Development and physiological degradation of tooth buds and development of rudiment of baleen plate in southern minke whale, Balaenoptera acutorostrata

The development and degradation of temporary tooth buds and the development of rudiment of baleen plate were observed by gross-anatomical and histological examinations in twenty-four fetuses of the southern minke whale, Balaenoptera acutorostrata. The primary patterns of development of tooth buds were similar to those of deciduous tooth buds in the terrestrial species. Degradation of tooth buds was observed in the fetuses more than 615 mm body length (BL) and might proceed throughout the dental surface of the tooth buds. That degradation pattern was a little different from that of deciduous tooth buds in terrestrial species, which has a limited degradation area at the root of the tooth buds. In the fetuses with 135 and 153 mm BL, the upper jaw had a larger number of tooth buds than the lower jaw, although the number of buds varied in different individuals. Formation of rudiment of baleen plate was observed with degraded tooth buds in the fetus of 903 mm BL and it may be induced by the degradation of tooth buds.

A compartmentalized bias for T-cell receptor V beta usage in summer-type hypersensitivity pneumonitis

Several monoclonal antibodies specific to the human T-cell receptor (TCR) variable (V) region were used to examine whether T-cell oligoclonality plays a key role in the development of the T-cell-mediated lung disease, summer-type hypersensitivity pneumonitis (SHP). The usage of TCR V-regions was examined using bronchoalveolar lavage (BAL) and matched peripheral blood lymphocytes (PBL) in patients with SHP. In 18 SHP patients, the majority of lymphocytes in both BAL and PBL was CD3+ cells (94.2 vs. 63.9%, respectively), which was similar to that in normals (n = 7). Of CD3+ lymphocytes in a SHP patient, the percentage of CD4+ cells in BAL was reduced compared to those in paired PBL, whereas the percentage of CD8+ cells was significantly elevated. In contrast, the percentage of CD4+ cells was much higher than that of CD8+ cells in both BAL and PBL of normal subjects. While a majority of CD3+ T cells expressed TCR alpha/beta+ in BAL and PBL from both SHP patients and normal controls, a marked increase of the expression of TCR gamma/delta+ was observed in PBL in 4 out of 18 SHP patients. A markedly increased prevalence (> 3 SD) of specific TCR alpha/beta+ V-region families in BAL was detected in 5 of 18 patients with SHP as compared to normal controls, whereas no specific increase was found in PBL. Increased V beta 8 was detected in 3 cases; V beta 6 was observed in 1 patient, and V beta 5 in another patient.(ABSTRACT TRUNCATED AT 250 WORDS)

[Two case reports of retroperitoneal leiomyosarcoma]

Two cases of retroperitoneal leiomyosarcoma are presented. The first case was in a 67-year-old female, whose chief complaint of right upper abdominal mass and dull pain. The tumor, 13 x 12 x 8 cm in size, developing in the retroperitoneum was removed with the right kidney and vena cava. The pathological diagnosis was reported as leiomyosarcoma. The second case was in a 62-year-old male, whose complaint was left abdominal swelling, also with general fatigue. A large tumor mass, invading over all of the left flank organs, was palpable by physical examinations, from which the mass was far beyond surgical approach. Needle biopsy revealed the pathological finding of leiomyosarcoma. One month later, the patient died of cachexia. Review of the literatures for the retroperitoneal leiomyosarcoma, revealed only a few cases; 1.7%, of all leiomyosarcoma to date.

Interventional trial for colorectal cancer prevention in Osaka: an introduction to the protocol

We established a protocol for an interventional randomized controlled trial for prevention of colorectal cancer by attaching special importance to feasibility. The subjects were patients with multiple colorectal tumors. Two regimens were formulated for prevention of colorectal cancer. One was dietary guidance alone (Regimen I), and the other was dietary guidance plus eating wheat bran biscuits (Regimen II). The main end points of the trial were examinations for recurrence of colorectal tumors after 2 and 4 years. The target number of patients was 200 in total, i.e. 100 for each group. During the 18 months from the beginning of recruiting of subjects (up to November 1994), 28 (97%) of the 29 patients recruited for Regimen I and 32 (97%) of the 33 patients recruited for Regimen II agreed to participate in the trial. The trial progressing well.

Primary sclerosing cholangitis with marked eosinophilic infiltration in the liver

A 16-year-old boy was diagnosed as having primary sclerosing cholangitis (PSC), based on retrograde cholangiography showing mixed features of narrowing and dilatation of the common hepatic and intrahepatic bile ducts. However, periductal fibrosis was not observed in the needle biopsy liver specimen. The liver biopsy specimen obtained 11 years previously, at the onset of the disease had disclosed a marked infiltration of eosinophils in the portal tract with eosinophilic catinonic protein immunostaining, with marked eosinophilia (54%) being noted. In Japanese reports, eosinophilia of more than 7% was reported in 13 of 32 (40.6%) PSC patients. However, the early stage of PSC, with marked eosinophilia and eosinophilic infiltration in the liver, such as in the present case, has rarely been reported. The findings in this case suggest that eosinocytes are related to the pathogenesis of PSC.

[A case of huge renal hamartoma]

We experienced a case of renal hamartoma of mesothelial origin. A 21-year-old was referred to our hospital with a complaint of growing abdominal mass. The diagnosis of right renal tumor was confirmed based on the radiographic examinations. The renal tumor was removed by partial nephrectomy. Histological examination revealed the tumor composed of fibroblasts, smooth muscle and a few tubule-like epithelial tissue. Thus, this case was classified as renal hamartoma of mesothelial origin.

[Repair of mitral valve prolapse by resection and sliding plasty]

There have been many techniques applied to the repair of mitral valve prolapse, and the method used in a particular case is usually selected according to the position and extent of the lesion. To simplify and standardize the technique of mitral valve repair, we have adopted the resection, sliding plasty and ring annuloplasty methods since December 1992. Of 10 consecutive surgical cases, 2 involved prolapse of the anterior leaflet, 1 the posteromedial commissural, and 7 the posterior leaflet. One patient with posterior leaflet prolapse required valve replacement due to dehiscence of the plastied site on the 3rd postoperative day, and one died because of sepsis. However, the remaining patients were doing well without mitral regurgitation at a mean of 20 months (range: 8-32) after the operation. The advantages of these techniques include easy adjustment of the height of the leaflet and a good chance of long-term durability, since the affected lesion is resected.

Gamma delta T cells play an important role in hsp65 expression and in acquiring protective immune responses against infection with Toxoplasma gondii

Previously, we reported that the expression of hsp65 within and on host macrophages correlates closely with protection against infection with Toxoplasma gondii in mice. Herein, we propose that gamma delta T cells play a crucial role in the induction of hsp65 and also in the protective immune response to T. gondii. Intraperitoneal inoculation with this protozoan resulted in hsp65 being expressed on and in host peritoneal macrophages and resulted in an increase of T cells bearing the gamma delta receptor with Thy-1+ and Thy-1- phenotypes in the peritoneal cavity and spleen. When mice were depleted of gamma delta T cells by the administration of a mAb, hsp65 expression was markedly decreased. In contrast, the expression of this protein was rather enhanced and gamma delta T cells were prominently expanded in mice depleted of alpha beta T cells. The protection in mice treated with the mAb paralleled the magnitude of hsp65 expression. Mice depleted of gamma delta T cells died most frequently in the early stages of infection, whereas most of those depleted of alpha beta T cells survived the early stages of lethal infection with T. gondii. However, the latter group of mice did not definitely control the T. gondii infection in its late stages. IFN-gamma was not essential for either the expression of hsp65 or the resistance induced by gamma delta T cells, as demonstrated in mice treated with mAb to murine IFN-gamma. These findings indicated that gamma delta T cells having both the Thy-1+ and Thy-1- phenotypes contribute to hsp65 expression within and on macrophages in an IFN-gamma-independent manner. This, in turn, plays a role in the development of protective immunity during the early stage of this parasitic infection.

The use of grommets for flexible hinge toe implants. A case report

The postmortem examination of bilateral first metatarsophalangeal flexible hinge toe implants in a 66-year-old woman with rheumatoid arthritis is reported. The prosthesis had been inserted with grommets in 1 joint and without grommets in the other 2.5 years before her death. The implants were removed, and the bone/implant interfaces were examined microscopically by hematoxylin eosin stains and an electron probe microanalyzer. Surfaces of the implants were examined by scanning electron microscopy. Silicone particles within the fibrous tissue at the bone/implant interface, and a tear and significant scuffing of the implant surface, were detected in the joint without grommets. Such changes were not detected in the joint with grommets. These findings suggest that grommets may improve implant durability and preventing silicone synovitis.

[Experience in seven cases of laparoscopic adrenalectomy]

We have experienced 7 cases of laparoscopic adrenalectomy for adrenal tumors during the past two years since our department opened in July, 1992. In four cases, the tumors were clinically diagnosed preoperatively as primary aldosteronism and in the other three cases as endocrine-inactive tumors. Four tumors were found on the left adrenal and three on the right. Five tumors were successfully resected with laparoscopic surgery, but in the other two cases it was immediately followed by open surgery because of an uncontrollable hemorrhage. Laparoscopically unresected tumors existed, one on the right and the other on the left adrenal. The average operation time for laparoscopic adrenalectomy was twice as much as that of open adrenalectomy previously performed. However, the operation time has been recently shortened to be less than 200 minutes. Hemorrhage during the operation was rather less in laparoscopic surgeries if they were successfully done. Postoperative recovery was found to be much faster and the hospital stay was shortened by more than 10 days in patients operated with a laparoscope. These findings indicate that laparoscopic adrenalectomy is a minimally invasive operation that can increase the QOL's of the patient. Although we consider that this operation may propagate as a method for adrenalectomy in future, it must be performed with a careful backup system in the case of an emergency.

Gamma delta T cells play an important role in hsp65 expression and in acquiring protective immune responses against infection with Toxoplasma gondii

Previously, we reported that the expression of hsp65 within and on host macrophages correlates closely with protection against infection with Toxoplasma gondii in mice. Herein, we propose that gamma delta T cells play a crucial role in the induction of hsp65 and also in the protective immune response to T. gondii. Intraperitoneal inoculation with this protozoan resulted in hsp65 being expressed on and in host peritoneal macrophages and resulted in an increase of T cells bearing the gamma delta receptor with Thy-1+ and Thy-1- phenotypes in the peritoneal cavity and spleen. When mice were depleted of gamma delta T cells by the administration of a mAb, hsp65 expression was markedly decreased. In contrast, the expression of this protein was rather enhanced and gamma delta T cells were prominently expanded in mice depleted of alpha beta T cells. The protection in mice treated with the mAb paralleled the magnitude of hsp65 expression. Mice depleted of gamma delta T cells died most frequently in the early stages of infection, whereas most of those depleted of alpha beta T cells survived the early stages of lethal infection with T. gondii. However, the latter group of mice did not definitely control the T. gondii infection in its late stages. IFN-gamma was not essential for either the expression of hsp65 or the resistance induced by gamma delta T cells, as demonstrated in mice treated with mAb to murine IFN-gamma. These findings indicated that gamma delta T cells having both the Thy-1+ and Thy-1- phenotypes contribute to hsp65 expression within and on macrophages in an IFN-gamma-independent manner. This, in turn, plays a role in the development of protective immunity during the early stage of this parasitic infection.

Modulation by bovine angiogenin of tubular morphogenesis and expression of plasminogen activator in bovine endothelial cells

Angiogenin is a potent angiogenic molecule in the chick chorioallantoic membrane assay and rabbit corneal assay. However, no angiogenic activity has been reported in in vitro system. In this study, we isolated and purified angiogenin from bovine milk, and the biological effect of the bovine angiogenin on bovine endothelial cells was examined in in vitro angiogenesis models. Bovine angiogenin significantly stimulated both cell migration and formation of tube-like structures in the collagen gel by bovine aortic endothelial cells. Angiogenin at 10-100 ng/ml stimulated about 2-fold higher the tube formation when basic fibroblast growth factor (bFGF) at 10 ng/ml stimulated about 3-fold over the control. Tubular morphogenesis stimulated by bFGF or angiogenin was almost completely blocked in the presence of aprotinin, an inhibitor of serine proteases. Angiogenin up-regulated both mRNA level and activity of urokinase type plasminogen activator, a key mediator of angiogenesis. Moreover, both bFGF and bovine angiogenin induced a marked increase of c-fos mRNA level at 30 min after stimulation. These novel effects of bovine angiogenin are to be discussed in relation to its structure specificity.

Synthesis and biological evaluation of a series of new parenteral optically active 3-[[(N-alkylpyridinium-4'-yl)thio]methyl]-2-oxaisocephems

The preparation and biological evaluation of a series of 7-[2-(2-aminothiazol-4-yl)-2-(Z)-[(cyclopentyloxy)imino]acetamido] optically active 2-oxaisocephems, substituted at the 3-position with [(N-alkylpyridinium-4'-yl)thio]methyl groups, are described. The resulting family of parenteral compounds displays a broad spectrum of in vitro antibacterial activity. These compounds exhibit increased activity against Gram-positive organisms including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis which are resistant to most cephalosporins with a similar level of Gram-negative activity to that of the third-generation antibiotics. In vivo efficacy of new antibacterial agents in this investigation is excellent against both Gram-positive and Gram-negative bacteria as compared with reference compounds. The in vitro and in vivo antimicrobial activity and the structure-activity relationships are presented.

Liver with hypoechoic nodular pattern as a risk factor for hepatocellular carcinoma

BACKGROUND/AIMS

Ultrasonography should be used for screening of hepatocellular carcinoma, but there are few reports on the relationship between liver ultrasonographic findings and the development of hepatocellular carcinoma (HCC). Using prospective follow-up studies, we examined the role of liver with a hypoechoic nodular pattern as a high-risk factor in HCC.

METHODS

The study was performed by follow-up on 593 patients with chronic liver disease recorded at our hospital. The ultrasonographic pattern of the liver parenchyma was classified either as a small or large hypoechoic nodular pattern or as a nonnodular pattern. Patients were followed up from the time of initial ultrasonographic examination (1985-1987) until January 1, 1991.

RESULTS

During the follow-up period (average, 4.2 years, range, 0.3-6.0 years), 62 patients were found to have HCC (12%). Patients whose livers showed small or large hypoechoic nodular pattern had a significantly higher risk of HCC than did patients whose livers showed a nonnodular pattern (rate ratios were 14.0 and 20.0, respectively, adjusted for age, sex, hepatitis virus markers, ICG R15, alpha-fetoprotein concentration, and ultrasonographic pattern of the liver).

CONCLUSIONS

Liver showing a hypoechoic nodular pattern is a major risk factor in HCC.

Interleukin 7 is produced by human intestinal epithelial cells and regulates the proliferation of intestinal mucosal lymphocytes

The interaction of mucosal lymphocytes and intestinal epithelial cells is thought to be important in regulating immune response in the intestinal mucosa, but conclusive evidence is limited. Here we demonstrate the expression of IL-7 mRNA in human intestinal mucosa by combined reverse transcription PCR and Southern blot hybridization. Immunohistochemistry and in situ hybridization confirm the presence of IL-7 in intestinal epithelial cells, especially in epithelial goblet cells. Moreover, IL-7 receptor expression in mucosal lymphocytes is demonstrated by immunohistochemistry and in situ hybridization, as well as by Southern blot and flow cytometric analysis of freshly isolated lamina propria lymphocytes. In contrast, IL-7 receptor could not be detected in the cell surface of freshly isolated PBLs. The functional activity of IL-7 receptor is demonstrated by the utility of recombinant IL-7 to stimulate the growth of lamina propria lymphocytes, and conversely inhibit CD3-dependent proliferation of these cells. In contrast, IL-7 caused no significant increase in DNA synthesis and cell numbers when added to PBLs. These findings suggest that human intestinal epithelial cells and epithelial goblet cells produce IL-7, and locally produced IL-7 may serve as a potent regulatory factor for intestinal mucosal lymphocytes.

Formation of oligosaccharides from lactose by Bacillus circulans beta-galactosidase

Eleven oligosaccharides formed by a transglycosylation reaction during lactose hydrolysis with Bacillus circulans beta-galactosidase were purified by gel permeation chromatography, charcoal chromatography, and HPLC. From the results of methylation analysis, and MS and NMR studies, it was concluded that these oligosaccharides were beta-D-Galp-(1-->3)-D-Glc, beta-D-Galp-(1-->6)-D-Glc, beta-D-Galp-(1-->2)-D-Glc, beta-D-Galp-(1-->4)-beta-D-Galp-(1-->4)-D-Glc, beta-D-Galp-(1-->6)-[beta-D-Galp-(1-->2)]-D-Glc, beta-D-Galp-(1-->6)-[beta-D-Galp-(1-->4)]-D-Glc, beta-D-Galp-(1-->4)-beta-D-Galp-(1-->3)-D-Glc, beta-D-Galp-(1-->4)-beta-D-Galp-(1-->2)-D-Glc, beta-D-Galp-(1-->4)-[beta-D-Galp-(1-->2)]-D-Glc, beta-D-Galp-(1-->4)-beta-D-Galp-(1-->6)-D-Glc, beta-D-Galp-(1-->6)[beta-D-Galp-(1-->3)]-D-Glc. The last five are newly observed oligosaccharides. The results of a use test (in vitro) by human intestinal bacteria showed that the oligosaccharides containing lactose units were predominantly used by human intestinal bifidobacteria.

Clinical evaluation of CYFRA 21-1 in malignant pleural fluids

The diagnostic value of the novel tumor marker CYFRA 21-1 in malignant pleural fluid was assessed in comparison to carcinoembryonic antigen (CEA). CYFRA 21-1 and CEA were measured in pleural fluid obtained from patients with 108 malignant and benign diseases. The levels of pleural fluid CYFRA 21-1 in malignant diseases (median: 84.5 ng/ml) were statistically higher than those in benign diseases (median: 13.9 ng/ml; p < 0.01). The CYFRA 21-1 test was able to discriminate significantly between squamous cell lung cancer and pneumonia (p < 0.01), while pleural fluid CEA levels could not. Receiver operating characteristic (ROC) curve analysis showed that the CYFRA 21-1 test has an advantage over CEA because of its higher specificity. These results indicate that measurement of CYFRA 21-1 in pleural fluid is a new tool, in addition to cytologic examination, to discriminate between malignant and benign diseases.

Increase of intracellular free [Ca2+] in single human motile spermatozoa treated with human follicular fluid

The intracellular free [Ca2+] concentration ([Ca2+]i) in individual human sperm was measured using a fluorescent Ca2+ indicator. In 18 of 23 motile sperm (78.3%), [Ca2+]i increased significantly and promptly after addition of 20% human follicular fluid (hFF), but in the others it did not increase. The mean resting [Ca2+]i level of sperm in which [Ca2+]i increased after addition of 20% hFF (the influx group) was significantly lower than those in which it did not increase (112.8 +/- 40.1 nM vs. 156.9 +/- 13.5 nM, p < .05). After addition of 20% hFF, the mean [Ca2+]i in the influx group reached a peak value of 210.7 +/- 24.7 nM within 30 s and then decreased slowly; the mean [Ca2+]i values 1, 5, 10, and 15 min after addition of 20% hFF were 179.3 +/- 31.4, 174.3 +/- 30.2, 172.5 +/- 27.8, and 175.1 +/- 27.2 nM, and all values were significantly higher than the resting level (p < .01). The frequency distribution of [Ca2+]i after addition of 20% hFF was shifted toward higher concentrations (p < .01). However, the addition of 20% hFF did not increase the percentage of live acrosome reaction (before 3.8 +/- 0.9% vs. after 2.9 +/- 0.5%, respectively). Thus, hFF increased [Ca2+]i in about 80% of the motile sperm. Relatively high [Ca2+]i levels persisted for at least 10-15 min after its addition. However, hFF did not trigger a rapid response in acrosome reaction.

[Horizontal gaze palsy due to lesion of the abducens nucleus detected with magnetic resonance imaging]

A case of unilateral horizontal gaze palsy is reported. The lesion of the abducens nucleus was clearly detected with magnetic resonance imaging. In the early stage, the adduction of the right eye and abduction of the left eye were completely limited and the vestibulo-ocular reflex was also impaired. However, during the recovery stage, the improvement of limitation of abduction was delayed compared with that of adduction. We suggest that this phenomenon is useful as a differential diagnosis between lesions of the abducens nucleus and of the paramedian pontine reticular formation.

Stage specificity of Ara-C induced carpal and tarsal bone anomalies in mice

Pregnant mice were injected intraperitoneally with a single dose of 5 mg/kg of cytosine arabinoside (Ara-C) on different gestational days (dg 9-12). On the 15th postnatal day, skeletal anomalies of the paws were examined, and associations between carpal and tarsal bone anomalies and digit anomalies were assessed. The types of carpal and tarsal bone anomalies differed according to the time of exposure to Ara-C during pregnancy. It was also found that the "critical period" for the carpal and tarsal bones is wider than that of the digits. The occurrence of anomalies of phalangeal and metacarpal/metatarsal bones was always associated with carpal or tarsal bone anomalies, although some carpal and tarsal bone anomalies occurred alone. It may be that the Ara-C threshold is considerably lower in the carpal and tarsal bones than in the digits.

Conversion of amylase-secreting rat pancreatic AR42J cells to neuronlike cells by activin A

When AR42J cells, an amylase-secreting pancreatic exocrine cell line, were treated with activin A, cells extended neuritelike processes, and, concomitantly, amylase-containing vesicles disappeared. Immunofluorescence and immunoelectron microscopy revealed that these processes had neurite-specific cytoskeletal architectures: neurofilaments and microtubule bundles with cross-bridges of microtubule-associated protein 2. In addition to such morphological changes, activin-treated cells exhibited a marked increase in cytoplasmic free calcium concentration in response to depolarizing concentration of potassium. Moreover, activin-treated AR42J cells expressed mRNA for alpha 1 subunit of the neuroendocrine/beta cell-type voltage-dependent calcium channel. In naive AR42J cells, a sulfonylurea compound, tolbutamide, did not affect free calcium concentration, while it induced a marked elevation of free calcium in activin-treated cells. Single channel recording of the membrane patch revealed the existence of ATP-sensitive potassium channel in activin-treated cells. These results indicate that activin A converts amylase-secreting AR42J cells to neuronlike cells. Given that pancreatic endocrine cells possess neuronlike properties and express ATP-sensitive potassium channel as well as neuroendocrine/beta cell-type voltage-dependent calcium channel, activin treatment of AR42J cells may provide an in vitro model system to study the conversion of pancreatic exocrine cells to endocrine cells in islets.

EDA-containing fibronectin is synthesized from rheumatoid synovial fibroblast-like cells

OBJECTIVE

To identify the cells that synthesize EDA-containing fibronectin (FN) and examine the role of EDA+FN in the pathogenesis of rheumatoid joint lesions.

METHODS

Localization of EDA+FN and c-Fos protein in rheumatoid joints was studied immunohistochemically by utilizing antibodies for EDA+FN and c-Fos. Expression of EDA+FN was studied by immunoelectron microscopy and in situ hybridization. The amount of EDA+FN was measured by enzyme-linked immunosorbent assay.

RESULTS

EDA+FN was specifically localized in the synovial lining layer of synovium with active rheumatoid arthritis (RA) (n = 17), but not in that with osteoarthritis (n = 4) or with inactive fibrous RA (n = 2). EDA+FN messenger RNA was localized in the synovial lining layer. EDA+FN was immunoelectron microscopically localized in the synovial lining fibroblast-like (type B) cells. EDA+FN was also detected at the cartilage-pannus junction and on the surface of RA cartilage. Double staining showed that EDA+FN colocalized with c-Fos protein in the rheumatoid synovial lining layer. Quantification of EDA+FN showed that it was highly concentrated in rheumatoid synovial fluids.

CONCLUSION

EDA+FN is synthesized by the synovial lining fibroblast-like (type B) cells in situ in rheumatoid synovium, and appears to be expressed in association with activated or transformed states of synovium.

Primary biliary cirrhosis (PBC)-CREST (calcinosis, Raynaud's phenomenon, esophageal dysfunction, sclerodactyly and telangiectasia) overlap syndrome complicated by Sjögren's syndrome and arthritis

A 36-year-old woman with primary biliary cirrhosis (PBC)-CREST (calcinosis, Raynaud's phenomenon, esophageal dysfunction, sclerodactyly and telangiectasia) overlap syndrome complicated by Sjögren's syndrome and arthritis is reported. She had suffered from Raynaud's phenomenon, sclerodactyly, morning stiffness, arthralgia and sicca symptoms since 34 years of age. She exhibited an increased level of alkaline phosphatase and hyperglobulinemia at 2.8 g/dl without any symptoms, and histological findings from the biopsy specimen of the liver were consistent with those of PBC. Her human leukocyte antigen (HLA) typing was DR8 homozygous.

Occurrence of fasciculated microtubules at nodes of Ranvier in rat spinal roots

Fascicles of microtubules, previously considered to be unique to the initial segments of myelinated axons, were found at nodes of Ranvier of sensory and motor axons in rat spinal roots, though their occurrence was limited to the proximal portion of the axons. No fasciculated microtubules were noticed in the internodes of myelinated axons or in unmyelinated axons. In transverse sections, microtubules in fascicles were characteristically cross-linked by short filamentous strands at a centre-to-centre distance of 36-40 nm. In sensory axons, the density of fasciculated microtubules at the node of Ranvier was 45-48% at the level of the dorsal root ganglion and decreased progressively as thin sections were made more distal to the ganglion in both directions. In motor axons, microtubule-fascicles involved about 24% of the microtubules in the ventral rootlets, but they were rarely seen in distal portions of the ventral roots. No fasciculation of microtubules was discerned in the sciatic and saphenous nerves. These findings suggest that cross-linking protein(s) for fasciculation, which are synthesized in the perikaryon and primarily used for the initial segment, may be further transported to fasciculate microtubules at some proximal nodes of Ranvier.