Modification of ischemia-reperfusion-induced changes in cardiac sarcoplasmic reticulum by preconditioning

To examine the effects of ischemic preconditioning on ischemia-reperfusion-induced changes in the sarcoplasmic reticulum (SR) function, isolated rat hearts were either perfused with a control medium for 30 min or preconditioned with three episodes of 5-min ischemia and 5-min reperfusion before sustained ischemia for 30 min followed by reperfusion for 30 min was induced. Preconditioning itself depressed cardiac function (left ventricular developed pressure, peak rate of contraction, and peak rate of relaxation) and SR Ca2+-release and -uptake activities as well as protein content and Ca2+/calmodulin-dependent protein kinase (CaMK) phosphorylation of Ca2+-release channels by 25-60%. Global ischemia for 30 min produced marked depressions in SR Ca2+-release and -uptake activities as well as SR Ca2+-pump protein content in control hearts; these changes were significantly attenuated by preconditioning. Compared with the control preparations, preconditioning improved the recovery of cardiac function and SR Ca2+-release and -uptake activities as well as Ca2+-release channel and Ca2+-pump protein contents in the ischemic-reperfused hearts. Unlike the protein kinase A-mediated phosphorylation in SR membranes, the CaMK-mediated phosphorylations at Ca2+-release channels, Ca2+ pump, and phospholamban were depressed in the ischemic hearts; these changes were prevented by preconditioning. These results indicate that ischemic preconditioning may exert beneficial effects on ischemia-reperfusion-induced alterations in SR function by preventing changes in Ca2+-release channel and Ca2+-pump protein contents in the SR membrane.

[Phase II study of KRN8602 (MX2) for malignant lymphoma]

We performed a clinical phase II study of KRN8602, a new anthracycline derivative, for relapsed or recurrent malignant lymphoma. KRN8602 was given at doses of 12-15 mg/m2 for 3 consecutive days, repeating every 3-4 weeks. Among 44 patients entered into the study, 36 were evaluable for safety, and 35 were evaluable for efficacy. The response rate was 18.2% (6PR/33) for non-Hodgkin's lymphoma and 0% (0/2) for Hodgkin's disease. Major toxicities were bone marrow suppression and gastrointestinal toxicity. Leukopenia was observed in 77.8%, thrombocytopenia in 44.4%, hemoglobin decrease in 44.4%, nausea and vomiting in 94.4% and anorexia in 80.6%. However, all toxicities were clinically manageable.

Expression of proliferating cell nuclear antigen in bronchial epithelium after lung transplantation in the rat

BACKGROUND

The normal, mature airway epithelium in experimental animals has a very slow cell turnover and minimal proliferation. The aim of this study was to investigate the expression of proliferating cell nuclear antigen (PCNA) as an index of bronchial cell proliferation in the Brown Norway to Lewis rat pulmonary allograft model with or without immunosuppression.

METHODS

Brown Norway left lungs were transplanted into Lewis recipients. Some recipients were treated with a high dose of cyclosporine and FK506. Lewis-to-Lewis donor-recipient combination was performed as a control. Lungs were excised on postoperative days 3 and 5. Routinely processed, paraffin-embedded sections were prepared and stained by PCNA. Counts of PCNA-positive cells in the perivascular cellular infiltrate and bronchial surface epithelium were compared with the histologic grade of rejection.

RESULTS

The PCNA index (percent of nuclei immunostaining for PCNA) in bronchial surface epithelium was significantly higher in allografts (21.0% +/- 3.1% at 3 days, 31.4% +/- 9.8 % at 5 days, p < 0.05) than in isografts (5.4% +/- 3.0% at 3 days, 4.7% +/- 4.6% at 5 days). The PCNA index was also greater in the perivascular infiltrates of rejecting lungs (23.9% +/- 3.7% at 3 days, 29.1% +/- 6.6% at 5 days). However, in the cyclosporine- and FK506-treated groups, the PCNA index in bronchial surface epithelium was suppressed to less than 5% at 3 and 5 days. Even at 50 days after transplantation, PCNA-positive cells were rare in bronchial epithelium of FK506-treated grafts.

CONCLUSIONS

Bronchial epithelium in isografts has a relatively low rate of proliferation. In rejection, allografts have a very rapid cell turnover and proliferation. Proliferating epithelium may be a consequence of immune events or it may contribute to the pathogenesis of those events.

Expression of neuronal type nitric oxide synthase and renin in the juxtaglomerular apparatus of angiotensin type-1a receptor gene-knockout mice

Angiotensin type-1a (AT1a) receptor gene-knockout (AT1a-/-) mice exhibit chronic hypotension and renin overproduction. In the kidneys of AT1a-/- mice, the activity of neuronal type nitric oxide synthase (N-NOS) was histochemically detected by nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase (NADPHd) reaction combined with N-NOS immunohistochemistry. The localization of renin was detected by immunohistochemistry and the results were analyzed morphometrically. The levels of N-NOS and renin mRNA in the renal cortical tissue were determined by reverse transcription-PCR and Northern blot analysis, respectively. In the renal sections from wild-type mice, NADPHd activity and N-NOS immunoreactivity were localized to the discrete region of the macula densa in contact with the parent glomerulus. In contrast, N-NOS-positive macula densa cells were distributed beyond the original location of the macula densa, occasionally extending to the opposite side of the distal tubules. The mean number of N-NOS positive macula densa cells was significantly increased in AT1a-/- mice (186 per 100 glomeruli) compared with wild-type mice (65 per 100 glomeruli). AT1a-/- mice showed 1.4-times higher N-NOS mRNA levels in the renal cortical tissues than wild-type mice. The plasma renin activity was significantly higher in AT1a-/- mice (205.5 +/- 26.1 ng/ml/hr) than in wild-type mice (8.0 +/- 0.2 ng/ml/hr). The renin-positive areas per glomerulus and renal renin gene expression were 12-times and 2.6-times higher in AT1a-/- mice than in wild-type mice, respectively. These abnormalities, however, were less remarkable in AT1a-/- mice compared with angiotensinogen-knockout mice. When AT1a-/- mice were fed a high-salt diet, the signal intensity of the NADPHd reaction and the number of positively-stained macula densa cells were significantly decreased. The levels of renal cortical N-NOS mRNA were also suppressed by the treatment. Dietary salt loading produced a parallel decrease in plasma renin activity, renal renin-immunoreactive areas, and the levels of renin mRNA without affecting systemic blood pressure. These results provide evidence for the possible involvement of N-NOS at the macula densa in the increased renin production in AT1a-/- mice.

Structure-function analysis of cell adhesion by neural (N-) cadherin

To investigate the possible biological function of the lateral "strand dimer" observed in crystal structures of a D1 domain extracellular fragment from N-cadherin, we have undertaken site-directed mutagenesis studies of this molecule. Mutation of most residues important in the strand dimer interface abolish the ability of N-cadherin to mediate cell adhesion. Mutation of an analogous central residue (Trp-2) in E-cadherin also abrogates the adhesive capacity of that molecule. We also determined the crystal structure of a Ca2+-complexed two-domain fragment from N-cadherin. This structure, like its E-cadherin counterpart, does not adopt the strand dimer conformation. This suggests the possibility that classical cadherins might stably exist in both dimeric and monomeric forms. Data from several laboratories imply that lateral dimerization or clustering of cadherins may increase their adhesivity. We suggest the possibility that the strand dimer may play a role in this activation.

[Radiofrequency catheter ablation therapy in elderly patients with supraventricular tachycardia]

138 patients with Wolf-Parkinson-White (WPW) syndrome (n = 96), atrioventricular nodal reentrant tachycardia (AVNRT; n = 27) and the other supraventricular tachycardia (n = 15), were divided into two groups, a control group (less than 65 years old; n = 108) and an elderly group (more than 66 years old; n = 30). We then estimated the success rate and safety of radiofrequency ablation for supraventricular tachycardia in elderly patients. For WPW syndrome, there were 76 (97%) successes and 9 (13%) recurrences in the control group (n = 78). In the elderly group of WPW patients, the number of successes was 18 (100%) and the number of recurrences one (63%). In 27 patients with AVNRT, the number of successes was 26 (96%) and there were no recurrences. In 15 patients with some other supraventricular tachycardia, there were 11 patients (73%) successes and one recurrence (11%). Major complications consisted of cardiac tamponade in 2 patients, dissecting aneurysm in one patient and cerebral embolism in one patients. All major complications occurred in patients with WPW syndrome. The cause of the complications, except the cerebral embolism was manipulation of the electrical or ablation catheter. Three of four patients with major complications belonged to the control group. It is possible that radiofrequency catheter ablation for supraventricular tachycardia in elderly patients is safe and highly effective. However, it is still invasive therapy. Ablation on a left accessory pathway by the transaortic valve approach especially needs meticulous care.

Recognition of tRNA(Gly) by three widely diverged glycyl-tRNA synthetases: evolution of tRNA recognition

Glycyl-tRNA synthetase (GlyRS) is an unusual aminoacyl-tRNA synthetase because it varies in its quarternary structure between organisms; Escherichia coli GlyRS is an alpha 2 beta 2 tetramer, whereas those of Thermus thermophilus and yeast are alpha 2 dimers. In contrast, the tRNA(Gly) sequence is virtually identical in E. coli and T. thermophilus but very different in yeast. In this study, we examined the molecular recognition of tRNA(Gly) by three widely diverged GlyRSs using in vitro tRNA transcripts. The results obtained in the mutation studies indicate that despite such large differences of the two prokaryotic GlyRSs, tRNA(Gly) identity has been essentially conserved in prokaryotes, and that there are also differences in the acceptor stem recognition between prokaryotes and yeast. The clear separation between prokaryotes and yeast is retained in the identity element location, whereas the apparent diversity of the two prokaryotic enzymes does not reflect on the tRNA recognition.

Role of the CCA end of tRNA and its vicinity in aminoacylation

The CCA sequence is common to all the 3' ends of tRNAs and more than half of the tRNAs possess the G1C72 base pair at the end of acceptor stem. To study the role of these terminal trinucleotides and their vicinity in the aminoacylation process, not only the substitutions of these bases but also the nucleotide-additions at the 5' end of tRNA were introduced into many kinds of Escherichia coli tRNA transcripts and the effects on the aminoacylation activity with cognate aminoacyl-tRNA synthetase were investigated. Basically the requirement of the CCA sequence in aminoacylation differed among each amino acid specific tRNA. Some rough conclusions could be drawn from the present results. It was found that the G1C72 base pair functioned as the negative identity elements in many tRNAs. The nucleotide-addition experiments suggested that proper spatial arrangement and flexibility were important for aminoacylation reaction. Functional and evolutional implications of the invariant CCA sequence and its vicinity were discussed.

Internalization with high targeting potential of mouse monoclonal antibody ONS-M21 recognizing human malignant glioma antigen

In order to evaluate the targeting potential of mouse monoclonal antibody ONS-M21 recognizing a human astrocytoma- and medulloblastoma-associated antigen, the internalization ability of this antibody and the selective cytotoxicity in the toxin-conjugated form were examined. Internalization assay with 125I-labeled ONS-M21 showed that about 20% of the total radioactivities was detected in the cellular fraction of human medulloblastoma cell line ONS-76 cells and that the reaction reached a plateau level in 30 min. To examine the selective delivery capacity of a high molecular substance in place of 125I, an immunotoxin was prepared with ricin A chain and ONS-M21 via disulfide bonds. A cytotoxic effect against ONS-76 cells was found with [3H]thymidine incorporation assay using the immunotoxin, but not against antigen-negative HuH-7 and SW480 cells. These results suggest that ONS-M21 could effectively deliver toxins, chemotherapeutic agents or radionuclei to malignant glioma specifically.

[A 4-week toxicity study of magnesium sulfate administered by 24-hr intravenous infusion in beagle dogs]

A 4-week toxicity study of magnesium sulfate administered by 24-hr intravenous infusion at the dosage levels of 0, 12.5, 50 and 100 mg/kg/hr in female beagle dogs was conducted. No death occurred in any group. Changes attributable to the treatment with magnesium sulfate were decreased food consumption and body weight gain, anemic change, increased urine volume, decreased serum calcium level, increased inorganic phosphorus level, slight prolongation of conduction time in electrocardiogram and tubular basophilia in the kidneys in the group treated with 100 mg/kg/hr. In addition, essentially similar changes were also observed at the same dosage level in the 2-week study of this drug, in which recoverability was recognized with 2-week follow-up observation after drug withdrawal. In conclusion, the nontoxic dosage level was judged to be 50 mg/kg/hr under the condition of the present study.

[Acute mediastinitis due to esophageal perforation--a case report]

A 55-year-old female consulted her family physician because of pharyngeal discomfort after eating a fish. She underwent rigid fiberscopy and was pointed out a fish bone. Family physician failed to extract the bone and the patient was referred to our hospital. However, there was no fish bone in the esophagus when she underwent second rigid fiberscopy. After eight days she complained of dyspnea and was referred to our hospital again. Chest X ray film showed marked enlargement of the mediastinum and she was diagnosed as acute mediastinitis. She underwent mediastinal drainage by thoracotomy. So tiny perforation was found in cervical esophagus by endoscopy that primary suture was not done. After two months' follow up with intravenous hyperalimentation, there was still esophageal perforation. She underwent the second operation of primary closure with reinforcement using sternocleidomastoid muscle. Two weeks after the second operation esophagogram still showed a fistula. So she received injections of alprostadil and factor XIII. One month after the injections esophagogram showed a diverticulum without leakage.

Characterization of substrates for use in X-ray multilayer optics

The optical performance of platinum-carbon multilayers deposited onto different substrates has been examined. Specular reflectivity and non-specular diffuse scattering were measured to study the replication of substrate roughness into the multilayer structure. Surface topography was measured before and after deposition using a scanning probe microscope and a mechanical profiler.

Health effects of indoor fluoride pollution from coal burning in China

The combustion of high fluoride-content coal as an energy resource for heating, cooking, and food drying is a major exhaust emission source of suspended particulate matter and fluoride. High concentrations of these pollutants have been observed in indoor air of coal-burning families in some rural areas in China. Because airborne fluoride has serious toxicological properties, fluoride pollution in indoor air and the prevalence of fluorosis have been analyzed in a fluorosis area and a healthy nonfluorosis area in China and in a rural area in Japan. For human health, fluoride in indoor air has not only been directly inhaled by residents but also has been absorbed in stored food such as corn, chilies, and potatoes. In the fluorosis area in China, concentrations of urinary fluoride in the residents have been much higher than in the nonfluorosis area in China and in the rural area in Japan. In the fluorosis area, almost all elementary and junior high school students 10-15 years of age had dental fluorosis. Osteosclerosis in the skeletal fluorosis patients was very serious. Urinary deoxypyridinoline in rural residents in China was much higher than in rural residents in Japan. Data suggest that bone resorption was extremely stimulated in the residents in China and that fluoride may stimulate both bone resorption and bone formation. Because indoor fluoride from combustion of coal is easily absorbed in stored food and because food consumption is a main source of fluoride exposure, it is necessary to reduce airborne fluoride and food contamination to prevent serious fluorosis in China.

[A 2-week toxicity study of magnesium sulfate administered by 24-hr intravenous infusion in beagle dogs followed by 2-week recovery period]

A 2-week toxicity study of magnesium sulfate administered by a 24-hr intravenous infusion at the dosage levels of 0, 12.5, 50, 100 and 200 mg/kg/hr in female beagle dogs was conducted, with 2-week follow-up observation after drug withdrawal. One of 2 animals in the 200 mg/kg/hr group died approx. 32 hr after the start of infusion. At the same time, the remaining 1 animal of the same group was sacrificed in a moribund state. Changes attributable to the treatment of magnesium sulfate were decreased food consumption and body weight gain, anemia, mild prolongation of conduction time in electrocardiogram and tubular basophilia in the kidneys in the animals treated with 100 mg/kg/hr. Furthermore, decreased calcium level was recorded in the animals treated with 50 mg/kg/hr or more. However, these changes disappeared after drug withdrawal, and reversibility was suggested. Judging from the mode of occurrence, since the change in calcium level observed in the group treated with 50 mg/kg/hr was slight, it was considered to be toxicologically insignificant. In conclusion, the nontoxic dosage level of magnesium sulfate was judged to be 50 mg/kg/hr under the condition of the present study.

Usefulness of K-ras gene mutation at codon 12 in bile for diagnosing biliary strictures

Point mutations of the K-ras gene at codon 12 are often detected in the pancreatic juice of patients with pancreatic cancer. Detection of these mutations may, thus, have diagnostic implications. K-ras mutations may also have diagnostic potential for other biliary tumors. We sought to detect K-ras mutations in DNA obtained from bile in patients with biliary tract cancers, pancreatic cancer and benign biliary disease but who had obstructive jaundice. In 35 patients, bile was collected during percutaneous transhepatic choledocal drainage (PTCD) catheters. K-ras gene mutations at codon 12 in the samples were examined using mutant-allele-specific-amplification (MASA). We compared these results with cytological analyses of bile. K-ras mutations at codon 12 in bile were detected in 11 of 14 (79%) of the patients with biliary duct cancer, 3 of 9 (33%) with pancreatic cancer but not in patients with gallbladder cancer (n=3), papilla of Vater's cancer (n=3) or benign biliary diseases (n=6). In the patients, where cytological evaluation did not reveal malignant cells, K-ras mutations in bile were detected in 5 of 7 (71%) patients with biliary duct cancer and 2 of 5 (40%) with pancreatic cancer. This approach, when used in conjunction with bile cytology, may improve the yield in diagnosing suspected malignant tumors of the pancreatic-biliary system.

Fabrication and characterization of multilayer supermirrors for hard X-ray optics

Multilayer supermirrors stacked with three sets of Pt/C combinations have been fabricated on a flat float-glass and conical replica foil mirror using a magnetron DC sputtering system, and applied to X-ray optical systems in the hard X-ray region. The design of the supermirror is optimized to obtain the highest integrated reflectivity in the energy band and at the grazing angle concerned. X-ray reflectivities of 30% in the 25-35 keV band at an incidence angle of 0.3 degrees were obtained.

gp130 is involved in stretch-induced MAP kinase activation in cardiac myocytes

We have recently reported that mitogen activated protein kinase (MAP kinase) is activated by the stretch of the cultured cardiac myocytes in the angiotensin II deficient state in the angiotensinogen-deficient mice (Atg-/-), suggesting that factors other than the cardiac renin-angiotensin system are involved in the stretch-induced MAP kinase activation. We examined the contribution of cytokines using RX435, an anti-gp130 antibody. Leukemia inhibitory factor, which is one of the cytokines and has the common receptor subunit gp130, activated MAP kinase and the response was completely blocked by pretreatment of the Atg-/- cardiac myocytes with RX435. RX435 pretreatment greatly reduced stretch-induced activation of MAP kinase in Atg-/- cardiac myocytes. Interestingly, the same results were obtained in the cardiac myocytes of control mice. These results suggest that cytokine-gp130 may play a role in the stretch-induced MAP kinase activation independently of Ang II in cardiac myocytes.

Limited reproducibility of circadian variation in blood pressure dippers and nondippers

The relation between blood pressure (BP) variation and hypertensive organ damage is controversial. The reproducibility of the circadian variation pattern acceptable as the standard for discriminating between "dippers" and "nondippers" has not yet been evaluated. We evaluated the reproducibility of "dipper" and "nondipper" patterns in essential hypertensives by monitoring BP for 48 h. Noninvasive ambulatory BP and heart rate (HR) monitoring for 48 h every 30 min were performed in 253 untreated patients with mild-to-moderate essential hypertension. Mean daytime (awake) and nighttime (sleeping) systolic BP, diastolic BP, and HR values were analyzed by reviewing the patients' diaries. Patients were divided into two groups by presence (dippers) and absence (nondippers) of a reduction of both systolic and diastolic BP during the night of > 10% of the daytime pressure. A subject who was a dipper on day 1 remained a dipper on day 2 in 41% (n = 103, DD group) and changed to nondipper in 16% (n = 41, DN group). A subject who was a nondipper on day 1 remained a nondipper on day 2 in 30% (n = 75, NN group) and changed to a dipper in 13% (n = 34, ND group). Our findings indicate that there is a high risk of false-positive or false-negative results when 24-h recordings are used to identify dipper and nondipper profiles.

Dipyridamole thallium-201 single-photon emission computed tomography for prediction of perioperative cardiac events in patients with arteriosclerosis obliterans undergoing vascular surgery

The aim of the study was to determine whether or not dipyridamole thallium-201 single-photon emission computed tomography (201Tl-SPECT) has significant additive value for predicting perioperative cardiac events in patients with arteriosclerosis obliterans (ASO) undergoing vascular surgery. Routine preoperative 201Tl-SPECT was performed in 106 consecutive patients with ASO (age 68+/-8.9 years; 91 men and 15 women). The frequency of reversible defects in a clinical high-risk group (n=44) was significantly higher than in a low-risk group (n=62; 55% vs 24%, p<0.01). Perioperative cardiac events occurred in 9 patients, including 4 cardiac deaths, 1 non-fatal myocardial infarction, and 4 cases of unstable angina. Although clinical risk stratification was useful in predicting cardiac events (19% in the high-risk group vs 2% in the low-risk group, p<0.01), the positive predictive value was low. When considering a combination of 2 or more than 2 risk factors and a large reversible defect as a predictor, the positive predictive value and specificity increased from 19% to 47% and from 64% to 91%, respectively, whereas the sensitivity remained unchanged (89%). These results suggest that the addition of 201Tl-SPECT data to clinical risk-stratified patients with ASO allows better prediction of perioperative cardiac events.

Prevalence of ventricular preexcitation in Japanese schoolchildren

BACKGROUND

Wolff-Parkinson-White syndrome is thought to be a congenital disease, however, its exact prevalence is not known. This may be because of the intermittent activity of accessory pathways in some cases and fluctuations in autonomic tone.

AIMS

To investigate the prevalence of ventricular preexcitation by electrocardiography and reported symptoms in each school age child in Yamanashi prefecture.

METHODS

From 1994 to 1996, answers to a questionnaire, results of physical examination, and electrocardiography were obtained from all schoolchildren in Yamanashi prefecture (n = 92,161; total population 880,000) on admission to elementary school (age 6 to 7 years, n = 28,395), junior high school (age 12 to 13 years, n = 31,206), and high school (age 14 to 15 years, n = 32,837).

RESULTS

Elementary and junior high school students had a significantly lower prevalence of preexcitation than high school students (0.073% and 0.070% v 0.174%, p < 0.001). The prevalence of left free wall pathway was highest in high school students (n = 27) compared with elementary (n = 6) and junior high school students (n = 5) (p < 0.005). The only symptom noted in the answers to the questionnaire was palpitations. The symptomatic cases were more frequent in high school (n = 13) than in elementary (n = 1) and junior high school (n = 2) children, but not significantly. No student with preexcitation had associated heart disease or family history of Wolff-Parkinson-White syndrome or sudden death.

CONCLUSIONS

The prevalence of preexcitation in younger schoolchildren was less frequent than previously reported. The prevalence of preexcitation and left free wall pathways increased with age. The symptoms were few and there was no significant morbidity.

Multiple digit formation in Xenopus limb bud recombinants

We prepared recombinant limb buds of Xenopus tadpoles by grafting a mesenchyme mass of the hindlimb bud. The Xenopus recombinant limb buds with dissociated and reaggregated mesenchyme developed more than 30 digits with cartilage segmentation, while those with undissociated mesenchyme developed a limb with normal cartilage pattern. Before the formation of multiple digits, a patchy expression pattern of fgf-8, an AER marker, was observed in the distal region of recombinant limb buds. shh, a ZPA (zone of polarizing activity) marker, was expressed broadly in the distal region of recombinants. Recombinant limb buds with the reaggregated mesenchyme of anterior halves formed anterior digits with claws, and those with the mesenchyme of posterior halves formed posterior digits without claws. The temporal and spatial changes in the potency of multiple digit formation are discussed with reference to the regenerative capacity of Xenopus limb buds.

[A case of severe hypernatremia complicated with rhabdomyolysis]

We report a 45-year-old male patient with severe hypernatremia followed by rhabdomyolysis and acute renal failure. He had developed hypernatremia for two years after a surgery for an intraventricular AVM involving the hypothalamic area, which was fed by the anterior cerebral artery. He was admitted to our hospital because of progressive muscle weakness. Because of loss of water intake due to impaired thirst sensation, he developed severe hypernatremia (191mEq/l) and marked rhabdomyolysis (CK 17,772 IU/l). He was treated with fluid supplement and hemodialysis for acute renal insufficiency. He had no thirst feeling. Blood studies revealed hyporeactivity to ADH in spite of marked hypernatremia and hyperosmorality. Therefore his condition was considered as adipsic hypernatremia. We concluded that rhabdomyolysis of this case was caused by severe hypernatremia. On reviewing the literature, only a few cases of rhabdomyolysis due to hypernatremia have been reported.

Coordinated expression of Hoxa-11 and Hoxa-13 during limb muscle patterning

The limb muscle precursor cells migrate from the somites and congregate into the dorsal and ventral muscle masses in the limb bud. Complex muscle patterns are formed by successive splitting of the muscle masses and subsequent growth and differentiation in a region-specific manner. Hox genes, known as key regulator genes of cartilage pattern formation in the limb bud, were found to be expressed in the limb muscle precursor cells. We found that HOXA-11 protein was expressed in the premyoblasts in the limb bud, but not in the somitic cells or migrating premyogenic cells in the trunk at stage 18. By stage 24, HOXA-11 expression began to decrease from the posterior halves of the muscle masses. HOXA-13 was expressed strongly in the myoblasts of the posterior part in the dorsal/ventral muscle masses and weakly in a few myoblasts of the anterior part of the dorsal muscle mass. Transplantation of the lateral plate of the presumptive wing bud to the flank induced migration of premyoblasts from somites to the graft. Under these conditions, HOXA-11 expression was induced in the migrating premyoblasts in the ectopic limb buds. Application of retinoic acid at the anterior margin of the limb bud causes duplication of the autopodal cartilage and transformation of the radius to the ulna, and at the same time induces duplication of the muscle pattern along the anteroposterior axis. Under these conditions, HOXA-13 was also induced in the anterior region of the ventral muscles in the zeugopod. These results suggest that Hoxa-11 and Hoxa-13 expression in the migrating premyoblasts is under the control of the limb mesenchyme and the polarizing signal(s). In addition, these results indicate that these Hox genes are involved in muscle patterning in the limb buds.