Impact of the COVID-19 pandemic on the incidence of surgical site infection after orthopaedic surgery: an interrupted time series analysis of the nationwide surveillance database in Japan

BACKGROUND

During the COVID-19 pandemic, hygiene awareness was increased in communities and hospitals. However, there is controversy regarding whether such circumstances affected the incidence of surgical site infections (SSIs) in the orthopaedic surgical field.

AIM

To examine the impact of the COVID-19 pandemic on the incidence of SSIs after orthopaedic surgery.

METHODS

The medical records of patients having undergone orthopaedic surgery were extracted from the nationwide surveillance database in Japan. The primary outcomes were the monthly incidences of total SSIs, deep or organ/space SSIs, and SSIs due to meticillin-resistant Staphylococcus aureus (MRSA). Interrupted time series analysis was conducted between pre-pandemic (January 2017 to March 2020) and pandemic (April 2020 to June 2021) periods.

RESULTS

A total of 309,341 operations were included. Interrupted time series analysis adjusted for seasonality showed no significant changes in the incidence of total SSIs (rate ratio 0.94 and 95% confidence interval 0.98-1.02), deep or organ/space SSIs (0.91, 0.72-1.15), or SSIs due to MRSA (1.07, 0.68-1.68) along with no remarkable slope changes in any parameter (1.00, 0.98-1.02; 1.00, 0.97-1.02; and 0.98, 0.93-1.03, respectively).

CONCLUSIONS

Awareness and measures against the COVID-19 pandemic did not markedly influence the incidence of total SSIs, deep or organ/space SSIs, or SSIs due to MRSA following orthopaedic surgery in Japan.

Risk factors for catheter-related bloodstream infections in patients with intestinal failure undergoing home parenteral nutrition: a single-center study

PURPOSE

The incidence and risk factors of catheter-related bloodstream infections (CRBSI) in patients with intestinal failure (IF) have not been established, partly because catheter management methods vary from different facilities. This study aimed to identify the risk factors and incidence rate of CRBSIs in patients with IF who were given prophylactic treatment.

METHODS

Sixteen patients with IF who required home parenteral nutrition were enrolled in this study. Prophylactic management of CRBSI included monthly ethanol lock therapy and standardized infection prevention education. The outcomes included the incidence and risk factors of CRBSI.

RESULTS

The median incidence rate of CRBSI was 1.2 per 1000 catheter days. Univariate analysis showed that the risk of developing CRBSI was significantly associated with short bowel syndrome (< 30 cm) (p = 0.016). Other relevant findings included a significant negative correlation between serum albumin and CRBSI rate (r = - 0.505, p = 0.046), and past history of mixed bacterial infections was significantly associated with increased CRBSI rate (p = 0.013).

CONCLUSION

CRBSIs can still develop despite undergoing prophylactic management. Risk factors for CRBSI include the residual intestinal length, nutritional status, and susceptibility to certain microorganisms.

Intraoperative Placement of an Absorbable Spacer Prior to Radiation Therapy for a Malignant Peripheral Nerve Sheath Tumor

A 7-year-6-month-old female was diagnosed with a pelvic malignant peripheral nerve sheath tumor and lymph node metastases. Tumorectomy was performed after four cycles of chemotherapy. A 33-mm cystic lesion was observed around the left iliac muscle after three cycles of postoperative chemotherapy, and proton beam therapy (PBT) was recommended. She was referred for absorbable spacer (AS) placement. The left ovarian appendage (OA) was resected due to the direct tumor infiltration. The right OA was fixed to the uterosacral ligament. The AS was fixed to the lateral pelvis. The PBT (70.3 Gy relative biological effectiveness) was performed successfully with the AS, and she also had the reproducing possibility due to prevention of severe irradiation damage of the right OA. AS eliminated the surgical removal of spacers and enabled us high-dose PBT for residual tumor without severe irradiation damage including infertility.

Intestinal Transplantation at a Single Institution in Japan

BACKGROUND

This study aimed to compare the clinical outcomes of intestinal transplantation (ITX) between 2 groups by using medications for induction treatment and assess the utility of the current protocol.

METHODS

From 2003 to 2020, 11 patients underwent ITX. Recipients were classified into 2 groups: group IL-2Ra (interleukin-2 receptor antagonist therapy, n = 6) and ATG (rabbit antithymocyte globulin therapy, n = 5). We conducted a retrospective review of patient and graft survival rates and the postoperative course.

RESULTS

The 1-, 5-, and 10-year patient and graft survival rates of the 11 primary grafts in the 11 recipients were 100%, 88.9%, 62.2% and 90.0%, 78.8%, 56.3%, respectively. The median duration of follow-up for the IL-2Ra and ATG groups was 197.3 and 87.3 months, respectively. The 1-, 5-, and 10-year patient survival rates were 100%, 83.3%, 50% and 100%, 100%, 100% for the IL-2Ra and ATG groups, respectively (P = .25) and 83.3%, 66.7%, 33.3% and 100%, 100%, 100% for graft survival in the IL-2Ra and ATG groups, respectively (P = .08). The incidence of moderate and severe acute rejection was 100% and 20% in the IL-2Ra and ATG groups, respectively (P = .02). The 1- and 5-year moderate and severe rejection-free survival rates were 33.3%, 0% and 80%, 80% in the IL-2Ra and ATG groups, respectively (P = .04).

CONCLUSIONS

ATG significantly suppressed moderate and severe acute rejection compared with IL-2Ra, thereby showing better short- and mid-term rejection-free survival rates. Additional clinical experience is needed to determine the optimal regimen for the management of ITX recipients.

Treatment of classic-type Hirschsprung's disease: rectoplasty with posterior triangular colonic flap versus transanal endorectal pull-through with rectoanal myotomy

PURPOSE

Our institution employs rectoplasty with a posterior triangular colonic flap (RPTCF) for classic-type Hirschsprung's disease. Recently, we employed a modified Soave procedure: transanal endorectal pull-through with rectoanal myotomy (TEPTRAM). In both procedures, the internal sphincter muscle is completely divided vertically at the 6 o'clock position. Unlike RPTCF, TEPTRAM does not require abdominal manipulation. We aimed to verify the usefulness of TEPTRAM.

METHODS

64 patients with classic-type Hirschsprung's disease who underwent surgery between 1970 and 2017 were divided into group R (RPTCF, 47 cases) and group T (TEPTRAM, 17 cases). We compared the defecation function of the groups.

RESULTS

No patient showed fecal incontinence (R: 0/41, T: 0/10, ns). Three patients (6%) in group R and four (24%) in group T developed postoperative enterocolitis (P = 0.16). Three patients (10%) in group R and one (20%) in group T needed an enema (P = 0.36).

CONCLUSION

There was no adverse effect of rectoanal myotomy; incontinence was not observed in either procedure. Although there was no significant difference, the incidences of enterocolitis and constipation were slightly higher in group T, perhaps because of the residual muscle cuff; therefore, it is necessary to provide best care with attention to constipation immediately after surgery.

Estimated glomerular filtration rate after nephrectomy for Wilms tumor

BACKGROUND

The aim of this study was to assess long-term residual kidney function after unilateral nephrectomy for non-syndromic Wilms tumor (NSWT).

METHODS

Of the patients who underwent one-sided NSWT at Tohoku University Hospital between 1977 and 2003, nine were followed up until age ≥18 years. For these nine patients, we retrospectively evaluated estimated glomerular filtration rate (eGFR) in childhood (3-10 years old), adolescence (11-17 years old) and adulthood (≥18 years).

RESULTS

Mean age at the last follow up was 23.0 years. Tumor classification was as follows: stage I tumor, n = 6; stage II tumor, n = 3; mixed-type nephroblastoma, n = 8; and congenital mesoblastic nephroma, n = 1. Mean eGFR was 101.3 ± 21.2 mL/min/1.73 m² in childhood, 106.0 ± 32.1 mL/min/1.73 m² in adolescence and 100.5 ± 20.7 mL/min/1.73 m² in adulthood. Therefore, no significant change in eGFR was observed over the three life stages evaluated. Further, none of the patients met the diagnostic criteria for chronic kidney disease by early adulthood.

CONCLUSIONS

eGFR after unilateral nephrectomy in patients with NSWT remained ≥60 mL/min/1.73 m² during the transition from childhood to early adulthood, with no development of chronic kidney disease or end-stage kidney failure.

A novel PHOX2B gene mutation in an extremely low birth weight infant with congenital central hypoventilation syndrome and variant Hirschsprung's disease

Congenital central hypoventilation syndrome is a disorder of respiratory control caused by mutations in the paired-like homeobox 2B gene. Mutations in the paired-like homeobox 2B gene are also responsible for Hirschsprung's disease. Variant Hirschsprung's disease is a rarer disorder that does not meet the diagnostic criteria of Hirschsprung's disease, although severe functional bowel obstruction persists. We present a case of an extremely low birth weight infant with congenital central hypoventilation syndrome and variant Hirschsprung's disease. A male infant who was diagnosed to have fetal growth restriction and polyhydramnios was delivered by emergency cesarean section at 30 weeks and 3 days of gestational age due to non-reassuring fetal status. The birth weight was 979 g, and intensive care was started immediately following delivery. The patient exhibited refractory apnea and was diagnosed with congenital central hypoventilation syndrome by genetic testing of the paired-like homeobox 2B gene. The patient also exhibited refractory functional bowel obstruction and was diagnosed to have variant Hirschsprung's disease through pathological examination of his intestinal specimens. The patient grew slowly but surely with intensive care including mechanical ventilation and parenteral nutrition. However, the patient repeatedly suffered from sepsis and died of fungemia at 197 days of age. This is the first congenital central hypoventilation syndrome case that was accompanied with variant Hirschsprung's disease, and the paired-like homeobox 2B mutation detected in this case (NM_003924.3: c.441G > C; p.(Gln147His)) is novel. This case suggests that the paired-like homeobox 2B mutation causes not only congenital central hypoventilation syndrome and Hirschsprung's disease, but also variant Hirschsprung's disease in humans. It also highlights the extreme difficulty in treating premature infants with severe and prolonged functional bowel obstruction.

Mediastinal tumor resection via open or video-assisted surgery in 31 pediatric cases: Experiences at a single institution

BACKGROUND

Video-assisted thoracic surgery (VATS) has been increasingly used for the diagnosis and treatment of thoracic diseases. Pediatric mediastinal tumors are often difficult to resect because of their proximity to important organs. For this reason, VATS is not established as a standard surgical approach for such tumors. We compared the efficacy and safety of mediastinal tumor resection in children using open thoracotomy (OT) and VATS.

METHODS

A total of 31 children underwent mediastinal tumor resection (21 by VATS and 10 by OT). These nonrandomized approaches were retrospectively compared for incidence of operative complications, morbidity, and mortality.

RESULTS

Tumor sizes and operation times were similar between groups. However, the VATS group required significantly fewer blood transfusions and shorter durations of thoracic drainage and hospital stays (p<0.05). Complications greater than grade 2 on the Clavien-Dindo classification occurred in four patients treated by VATS and OT. No delayed effects were noted in the survivors of either group. A patient with clear cell sarcoma of the kidney who underwent OT relapsed and died.

CONCLUSION

Although complication rates were similar between the two approaches, VATS was suggested as less invasive because of fewer blood transfusions required, and shorter thoracic drainage and hospital stay durations.

Tofogliflozin, a novel sodium-glucose co-transporter 2 inhibitor, improves renal and pancreatic function in db/db mice

BACKGROUND AND PURPOSE

Although inhibition of renal sodium-glucose co-transporter 2 (SGLT2) has a stable glucose-lowering effect in patients with type 2 diabetes, the effect of SGLT2 inhibition on renal dysfunction in type 2 diabetes remains to be determined. To evaluate the renoprotective effect of SGLT2 inhibition more precisely, we compared the effects of tofogliflozin (a specific SGLT2 inhibitor) with those of losartan (an angiotensin II receptor antagonist) on renal function and beta-cell function in db/db mice.

EXPERIMENTAL APPROACH

The effects of 8-week tofogliflozin or losartan treatment on renal and beta-cell function were investigated in db/db mice by quantitative image analysis of glomerular size, mesangial matrix expansion and islet beta-cell mass. Blood glucose, glycated Hb and insulin levels, along with urinary albumin and creatinine were measured

KEY RESULTS

Tofogliflozin suppressed plasma glucose and glycated Hb and preserved pancreatic beta-cell mass and plasma insulin levels. No improvement of glycaemic conditions or insulin level was observed with losartan treatment. Although the urinary albumin/creatinine ratio of untreated db/db mice gradually increased from baseline, tofogliflozin or losartan treatment prevented this increase (by 50-70%). Tofogliflozin, but not losartan, attenuated glomerular hypertrophy. Neither tofogliflozin nor losartan altered matrix expansion.

CONCLUSIONS AND IMPLICATIONS

Long-term inhibition of renal SGLT2 by tofogliflozin not only preserved pancreatic beta-cell function, but also prevented kidney dysfunction in a mouse model of type 2 diabetes. These findings suggest that long-term use of tofogliflozin in patients with type 2 diabetes may prevent progression of diabetic nephropathy.

Tofogliflozin, a sodium/glucose cotransporter 2 inhibitor, attenuates body weight gain and fat accumulation in diabetic and obese animal models

OBJECTIVE

Tofogliflozin, a highly selective inhibitor of sodium/glucose cotransporter 2 (SGLT2), induces urinary glucose excretion (UGE), improves hyperglycemia and reduces body weight in patients with Type 2 diabetes (T2D). The mechanisms of tofogliflozin on body weight reduction were investigated in detail with obese and diabetic animal models.

METHODS

Diet-induced obese (DIO) rats and KKAy mice (a mouse model of diabetes with obesity) were fed diets containing tofogliflozin. Body weight, body composition, biochemical parameters and metabolic parameters were evaluated.

RESULTS

In DIO rats tofogliflozin was administered for 9 weeks, UGE was induced and body weight gain was attenuated. Body fat mass decreased without significant change in bone mass or lean body mass. Food consumption (FC) increased without change in energy expenditure, and deduced total calorie balance (deduced total calorie balance=FC-UGE-energy expenditure) decreased. Respiratory quotient (RQ) and plasma triglyceride (TG) level decreased, and plasma total ketone body (TKB) level increased. Moreover, plasma leptin level, adipocyte cell size and proportion of CD68-positive cells in mesenteric adipose tissue decreased. In KKAy mice, tofogliflozin was administered for 3 or 5 weeks, plasma glucose level and body weight gain decreased together with a reduction in liver weight and TG content without a reduction in body water content. Combination therapy with tofogliflozin and pioglitazone suppressed pioglitazone-induced body weight gain and reduced glycated hemoglobin level more effectively than monotherapy with either pioglitazone or tofogliflozin alone.

CONCLUSION

Body weight reduction with tofogliflozin is mainly due to calorie loss with increased UGE. In addition, tofogliflozin also induces a metabolic shift from carbohydrate oxidation to fatty acid oxidation, which may lead to prevention of fat accumulation and inflammation in adipose tissue and liver. Tofogliflozin may have the potential to prevent obesity, hepatic steatosis and improve insulin resistance as well as hyperglycemia.

Laparoscopy-assisted appendectomy through an umbilical port in children

INTRODUCTION

We report surgical techniques for single-incision laparoscopy-assisted surgery (SILAS) in the treatment of pediatric acute appendicitis.

METHODS

We performed SILAS in 15 cases of acute appendicitis between January and September of 2009. SILAS is a surgical method that involves making the incision at the umbilicus, inserting a wound retractor XS, suspending the abdominal wall with a hook, and appendectomy with the same procedures as conventional appendectomy.

RESULTS

SILAS appendectomy was performed in all 15 cases with the exception of one case where one 3-mm port was added. Compared to open appendectomy, blood loss was significantly lower and postoperative hospitalization time was shorter, although there was no significant decrease in operative time, or postoperative fasting time. No postoperative complications, such as wound infection, intestinal obstruction, intra-abdominal abscess, or bleeding, were encountered.

CONCLUSION

SILAS was safely performed and is superior to open appendectomy with regard to cosmetic outcome.

Hemodynamics in the left gastric vein after endoscopic ligation of esophageal varices combined with sclerotherapy

BACKGROUND AND METHODS

We examined the changes in portal hemodynamics after endoscopic variceal ligation (EVL) combined with endoscopic injection sclerotherapy (EIS) in relation to post-treatment relapse. The present study included 93 patients who underwent EVL-EIS combination therapy. Portal hemodynamics were examined by Doppler ultrasonography and percutaneous transhepatic portography (PTP).

RESULTS

Therapy with EVL-EIS resulted in the complete disappearance of varices in 89 of 93 patients. Cumulative relapse-free rates (Kaplan-Meier method) were 75.8 and 50.2%, respectively, 1 and 3-5 years after treatment. At the end of treatment, the flow in the left gastric vein was examined by Doppler ultrasonography. In 50 of 63 patients, the flow remained hepatofugal. In 23 of these patients, PTP was performed at the end of treatment; selective left gastric venography did not reveal any palisade zone vessels or varices. However, fine blood vessels were seen around the lower esophagus in nine patients, only the paraesophageal vein was found in 10 patients and these two findings were present in four patients, indicating that collateral blood flow remained in the lower esophagus in 13 of 23 patients. These findings suggest that frequent relapse of varices results from insufficient blockage of blood flow from the left gastric vein to the lower esophagus. However, in patients with a patent paraesophageal vein, long-term effects obtained by EVL-EIS combination therapy were satisfactory.

CONCLUSIONS

The pattern of the development of collateral left gastric veins represents important hemodynamic changes that predict the long-term prognosis of patients after treatment.

Melanophore lineage and clonal organization of the epidermis in Xenopus embryos as revealed by expression of a biogenic marker, GFP

Melanophore lineage during embryogenesis of Xenopus laevis was traced using the overexpression of a biogenic marker, green fluorescent protein (GFP). Two different approaches were applied after injection of GFP mRNA (hence a marker construct) into each blastomere at the 16-cell stage. In in vivo experiments, the embryos injected with a marker construct were grown until stage 45, in which melanophores were distributed over the whole body and were good enough for checking GFP expression at their migratory destination. In in vitro experiments, neural tubes of the embryos injected with a marker construct were isolated and cultured at stage 21 to examine by virtue of GFP expression how neural crest cells differentiate into melanophores. The results obtained from both in vivo and in vitro experiments indicated the following: 1) selected animal blastomeres vastly contribute to the development of melanophores, whereas other animal blastomeres do so slightly at a limited pace; and 2) vegetal blastomeres never contribute to melanophores in normal development, whereas certain vegetal blastomeres have a potential to give rise to melanophores in vitro. The analyses using GFP also disclosed that the dorsal and ventral epidermis derive from the restricted animal blastomeres in the normal development. Since the dorso-ventrality of the epidermis has been inseparably coupled with integumental pigmentation, the clonal organization of the epidermis observed in the present study is discussed in the light of pigment pattern formation attributed by melanophores.

White ball appearance in endoscopic ligation of bleeding esophageal varices

BACKGROUND

Endoscopic variceal ligation is useful in the control of bleeding from esophageal varices. However, confirmation of ligation precisely at the site of bleeding is usually difficult when treating massive variceal bleeding. Characteristic endoscopic findings that appeared when ligation was performed at the site of bleeding are reported in this article.

METHODS

Emergency endoscopic variceal ligation was performed in 14 patients with active bleeding from esophageal varices. Endoscopic findings after variceal ligation at the site of bleeding were compared with those at sites without bleeding.

RESULTS

Active bleeding ceased just after endoscopic ligation at the site of bleeding in all patients. After ligation of the bleeding site of the varix, an unusual white-colored ball-like appearance (white ball appearance) was observed in all patients. This finding was markedly different from the purple-colored ball-like appearance that is usually observed after ligation of a varix at a site without bleeding.

CONCLUSIONS

White ball appearance was a characteristic finding that appeared after ligation of a varix at the site of bleeding. This finding may be useful in the confirmation of successful ligation of a varix at its bleeding site.

The site and time of expression of MIF in frog development

A ventrally localized melanization-inhibiting factor (MIF) has been suggested to play a role in the expression of dorsal-ventral pigment patterns in amphibia. Here we investigate the onset and localization of MIF appearance in frog development. The expression of MIF was analyzed in the wild-type and gray-eyed mutant (g/g) of Rana japonica by immunoblotting and immunohistochemistry using an anti-MIF neutralizing monoclonal antibody. Western blot analysis revealed that the anti-MIF antibody recognized approximately 51 kDa and approximately 58 kDa bands. The 51 kDa band first appeared at the external gill stage, while 58 kDa band was additionally detected at the hindlimb bud stage. With the use of immunohistochemistry, it was found that the anti-MIF antibody stained the whole epidermis of the embryos at the external gill stage; however, the staining was stronger in lateral and ventral epidermis than in dorsal. Staining with the anti-MIF antibody was observed only in the outer epidermis of the ventral skin, but not in the dorsal skin during and after metamorphosis. The spatial expression of MIF in the wild-type was the same as that in the gray-eyed mutant. The same immunohistochemical result was obtained in the adults of R. nigromaculata. These results suggest that MIF is involved in the formation of the dorsal-ventral pigment pattern.

Response of blood flow to vasopressin in the collateral left gastric vein in patients with portal hypertension

BACKGROUND/AIMS

A problem in pharmacotherapy for bleeding varices in portal hypertension is non-responders. The aim of this study was to elucidate the features of hemodynamic response to vasopressin in the gastroesophageal collateral vein in patients with esophageal varices.

METHODS

Flow velocity in the portal and the collateral left gastric vein was measured with an echo-Doppler flowmeter before and during infusion of vasopressin, 0.2 U/min, in 41 patients with cirrhosis and esophageal varices.

RESULTS

The decrease in flow velocity in the left gastric vein with vasopressin (-29 +/- 25%) was significantly smaller than that in the portal vein (-56 +/- 20%). There was no or only minimal change in flow velocity in the left gastric vein in 39% of the patients, especially in those with large-size varices. In 28 patients examined by portal catheterization, changes in flow velocity in the left gastric vein were correlated with portal pressure, and portal pressure in non-responders was significantly higher than that in responders (non-responders: 363 +/- 49, responders: 312 +/- 41 mmH2O, p < 0.05).

CONCLUSIONS

It was concluded that hepatofugal blood flow in the gastroesophageal collateral is not readily reduced by vasopressin. However, as the study was performed in a stable condition without variceal bleeding, whether these hemodynamic features will apply during acute variceal bleeding in patients who are known to have a poor hemodynamic response to vasopressin remains to be elucidated.

N-CAM and N-cadherin are specifically expressed in xanthophores, but not in the other types of pigment cells, melanophores, and iridiphores

Little is known about cell-cell communication in pigment cells, whereas a number of signalling molecules have been implicated to control their migration, differentiation, and proliferation. We set out to investigate the expression of cell adhesion molecules (CAMs) in the three different types of pigment cells in poikilotherms, Oryzias latipes and Xenopus laevis. In the present experiments, the expression of N-CAM and N-cadherin in the pigment cells in vitro was examined by immunocytochemistry. Melanophores and xanthophores were isolated and cultured from scales or skins, while iridophores were harvested from skins or peritoneum. The results showed that N-CAM and N-cadherin were specifically expressed in xanthophores, but not in melanophores or iridophores in both O. latipes and X. laevis. N-CAM and N-cadherin basically colocalized in the restricted regions of xanthophores, although the N-caderin-expressed region was broader than the N-CAM-expressed region in the same cell. The incidence of N-cadherin expression was higher than that of N-CAM expression. N-CAM and N-cadherin were expressed at the tip or the base of dendrites, or at the edge between dendrites in dendritic xanthophores. N-CAM and N-cadherin usually localized in small and narrow regions of xanthophores. This distribution pattern was essentially similar in xanthophores with round morphology, which exhibited spot, band, or semicircular immunoreactive regions on the peripheral edge of the cells. The difference in the distribution of pigment granules within the cells, culture period, fixatives, or immunofluorescent markers used in the experiments did not alter the immunostaining pattern.

Evidence that MIF plays a role in the development of pigmentation patterns in the frog

A ventrally localized melanization-inhibiting factor (MIF) may play an important role in the expression of dorsal-ventral pigment patterns of amphibians. In efforts to purify this putative MIF, ventral skin conditioned medium (VCM) from Rana forreri was partially fractionated and used to immunize mice. A monoclonal antibody that has the ability to block the activity of MIF was isolated, and an immunoaffinity matrix was prepared by cross-linking the antibody to protein G-Sepharose. The fraction of VCM that bound to the affinity matrix decreased the number of melanized cells in the Xenopus laevis neural tube explant assay, but did not reduce significantly the number of cells that emigrated. The monoclonal antibody was used for immunohistochemical studies on R. pipiens skin. Strong staining with the antibody was observed beneath the basement membrane, in mucous glands, and in the subcutaneous tissue of the ventral skin. A weak staining was also observed in the ground substances of both ventral and dorsal skin. These results confirm that a monoclonal antibody has been secured against at least one of the MIF constituents and that it is useful as a probe in detecting the distribution of MIF in tissues. The results of its use in this study support the hypothesis that MIF plays a role in the expression, development, and maintenance of the dorsal-ventral pigmentation patterns of frogs.

[Ultrasonography in the diagnosis of liver cirrhosis]

Ultrasound is now widely used in the diagnosis of liver diseases. Applications of ultrasound in the diagnosis of liver cirrhosis are reviewed in this paper. Characteristic findings of liver cirrhosis in ultrasound are nodular liver surface, round edge, and hypoechoic nodules in liver parenchyma which represent regenerative nodules of cirrhotic liver. Detection of hypoechoic nodule more than 10 mm is important in the early diagnosis of hepatocellular carcinoma. Detection of splenomegaly, ascites, and portosystemic collaterals is possible by ultrasound. Evaluation of portosystemic collaterals is beneficial in the management of esophagogastric varices and portosystemic encephalopathy. Ultrasound is useful in the non-invasive diagnosis and long-term management of cirrhotic patients.

Fracture of the tibial tray following PCA knee replacement. A report of two cases

We report two cases in which fracture of the tibial metal tray was thought to be due to improper design of the tray and heavy polyethylene wear. The bone beneath the fractured portion of the tray was deficient and had been replaced by granulomatous fibrous tissue including numerous polyethylene wear particles and foreign-body giant cells. Osteolysis occurred as a tissue reaction to these particles.

Cytoskeletal architecture of dermal chromatophores of the freshwater teleost Oryzias latipes

Cytoskeletal construction of dermal chromatophores of Oryzias latipes was studied by immunofluorescence microscopy. A microtubule system was most prominent in melanophores where a large number of microtubules emanated from the center of the cell. Xanthophores had an arrangement basically similar to that of melanophores, though the radial pattern became more irregular in the peripheral region where intersecting wavy microtubules were quite frequent. Oval-shaped leucophores exhibited the least-developed microtubule system, where the limited number of microtubules formed a loose basket-like architecture. Intermediate filaments were ubiquitously present in all types of chromatophores and were found to be vimentin-immunoreactive. Examination of doubly-labeled cells indicated that vimentin filaments had similar distribution patterns with microtubules. Orderly arranged bundles of actin filaments were found only in xanthophores, while in melanophores and xanthophores, actin expression was diffuse without displaying a conspicuous filamentous organization. Colchicine treatment induced depolymerization of microtubules and retraction of dendrites in varying degrees in cells in culture and in situ. Melanophores in culture are very sensitive to the treatment while xanthophores appeared to be more resistant in respect to the maintenance of cell morphology.

Extracellular matrix constituents and pigment cell expression in primary cell culture

Three types of pigment cells were isolated and cultured from larval Rana pipiens, and their attachment, maintenance, and proliferation were examined in the presence of extracellular matrix constituents (ECMs) in primary cell culture. The initial profile of pigment cell types present on day 2 of culture reflects the relative attachment of the cells to the dishes. Changes in the numbers of cells present after day 2 reflects the influence of factors present in the culture media on the maintenance, proliferation, or detachment of each type of pigment cell. Fetal bovine serum (FBS) promoted melanophore expression, but inhibited iridophore expression. FBS had no effect on xanthophores. In contrast, ventral skin conditioned medium (VCM), which contains melanization inhibiting factor, strongly stimulated iridophore expression, while it markedly inhibited melanophore expression. VCM had little effect on xanthophores. Of the ECMs tested, collagen type I had no effect on pigment cells. Fibronectin slightly inhibited melanophore expression, while it moderately stimulated iridophores and xanthophores. The stimulatory effect of fibronectin was not as strong as that of FBS or VCM. Laminin was also tested; however, it did not allow pigment cells to attach to the dishes, at least under the culture conditions utilized. The results of these experiments are discussed in terms of the general mechanisms of pigment pattern formation.

Intrinsic pigment cell stimulating activity in the skin of the leopard frog, Rana pipiens

Consistent with the concept that specific pigment patterns of amphibians might result from the highly localized distribution of stimulators and inhibitors of pigment cell expression in the skin, the spot pattern of the leopard frog, Rana pipiens, was examined through the use of the Xenopus neural tube explant assay system (Fukuzawa and Ide, 1988). Media conditioned with pieces of skin from dorsal black spotted areas promoted melanization of neural crest cells at a significantly higher level than did media conditioned with dorsal interspot skin in the absence of extra tyrosine. All conditioned media contained exceedingly low concentrations of tyrosine. With the addition of supplemental tyrosine, the melanization capacity of conditioned media from the interspot areas was elevated to that of the spotted skin. Control media conditioned with ventral frog skin inhibited melanization, as usual, because of the presumed presence of melanization inhibiting factor (MIF). It is considered that dorsal skin contains a melanization stimulating factor (MSF) which is present in significantly higher levels in spotted skin than in interspot areas and that expression of the particular pigmentary pattern of this leopard frog is regulated by the relative distribution of MIF, MSF, and possibly other intrinsic substances present in the skin.

Stimulation of cultured iridophores by amphibian ventral conditioned medium

That the ventral integument of adult frogs (Rana pipiens) contains factor(s) that stimulate iridophore expression (adhesion, morphologic appearance, proliferation) was demonstrated on iridophores derived from tadpoles of R. pipiens and Pachymedusa dacnicolor, and maintained in primary culture in a growth medium based upon Leibovitz's L-15. Experimental growth medium (VCM) conditioned by a one-hour exposure to pieces of ventral skin of adult R. pipiens induced iridophores to assume a broad and stellate appearance, to form confluent sheets, and to proliferate over a nine-day period. Iridophores in control medium assumed long thin profiles, detached easily, and exhibited no signs of proliferation. Unknown cells containing reflecting platelets and unusual other organelles appeared uniquely in chromatophore cultures of P. dacnicolor in VCM. The intense stimulation of iridophore expression in VCM is consistent with the known inhibitory effect of this medium on melanization and with its purported role in the determination of dorsal/ventral pigment patterns of amphibians. The results are discussed in terms of a prevailing theory about pigment cell origins and development.

Control of melanoblast differentiation in amphibia by alpha-melanocyte stimulating hormone, a serum melanization factor, and a melanization inhibiting factor

A ventrally localized melanization inhibiting factor (MIF) has been suggested to play an important role in the establishment of the dorsal-ventral pigment pattern in Xenopus laevis [Fukuzawa and Ide:Dev. Biol., 129:25-36, 1988]. To examine the possibility that melanoblast expression might be controlled by local putative MIF and melanogenic factors, the effects of alpha-melanocyte stimulating hormone (alpha-MSH), a serum melanization factor (SMF) from X. laevis or Rana pipiens, and MIF on the "outgrowth" and "melanization" of Xenopus neural crest cells were studied. Outgrowth represents the number of neural crest cells emigrating from cultured neural tubes, and melanization concerns the percentage of differentiated melanophores among the emigrated cells. MSH or SMF stimulate both outgrowth and melanization. The melanogenic effect of Xenopus serum in this system is more than twice that of Rana serum. The actions of MSH and Xenopus serum on melanization seem to be different: 1) Stronger melanization is induced by Xenopus serum than by MSH, and the onset of melanization occurs earlier with Xenopus serum; 2) MSH stimulates melanization only in the presence of added tyrosine; and 3) MSH causes young melanophores to assume a prominent state of melanophore dispersion during culture, while Xenopus serum (10%) had only a slight dispersing effect and not until day 3. A fraction of Xenopus serum presumably containing molecules of a smaller molecular weight (MW less than 30 kDa) than that of a pigment promoting factor reported in calf serum [Jerdan et al.: J. Cell Biol., 100:1493-1498, 1985] produces the same remarkable melanogenic effects as does intact serum. While this fraction stimulates outgrowth, another fraction presumably containing larger molecules (MW greater than 100 kDa) does not. MIF contained in Xenopus ventral skin conditioned medium (VCM) inhibits both outgrowth and melanization dose dependently. When VCM is used in combination with MSH, the stimulating effects of MSH on both outgrowth and melanization are completely inhibited. In contrast, the stimulatory effects of Xenopus serum are not completely inhibited when combined with VCM, although melanization is reduced to approximately 40% that of controls. MIF activity was also found to be present in ventral, but not in dorsal, skin conditioned media of R. pipiens when tested in the Xenopus neural crest system.(ABSTRACT TRUNCATED AT 400 WORDS)

A ventrally localized inhibitor of melanization in Xenopus laevis skin

Melanophores normally differentiate in dorsal but not in ventral skin of Xenopus laevis. We have sought factors which might regulate this differentiation pattern, and we have obtained a putative melanization inhibiting factor (MIF) from ventral but not from dorsal skin. Preliminary studies reveal that MIF is destroyed by heat or trypsin treatment, indicating its protein composition, and has a molecular weight in the range of 300 kDa. The effects of MIF on the differentiation of neural crest derivatives to melanophores were examined in vitro in the presence of tyrosine and fetal calf serum (FCS). Tyrosine enhances melanophore differentiation in vitro at concentrations equivalent to those estimated in adult Xenopus blood plasma (20 microM). FCS also stimulates melanization, by way of materials other than the tyrosine contained in FCS. MIF strongly inhibits outgrowth and melanization of neural crest cells from neural tube explants. MIF also inhibits the differentiation of melanoblasts contained in cultured explants of ventral skin. Inhibition of melanization or melanophore differentiation by MIF occurs even in the presence of L-tyrosine and/or FCS. We suggest that MIF plays an important role in the establishment of dorso-ventral pigment patterns in amphibia.

Melanophore differentiation in the periodic albino mutant of Xenopus laevis

That embryonic ventral truck tissue might play a role in expression of the periodic albino mutant phenotype (ap/ap) in Xenopus laevis was suggested from the experiments of MacMillan (1980). In contrast, the present experiments, involving the culture of isolated regions of Xenopus embryos, have demonstrated that both mutant and wild-type melanoblasts differentiate independently of a ventral trunk factor. A similar conclusion, that mutant melanoblasts differentiate independently of a ventral trunk factor, is derived from observations on neural crest cultures, wherein melanization of neural crest cells in both wild-type and mutant cultures occurred in a manner consistent with their genotype.

Further studies on the melanophores of periodic albino mutant of Xenopus laevis

It is still unknown why dermal melanophores disappear during larval development, and why no or very few epidermal melanophores appear during and after metamorphosis, in Xenopus laevis showing periodic albinism (ap). To elucidate these points, we investigated the occurrence of depigmentation in mutant (ap/ap) melanophores during in vitro proliferation and the incidence of melanophore differentiation from mutant melanoblasts in the skin in vitro. During in vitro proliferation of mutant melanophores, ap-type melanosomes decreased in number gradually and instead the number of premelanosomes increased in the cells, which caused depigmentation at the light microscopic level in the culture. Depigmentation was observed only in mutant melanophores, and not in wild-type (+/+) melanophores. These results suggest that autonomous depigmentation of mutant dermal melanophores is the cause of the disappearance of these cells in vivo. Dopa-positive melanoblasts were demonstrated in both wild-type and mutant skins. However, the melanoblasts of metamorphosed mutant froglets did not differentiate in vitro, while those of wild-type froglets did. These results suggest that mutant melanoblasts in the skin of froglets lose the potency to differentiate into melanophores, and that this causes the lack of mutant melanophores in the froglets. The site of action of the ap gene is also discussed.

Further studies on the melanophores of periodic albino mutant of Xenopus laevis

It is still unknown why dermal melanophores disappear during larval development, and why no or very few epidermal melanophores appear during and after metamorphosis, in Xenopus laevis showing periodic albinism (ap). To elucidate these points, we investigated (1) the occurrence of depigmentation in mutant (ap/ap) melanophores during in vitro proliferation and (2) the incidence of melanophore differentiation from mutant melanoblasts in the skin in vitro.

During in vitro proliferation of mutant melanophores, ap-type melanosomes decreased in number gradually and instead the number of premelanosomes increased in the cells, which caused depigmentation at the light microscopic level in the culture. Depigmentation was observed only in mutant melanophores, and not in wild-type (+/+) melanophores. These results suggest that autonomous depigmentation of mutant dermal melanophores is the cause of the disappearance of these cells in vivo.

Dopa-positive melanoblasts were demonstrated in both wild-type and mutant skins. However, the melanoblasts of metamorphosed mutant froglets did not differentiate in vitro, while those of wild-type froglets did. These results suggest that mutant melanoblasts in the skin of froglets lose the potency to differentiate into melanophores, and that this causes the lack of mutant melanophores in the froglets. The site of action of the ap gene is also discussed.

15 N DILUTION METHOD FOR ESTIMATING THE ABSORPTION OF ATMOSPHERIC NO2 BY PLANTS

The ¹⁵ N dilution method was used for the quantitative estimation of nitrogen dioxide (NO₂ ) absorbed by Helianthus annuus and Zea mays during a relatively long period. The relationships between the amount of NO₂ absorbed and the concentration of NO₂ and length of exposure were investigated, in order to ascertain the reliability of this method. The total amount of NO₂ -nitrogen absorbed by the plants over two weeks (from two to four weeks after the sowing) increased with increasing concentrations of NO₂ . The rate of absorption of NO₂ per unit leaf area also increased linearly with increasing concentrations of NO₂ from 0 to 1 μl l^-1 . This means that the diffusive resistances of stomata or mesophyll tissues were not changed by the continuous exposure to NO₂ at 1 μl l^-1 for two weeks. The absorption rate per unit leaf area in H. annuus was about three times greater than that in Z. mays. The total amount of NO₂ -nitrogen absorbed by the plants which were continuously exposed to 0.5 μl l ^-1 NO₂ rose not linearly but exponentially as the exposure time increased from zero to three weeks. This might in part have reflected the growth characteristics of the plants, since dry weight and leaf area increased exponentially during the period of exposure to the pollutant. The absorption rate per unit leaf area remained constant during the first two weeks, but thereafter increased significantly, probably due to the uptake of NO₂ -nitrogen through the air-soil-root pathway. These results demonstrated that the values estimated by the¹⁵ N dilution method were reliable, and this method can be recommended for the quantitative determination of NO₂ absorbed by plants during a long period.

Proliferation in vitro of melanophores from Xenopus laevis

Melanophores of wild-type and periodic albino mutants of Xenopus laevis were successfully cultured in vitro. They proliferated in the presence of alpha-melanocyte-stimulating hormone (alpha-MSH or cyclic adenosine monophosphate (cAMP) at a doubling time of 8-10 days. These proliferating melanophores retained their phenotypes, ability to synthesize melanin, and melanin-dispersing response to MSH stimulation. Neither depigmentation nor selective cell death of periodic albino melanophores was observed for at least 4 months during the cultivation.

Inhibition of platelet aggregation by 1-alkylimidazole derivatives, thromboxane A synthetase inhibitors

1-Alkylimidazole derivatives of various sidechain lengths with various functional groups at the terminal end of the alkylchain inhibited the synthesis of thromboxane A2 from arachidonic acid by rabbit platelets and the conversion of prostaglandin H2 to thromboxane A2 by the microsomes of rabbit platelets. These enzyme inhibitors were anti-aggregatory as examined with rabbit and human platelet-rich plasma under various experimental conditions.

Mode coupling in thin-film chirped gratings

Mode coupling in thin-film chirped gratings is discussed. TE-TM-mode coupling is shown to occur for inclined incident light. The wavelength resolution of a chirped-grating demultiplexer is described in terms of mode coupling.