Posterior capsular release is a biomechanically safe procedure to perform in total knee arthroplasty.

PURPOSE: Surgeons may attempt to strip the posterior capsule from its femoral attachment to overcome flexion contracture in total knee arthroplasty (TKA); however, it is unclear if this impacts anterior-posterior (AP) laxity of the implanted knee. The aim of the study was to investigate the effect of posterior capsular release on AP laxity in TKA, and compare this to the restraint from the posterior cruciate ligament (PCL). METHODS: Eight cadaveric knees were mounted in a six degree of freedom testing rig and tested at 0°, 30°, 60° and 90° flexion with ± 150 N AP force, with and without a 710 N axial compressive load. After the native knee was tested, a deep dished cruciate-retaining TKA was implanted and the tests were repeated. The PCL was then cut, followed by releasing the posterior capsule using a curved osteotome. RESULTS: With 0 N axial load applied, cutting the PCL as well as releasing the posterior capsule significantly increased posterior laxity compared to the native knee at all flexion angles, and CR TKA states at 30°, 60° and 90° (p < 0.05). However, no significant increase in laxity was found between cutting the PCL and subsequent PostCap release (n.s.). In anterior drawer, there was a significant increase of 1.4 mm between cutting the PCL and PostCap release at 0°, but not at any other flexion angles (p = 0.021). When a 710 N axial load was applied, there was no significant difference in anterior or posterior translation across the different knee states (n.s.). CONCLUSIONS: Posterior capsular release only caused a small change in AP laxity compared to cutting the PCL and, therefore, may not be considered detrimental to overall AP stability if performed during TKA surgery. LEVEL OF EVIDENCE: Controlled laboratory study.

Oxygen and pH-sensitivity of human osteoarthritic chondrocytes in 3-D alginate bead culture system.

OBJECTIVE: To identify the effect of alterations in physical parameters such as oxygen and pH on processes associated with cellular redox balance in osteoarthritic chondrocytes. METHOD: Human osteoarthritic chondrocytes (HOAC) were isolated from total knee arthroplasty samples and cultured in 3-D alginate beads in four different oxygen tensions (<1%, 2%, 5% and 21% O2), at pH 7.2 and 6.2 and in the presence or absence of 10 ng/ml, interleukin-1ß (IL-1ß). Cell viability, media glycosaminoglycan (GAG) levels, media nitrate/nitrate levels, active matrix metalloproteinase (MMP)-13 and intracellular adenosine triphosphate (ATPi) were measured over a 96-h time course. Intracellular reactive oxygen species (ROS), mitochondrial membrane potential, intracellular pH and reduced/oxidised glutathione (GSH/GSSG) were additionally measured after 48-h incubation under these experimental conditions. RESULTS: Hypoxia (2% O2) and anoxia (<1% O2), acidosis (pH 6.2) and 10 ng/ml IL-1ß reduced HOAC cell viability and increased GAG media levels. Acidosis and IL-1ß increased nitrite/nitrate release, but increases were moderate at 2% O2 and significantly reduced at <1% O2. ATPi was significantly reduced following hypoxia and anoxia and acidosis. At 48 h cellular ROS levels were increased by acidosis and IL-1ß but reduced in hypoxia and anoxia. Mitochondrial membrane potential was reduced in low oxygen, acidosis and IL-1ß. Anoxia also resulted in intracellular acidosis. GSH/GSSG ratio was reduced in low oxygen conditions, acidosis and IL-1ß. CONCLUSIONS: This study shows that oxygen and pH affect elements of the redox system in HOAC including cellular anti-oxidants, mitochondrial membrane potential and ROS levels.

Distribution of purinergic P2X receptors in the equine digit, cervical spinal cord and dorsal root ganglia.

Purinergic pathways are considered important in pain transmission, and P2X receptors are a key part of this system which has received little attention in the horse. The aim of this study was to identify and characterise the distribution of P2X receptor subtypes in the equine digit and associated vasculature and nervous tissue, including peripheral nerves, dorsal root ganglia and cervical spinal cord, using PCR, Western blot analysis and immunohistochemistry. mRNA signal for most of the tested P2X receptor subunits (P2X1-5, 7) was detected in all sampled equine tissues, whereas P2X6 receptor subunit was predominantly expressed in the dorsal root ganglia and spinal cord. Western blot analysis validated the specificity of P2X1-3, 7 antibodies, and these were used in immunohistochemistry studies. P2X1-3, 7 receptor subunits were found in smooth muscle cells in the palmar digital artery and vein with the exception of the P2X3 subunit that was present only in the vein. However, endothelial cells in the palmar digital artery and vein were positive only for P2X2 and P2X3 receptor subunits. Neurons and nerve fibres in the peripheral and central nervous system were positive for P2X1-3 receptor subunits, whereas glial cells were positive for P2X7 and P2X1 and 2 receptor subunits. This previously unreported distribution of P2X subtypes may suggest important tissue specific roles in physiological and pathological processes.

Feasibility of using microbiology diagnostic tests of moderate or high complexity at the point - of - care in a delivery suite.

Point-of-care testing (POCT) is one of the fastest growing sectors of laboratory diagnostics. Most tests in routine use are haematology or biochemistry tests that are of low complexity. Microbiology POCT has been constrained by a lack of tests that are both accurate and of low complexity. We describe our experience of the practical issues around using more complex POCT for detection of Group B streptococci (GBS) in swabs from labouring women. We evaluated two tests for their feasibility in POCT: an optical immune assay (Biostar OIA Strep B, Inverness Medical, Princetown, NJ) and a PCR (IDI-Strep B, Cepheid, Sunnyvale, CA), which have been categorised as being of moderate and high complexity, respectively. A total of 12 unqualified midwifery assistants (MA) were trained to undertake testing on the delivery suite. A systematic approach to the introduction and management of POC testing was used. Modelling showed that the probability of test results being available within a clinically useful timescale was high. However, in the clinical setting, we found it impossible to maintain reliable availability of trained testers. Implementation of more complex POC testing is technically feasible, but it is expensive, and may be difficult to achieve in a busy delivery suite.

Diagnostic accuracy of the Abbott ID NOW SARS-CoV-2 rapid test for the triage of acute medical admissions.

BACKGROUND: Decisions to isolate patients at risk of having coronavirus disease 2019 (COVID-19) in the emergency department (ED) must be rapid and accurate to ensure prompt treatment and maintain patient flow whilst minimising nosocomial spread. Reverse transcription polymerase chain reaction (RT-PCR) assays are too slow to achieve this, and near-patient testing is being used increasingly to facilitate triage. The ID NOW severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) assay is an isothermal nucleic acid amplification near-patient test which targets the RNA-dependent RNA-polymerase gene. AIM: To assess the diagnostic performance of ID NOW as a COVID-19 triage tool for medical admissions from the ED of a large acute hospital. METHODS: All adult acute medical admissions from the ED between 31st March and 31st July 2021 with valid ID NOW and RT-PCR results were included. The diagnostic accuracy of ID NOW [sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV)] was calculated against the laboratory reference standard. Discrepant results were explored further using cycle threshold values and clinical data. FINDINGS: Two percent (124/6050) of medical admissions were SARS-CoV-2 positive on RT-PCR. Compared with PCR, ID NOW had sensitivity and specificity of 83.1% [95% confidence interval (CI) 75.4-88.7] and 99.5% (95% CI 99.3-99.6), respectively. PPV and NPV were 76.9% (95% CI 69.0-83.2) and 99.6% (95% CI 99.5-99.8), respectively. The median time from arrival in the ED to ID NOW result was 59 min. CONCLUSION: ID NOW provides a rapid and reliable adjunct for the safe triage of patients with COVID-19, and can work effectively when integrated into an ED triage algorithm.

Regulation of SOX9 in normal and osteoarthritic equine articular chondrocytes by hyperosmotic loading.

OBJECTIVES: SOX9 is a transcription factor that is essential for cartilage extracellular matrix (ECM) formation. Osteoarthritis (OA) is characterised by a loss of cartilage ECM. In chondrocytes SOX9 gene expression is regulated by osmotic loading. Here we characterise SOX9 mRNA regulation through static and cyclical application of hyperosmotic conditions in normal and OA monolayer equine chondrocytes. Furthermore, we investigate whether extracellular signal-regulated protein kinase (ERK)1/2 mitogen-activated protein kinases (MAPK) pathways have a role in this regulation of SOX9. METHODS: Equine chondrocytes harvested from normal or OA joints were subjected to different osmotic loading patterns as either primary (P0) or passaged (P2) cells. The involvement of MEK-ERK signalling was demonstrated by using pharmacological inhibitors. In addition SOX9 gene stability was determined. Levels of transcripts encoding SOX9, Col2A1 and aggrecan were measured using qRT-PCR. De novo glycosaminoglycan synthesis of explants was determined with (35)S sulphate during static hyperosmolar loading. RESULTS: MEK-ERK signalling increases glycosaminoglycans (GAG) synthesis in explants. Static hyperosmotic conditions significantly reduced SOX9 mRNA in normal P2 and OA P0 but not normal P0 chondrocytes. SOX9 mRNA was stabilised by hyperosmotic conditions. Cyclical loading of normal P2 and OA P0 but not normal P0 cells led to an increase in SOX9 gene expression and this was prevented by MEK1/2 inhibition. CONCLUSIONS: The response to osmotic loading of SOX9 mRNA is dependent on the nature of the osmotic stimulation and the chondrocyte phenotype. This variation may be important in disease progression.

Cost-effectiveness of rapid tests and other existing strategies for screening and management of early-onset group B streptococcus during labour.

OBJECTIVE: To determine the cost-effectiveness of alternative screening and prevention strategies, including rapid intrapartum testing, for prevention of early-onset neonatal group B streptococcus (GBS) infection in the UK. DESIGN: A decision model was developed to investigate the cost-effectiveness of screening and prevention strategies for GBS. A strategy of doing nothing was also considered. Deterministic and probabilistic sensitivity analyses were carried out. SETTING: Two large UK based obstetric units. PARTICIPANTS: Test accuracy data were obtained from a primary study of rapid tests at the onset of labour and risk factors from 1400 women. MAIN OUTCOME MEASURES: Incremental health sector costs per case of early-onset GBS death avoided. RESULTS: Compared with a strategy of do nothing, the incremental cost-effectiveness ratio was £32,000 per Early-Onset GBS Disease avoided and £427,000 per Early-Onset GBS Death avoided for the strategy of providing routine intrapartum antibiotic prophylaxis to all women without prior screening; Based on their current sensitivity, specificity and cost, screening using rapid tests was dominated by other more cost-effective strategies. CONCLUSIONS: The most cost-effective strategy was shown to be the provision of routine intrapartum antibiotic prophylaxis to all women without prior screening but, given broader concerns relating to antibiotic use, this is unlikely to be acceptable. In its absence, intrapartum antibiotic prophylaxis directed by screening with enriched culture becomes cost-effective. The current strategy of risk-factor-based screening is not cost-effective compared with screening based on culture.

Injected human umbilical cord-derived mesenchymal stromal cells do not appear to elicit an inflammatory response in a murine model of osteoarthritis.

OBJECTIVE: This study investigated the effect of hUC-MSCs on osteoarthritis (OA) progression in a xenogeneic model. DESIGN: Male, 10 week-old C57BL/6 mice underwent sham surgery (n = 15) or partial medial meniscectomy (PMM; n = 76). 5x105 hUC-MSCs (from 3 donors: D1, D2 and D3) were phenotyped via RT-qPCR and immunoprofiling their response to inflammatory stimuli.They were injected into the mouse joints 3 and 6 weeks post-surgery, harvesting joints at 8 and 12 weeks post-surgery, respectively. A no cell 'control' group was also used (n = 29). All knee joints were assessed via micro-computed tomography (µCT) and histology and 10 plasma markers were analysed at 12 weeks. RESULTS: PMM resulted in cartilage loss and osteophyte formation resembling human OA at both time-points. Injection of one donor's hUC-MSCs into the joint significantly reduced the loss of joint space at 12 weeks post-operatively compared with the PMM control.This 'effective' population of MSCs up-regulated the genes, IDO and TSG6, when stimulated with inflammatory cytokines, more than those from the other two donors.No evidence of an inflammatory response to the injected cells in any animals, either histologically or with plasma biomarkers, arose. CONCLUSION: Beneficial change in a PMM joint was seen with only one hUC-MSC population, perhaps indicating that cell therapy is not appropriate for severely osteoarthritic joints. However, none of the implanted cells appeared to elicit an inflammatory response at the time-points studied. The variability of UC donors suggests some populations may be more therapeutic than others and donor characterisation is essential in developing allogeneic cell therapies.

Schedule control of behavior reinforced by electrical stimulation of the brain.

Electrical stimulation of the brain was used to train rats to respond on random interval schedules. Stimulation was either delayed for 0.5 second and preceded by a brief signal, delayed and unsignaled, or presented contiguously with the response. In every case, responding was maintained on schedules and showed resistance to extinction typical of food-reinforced responding. Priming was never necessary. These data cast doubt on the generality of beliefs about the behavioral effects of brain stimulation reinforcement.

Corrosion of electronic materials and devices.

Electronic materials and devices corrode in the same ways as automobiles, bridges, and pipelines, but their typically small dimensions make them orders of magnitude more susceptible to corrosion failure. As elsewhere, the corrosion involves interactions with the environment. Under control, these interactions can be put to use, as in the formation of protective and functional oxide films for superconducting devices. Otherwise, they cause damage, as in the electrolytic dissolution of conductors, even gold, in the presence of humidity and ionic contamination from atmospheric particles and gases. Preventing corrosion entails identifying the damaging interactions and excluding species that allow them to occur.

Cloning and expression of a developmentally regulated protein that induces mitogenic and neurite outgrowth activity.

A heparin binding mitogenic protein isolated from bovine uterus shares NH2-terminal amino acid sequence with a protein isolated from newborn rat brain. The cDNA's of the bovine, human, and rat genes have been isolated and encode extraordinarily conserved proteins unrelated to known growth or neurotrophic factors, although identity of nearly 50 percent has been found with the predicted sequence of a retinoic acid induced transcript in differentiating mouse embryonal carcinoma cells. Lysates of COS-7 cells transiently expressing this protein were mitogenic for NRK cells and initiated neurite outgrowth from mixed cultures of embryonic rat brain cells. RNA transcripts encoding this protein were widely distributed in tissues and were developmentally regulated. This protein, previously designated as heparin binding growth factor (HBGF)-8, is now renamed pleiotrophin (PTN) to reflect its diverse activities. PTN may be the first member of a family of developmentally regulated cytokines.

Differences in plasma and peritoneal fluid proteomes identifies potential biomarkers associated with survival following strangulating small intestinal disease.

BACKGROUND: Strangulating small intestinal disease (SSID) carries a poor prognosis for survival in comparison to other types of colic, particularly if resection is required. Identification of markers which aid early diagnosis may prevent the need for resection, assist with more accurate prognostication and/or support the decision on whether surgical intervention is likely to be successful, would be of significant welfare benefit. OBJECTIVES: To apply an unbiased methodology to investigate the plasma and peritoneal fluid proteomes in horses diagnosed with SSID requiring resection, to identify novel biomarkers which may be of diagnostic or prognostic value. STUDY DESIGN: Prospective clinical study. METHODS: Plasma and peritoneal fluid from horses presented with acute abdominal signs consistent with SSID was collected at initial clinical examination. Samples from eight horses diagnosed with SSID at surgery in which resection of affected bowel was performed and four control horses subjected to euthanasia for orthopaedic conditions were submitted for liquid chromatography tandem mass spectrometry. Protein expression profiles were determined using label-free quantification. Data were analysed using analysis of variance to identify differentially expressed proteins between control and all SSID horses and SSID horses which survived to hospital discharge and those which did not. Significance was assumed at P≤0.05. RESULTS: A greater number of proteins were identified in peritoneal fluid than plasma of both SSID cases and controls, with 123 peritoneal fluid and 13 plasma proteins significantly differentially expressed (DE) between cases and controls (P<0.05, ≥2 fold change). Twelve peritoneal fluid proteins (P<0.036) and four plasma proteins (P<0.05) were significantly DE between SSID horses which survived and those which did not. MAIN LIMITATIONS: A low number of samples were analysed, there was variation in duration and severity of SSID and only short-term outcome was considered. CONCLUSIONS: Changes in peritoneal fluid proteome may provide a sensitive indicator of small intestinal strangulation and provide biomarkers relevant to prognosis.

An NIHR-approved two-year observational study on magnetically controlled growth rods in the treatment of early onset scoliosis.

Aims: The primary aim of this study was to evaluate the performance and safety of magnetically controlled growth rods in the treatment of early onset scoliosis. Secondary aims were to evaluate the clinical outcome, the rate of further surgery, the rate of complications, and the durability of correction. Patients and Methods: We undertook an observational prospective cohort study of children with early onset scoliosis, who were recruited over a one-year period and followed up for a minimum of two years. Magnetically controlled rods were introduced in a standardized manner with distractions performed three-monthly thereafter. Adverse events which were both related and unrelated to the device were recorded. Ten children, for whom relevant key data points (such as demographic information, growth parameters, Cobb angles, and functional outcomes) were available, were recruited and followed up over the period of the study. There were five boys and five girls. Their mean age was 6.2 years (2.5 to 10). Results: The mean coronal Cobb angle improved from 57.6° (40° to 81°) preoperatively, 32.8° (28° to 46°) postoperatively, and 41° (19° to 57°) at two years. Five children had an adverse event, with four requiring return to theatre, but none were related to the device. There were no neurological complications or infections. No devices failed. One child developed a proximal junctional kyphosis. The mean gain in spinal column height from T1 to S1 was 45.4 mm (24 to 81) over the period of the study. Conclusion: Magnetically controlled growth rods provide an alternative solution to traditional growing rods in the surgical management of children with early onset scoliosis, supporting growth of the spine while controlling curve progression. Their use has clear psychosocial and economic benefits, with the reduction of the need for repeat surgery as required with traditional growing rods. Cite this article: Bone Joint J 2018;100-B:507-15.

Irreversibly sickled erythrocytes: a consequence of the heterogeneous distribution of hemoglobin types in sickle-cell anemia.

THE AMOUNT OF FETAL HEMOGLOBIN (HB F) IN ERYTHROCYTES OF PATIENTS WITH SICKLE CELL ANEMIA (HB SS DISEASE) WAS MEASURED BY TWO METHODS: (a) photometry of individual cells stained for Hb F by the Kleihauer-Betke technique; and (b) chemical assay of alkali-resistant hemoglobin in cells distributed according to specific gravity by ultracentrifugation. Irreversibly sickled cells (ISC), which could be identified directly during photometry and which were found to gather in high concentration at the bottom of ultracentrifuged cell columns, contained significantly less Hb F than non-ISC. Cell content of total Hb was constant regardless of cell size, shape, or ultracentrifugal behavior: thus absolute amounts of Hb F and S varied reciprocally from cell to cell. In experiments designed to estimate age, at formation, and rate of destruction of ISC, Hb SS blood was incubated with selenomethionine-(75)Se (which labels reticulocytes) or (51)Cr (which labels erythrocytes at random) and reinfused. Sequential blood samples were separated by ultracentrifugation into fractions rich in reticulocytes, non-ISC, and ISC; and chronological changes in the specific activity of each fraction were determined. Analogous information was obtained from radioautography of sequential blood samples after reinfusion of whole blood labeled with amino acids-(3)H: this technique permitted direct visual characterization of labeled erythrocytes as ISC or non-ISC, all of which had been reticulocytes at the time of reinfusion. The transformation of non-ISC into ISC, presumably a manifestation of membrane damage, proved to begin soon after cell release from the marrow; and ISC subsequently underwent rapid removal from the circulating blood. IT IS THEREFORE APPARENT FROM THESE STUDIES THAT, IN HB SS DISEASE, RELATIVELY SMALL RECIPROCAL CHANGES IN THE AMOUNTS OF THE TWO MAJOR HEMOGLOBINS CARRY PREDICTIVE IMPORTANCE: (a) net synthesis of Hb F is least in erythroid cells destined to become ISC; and (b) these irreversibly deformed erythrocytes suffer preferential destruction.

Hemoglobin Okaloosa (beta 48 (CD7) leucine leads to arginine). An unstable variant with low oxygen affinity.

A slow-moving hemoglobin with electrophoretic mobility similar to that of hemoglobin S was discovered in a white laboratory technologist. She had an elevated reticulocyte count, as did several members of her family. Her red cell survival was shortened. Amino acid analysis indicated that leucine at position beta48 (CD7) had been replaced by arginine. The abnormal hemoglobin, called Okaloosa, was heat-precipitable and had decreased oxygen affinity. It exhibited a greater change in oxygen affinity than hemoglobin A when 2,3 DPG was added to "stripped" hemolysates. These findings cannot be readily explained by current views of structure-function relationships in the hemoglobin molecule. However, it is of interest that the amino acid in position CD7 is normally leucine in the alpha, beta, delta, and gamma-hemoglobin chains and in the myoglobin chain of man and a wide variety of other vertebrates.

Life span of carbamylated red cells in sickle cell anemia.

By using three isotopes of diisopropyl-phosphofluoridate ([(3)H]-, [(14)C]-, and [(32)P]DFP) simultaneously, the life span of red cells from 20 patients with sickle cell anemia (Hb SS) has been studied after varying degrees of carbamylation in vitro with cyanate (NCO) and carbamyl phosphate (CP). The results are expressed in terms of the red cell mean life span (MLS). The MLS of red cells in the patients studied averaged 15.2+/-6.3 (SD) days. After carbamylation the increase in red cell life span was linearly proportional to the concentration of cyanate used, so that at 0.01. 0.02, and 0.3 M NCO (approximately 1, 1.6, and 2 mol NCO/mol Hb) the average increase in MLS was 8.14+/-4.9 days, 14.7+/-4.1 days, and 18.4+/-8.8 days, respectively. Analysis of survival curves and the results of an experiment using a population of Hb SS cells separated by centrifugation indicated that carbamylation had a disproportionate effect on the survival of the youngest cells in the population. Improvement in MLS correlated with the reticulocyte count of the cells carbamylated. This finding is explained on the hypothesis that the life span of irreversibly sickled and other damaged cells is not improved by carbamylation but that carbamylation greatly improves the life span of the young, and as yet undamaged, cells. For this reason extracorporeal carbamylation is not favored as a form of therapy. At the level of carbamylation attainable by oral therapy, however, it would appear likely that only a modest increase in red cell life span will be achieved.

Erythrocyte Hb-S concentration. An important factor in the low oxygen affinity of blood in sickle cell anemia.

The blood in sickle cell anemia has a very low oxygen affinity and, although 2,3-diphosphoglycerate (2,3-DPG) is increased, there is doubt as to whether this is the only factor responsible. In this study of 15 patients with sickle cell anemia (Hb SS) no correlation was found between oxygen affinity (P(50) at pH 7.13) and 2,3-DPG in fresh venous blood. Whole populations of Hb SS erythrocytes were therefore separated, by an ultracentrifuge technique, into fractions of varying density. The packed red cell column was divided into three fractions; a bottom fraction rich in deformed cells or irreversibly sickled cells (ISC), with a very high mean corpuscular hemoglobin concentration (MCHC); a middle fraction containing cells with the highest content of fetal hemoglobin; and a top fraction containing reticulocytes and discoid cells but free of deformed cells. Oxygen affinity was shifted to the right in all layers (mean P(50) (pH 7.13)+/-1SD: top 46.3+/-2.9 mm Hg: middle 49.8+/-4.9 mm Hg; bottom 61.0+/-5.8 mm Hg) compared with normal blood (top 32.1+/-0.7 mm Hg: bottom 30.1+/-0.5 mm Hg). 2.3-DPG was increased in the top fraction, but was low or normal in the bottom fraction (top 21.8+/-3.4 mumol/g Hb: middle 17.7+/-2.2 mumol/g Hb; bottom 13.8+/-3.1 mumol/g Hb; normal whole blood 14.3+/-1.2 mumol/g Hb). The level of 2,3-DPG in top fractions could not account for the degree of right shift of P(50), and in the middle and bottom fractions the even greater right shifts were associated with lower levels of 2,3-DPG. Top fraction cells depleted of 2,3-DPG had a higher, but still abnormally low, oxygen affinity. A strong relationship was found between oxygen affinity and MCHC. The fractions with the greatest right shift in P(50) had the highest MCHC (top 32.4+/-2.0; middle 36.2+/-3.1; bottom 44.6+/-3.2 g/100 ml, respectively) and the plot of P(50) vs. MCHC showed a positive correlation (r = 0.90, P < 0.001). The red cell population in sickle cell anemia is not homogeneous but contains cells of widely varying Hb F content, 2,3-DPG, and hemoglobin concentration. Paradoxically, the cells with the lowest O(2) affinity have the lowest 2,3-DPG, but they also have the highest concentration of Hb S. The dense, deformed cell called the ISC is but the end stage in a process of membrane loss and consequent increase in hemoglobin concentration. The P(50) of Hb SS blood is, to a large extent, determined by the presence of these cells (r = 0.85, P < 0.001). Increased concentration of Hb S in the cell favors deoxygenation and crystallization even at relatively high P(o2). Lowered affinity for oxygen appears to be closely associated with Hb S concentration and not with 2,3-DPG content.

Endothelium-dependent relaxation is independent of arachidonic acid release.

Endothelium-dependent relaxation is mediated by the release from vascular endothelium of an endothelium-derived relaxing factor (EDRF). It is not clear what role arachidonic acid has in this process. Inhibition of phospholipase A2, and diacylglycerol lipase in cultured bovine aortic endothelial cells caused a marked reduction in agonist-induced arachidonic acid release from membrane phospholipid pools, and complete inhibition of prostacyclin production. EDRF release, assayed by measuring endothelium-dependent cGMP changes in mixed endothelial-smooth muscle cell cultures, was not inhibited under these conditions. In fact, EDRF release in response to two agonists, melittin and ATP, was actually increased in cells treated with phospholipase A2 inhibitors. In addition, pretreatment of rats with high-dose dexamethasone, an inhibitor of PLA2, did not attenuate endothelium-dependent relaxation in intact aortic rings removed from the animals, or depressor responses in anesthetized animals induced by endothelium-dependent vasodilators. In summary, inhibition of arachidonic acid release from membrane phospholipid pools does not attenuate endothelium-dependent relaxation in rats, or the release and/or response to EDRF in cultured cells.

A test of the universal applicability of a commonly used principle of hoof balance.

This study used a UK trimming protocol to determine whether hoof balance is achieved (as defined by equivalence of geometric proportions) in cadaver limbs (n = 49) and two cohorts of horses (shod, n = 6, and unshod, n = 20; three trimming cycles). To determine equivalence, dorsal hoof wall length (DHWL), distance from the heel buttress to the centre of pressure (HBUT-COP) and distance from dorsal toe to centre of rotation (DT-COR) were calculated as a proportion of bearing border length (BBL) using digital photography. Geometric proportions were tested using Fieller's test of equivalence with limits of difference of 2.8%. In 22 cadaver limbs the location of external COR and COP was also mapped radiographically to the extensor process of the third phalanx and the centre of rotation of the distal interphalangeal joint. Equivalence of geometric proportions was not present following trimming in cadaver limbs or in the two cohorts. Although the dorsal hoof wall to heel wall ratio improved in cadaver and unshod horses after trimming, dorsal hoof wall and lateral heel parallelism was absent in all groups and COP was not consistently in line with the extensor process. Increased COP-COR distance occurred in shod horses and may relate to solar arch flattening. Palmar heel migration, however, occurred more in unshod horses. The study shows that equivalence of geometric proportions as a measure of static hoof balance was not commonly present and widely published measures and ratios of hoof balance rarely occurred in this sample population of horses.

Selective damage to sensorimotor perivascular nerves in the mesenteric vessels of diabetic rats.

The perivascular innervation of the superior mesenteric artery and vein was examined using immunohistochemical and immunoassay techniques in rats 8 weeks after induction of diabetes with streptozotocin (STZ). Increased density of innervation and fluorescence intensity was noted for substance P- and calcitonin gene-related peptide-immunoreactive nerves in the diabetic vessels. A slight increase in the density of vasoactive intestinal polypeptide-immunoreactive nerve fibers innervating the mesenteric artery was also noted. However, there was no change in the density of neuropeptide Y- and dopamine beta-hydroxylase-immunoreactive nerve fibers, although the fluorescence intensity of neuropeptide Y-immunoreactive nerve fibers was reduced in diabetic rat vessels. Immunoassays showed that the levels of substance P- and calcitonin gene-related peptide were increased > 10-fold in the diabetic mesenteric vein, while levels of neuropeptide Y and vasoactive intestinal polypeptide were unchanged. In summary, there is a marked increase in nerve fibers containing sensory neuropeptides in mesenteric vessels of STZ-induced diabetic rats, which, in view of the reported impaired sensorimotor function in these vessels, is likely to reflect a neuropathic change.