mL, respectively) (P < .001). This difference was not dependent on the performance of anterior or posterior repair. MP was associated with shorter operative time and less blood loss when compared to VH. This, coupled with apparently similar operative outcomes, suggests the use of MP as an alternative to VH in the absence of uterine pathology in appropriate candidates with uterine prolapse. Prospective, controlled, long-term studies comparing the operative results of these two procedures are needed.

Characterization of the Behavior of Rubber for Engineering Design Purposes. 1. Stress-Strain Relations

The stress-strain behavior of a range of black-filled rubbers has been studied in extension, compression, pure shear and simple shear. The data have been analyzed to examine the validity of Gregory's hypothesis that the stored energy function U of filled rubbers can be expressed solely in terms of the strain invariant I1, ignoring I2, to an accuracy adequate for most engineering design requirements. Our results confirm his suggestion. An analytical form for U is proposed which gives a very good fit to the experimental data for strains from less than 0.1% to somewhat greater than 100%, which cover the range of interest for most engineering applications. The dependencies of the parameters in the expression for U on filler level and degree of crosslinking have been examined. It has thus been demonstrated that, for a given material, the form of U can be determined from the measured stress-strain relation in any simple deformation mode, shear or tension for example, without the necessity of relatively difficult biaxial measurements, and that this function should then be applicable to any deformation mode, complex or simple.

Selenium and glutathione peroxidase status in paediatric health and gastrointestinal disease

To examine the effect of paediatric GI disease on selenium concentration in plasma and glutathione peroxidase activity in plasma and red cells, results in children with Crohn's disease (n = 39), cystic fibrosis (n = 14), intractable diarrhoea (n = 13), and biliary atresia (n = 10) were compared with those from 86 healthy children undergoing routine operations. In Crohn's disease, plasma selenium concentrations were rarely low, but glutathione peroxidase activity was increased in the plasma and reduced in the red cells. Selenium concentration and glutathione peroxidase activity increased with steroid treatment but decreased with a selenium-deficient elemental diet. Plasma selenium concentration was normal in children with cystic fibrosis but very low in severely malnourished children with biliary atresia and intractable diarrhoea. Selenium concentration and glutathione peroxidase activity should be monitored in children with severe malnutrition or requiring prolonged nutritional support. Supplementation is recommended in cases of severe selenium depletion.

Laparoscopic Pomeroy tubal ligation in a residency training program

STUDY OBJECTIVE

To evaluate the efficacy of the laparoscopic Pomeroy method of tubal ligation as a teaching tool during the initial acquisition of advanced laparoscopic skills by 14 residents in a 28-person, 4-year program.

DESIGN

A prospective, nonrandomized study.

SETTING

A metropolitan teaching hospital.

PATIENTS

Fifty-seven women who desired permanent sterilization, and 56 controls who underwent laparoscopic sterilization by standard coagulation. One refused entry and had standard sterilization by bipolar coagulation. In two women, both with several previous laparotomies, visualization of the pelvic organs was incomplete and the procedure was abandoned at the discretion of the surgeon. One had a minilaparotomy Pomeroy tubal ligation and the other was sterilized by standard two-puncture laparoscopic coagulation. One patient was excluded due to an incomplete data profile.

INTERVENTIONS

Laparoscopic sterilizations using the Pomeroy technique and standard coagulation were performed by gynecology residents with an attending physician present. First-year residents performed 36 (68%) of the 53 procedures.

MEASUREMENTS AND MAIN RESULTS

Operative times to teach this technique to house officers rotating on the gynecologic service were recorded by postgraduate year and stratified by the number of cases performed by each operator. The average operative times for residents in postgraduate years 1 through 4 were 18.6, 15.4, 21.7, and 14.8 minutes, respectively. These diminished with experience. A statistically longer time of 7.1 minutes was required to teach residents the Pomeroy technique compared with standard bipolar coagulation (p<0.0003).

CONCLUSION

Laparoscopic Pomeroy tubal ligation as a method to begin educating residents in advanced operative video-laparoscopy appears to have great potential.

The Development of Fracture Mechanics for Elastomers

The energy balance, or fracture mechanics, approach has proved successful in treating a number of fracture phenomena and unifying them in terms of what is believed to be a basic characteristic, the crack growth behavior when expressed in terms of the energy release rate T. It has also enabled some of the underlying physical factors to be identified and incorporated into appropriate theories. There are, however, some important limitations and outstanding problems which remain. For example, we do not at present have any quantitative understanding of what determines the precise form of the crack growth characteristic under repeated stressing. During the development of the approach, numerous checks were made of its validity by comparative experiments on different test piece geometries. This is important, as it is not certain that such comparisons will invariably give equivalent results and that the T vs. rate of tear relation is a true material characteristic. For example, if a test piece, such as the “split” test piece in Figure 2(d), is subjected to large pre-extensions in the direction of tearing, the tear resistance in some cases may apparently be much reduced from its unprestrained value. (Anisotropy is produced which is believed to be important in knotty tear development). Gent and Kim found a similar effect with laterally pre-strained pure shear test pieces. Also, if tear measurements are made with an edge crack test piece of natural rubber and the strains become great enough to produce crystallization in the main bulk of the test piece, the stick-slip behavior is suppressed and the tear strength appears to be increased. Thus it appears that in some cases the assumption that the strains just around the tip at the instant of tearing are independent of the bulk deformation is not true. Fortunately these cases seem to be the exception rather than the rule, but their occurrence demands continuing caution. Some peel tests of rubber-to-metal bonds for example show apparently anomalous force dependencies on peel angle. The current interest in the understanding and prediction of strength and durability of elastomer articles stems from the increasing importance attached to avoiding premature failure in service. The growing availability of finite element programs capable of dealing with large strains has already meant that force-deflection behavior can be at least approximately designed for; but a corresponding failure design procedure based on fracture mechanics is still in the stage of development.

The effect of placenta previa on blood loss in second-trimester pregnancy termination

OBJECTIVE

To determine whether placenta previa increases bleeding during second-trimester pregnancy termination.

METHODS

The records of 131 consecutive women undergoing elective pregnancy termination at 13-24 weeks' gestation were reviewed and divided into those with and without placenta previa based on an ultrasound examination before the procedure. These two groups were then compared for differences in maternal characteristics, estimated blood loss, operative time, infection, and hospital admission.

RESULTS

Twenty-three of 131 women (17.6%) had placenta previa. Sixty-seven percent of the previa patients smoked, versus 37% in the control group, a statistically significant difference. A statistical difference was noted with respect to placenta previa in intraoperative blood loss (P < .05), but not operative time, time to discharge, infection, hemorrhage, or other complications.

CONCLUSION

Second-trimester pregnancy terminations in the presence of placenta previa are associated with a higher estimated blood loss, but no apparent increase in abortion-related infection, postoperative transfusion requirements, hysterectomy, or other complications.

Dietary intake and nutritional treatment in childhood Crohn's disease

Dietary intake was assessed in 24 children with active Crohn's disease. Seventeen of the children were sex and height matched with healthy siblings of other patients. The mean energy intake was 1,764 KJ/day (420 kcal/day) lower in patients during relapse than controls (p < 0.05). All 24 children entered a randomised controlled trial of high-dose steroids compared to an elemental diet. The elemental diet was well tolerated orally in most cases; only one patient required nasogastric administration. There was a similar improvement in disease activity and duration of remission in both groups regardless of the site of disease. Subsequent growth velocity was significantly better in the group treated with the elemental diet despite a greater and more sustained increase in energy intake in the group treated with steroids. Reintroduction of specific foods in the elemental diet group initially caused symptoms in three children but were subsequently tolerated. During remission, there was no significant difference in energy intake, but vegetables were consumed significantly less frequently (p < 0.01) and confectionery significantly more frequently (p < 0.05) when patients were compared with their own siblings.

Insulin like growth factor-I, insulin like growth factor binding protein-1, and insulin in childhood Crohn's disease

Twenty nine children with Crohn's disease were studied before and after treatment with steroids or an elemental diet to assess the effect of disease activity and treatment on serum insulin like growth factor I (IGF-I), insulin like growth factor binding protein (IGFBP-1), and insulin concentrations. The median serum IGF-I concentration was lower in patients with active disease than in matched controls, and lower in stunted than well grown patients, but insulin and IGFBP-1 concentrations were not significantly different between any group. After four weeks of either treatment there was an increase in the median serum IGF-I concentration; this was greater in the steroid group than the elemental diet group. The median serum insulin concentration increased and median serum IGFBP-1 concentration decreased in the steroid treated group but not in the elemental diet group. These changes were accompanied by a greater and more sustained increase in energy intake in the steroid group. Despite this the median height velocity SD score was greater in the elemental diet group than in the steroid group.

Operating room personnel morbidity from carbon dioxide laser use during preceptored surgery

OBJECTIVE

To determine the extent of laser-induced morbidity away from the operative site during the preceptor phase of laser credentialing in our institution.

METHODS

All laser surgeries performed from June 1, 1990 through May 31, 1991 and preceptored by one of the authors (MB) were included in the study. All of the surgeries were performed by a resident or attending physician seeking laser privileges in our institution. During that time, 141 such cases were performed.

RESULTS

In 13 of 141 cases (9%), there were injuries unrelated to the surgical procedure itself to either the patient or operating personnel. There were nine accidents associated with laser use during 42 laparotomy procedures (21%) and four accidents at the time of 44 vulvar surgeries (9%). There were no accidents during laparoscopic or colposcopic surgery of the vagina or cervix.

CONCLUSIONS

Despite extensive training requirements before use of the CO2 laser, accidents did occur. Operating room safety requirements should be a high priority to minimize morbidity. We report our experience with intraoperative morbidity caused by surgeons' errors and present recommendations to limit further complications.

Environmental factors including management practices as correlates of weed community composition in spring seeded crops

The relationship between the weed communities and environmental variables such as soil, crop, and management was investigated in two provinces of Canada. The frequencies of weed species were recorded in cereal and oilseed fields in Saskatchewan (2244 fields over 4 years) and Manitoba (864 fields over 3 years), Canada. Information on some of the physical characteristics of the fields and on the management practices imposed on them was also collected, in part by questionnaire. The two kinds of data were ordinated together using canonical correspondence analysis to assess the relationships between the species and the environmental variables. In the Saskatchewan data, there was a clear and consistent separation of the species into groups along an axis correlated with soil zone and the associated climatic gradient. In the Manitoba data, the same groups of species did not separate as clearly or as consistently, although geographic region was a major determinant of the weed communities. The greater variability may be due to the fact that the gradient of soil types is much more restricted in Manitoba and not as closely correlated with climatic conditions. In both provinces, culture practices were less important as correlates of the weed community composition than soil type or, to a certain extent, the previous crop. Key words: canonical correspondence analysis, cereal crops, oil seed crops.

Cryptosporidium, chronic diarrhoea and the proximal small intestinal mucosa

The association between Cryptosporidium, chronic diarrhoea and a proximal small intestinal mucosal enteropathy was reviewed over a six and a half year period. One hundred and twenty three children with cryptosporidiosis and no clinical evidence of immune deficiency were identified. 50% of children excreting only Cryptosporidium had chronic diarrhoea. Most cases (63%) of chronic diarrhoea occurred in the first two years of life. A mild to moderate enteropathy was present in all nine children undergoing a small intestinal biopsy and seven showed the presence of Cryptosporidium adhering to villous epithelium. All patients eventually recovered spontaneously. Cryptosporidium is a cause of chronic diarrhoea and a proximal small intestinal mucosal enteropathy in children without immune deficiency. Screening for the parasite should be part of the investigative procedures in children with chronic diarrhoea.

The value of proximal small intestinal biopsy in the differential diagnosis of chronic diarrhoea

The value of proximal intestinal mucosal biopsy was reviewed in 381 children presenting with chronic diarrhoea over an eight year period. An enteropathy was detected in 44% of cases and was more frequently seen in those aged less than 6 months. A diagnosis was established in 91% of cases. The most common diagnosis was the postenteritis syndrome where the presence of an enteropathy indicated those requiring treatment with a cows' milk free diet. Other conditions where a biopsy facilitated diagnosis or treatment included giardiasis, enteropathogenic Escheriichia coli, crytosporidiosis, autoimmune enteropathy, and microvillous atrophy. Coeliac disease was considered in 55% of children and established in 8%, clearly identifying those requiring a gluten free diet. This also emphasises the important role of the biopsy procedure in the exclusion of specific diseases. Proximal small intestinal mucosal biopsy is an essential investigation in children with chronic diarrhoea in whom an enteropathy is suspected.

Whole body protein turnover in childhood Crohn's disease

In order to investigate the effects of treatment on protein metabolism in childhood Crohn's disease whole body protein turnover was measured using a primed constant intravenous infusion of L-[1-13C]leucine and mass spectrometry in 10 children with active disease. Mean rates of protein synthesis and breakdown markedly decreased after treatment with steroids (four) or an elemental diet (six). This suggests that protein synthesis and breakdown are increased during active Crohn's disease in children and are reduced after induction of remission regardless of the type of treatment.

Incarcerated hernia after laparoscopic sterilization. A case report

Small bowel incarceration after laparoscopic procedures is rare. Such a complication occurred after an elective laparoscopic sterilization in a 36-year-old woman.