Intramedullary Insetting of Silicone Implant for Lateral Stability in Distal Interphalangeal Joint Arthroplasty

Silicone implant arthroplasty is an alternative surgical intervention for painful and deformed osteoarthritis of the distal interphalangeal (DIP) joints. DIP joint stability is essential for hand function; however, it carries a potential risk of postoperative joint instability. To address this concern, an intramedullary implant insetting method was used to maintain joint stability by minimum resection of the head of the middle phalanx and preserving the collateral ligament. In the new method, the length of the bone excision was limited to maintain the lateral cortical bone with the insertion of the collateral ligament, and the medullary cavity of the middle phalanx was partially removed to intentionally set the hinge part of the silicone implant in the medullary canal. Between 20 digits of the conventional approach and 23 digits of the intramedullary insetting method, there were no significant differences in patient demographics (ie, age, affected hand, and finger), and clinical characteristics (ie, active DIP joint arc, DIP joint extension loss, grip strength, visual analog scale, and Quick Disabilities of the Arms, Shoulder and Hand questionnaire score) before and over 6 months after surgery. However, postoperative joint instability was significantly lower with the intramedullary insetting method, with a significantly shorter length of bone excision of the middle phalanx. This new approach is more beneficial than the conventional approach for preventing postoperative joint instability.

Band-like hyperintensity along the ventral surface of the brain stem on FLAIR and DWI in leptomeningeal carcinomatosis of lung adenocarcinoma

Since leptomeningeal carcinomatosis is rarely observed before diagnosis of the primary cancer, its detection is often delayed. We report the case of a 60-year-old woman who presented with lung adenocarcinoma with leptomeningeal carcinomatosis. Magnetic resonance imaging showed the characteristic abnormal hyperintensity along the ventral surface of the brain stem on fluid-attenuated inversion recovery and diffusion weighted imaging. It had no contrast uptake. Based on these findings, we were able to make an early diagnosis of leptomeningeal carcinomatosis of lung adenocarcinoma. This condition was resolved after treatment with a tyrosine kinase inhibitor.

Multidimensional Deep Learning Reduces False-Positives in the Automated Detection of Cerebral Aneurysms on Time-Of-Flight Magnetic Resonance Angiography: A Multi-Center Study

Current deep learning-based cerebral aneurysm detection demonstrates high sensitivity, but produces numerous false-positives (FPs), which hampers clinical application of automated detection systems for time-of-flight magnetic resonance angiography. To reduce FPs while maintaining high sensitivity, we developed a multidimensional convolutional neural network (MD-CNN) designed to unite planar and stereoscopic information about aneurysms. This retrospective study enrolled time-of-flight magnetic resonance angiography images of cerebral aneurysms from three institutions from June 2006 to April 2019. In the internal test, 80% of the entire data set was used for model training and 20% for the test, while for the external tests, data from different pairs of the three institutions were used for training and the remaining one for testing. Images containing aneurysms > 15 mm and images without aneurysms were excluded. Three deep learning models [planar information-only (2D-CNN), stereoscopic information-only (3D-CNN), and multidimensional information (MD-CNN)] were trained to classify whether the voxels contained aneurysms, and they were evaluated on each test. The performance of each model was assessed using free-response operating characteristic curves. In total, 732 aneurysms (5.9 ± 2.5 mm) of 559 cases (327, 120, and 112 from institutes A, B, and C; 469 and 263 for 1.5T and 3.0T MRI) were included in this study. In the internal test, the highest sensitivities were 80.4, 87.4, and 82.5%, and the FPs were 6.1, 7.1, and 5.0 FPs/case at a fixed sensitivity of 80% for the 2D-CNN, 3D-CNN, and MD-CNN, respectively. In the external test, the highest sensitivities were 82.1, 86.5, and 89.1%, and 5.9, 7.4, and 4.2 FPs/cases for them, respectively. MD-CNN was a new approach to maintain sensitivity and reduce the FPs simultaneously.

Conversion to Extension Contracture as a Means of Correction of Severe Flexion Contracture of the PIP Joint Using a Modified Dynamic External Fixator

Background: This is a retrospective case series investigating the outcomes using a dynamic external fixator (DEF) for treatment on severe flexion contractures at the proximal interphalangeal (PIP) joint. Severe flexion contractures of the PIP joint occurring after multiple operations and neglected over a long period of time are difficult to treat. The recurrence of contracture, even after successful treatment, is inevitable in patients with severe cases. In this study, we defined the severity of PIP joint contracture based on the active range of motion (ROM), soft tissue condition, and duration of the contracture. We also illustrated the strategy, results, and complications of using a DEF with rubber bands in these severe cases. Methods: We studied 11 fingers of 10 patients with PIP joint contracture treated by DEF. These were fixed at a small arc and neglected for an average 4.1 years (range, 1-9 years). The temporal Kirshner wire (K-wire) fixation after achieving an extension via DEF was maintained for 9.1 weeks on average. We retrospectively reviewed the results of these patients with an average 2-year follow-up. Results: Our method yielded favorable results upon retrospective evaluation. The average active ROM of the affected PIP joint improved from 90/96° to 34/83° with a functional arc and good patient satisfaction. The elastic force induced by strong rubber bands was safe and effective. The first step of joint space widening was the key to obtaining a successful joint extension afterwards. Serious progression of osteoarthritis at the PIP joint and pin-site fracture were a complication in each one case. Conclusions: In this study, we evaluate the surgical strategy of using DEFs powered by elastic torque from rubber bands to treat severe cases of flexion contractures of fingers. We first created extension contracture intentionally, followed by promoting flexion movement during follow-up in this group of patients.

Dynamic External Fixator as Treatment for Congenital Little Finger Contracture

The surgical soft tissue release of extension contracture at metacarpophalangeal (MP) joint is technically easy; however, the preventive hand therapy after surgery is really difficult in clinical practice. Congenital MP joint contracture, especially little finger, is also difficult to spread its limited range of motion (ROM). Here, we present a patient with a congenital MP joint contracture of the little finger managed with dynamic external fixator (DEF). A 21-year-old male irritated from limited ROM associated with pain of the right little finger of more than 1 year. The symptom started after trauma on his hand while playing lacrosse. Further examination revealed that his MP joint was congenitally contracted. To address this pathology, DEF followed by orthotic therapy was done. Two years after the procedure and therapy, the MP joint ROM of the finger surpassed that of the contralateral unaffected digit without pain and recurrence. The patient was able to return to his sports of lacrosse.

Clinical feasibility of single-shot fluid-attenuated inversion recovery with wide inversion recovery pulse designed to reduce cerebrospinal fluid and motion artifacts for evaluation of uncooperative patients in acute stroke protocol

Fluid-attenuated inversion recovery (FLAIR) imaging is a key sequence for stroke assessment. Motion artifact reduction with short acquisition time is still challenging, but necessary in the magnetic resonance (MR) stroke protocol, especially for uncooperative patients suspected of stroke. The aim of this study is to investigate the feasibility of modified single-shot FLAIR with wide inversion recovery pulses for use in stroke patients. This is a prospective study, which included 30 patients clinically suspected of stroke who were examined by MR stroke protocol from January 2018 to September 2018. A 1.5 T, multi-shot-turbo spin-echo (TSE) conventional FLAIR, and single-shot-TSE-FLAIR with wide inversion recovery pulse were used. Modified single-shot FLAIR was obtained for 30 patients with suspected stroke who moved during conventional FLAIR scan. Motion artifacts were randomly and independently scored using a 5-grade scale by three radiologists in blinded fashion. Whether the FLAIR vessel hyperintensity sign was present was visually evaluated. Statistical tests included Wilcoxon-signed rank test and weighted Cohen's kappa statistics. The motion artifact score was significantly lower in single-shot FLAIR than in conventional FLAIR (0.37 ± 0.56 vs. 1.83 ± 1.18; p < 0.05. The vessel hyperintensity sign was visualized in 6 and 5 patients on single-shot and conventional FLAIR images, respectively. This study demonstrates the value of single-shot FLAIR for stroke assessment. Single-shot FLAIR reduced motion artifact and visualized vessel hyperintensity sign more than conventional FLAIR. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2.

[Imaging Findings of Sarcoidosis in Neurology]

Sarcoidosis is a systemic granulomatous inflammation of unknown etiology that is reported in all age groups but with a higher prevalence in young adults. Sarcoidosis frequently involves the lungs, eyes, lymph nodes and skin. The involvement of the central nervous system (CNS) is reported with other sarcoidosis forms. Although only nervous system involvement presenting as CNS lesions are seen in 1% of cases, autopsy studies have confirmed CNS lesions in up to 25% of the cases. The nervous system including the brain, spinal cord, cerebral meninges, cranial nerves, pituitary gland, peripheral nerves, and muscles are reported to be affected. Although imaging findings of the nodules in sarcoidosis are nonspecific and atypical in 25-30% of cases, familiarity with the relevant clinical symptoms is helpful in recognizing sarcoidosis presence. The histopathological biopsy results of the organ affected by sarcoidosis help identify the characteristic noncaseating granuloma and its aggregation, and together with the imaging findings often reflecting such microstructure aid in sarcoidosis confirmation. This section describes the characteristic features seen in each image along with the image findings for each site.

Ultrasound Evaluation of Dermal Sinuses/Fistulas in Pediatric Patients

A dermal sinus/fistula is a common condition; the relevant department should be consulted for appropriate treatment. It is important for radiologists to have adequate knowledge of these conditions to provide the correct diagnosis and recommend subsequent management. This review describes the following lesions: preauricular sinus, midline sinus of the upper lip, nasal dermoid sinus cyst, cheek fistula, first branchial cleft anomaly/sublingual branchial cleft anomaly, thyroglossal duct cyst/fistula, lateral cervical sinus/fistula, congenital dermal sinus/fistula of the anterior chest region, congenital skin sinus/fistula with a sternal cleft, and congenital prepubic sinus. On the basis of the skin orifice location and ultrasound images, radiologists can provide useful information to physicians.

Three-dimensional SAFT imaging for anisotropic materials using photoacoustic microscopy

A pulsed laser illuminates a target zone that causes rapid thermoelastic expansion, generating broadband high-frequency ultrasonic wave (photoacoustic wave, PA wave). We developed a PA microscopy (PAM) with a confocal area of laser and ultrasonic wave for applications in nondestructive testing (NDT). The synthetic aperture focusing technique (SAFT) is applied in the PAM for the three-dimensional (3D) imaging of interior flaws. Here, we report proof-of-concept experiments for the NDT of a subsurface flaw in a thin laminar material. Graphical abstract (a) shows a specimen of carbon-fiber-reinforced plastic (CFRP) with an artificial delamination. Here, it should be noted that the group velocity varies directionally due to the strong anisotropy of the CFRP specimen (see Graphical abstract (b)). By considering the group velocity distribution in the SAFT, the shape and location of the subsurface delamination were accurately estimated as shown in Graphical abstract (c). Coating the surface of the CFRP specimen with a light-absorbent material improved the amplitude of the PA wave. This finding showed that the signal-to-noise ratio of the waves scattered from the flaws can be improved.

Ultrasound imaging of the anorectal malformation during the neonatal period: a comprehensive review

Anorectal malformation (ARM) is classified as low, intermediate, or high; accurate diagnosis of the type during the early neonatal period is important to determine the appropriate initial surgical approach. This review assesses the role of ultrasound examination in the classification of ARM during the neonatal period, with a focus on landmarks on the sonogram, the approach used for sonography, and the optimal examination timing. The following three factors on the sonogram are used for the classification: location of the fistula, the distance between the distal rectal pouch and the anal dimple (perineum) (P-P distance), and the relationship between the puborectalis muscle and the distal rectal pouch. Three approaches can be used to evaluate ARM by ultrasonography, namely, suprapubic, perineal, and infracoccygeal approaches. Each approach has its own advantages and disadvantages. Optimal timing of the ultrasound examination is also important with respect to each factor to classify ARM. We have described the pitfalls of ultrasound in diagnosis of cases, namely ARM with Down syndrome (which tends to be without fistula), ARM with low birth weight, ARM with unusual location of fistula, ARM with opened fistula (where the P-P distance is unreliable), and cloacal malformation (variation of the high-type ARM).

Why chronically ill children face challenges in regular classrooms: perspectives from nursing teachers in Japan

BACKGROUND

Chronically ill children are increasingly expected to join their peers in regular classrooms. However, sometimes schools do not provide adequate assistance. This study explores nursing teachers' thoughts and experiences on integrating such students into regular classrooms in Japan.

METHODS

We analysed 79 essays written by nursing teachers collectively titled 'The challenges of having chronically ill children in regular classrooms'. We conducted a qualitative study using Kinoshita's Modified Grounded Theory Approach.

RESULTS

Nursing teachers identified three main obstacles: insufficient resources to support chronically ill students, parents not playing a supporting role in aiding them at school and a regular classroom not being suitable for them. However, collaborating with the children's medical staff proved successful at integrating them into regular classrooms.

CONCLUSIONS

Given these obstacles, it seems very difficult for nursing teachers to lead the way toward establishing cooperative support systems for the children. Instructions from medical staff could empower teachers to set up such systems.

Disclosing haemophilia at school: strategies employed by mothers of children with haemophilia in Japan

INTRODUCTION

Most children with haemophilia in Japan study in mainstream schools. However, many mothers have difficulty deciding whether to inform teachers of their child's haemophilia because of the accompanying potential discrimination and prejudice, particularly after the press coverage on the HIV scandal in the 1980s.

AIMS

We therefore aim to explore and describe disclosure strategies of mothers of children with haemophilia.

METHODS

A qualitative study was conducted using the modified grounded theory approach to explore disclosure strategies of mothers of children with haemophilia. Semi-structured interviews were conducted with 19 selected mothers (12 children were HIV positive and 7 were HIV-negative).

RESULTS

In the pre-HIV/AIDS crisis period, the kind of strategy employed - full disclosure, conditional full disclosure and partial disclosure - depended on the extent of mothers' fears about mainstream schools refusing admission because of their child's haemophilia. After the HIV/AIDS crisis in the 1980s in Japan, the three categories of strategies employed by mothers of children with haemophilia were limited disclosure, non-disclosure and full disclosure. These depended on mothers' expectations of discrimination towards their child because of the social stigma around haemophilia and being HIV-positive.

CONCLUSION

For children with haemophilia to feel safe attending school, public schools must establish care management and anti-discrimination systems for children with chronic diseases, thus assuring parents of their children's welfare at school.

A new aspect of the TrkB signaling pathway in neural plasticity

In the central nervous system (CNS), the expression of molecules is strictly regulated during development. Control of the spatiotemporal expression of molecules is a mechanism not only to construct the functional neuronal network but also to adjust the network in response to new information from outside of the individual, i.e., through learning and memory. Among the functional molecules in the CNS, one of the best-studied groups is the neurotrophins, which are nerve growth factor (NGF)-related gene family molecules. Neurotrophins include NGF, brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and NT-4/5 in the mammal. Among neurotrophins and their receptors, BDNF and tropomyosin-related kinases B (TrkB) are enriched in the CNS. In the CNS, the BDNF-TrkB signaling pathway fulfills a wide variety of functions throughout life, such as cell survival, migration, outgrowth of axons and dendrites, synaptogenesis, synaptic transmission, and remodeling of synapses. Although the same ligand and receptor, BDNF and TrkB, act in these various developmental events, we do not yet understand what kind of mechanism provokes the functional multiplicity of the BDNF-TrkB signaling pathway. In this review, we discuss the mechanism that elicits the variety of functions performed by the BDNF-TrkB signaling pathway in the CNS as a tool of pharmacological therapy.

Fluctuations in chemical gelation

We study a chemical gelation model in two dimensions which includes both monomer aggregations and bond fluctuations. Our numerical simulation shows that a sol-gel transition occurs when an initial monomer concentration is above a critical concentration. Fractal aggregates grow until the sol-gel transition occurs. After the gelation, however, bond fluctuations break the fractal structure and an interesting inhomogeneous gel fiber network appears instead. A pore size distribution of the inhomogeneous structure shows the existence of hierarchical structures in the gel phase. It is also found that slow dynamics appear near the critical concentration.

Efficient gene transduction of neurons by lentivirus with enhanced neuron-specific promoters

In the field of basic and clinical neurosciences, it is important to develop a method for easy delivery and persistent expression of transgene in central neurons. We firstly generated lentiviral vectors with five kinds of neuron-specific promoters, such as synapsin I (SYN), calcium/calmodulin-dependent protein kinase II, tubulin alpha I, neuron-specific enolase and platelet-derived growth factor beta chain promoters and then novel hybrid promoters by fusing cytomegalovirus enhancer (E) to those neuron-specific promoters. Neuron-specific expression of green fluorescent protein (GFP) with those promoters was examined in vivo by injecting the lentiviral vectors into the rat neostriatum, thalamus and neocortex. Among all the promoters, SYN promoter displayed the highest specificity for neuronal expression in all the regions examined (more than 96%). Although GFP production by the hybrid promoters was about 2-4 times larger than the non-enhanced promoters, the neuronal specificity was significantly decreased in most cases. However, the neuronal specificity of E/SYN hybrid promoter exhibited the least decrease only in the thalamus. Furthermore, the transcriptional activity and neuronal specificity of E/SYN promoter were sustained for up to 8 weeks. Thus, lentivirus with E/SYN promoter is the best vector for strong persistent expression in neurons.

Changes in BDNF-immunoreactive structures in the hippocampal formation of the aged macaque monkey

We investigated the changes of brain-derived neurotrophic factor (BDNF)-immunoreactive structures in the hippocampal formation of aged macaques (Macaca fuscata fuscata). At adult stages (10 and 12 years), BDNF immunoreactivity occurred in the neurons of the dentate gyrus, the pyramidal neurons in the CA1, CA2, CA3 subfields and the subiculum, and the neurons in the CA4 subfield and the entorhinal cortex. The apical dendrites were also BDNF immunopositive. In aged monkeys (26, 30 and 32 years), the intensity of the BDNF-immunoreactivity declined significantly in cell bodies and dendrites of the neurons in the hippocampal formation except the CA2 pyramidal neurons. These findings indicate that BDNF is one of the vulnerable signal molecules during the aging process of the primate hippocampal formation.

Increased apoptosis associated with depressed type of early intestinal gastric cancer

Early gastric cancer can be macroscopically classified into elevated and depressed types. To clarify the relationship between macroscopic appearance of early gastric cancer and apoptosis or cell proliferation, formalin-fixed paraffin-embedded tissue specimens of 44 intestinal-type early gastric cancers were investigated by the TUNEL method and immunohistochemical techniques. Diffuse type was excluded in this study. When tissue sections of gastric cancer were vertically classified into the 3 compartments of luminar, intermediate and basal, the apoptosis index (%) was significantly higher in the basal compartment of depressed type (1.76 +/- 2.04, mean +/- SD) than in the basal compartment of elevated type (0.63 +/- 0.81, P = 0.01). In depressed type, the apoptosis index (%) was significantly higher in the basal compartment than in the luminar compartment (0.76 +/- 0.85, P = 0.03). Apoptosis-inducing protein, Bax, was expressed more in each of the compartments of depressed type than in those of elevated type, while there were no significant differences in expression of anti-apoptotic protein, Bcl-2, between the two types. Moreover, the apoptosis index (%) of Bax-positive gastric cancer was significantly higher in the basal compartment (P = 0.03), compared to that of Bax-negative gastric cancer, while there were no significant differences in apoptosis index (%) in any compartment between Bcl-2-positive and Bcl-2-negative gastric cancers. There were no significant differences in Ki-67 expression, either between the two types, or among the compartments of depressed type. These results indicate that increased apoptosis with excessive expression of Bax in the basal compartment is involved in the morphogenesis of the depressed type in intestinal-type early gastric cancer.

Dioxin and fly ash free incineration by ash pelletization and reburning

Dioxins (DXNs) in municipal waste incinerator fly ash were effectively reduced by pelletizing the mixture of ash, cement, and sodium phosphate and reburning the pellets in a laboratory scale bubbling fluidized bed (BFB) furnace. Three types of pellets--A, B and C, of various sizes and compositions were used in the experiments. The efficiency of DXN reduction in the pellet matrix was proportional to the incineration time, temperature, and degree of pellet incineration. At 700 degrees C and incineration time sufficient for a complete burnout, the efficiency of DXN reduction in the pellets of type A and C was found to be 99.9% and 99.7%, respectively. Correspondingly, the DXN concentration in the pellets decreased from 862 ng TEQ/kg to 0.9 ng TEQ/kg for pellets A and 2.2 ng TEQ/kg for pellets C. The residual concentration of coplanar polychlorinated biphenyls (coplanar PCBs) was below 0.2 ng TEQ/kg and 0.4 ng TEQ/kg, respectively. Assuming a tortuosity factor of tau = 3 and the reaction rate constants of 0.013 m/s (at 700 degrees C) and 0.025 m/s (at 800 degrees C), the experimental pellet incineration times were reasonably predicted by using the shrinking core model. Possible DXN evaporation from the pellets was also studied. The amount of DXNs in the flue gas captured by an impinger trap was less than 3% when the reactor was operated at 700 and 800 degrees C. The described method of fly ash pelletization and reburning seems to be a relatively easy and inexpensive way to reduce both the emission of DXNs and the amount of fly ash.

TrkB dimerization during development of the prefrontal cortex of the macaque

To date, two subtypes of TrkB, a BDNF receptor, have been described. One is full-length TrkB (TK+), which has a tyrosine kinase-containing intracellular domain. The other is truncated TrkB (TK-), which has a short intracellular domain lacking the tyrosine kinase. In this study, we investigated the dimerization of TrkB subtypes in the developing monkey prefrontal cortex by means of cross-linking. At embryonic day 120, the TK+/TK+ and the 100 kDa/100 kDa homodimers were observed with BDNF stimulation. At the newborn stage, the TK+/TK+ and the TK-/TK- homodimers were observed with BDNF stimulation. At the adult stage, the TK-/TK- homodimer and the TK+/TK- heterodimer were formed by BDNF stimulation. The levels of all dimers increased in proportion to the concentration of BDNF. Moreover, the dimers were clearly formed within 5 min of treatment with BDNF. BDNF and NT-4/5 induced the dimers, whereas NT-3 formed slight dimers but NGF did not. Furthermore, anti-BDNF antibody inhibited the TrkB dimerization. Moreover, the intercellular binding proteins of TrkB were not cross-linked by BS3. Therefore, these results suggest that the change in dimerization among TrkB subtypes occurs during development of the monkey prefrontal cortex.

[Helicobacter pylori infection and eradication]

H. pylori infection is associated with various gastroduodenal diseases such as gastritis, peptic ulcer, gastric cancer, gastric MALT lymphoma. H. pylori infection is suggested that it plays a role as protective factor not promoting factor for reflux esophagitis and GERD. Epidemiological studies showed lower prevalence of H. pylori infection in reflux esophagitis and Barrett's esophagus comparing the control. Increased occurrence of reflux esophagitis after curing of H. pylori infection was reported. However, the relationship between H. pylori infection and reflux esophagitis has not been actually made clear. Also the mechanism of reflux esophagitis occurrence after H. pylori eradication is not obscure.

A case of idiopathic constrictive bronchiolitis in a middle-aged male smoker

When one sees a middle-aged male smoker who presents with progressive exertional dyspnoea and irreversible airflow obstruction, the most likely clinical diagnosis is pulmonary emphysema or chronic obstructive pulmonary disease (COPD). We report a 45-year-old male smoker who was initially suspected to have such a disease but was eventually diagnosed as having idiopathic constrictive bronchiolitis by lung biopsy, clinical history, and laboratory findings. A finding on lung computed tomography of diffuse hyperinflation but few low attenuation areas and relatively well-preserved diffusing capacity of carbon monoxide seems to be the key for suspecting this rare clinical entity. The pathological difference between this bronchiolitis and small airway disease observed in COPD will be also discussed.

Marked and prompt hemodynamic improvement by carperitide in refractory congestive heart failure due to dilated cardiomyopathy

A 16-year-old Japanese male diagnosed with congestive heart failure (CHF) due to dilated cardiomyopathy was treated by conventional intensive treatment such as intravenous infusion of diuretics, catecholamines, and phosphodiesterase inhibitors with vasodilators. However, he developed a low output syndrome with appearances of hyponatremia and hypochloremia. As a consequence, intravenous infusion of carperitide (synthetic atrial natriuretic peptide) was added to the therapy. Thereafter his symptoms and hemodynamic parameters promptly and dramatically improved without significant diuresis, and this amelioration persisted for more than 20 days without drug intolerance. This outcome suggests that use of carperitide may be a safe and efficacious means to reduce cardiac preload without hypotension and tachycardia in patients with refractory CHF in whom intensive treatment has already been performed.

Absence of TrkB and insulin receptor beta in the Triton insoluble low-density fraction (raft)

Cholesterol- and glycolipid-enriched microdomains within the plasma membrane of animal cells, including neurons, have been purified and used as a low-density membrane domain after extraction with Triton X-100 (raft), or after subcellular fractionation without detergent (LDM). In this study, we compared the protein compositions in the raft and the LDM. Membrane receptors, acylated- and glycosylphosphatidylinositol (GPI)- anchored proteins were enriched in the LDM. Further treatment of the LDM with Triton X-100 excluded the membrane receptors, TrkBs and insulin receptor beta. In the presence of calcium ions, the endogenous tyrosine kinase activities in the LDM and the raft were enhanced, suggesting an important role of calcium ions in the signal transduction via the LDM and the raft.

Development of full-length Trk B-immunoreactive structures in the hippocampal formation of the macaque monkey

Distribution and morphological changes of cells containing the signal transducing neurotrophin receptor, full-length Trk B (fl-Trk B), were investigated in the hippocampal formation of the macaque monkey between embryonic day 140 and the adult stage. Western blot analysis showed that one main protein band, which migrated at 141 kDa, was detected in both the embryonic and adult hippocampal formation. In the pyramidal cells in CA1 and CA3 subfields, the subiculum, and the entorhinal cortex, fl-Trk B-immunoreactive dendrites were observable in the embryonic stage. In contrast, in the granule cells of the dentate gyrus, few dendrites were immunoreactive during embryonic and early developmental stages. This difference may be due to the later growth of the granule cells of the dentate gyrus. The existence of fl-Trk B immunoreactivity in the cell body and dendrites in the embryonic hippocampal neurons, suggests that BDNF and/or NT4/5 act on the hippocampal cells by autocrine/paracrine mechanisms. In the entorhinal cortex, fl-Trk B immunoreactivity became localized in the stellate cells in layer II and the pyramidal cells in layers III, V and VI in adulthood. This indicates that BDNF and/or NT4/5 are important for the maintenance of the projection neurons in the entorhinal cortex at the adult stage. The strongest fl-Trk B immunoreactivity in the hippocampal neurons occurred at postnatal month 4, corresponding to the period of greatest synapse production in the monkey hippocampus, suggesting that BDNF and/or NT4/5 with fl-Trk B may play a role in synapse formation in the monkey hippocampus.

Change of expression of full-length and truncated TrkBs in the developing monkey central nervous system

We examined the expression of full-length TrkB (TrkBTK+) and truncated TrkB (TrkBTK-) in the central nervous system (CNS) of the macaque monkey (Macaca fascicularis) using a western blot analysis. At the adult stage, the levels of TrkBTK+ in cerebral cortices were higher than those in other structures of CNS and the expressions of TrkBTK+ in the association cortices (except area PE) were relatively lower than those in the primary cortices. In contrast, TrkBTK- in the hippocampus and the cerebellum was significantly higher than in other structures. In various developing cerebral cortices, TrkBTK+ was detected at the same levels from embryonic day 120 (E120) to the adult period. In contrast, the expression of TrkBTK- increased remarkably after the newborn stage (NB), reached the maximum level at postnatal day 60 (P60) and maintained the same level into adulthood. The peaks of TrkBTK- in the association cortices were more delayed than in the primary cortices. The expression of TrkBTK- occurred at a time that correlates with the elimination of axons and the down-regulation of neuropeptides. The present study suggests that TrkBTK- plays an important role in the axonal remodelling and that it may act as a negative effector of TrkBTK+ in the primate CNS, reducing responsiveness to BDNF and/or NT-4/5.

[Changes of 24-h Holter monitor recordings in association with interferon alpha therapy for chronic hepatitis C]

We examined cardiovascular complication of interferon (IFN) therapy in 23 patients with chronic hepatitis C who did not have cardiac disease prospectively. Twenty four-h Holter monitor recordings were performed before and during IFN therapy. Seven of these patients (30%) showed abnormalities on their 24-h Holter monitoring recordings. Premature ventricular contraction (PVC) occurred in two patients, intermittent WPW syndrome in one, and ST-T change in four. Only one patient with PVC complained of palpitation. These complications were not severe and immediately after IFN therapy was stopped. There was no correlation between Holter ECG abnormalities and sex, age, quantity of HCV, or 2-5 oligoadenylate synthetase activity. It was suggested that cardiovascular complications caused by IFN therapy occurred more frequently than expected. However, diagnosis of these complications is difficult because most patients have no subjective symptoms and there is scarcely any change in laboratory test results. Careful observation of patients may be required during IFN therapy regardless of cardiovascular symptoms.

The use of the block cycle length as a safe and efficient means of interrupting sustained ventricular tachycardia and its pharmacological modification

In nine patients who had inducible monomorphic sustained ventricular tachycardia (VT), rapid pacing was performed in 11 episodes of morphologically distinct VT at progressively shorter cycle lengths and VT was interrupted at a critical cycle length. The VT interrupting critical cycle length was defined as the block cycle length (BCL) and the effect of Class I antiarrhythmic drugs were examined. Both the VT cycle length (VTCL) and the BCL were prolonged after administration of either drug. The overall mean ratio of the BCL to the VTCL was unchanged after procainamide administration, but increased after the use of mexiletine. The ratio, however, varied in individual VTs and the BCL after treatment with Class I antiarrhythmic drugs could not be predicted from the ratio baseline value, although the ratio was always > 60% and the hazard of VT acceleration might be avoided if the BCL is used.

The usefulness of Holter monitoring in selecting pharmacologic therapy for patients with sustained monomorphic ventricular tachycardia: studies in patients in whom no effective pharmacologic therapy could be determined by electrophysiologic study

The usefulness of Holter monitoring (HM) in selecting pharmacologic therapy for patients with sustained monomorphic ventricular tachycardia (VT) was evaluated in patients in whom no effective pharmacologic therapy could be determined in an electrophysiologic study (EPS). The study population consisted of 49 consecutive patients with sustained VT who were receiving long-term pharmacologic therapy despite the fact that no pharmacologic therapy had been found to be effective in the EPS. The efficacy of the pharmacologic therapies was assessed by HM. A reduction in frequent (10/h) premature ventricular contractions (PVCs) was used as an index of treatment efficacy, with therapies achieving substantial PVC suppression (>70% of all PVCs) being considered to be effective (HM effective group). When no therapy was found to be effective when assessed by HM, a drug with any other beneficial effect, eg, reduction in VT rate, was chosen (HM ineffective group). VT recurrence and survival were compared between groups. During the follow-up period of 31+/-28 months, VT recurrence was observed in a total of 25/49 patients: 3/17 patients in the HM effective group, in 18/25 in the HM ineffective group, and in 4/7 in the HM undetermined group (p=0.0487). Sudden cardiac death occurred in a total 7/49 patients: 2/17 patients in the HM effective group, 4/25 patients in the HM ineffective group, and 1/7 patient in the HM undetermined group (p=0.2828). Among patients in whom no effective therapy could be determined by EPS, the VT recurrence rate was significantly lower in the group in whom treatment was effective as assessed by HM than among those in whom treatment was assessed by HM to be ineffective. Sudden cardiac death rate was also lowest in the HM effective group, although the difference was not statistically significant. HM assessment was considered useful in selection of pharmacologic therapy for patients in whom no effective therapy could be determined in the EPS.

Use-dependent electrophysiologic effects of DL-sotalol and modulation by isoproterenol in the human ventricle

The interaction between dl-sotalol and isoproterenol on the ventricular effective refractory period (VERP) and conduction were examined in an electrophysiologic study of 9 patients at drug-free baseline, after 14 days of dl-sotalol administration (320 mg/day), and after the administration of isoproterenol. In all 9 patients, ventricular tachyarrhythmia could not be induced after dl-sotalol treatment. Isoproterenol was administered as a loading dosage of 0.025 microgram/kg for 5 min with a maintenance dosage of 0.0025 microgram/kg/min. The VERP and the QRS duration were determined at paced cycle lengths of 600, 400 and 300 msec. DL-sotalol and dl-sotalol + isoproterenol had no effect on ventricular conduction at the three cycle lengths. The VERP was significantly prolonged after dl-sotalol treatment at paced cycle lengths of 600 (241 +/- 16 to 302 +/- 28 msec, p < 0.001), 400 (223 +/- 21 to 280 +/- 23 msec, p < 0.001) and 300 msec (202 +/- 16 to 256 +/- 24 msec, p < 0.005), but there was a parallel shift of the VERP, suggesting the absence of use-dependent effects on the VERP. The dl-sotalol-induced VERP prolongation was partially reversed by isoproterenol, but it remained significantly prolonged above baseline values at paced cycle lengths of 600 (241 +/- 16 to 281 +/- 18 msec, p < 0.01), 400 (223 +/- 21 to 258 +/- 20 msec, p < 0.01) and 300 msec (202 +/- 16 to 247 +/- 22 msec, p < 0.01). The shortening of the VERP was greater at longer basic cycle lengths (600 and 400 msec) than at the shorter paced cycle length (300 msec, p < .05), but the percentage increase of the VERP was similar at the three basic cycle lengths of 600 (16%), 400 (15%) and 300 (20%) msec, indicating the lack of reverse use-dependency. The absence of reverse use-dependency of dl-sotalol on the VERP, even after isoproterenol administration, may be beneficial in the therapy of ventricular tachyarrhythmias and may account in part for the high efficacy of this drug.

Preferential action of mexiletine on central common pathway of reentrant ventricular tachycardia

OBJECTIVES

The action of mexiletine on diseased myocardium was assessed in reentrant ventricular tachycardia (VT).

BACKGROUND

Whether class Ib antiarrhythmic agents exert a preferential action on the central common pathway of reentrant ventricular tachycardia has not yet been studied in humans.

METHODS

In 10 consecutive patients (7 with a previous myocardial infarction, 3 with nonischemic disease), VT was induced and entrained with rapid pacing. The orthodromic conduction time was measured from stimulus to the entrained electrogram at the exit from the presumed central common pathway (i.e., the earliest site of activation). Mexiletine at 125 to 250 mg was administered intravenously, and when VT with the same configuration was induced, the study was repeated. The action of mexiletine on the central common pathway was assessed from the changes in VT cycle length and orthodromic conduction time. The effects on QRS complex duration, local conduction time between the exit and the pacing site and duration of the local electrogram were compared between normal and diseased myocardium.

RESULTS

Mexiletine prolonged the VT cycle length in all patients, from (mean +/- SD) 316 +/- 30 to 360 +/- 64 ms (mean change 20 +/- 7%, p < 0.001); during entrainment of VT, the orthodromic conduction time was prolonged, from 306 +/- 58 to 367 +/- 89 ms (mean change 18 +/- 9%, p < 0.001). These changes were highly correlated (r = 0.95, p < 0.001). QRS duration changed little (4 +/- 3%), and local conduction time showed no change. The duration of the fragmented electrogram width was prolonged by mexiletine: from 146 +/- 50 to 176 +/- 56 ms (mean change 23 +/- 8% during VT, p < 0.001). Only a slight change occurred in the effective refractory period, both at the pacing site and at the exit.

CONCLUSIONS

Mexiletine caused little change in conduction time in normal myocardium but prolonged VT cycle length, orthodromic conduction time and duration of the local electrogram at the earliest site of activation of VT. From these findings, a preferential action of mexiletine on diseased myocardium was suggested but seemed to occur only at higher frequencies during tachycardia.

Complete sequence of an infectious full-length cDNA clone of citrus tatter leaf capillovirus: comparative sequence analysis of capillovirus genomes

The complete nucleotide sequence of citrus tatter leaf capillovirus (CTLV lily strain) was determined. It is 6496 nucleotides long, excluding the 3'-terminal poly(A) tract, and contains two putative overlapping open reading frames (ORFs). ORF1 (positions 37-6354) encodes a potential polyprotein of molecular mass 242 kDa. ORF2 (positions 4788-5750) codes for a 36 kDa protein. The 242 kDa polypeptide contains several non-structural protein domains (i.e. methyltransferase, NTP-binding helicase, papain-like proteinase and polymerase) and, at its C terminus, the putative coat protein. The N-terminal region of the 36 kDa protein displays sequence similarity to the cell-to-cell movement proteins of the '30 K superfamily'. Such a genome structure is conserved between CTLV and apple stem grooving capillovirus. Capped transcripts from a plasmid containing the complete sequence of CTLV, with a T7 RNA promoter, successfully infected Chenopodium quinoa plants and caused symptoms characteristic of CTLV. Uncapped transcripts were noninfectious.

Inhibitory effects of perillosides A and C, and related monoterpene glucosides on aldose reductase and their structure-activity relationships

Monoterpene glucosides, perillosides A and C, obtained from the leaves of Perilla frutescens, were found to be inhibitors of aldose reductase (EC 1.1.1.21) which is considered to be a key enzyme in diabetic complications such as cataract. The apparent type of inhibition of rat lens aldose reductase by perillosides A and C was competitive with respect to glyceraldehyde and their K(i) values were 1.4 x 10(-4) and 2.3 x 10(-4) M, respectively. The type of inhibition by their tetraacetates was non-competitive with respect to the same substrate, although their inhibitory effects were increased by about one order of magnitude compared with those of the perilllosides and the K(i) values were 2.5 x 10(-5) and 7.1 x 10(-5) M, respectively. We also prepared related monoterpene glucosides and their tetraacetates and determined their inhibitory activities towards aldose reductase in order to elucidate the relationship between structure and inhibitory activity.

Nucleotide sequence of the 3'-terminal region of citrus tatter leaf virus RNA

The 3'-terminal sequence of citrus tatter leaf virus lily isolate (CTLV-L) was determined from cloned cDNA. The sequence contains two open reading frames (ORFs). ORF1 encodes a protein that contains consensus sequences associated with the RNA-dependent RNA polymerase. ORF2, which is in a different reading frame within ORF1, can encode a 36 kD protein, putatively identified as a movement protein. CTLV-L coat protein (CP) was found to be located in the C-terminal region of the polyprotein encoded by ORF1. Evolutionary relationships and classification of capilloviruses is discussed.

Nucleotide sequence of the coat protein coding region of tulip breaking virus

cDNA of tulip breaking virus-tulip (TBV-tulip) RNA was synthesized and cloned in E. coli. One clone that contains a 4.5 kb insert was identified by restriction enzyme analysis, dot immunobinding assay (DIBA), and partial sequencing. Then 1479 nucleotides of the 3'-terminus of the clone were sequenced and revealed that the sequence contains one open reading frame (ORF), followed by an untranslated region of 255 nucleotides and a poly(A) tract. The deduced amino acid sequence was found to include the C terminus of the predicted RNA-dependent RNA polymerase and the coat protein. A glutamine-alanine dipeptide was identified as a putative NIa protease cleavage site at the N terminus of the coat protein.

Intracellular signal transduction for interleukin-1 beta-induced endothelin production in human umbilical vein endothelial cells

The authors investigated the intracellular signal transduction for interleukin (IL)-1 beta-induced endothelin (ET) production by endothelial cells from cultured human umbilical vein (HUVEC). Cultured HUVEC released immunoreactive (iR)-ET into the media in a time-dependent manner and a significant increase of iR-ET production was observed by the addition of IL-1 beta. The stimulating effect of IL-1 beta on iR-ET production was respectively inhibited by protein kinase C (C kinase) inhibitor (H-7), Ca-calmodulin inhibitor (W-7), cyclic AMP-dependent protein kinase (A kinase) inhibitor (H-8) and tyrosine kinase inhibitor (genistain) in a dose-dependent fashion. The data suggested that intracellular signal transduction for IL-1 beta-induced iR-ET production were via such pathways as C kinase, A kinase, Ca-calmodulin and tyrosine kinase in combination or independently, though possible mediation by other pathways cannot be ruled out.

Angular spectral approach to reflection of focused beams with oblique incidence in spherical-planar-pair lenses

The characteristics of the output signal from spherical-planar-pair (SPP) lenses in the ultrasonic microspectrometer (UMSM) are described. The angular spectral approach is used to obtain the mathematical formula of the output signal. Although isotropic specimens are assumed, anisotropic materials can be treated as well with a small modification. A 2-D approximation is introduced to analyze the specular reflection, the Rayleigh critical angular phenomenon, and V (z) of the specular reflection. Numerical calculations are also performed for specimens with copper substrate, steel substrate, and layered structures, by numerically integrating the 2-D formulas of the output signal. It is found that a ray optical treatment is a good approximation of the wave propagation in the SPP lenses. The incident angular dependence of a reflection coefficient can be estimated by tilting the sensor unit.

T cell activation via the T cell receptor: a comparison between WT31 (defining alpha/beta TcR)-induced and anti-CD3-induced activation of human T lymphocytes

The T cell receptor (TcR) heterodimer of alpha/beta glycoprotein is noncovalently associated with CD3 glycoprotein forming TcR/CD3 complex. The TcR have been shown to recognize antigen, and CD3 antigen is responsible for signal transduction. In this study we compared the effects of WT31 (defining alpha/beta TcR) monoclonal antibody (MoAb) and anti-CD3 MoAb on various steps of human T cell activation. Both antibodies depolarized plasma membranes, increased cell volume, induced IL-2 production and the expression of IL-2 receptors (CD25 antigen) and induced DNA synthesis. Furthermore, the two antibodies showed no synergistic effect on any of these parameters. However, both MoAb showed synergism with phorbol ester (PMA). WT31-induced T cell activation was Ca(2+)-dependent because the addition of EGTA to the medium inhibited DNA synthesis and CD25 antigen expression. The blockers of protein kinase C (PKC), 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7) and staurosporin, in a dose-dependent manner inhibited WT31-induced DNA synthesis. Cholera toxin but not the pertussis toxin inhibited WT31-induced T cell activation, suggesting involvement of G protein in WT31-induced T cell activation. These data indicate that WT31 antibody activates human T cells by a pathway that is similar to that of anti-CD3-induced T cell activation.

Tetraethylammonium, a K+ channel blocker, inhibits interferon-gamma-induced major histocompatibility class II antigen (Ia) expression and DNA synthesis in rat astrocytes

Astrocytes play an important role in antigen presentation to T lymphocytes by their ability to express major histocompatibility class II (Ia) antigen upon exposure to a number of agents, including interferon-gamma (IFN-gamma). Astrocytes have been shown to express a variety of voltage-sensitive ion channels including voltage-sensitive K+ channels. The function(s) of these channels in astrocyte functions is not clearly understood. In this investigation, we examined: (1) the comparative effects of mouse, rat, and human recombinant IFN-gamma (rIFN-gamma) on the induction of Ia antigen and DNA synthesis in rat astrocytes; (2) the effect of tetraethylammonium (TEA), a K+ channel blocker, on rat IFN-gamma-induced Ia expression and DNA synthesis in rat astrocytes. Our data show that all INF-gamma induce DNA synthesis in rat astrocytes but only rat and mouse and not the human IFN-gamma will induce Ia expression. TEA in a dose-dependent manner inhibited both Ia expression and DNA synthesis in rat astrocytes. The concentration kinetics of TEA with regard to maximum inhibition of Ia and DNA synthesis were different. Furthermore, these inhibitory effects were not a result of toxic or nonspecific effect of TEA on astrocytes as demonstrated by viability data and lack of any effect of tetramethylammonium, an analogue of TEA, that does not block K+ ion channels. These data suggest a role of K+ channels in Ia expression and DNA synthesis, therefore in immunological functions of astrocytes.

Role of monocytes in anti-CD3-induced T-cell DNA synthesis: effect of chloroquine and monensin on anti-CD3-induced human T-cell activation

Anti-CD3 monoclonal antibody (MoAb) induces proliferation of freshly isolated peripheral blood T cells only in the presence of monocytes/macrophages and requires binding of the Fc portion of antibody to monocytes/macrophages. In this investigation, we examined whether monocytes process anti-CD3 similar to any soluble antigen and present to T cells in context with HLA-DR to induce maximal DNA synthesis. Adherent monocytes were pulsed with anti-CD3 MoAb in the presence or absence of the lysozomotropic agents chloroquine and monensin, which are known to inhibit processing of soluble antigens, washed extensively, and then incubated with autologous T cells in the absence of soluble anti-CD3, and 3H-thymidine incorporation and CD25 expression were measured. Both monensin and chloroquine inhibited anti-CD3-pulsed monocyte-induced T-cell DNA synthesis and CD25 expression in a dose-dependent manner. This inhibitory effect was not due to any loss in cell viability or the effect on the expression of HLA-DR on monocytes. Paraformaldehyde-fixed monocytes pulsed with anti-CD3 MoAb induced significantly less DNA synthesis, HLA-DR expression, and CD25 antigen expression on autologous T cells as compared to responses induced by unfixed anti-CD3-pulsed monocytes. The treatment of anti-CD3-pulsed monocytes with framework-specific anti-HLA-DR MoAb inhibited their capacity to induce T-cell DNA synthesis. These data suggest that monocytes, in addition to serving as the matrix for cross-linking, also process anti-CD3 MoAb and present to the T cells in the context of HLA-DR antigens to induce optimal DNA synthesis.

Effect of CV-3988, a specific antagonist against platelet activating factor, on homologous passive cutaneous anaphylaxis in the mouse ear

Effect of CV-3988, a specific antagonist against platelet activating factor (PAF), on homologous passive cutaneous anaphylaxis (PCA) elicited in the mouse ear was investigated. PAF caused a potent increase in vascular permeability in the mouse ear. The potency was slightly lower than that of serotonin but higher than those of histamine, leukotriene (LT) C4, LTD4, prostaglandin (PG) E1 and PGE2 on a weight basis. The increased vascular permeability caused by PAF was inhibited by CV-3988 in a dose-dependent manner. CV-3988 did not affect the increase in vascular permeability caused by histamine or serotonin. IgG1 antibody-mediated PCA in the mouse ear was inhibited by CV-3988, although it did not affect IgE antibody-mediated PCA. These results suggest a possibility that PAF might be involved in IgG1 antibody-mediated PCA in the mouse.

A case of Turner syndrome with the karyotype of 45,X/46,X,i(Xq) associated with acute monocytic leukemia

An infertile 37-year-old woman was diagnosed as having acute monocytic leukemia (AMoL) (FAB classification; M5b). In addition, a diagnosis of infertile Turner syndrome was made, based on the presence of the ovarian dysplasia, abnormal physical features (short stature, lack of pubic hair, shield-like chest, etc.), and low urinary estrogen excretion with high plasma gonadotropin level. Karyotypes in the peripheral blood and bone marrow cells were mosaic 45,X and 46,X,i(Xq): isochromosome Xq, which were consistent with infertile Turner syndrome. No further chromosomal abnormalities were found during the course of her treatment for leukemia. This is the first report of the combination of Turner syndrome and AMoL. However, this patient did not have any of the other autosomal chromosomal abnormalities which are common in acute non-lymphocytic leukemias.

Differences between wheat and rice in the enzymic properties of ribulose-1,5-bisphosphate carboxylase/oxygenase and the relationship to photosynthetic gas exchange

The kinetic parameters of ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (EC 4.1.1.39) in wheat (Triticum aestivum L.) and rice (Oryza sativa L.) were determined by rapidly assaying the leaf extracts. The respective K m and V max values for carboxylase and oxygenase activities were significantly higher for wheat than for rice. In particular, the differences in the V max values between the two species were greater. When the net activity of CO2 exchange was calculated at the physiological CO2-O2 concentration from these kinetic parameters, it was 22% greater in wheat than in rice. This difference in the in-vitro RuBP-carboxylase/oxygenase activity between the two species reflected a difference in the CO2-assimilation rate per unit of RuBP-carboxylase protein. However, there was no apparent difference in the CO2-assimilation rate for a given leaf-nitrogen content between the two species. When the RuBP-carboxylase/oxygenase activity was estimated at the intercellular CO2 pressure from the enzyme content and kinetic parameters, these estimated enzyme activities in wheat and rice were similar to each other for the same rate of CO2 assimilation. These results indicate that the difference in the kinetic parameters of RuBP carboxylase between the two species was offset by the differences in RuBP-carboxylase content and conductance for a given leaf-nitrogen content.

Photosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase in rice leaves from emergence through senescence. Quantitative analysis by carboxylation/oxygenation and regeneration of ribulose 1,5-bisphosphate

Changes in gas-exchange rates during the life span of the leaves of rice (Oryza sativa L.) were analyzed quantitatively by measuring changes in the carboxylation/oxygenation and regeneration of ribulose 1,5-bisphosphate (RuBP) at photon fluence rates of 2000 (saturating) and 500 (subsaturating) μmol quanta·m(-2)·s(-1) under ambient air conditions. The RuBP levels were always higher than the active-site concentrations of RuBP carboxylase (EC 4.1.1.39), irrespective of the irradiance supplied. Analysis of the CO2-assimilation rate as a function of intercellular CO2 concentration indicated that RuBP regeneration does not limit CO2 assimilation. The estimated RuBP-carboxylase/oxygenase activity in vivo was linearly correlated to the rate of CO2 assimilation at each level of irradiance. This enzyme activity was just enough to account for the rate of CO2 assimilation at the saturating irradiance and was 35% more than the rate of CO2 assimilation at the subsaturating irradiance. Analysis of the assimilation rate at subsaturating irradiance as a function of intercellular CO2 concentration indicated that a limitation caused by enzyme activation comes into play. The results indicate that the rate of CO2 assimilation in rice leaves under ambient air conditions is limited during their entire life span by the RuBP-carboxylation/oxygenation capacity.

Enzymic Properties of Ribulose-1,5-bisphosphate Carboxylase/Oxygenase Purified from Rice Leaves

The enzymic properties of ribulose 1,5-bisphosphate (RuBP) carboxylase/oxygenase purified from rice (Oryza sativa L.) leaves were studied. Rice RuBPcarboxylase, activated by preincubation with CO(2) and Mg(2+) like other higher plant carboxylases, had an activation equilibrium constant (K(c)K(Mg)) of 1.90 x 10(5) to 2.41 x 10(5) micromolar(2) (pH 8.2 and 25 degrees C). Kinetic parameters of carboxylation and oxygenation catalyzed by the completely activated enzyme were examined at 25 degrees C and the respective optimal pHs. The K(m)(CO(2)), K(m)(RuBP), and V(max) values for carboxylation were 8 micromolar, 31 micromolar, and 1.79 units milligram(-1), respectively. The K(m)(O(2)), K(m)(RuBP), and V(max) values for oxygenation were 370 micromolar, 29 micromolar, and 0.60 units milligram(-1), respectively.Comparison of rice leaf RuBP carboxylase with other C(3) plant carboxylases showed that it had a relatively high affinity for CO(2) but the lowest catalytic turnover number (V(max)) among the species examined.

Photosynthesis and Ribulose 1,5-Bisphosphate Carboxylase in Rice Leaves: Changes in Photosynthesis and Enzymes Involved in Carbon Assimilation from Leaf Development through Senescence

Changes in photosynthesis and the ribulose 1,5-bisphosphate (RuBP) carboxylase level were examined in the 12th leaf blades of rice (Oryza sativa L.) grown under different N levels. Photosynthesis was determined using an open infrared gas analysis system. The level of RuBP carboxylase was measured by rocket immunoelectrophoresis. These changes were followed with respect to changes in the activities of RuBP carboxylase, ribulose 5-phosphate kinase, NADP-glyceraldehyde 3-phosphate dehydrogenase, and 3-phosphoglyceric acid kinase.RuBP carboxylase activity was highly correlated with the net rate of photosynthesis (r = 0.968). Although high correlations between the activities of other enzymes and photosynthesis were also found, the activity per leaf of RuBP carboxylase was much lower than those of other enzymes throughout the leaf life. The specific activity of RuBP carboxylase on a milligram of the enzyme protein basis remained fairly constant (1.16 +/- 0.07 micromoles of CO(2) per minute per milligram at 25 degrees C) throughout the experimental period.Kinetic parameters related to CO(2) fixation were examined using the purified carboxylase. The K(m)(CO(2)) and V(max) values were 12 micromolar and 1.45 micromoles of CO(2) per minute per milligram, respectively (pH 8.2 and 25 degrees C). The in vitro specific activity calculated at the atomospheric CO(2) level from the parameters was comparable to the in situ true photosynthetic rate per milligram of the carboxylase throughout the leaf life.The results indicated that the level of RuBP carboxylase protein can be a limiting factor in photosynthesis throughout the life span of the leaf.