An infantile case of cytomegalovirus induced idiopathic thrombocytopenic purpura with predominant proliferation of CD10 positive lymphoblast in bone marrow

An infant with cytomegalovirus infection (CMV) developed idiopathic thrombocytopenic purpura (ITP) at 4 months of age. A bone marrow (BM) aspiration showed a remarkable increase of immature megakaryocytes and prominent proliferation of lymphoblasts. Flow cytometric analysis of the bone marrow cells showed that the predominant cells in the lymphocyte cluster were of B-lineage (CD19) with CD10 (common acute lymphoblastic leukemia antigen) positive. Virus study showed a higher titer of CMV antibody. Cytomegalovirus DNA was detected by the polymerase chain reaction (PCR) method in urine, peripheral cells and marrow cells. Low-grade fever, diarrhea and petechiae were accompanied by mild liver dysfunction. Complete remission was made with intravenous high-dose immunoglobulin (IVIg) without progression to overt acute leukemia. The percentage of CD10+/CD19+ lymphocytes in bone marrow also diminished. We postulated that the proliferation of immature lymphocytes and megakaryocytes in bone marrow was caused by maturation arrest that might result from CMV infection.

Cutaneous ciliated cyst: a case report and histochemical, immunohistochemical, and ultrastructural study

A 19-year-old woman with a cutaneous ciliated cyst on her buttock is reported. Histological, histochemical, and electron microscopic studies revealed ciliated cells, mucinous cells showing merocrine secretion, and areas of squamous metaplasia in the cyst wall. This is the first case of cutaneous ciliated cyst that contained non-ciliated mucinous cells as a component.

Suppressive doses of thyroxine do not accelerate age-related bone loss in late postmenopausal women

To examine whether suppressive doses of thyroxine have any adverse effects on bone, we evaluated various bone metabolic markers (lectin-precipitated alkaline phosphatase, osteocalcin, carboxyl-terminal region of type I collagen propeptide, tartrate-resistant alkaline phosphatase, and urinary excretion of hydroxyproline and pyridinium crosslinks), incidence of vertebral deformity, total body and regional (lumbar spine and radius) bone mineral densities (BMDs), and rates of bone loss in 24 late postmenopausal (more than 5 years after menopause) women who were treated with levothyroxine (L-T4) after total thyroidectomy for differentiated carcinoma. Depending on the clinical records, including serum TSH levels measured by immunoradiometric assay, these patients were divided into two groups. One group of patients was given suppressive doses of L-T4 (TSH < 0.1 mU/L, n = 12) and the other group was given nonsuppressive doses of L-T4 (TSH > 0.1 mU/L, n = 12). There was no difference in bone metabolic markers and incidence of vertebral deformity between the groups. In patients with TSH suppression, Z-scores of BMDs calculated from age-matched healthy women (n = 179, aged 55 to 80) were nearly in the zero range of values (0.077 at total body, 0.228 at lumbar spine, and -0.117 at trabecular region of lumbar spine). The rate of bone loss in TSH-suppressed patients (-0.849 +/- 0.605%/year) was not significantly different from that of nonsuppressed patients (-0.669 +/- 0.659). These prospective and cross-sectional data suggest that long-term levothyroxine therapy using suppressive doses has no significant adverse effects on bone.

Does psychological refractoriness depend on the similarity of the required responses?

The purpose of this study was to examine whether the similarity of R1 and R2 is a moderating variable in the psychological refractoriness effect. 10 subjects were required to react and produce the sequence of two homogeneous or heterogeneous peak forces as soon as possible after Stimulus 1 and 2 separated by variable interstimulus intervals. The heterogeneous condition produced a significantly longer RT and premotor time to Stimulus 2 than the control condition for the intervals up to 200 msec. The homogeneous condition, however, produced a significantly shorter RT and premotor time to Stimulus 2 than the control condition when the intervals were from 100 to 1000 msec. These findings suggest that the psychological refractoriness effect depends on the similarity of the required responses. These results were discussed from the view of a limited-capacity mechanism during the response-programming stage.

Effect of clenbuterol on sulfur dioxide-induced acute bronchitis in guinea pigs

When guinea pigs were exposed to sulfur dioxide (SO2) gas (800 ppm, 2 h), they showed hyperresponsiveness to intravenously administered serotonin (5-hydroxytryptamine (5-HT)). This hyperresponsiveness continued for over 24 h after the exposure to the gas. The degeneration, desquamation of epithelium, and edema of the lamina propria of the trachea and bronchi were observed in animals after a 2-h exposure of SO2 histopathologically. These changes seemed to be the early phase of acute bronchitis. Then, we examined the effect of clenbuterol, a selective beta-2 adrenoceptor agonist, on the SO2-induced bronchial hyperresponsiveness in these animals. Orally administered clenbuterol (1-10 micrograms/kg) suppressed the hyperresponsiveness to 5-HT in a dose-dependent manner. These results suggest that clenbuterol might inhibit the hyperresponsiveness that accompanies acute bronchitis and that this agent may be useful for remission of broncho-spasm.

Increased expression of adhesion molecules (CD54, CD29 and CD44) on fibroblasts infected with cytomegalovirus

The expression of ICAM-1 (CD54), beta 1 integrin (CD29), and CD44 on cytomegalovirus (CMV)-infected human embryonic fibroblasts (HEF) was analyzed by flow cytometry. The expression of these adhesion molecules increased significantly on CMV-infected HEF, on days 2 and 5 after inoculation, compared to uninfected HEF. However, the expression of these adhesion molecules decreased on herpes simplex virus (HSV)-1 and varicella-zoster virus (VZV)-infected HEF. Increased expression was not observed on HEF treated either with inactivated CMV or with supernatant fluid of CMV-infected cells. The addition of anti-cytokine (TNF-alpha, IL-1 beta, or IFN-gamma) antibodies had no effect on the increase of these adhesion molecules. This suggests that the increase in CD54, CD29, and CD44 on CMV-infected cells requires active virus replication and was not mediated by a soluble factor released from CMV-infected cells. Changes in adhesion molecules on CMV-infected fibroblasts may contribute to inflammation induced by CMV infection.

Fas antigen and bcl-2 expression on lymphocytes cultured with cytomegalovirus and varicella-zoster virus antigen

Fas antigen and bcl-2 expression on peripheral blood mononuclear cells (PBMC) cultured with cytomegalovirus (CMV) and varicella-zoster virus (VZV) antigen was analyzed by three-color flow cytometry. Expression of Fas antigen increased significantly in CD45RO+ populations of both CD4+ and CD8+ cells obtained from CMV and VZV seropositive donors after culture with CMV and VZV antigen for 6 days. Fas antigen expression did not increase in PBMC cultured with control antigen. In contrast, bcl-2 expression decreased both in CD4+CD45RO+ and CD8+CD45RO+ cells from the same donors. Fas antigen and bcl-2 expression in CD45RA+ populations did not change. Cell viability of cultured cells with CMV and VZV antigen decreased after treatment with anti-Fas antibody and DNA fragments indicating apoptosis were detected in the cell lysate of these cultured cells after treatment with anti-Fas antibody. These data suggest that Fas antigen and bcl-2 protein may interact in regulating the cell death process of activated memory lymphocytes and eliminating lymphocytes activated by viral infection.

A unique role of protein phosphatases in cerebellar long-term depression

In order to investigate phosphorylation-dephosphorylation processes underlying long-term depression (LTD) in cerebellar Purkinje cells, the protein phosphatase inhibitors calyculin A and microcystein-LR were applied to Purkinje cells in guinea pig cerebellar slices either by bath application or by intracellular pressure injection. Under the influence of these protein phosphatase inhibitors, excitatory post-synaptic potentials evoked by stimulation of parallel fibres exhibited marked depression which developed at a rate dependent on the rate of parallel fibre stimulation. The protein phosphatase inhibitors thus substitute climbing fibre signals which induce LTD when combined with parallel fibre signals. Peculiarly, this is opposite to the effect in pyramidal cells, where protein phosphatase inhibitors block LTD.

Cholecystokinin-B/gastrin receptor: a novel molecular probe for human small cell lung cancer

The brain-gut hormones, gastrin and cholecystokinin, have a trophic effect on the gastrointestinal mucosa in vivo and promote the growth of several neoplastic cell lines. In this study, cholecystokinin-B/gastrin receptor has been demonstrated to provide a novel molecular marker for the diagnosis of small cell lung cancer by using biopsy specimens. Physiological expression of the receptor mRNA is detectable in particular areas of the human brain, stomach, and pancreas but not in the lung. The receptor mRNA was detected selectively in all small cell lung cancer (10 cases) with a RT-PCR assay. By contrast, it was detectable in only 1 of 13 squamous cell carcinomas or 21 adenocarcinomas of the lung. Thus, the cholecystokinin-B/gastrin receptor could be an attractive therapeutic target for small cell lung cancer.

Differentiation of the olfactory epithelium during development

Maturation of the olfactory epithelium was studied in the rat. As a developmental index of the olfactory epithelium, quantitation was based on the thickness and the number of cell layers of the epithelium. Mean epithelial thicknesses were 84 microns on embryonic day (E) 19, 94 microns on postnatal day (P) 0, 98 microns on P10 and 57 microns in adult. Average numbers of cell layers were 7 (E19), 8 (P0), 10 (P10) and 7 (adult). Thus the olfactory epithelium progressively increased in thickness between P0-P10, and later decreased in thickness as well as in number of cell layers toward adult. To clarify the number of mature receptor cells sending their axons to the olfactory bulb, the percentages of receptor cell labeling (number of labeled cells/total number of receptor cells) were estimated with an aid of retrograde fluorescent tracer injected into the olfactory bulb. As a result, their percentages were 34% (P1-P3), 50% (P8-P10) and 78% (adult). The ablation experiment of the bulb on P1 pups and adult rats revealed that the percentages of receptor cell degeneration were 31% in neonates (P1) and 76% in adults, confirming the results obtained from the retrograde tracing. Thus the present study shows the substantial increase of mature receptor cells during development and may provide a morphological basis in understanding of the functional maturity of olfaction.

Detection of human cytomegalovirus DNA in immunocompromised children by polymerase chain reaction

BACKGROUND

Cytomegalovirus (CMV) infection is a major complication in immunocompromised patients, such as those with leukemia, acquired immunodeficiency syndrome (AIDS) and allograft recipients. A sensitive and specific diagnostic procedure of CMV infection is required. The polymerase chain reaction (PCR) procedure has been demonstrated to be more sensitive than conventional virus isolation. However, CMV DNA can be detected in patients with latent or asymptomatic infections by PCR because of its extreme sensitivity.

OBJECTIVES

In this study, we used PCR and reverse transcription PCR (RT-PCR) to detect CMV DNA and mRNA in immunocompromised patients and evaluated the value of PCR and RT-PCR for diagnosis of active CMV infection.

STUDY DESIGN

We examined thirty immunocompromised children for CMV DNA using peripheral blood mononuclear cells (PBMC), polymorphonuclear leukocytes (PMNL). urine and throat swabs from October 1991 to March 1992. Eighteen of the patients had acute lymphoblastic leukemia, four had non-Hodgkin's lymphoma, two had Wilms' tumor and six were recipients of an allogeneic bone marrow transplantation. Four patients developed CMV-related clinical symptoms during the observation period: two patients with pneumonia and two patients with hepatitis.

RESULTS

CMV DNA was detected in four patients with clinical symptoms and in five patients without evidence of CMV infection. The incidence of CMV DNA was significantly higher in symptomatic patients than asymptomatic patients. CMV mRNA encoding the late antigen was detected by RT-PCR only in patients with clinical symptoms of CMV infection.

CONCLUSIONS

We concluded that detection of CMV DNA by PCR is of little clinical significance for distinguishing latent form active CMV infection. It is suggested that detection of CMV mRNA by RT-PCR is useful for diagnosis of active CMV infection.

Changes of adhesion molecule (LFA-1, ICAM-1) expression on memory T cells activated with cytomegalovirus antigen

The expression of adhesion molecules (LFA-1, ICAM-1, CD29) on T cells activated with cytomegalovirus (CMV) antigen was investigated by three-color flow cytometry analysis. Peripheral blood mononuclear cells (PBMC) from CMV-seropositive adults were cultured with CMV or control antigen for 6 days. After culture, the expression of LFA-1, ICAM-1, and CD29 on T cells in subpopulations defined as CD45RO+ or CD45RO- was analyzed. The population of cells that expressed LFA-1 at high levels (LFA-1high) among CD4+C-D45RO+ cells increased when cultured with CMV antigen compared to control antigen. The population of cells that expressed LFA-1high cells among CD8+C-D45RO+ cells was down-regulated by culture for 6 days; however, the population of LFA-1high cells among CD8+CD45RO+ cells cultured with CMV antigen was higher than when cultured with control antigen. The population of LFA-1high cells among CD4+CD45RO- and CD8+CD45RO- cells did not change after culture with CMV antigen. The intensity of CD29 and expression of ICAM-1 also increased on both CD4+CD45RO+ and CD8+CD45RO+ cells after culture with the CMV antigen. Up-regulation of adhesion molecules occurred on activated T cells by culture with the CMV antigen. This change was observed mainly on CD45RO+ T memory cells. The results suggested that these changes of adhesion molecules on activated T cells with CMV may contribute to some immune reaction or inflammatory change.

[Interferon treatment for chronic hepatitis C--assessment of 3 regimens in patients received more than 500MU interferon treatment and their effect predictive factors for interferon treatment using multivariate analysis with the logistic regression model]

Chronic hepatitis C patients (n = 115) were treated with interferon (IFN). Total dose employed was more than 500 MU. The response rate was assessed among the three treatment groups: 2W continuous+TIW, 4W continuous+TIW, 8W continuous+TIW. The IFN treatment effect predictive factors were also assessed. Complete response (CR) rate, CR with serum HCV-RNA disappearance rate, responders' histology activity index score changes between before and after treatment, and responders' hepatocytes HCV-RNA disappearance rate did not differ among the three treatment regimens. CR to IFN treatment was dependent on serum HCV-RNA and HCV serotype. Patients of low serum HCV-RNA and serotype II were responsive to IFN treatment.

Spontaneous dissecting aneurysm of the main trunk of the superior mesenteric artery: report of a case

A 47-year-old man with a sudden onset of abdominal pain was diagnosed as having an aneurysm of the main trunk of the superior mesenteric artery (SMA), which induced ischemic colitis of the transverse colon probably because of a transient decrease in the SMA blood flow. The patient was successfully treated by resection of the aneurysm and an end-to-side anastomosis of the SMA to the aorta. A histological examination revealed a spontaneous dissecting aneurysm of the SMA.

Molecular genetic analysis of a female patient with pyruvate dehydrogenase deficiency: detection of a new mutation and differential expression of mutant gene product in cultured cells

A new 18 bp insertion mutation in the gene for the alpha subunit of pyruvate dehydrogenase (E1 alpha) was found in a female patient with congenital lactic acidaemia. Cultured skin fibroblasts and Epstein-Barr virus-transformed lymphoblastoid cells from this patient showed decreased and normal pyruvate dehydrogenase complex (PDHC) activity, respectively. This 18 bp insertion was a de novo mutation, because it was not present in her parents. Although this female patient was heterozygous for the normal and the mutant alleles, 97% of cultured skin fibroblasts expressed the mutant allele, while 100% of cultured lymphoblastoid cells, 94% of peripheral blood lymphocytes and 98% of IL-2-activated T-cells expressed the normal allele. These results suggest that in this patient the X chromosome containing the normal allele was predominantly inactivated in fibroblasts and the X chromosome containing the mutant allele was predominantly inactivated in lymphocytes. The diagnosis of E1 alpha deficiency is usually established by measurement of PDHC activity and the level of immunoreactive proteins. However, these methods are not sufficient to diagnose the disorder in female patients with E1 alpha deficiency due to differential inactivation of the X chromosome. Therefore, it is necessary to develop a new method to firmly establish the diagnosis of E1 alpha deficiency.

Inhibition by wortmannin of M-current in bullfrog sympathetic neurones

1. The actions of wortmannin, an inhibitor of myosin light chain kinase (MLCK), on M-type potassium current of dissociated bullfrog sympathetic neurones have been examined. 2. The amplitude of M-current was measured by whole cell recordings from cells pretreated with wortmannin (0.01-10 microM) or the wortmannin vehicle, dimethylsulphoxide (0.0001-0.1 vol%), for 30 min. Internal (recording pipette) solutions having three different pCa values (6, 7 and 8) were used for the measurements. 3. Irrespective of the pCa, M-current was not detectable when the cells were pretreated with 10 microM wortmannin. Wortmannin, 3 microM, produced 85-95% inhibition of the M-current. Pretreatment with 10-30 nM wortmannin was without effect on M-current. 4. The M-current inhibition by wortmannin at concentrations of 0.1-1 microM depended on the pCa of the internal solution. Inhibition occurred only when the calcium-rich (pCa = 6) internal solution was used. 5. Pre-treatment of the cells with wortmannin (10 microM) did not affect rapidly-inactivating A-type or delayed rectifier-type potassium currents not did it alter inwardly rectifying sodium-potassium current (IH). 6. These observations show that M-current inhibition by wortmannin has two pharmacological profiles. One is calcium-dependent and occurs at lower concentrations (0.1-1 microM), and is attributed to inhibition of MLCK by wortmannin. At higher concentrations (3-10 microM), wortmannin has an additional, calcium-independent action, inhibiting the M-current by an unknown mechanism.

[Clinical and biochemical analysis of 27 patients with myoglobinuria of unknown causes]

We examined the clinical and biochemical features of 27 cases with acute myoglobinuria who had been suspected of having metabolic myopathies. The systematic biochemical studies included the measurements of 13 glycolytic enzymes, mitochondrial respiratory chain enzymes, carnitine palmitoyltransferase (CPT) and 5 enzymes of fatty acid beta-oxidation. Enzyme defects were found in 9 patients using muscle biopsy specimens: phosphorylase deficiency in 3, CPT deficiency in 4 and phosphoglycerate kinase deficiency in 2. One patient was diagnosed as MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) with the histopathological examination and clinical data. A suspicion of beta-oxidation disorder was entertained in some patients of which the activities were about 50% of control means. However, no evidence to substantiate its significance as the enzyme defects was obtained from our data. Sixteen of 17 undiagnosed cases could be divided into two groups according to precipitating factors as follows: one had exercise as the factors and the other had infection. These groups also showed some differences in clinical features. In the infection group, myoglobinuria tended to progress more rapidly and was occasionally followed by acute renal failure. And some cases had additional associated conditions such as mental retardation or epilepsy. On the other hand, the exercise group had only myopathic symptoms. The difference in these clinical features between the two groups suggested that they had the different pathogenic mechanisms respectively.

Clinical application of 18F-FUdR in glioma patients--PET study of nucleic acid metabolism

Positron emission tomography was used to investigate the metabolism of nucleic acids by 18F-fluoro-2'-deoxyuridine (18F-FUdR) in 22 patients with gliomas. Sixteen cases of high grade glioma clearly demonstrated a region of high activity with a differential absorption rate (DAR) of 0.64 +/- 0.34. Six cases of low grade glioma failed to reveal a positive image of the tumor and the DAR in tumor was 0.21 +/- 0.042 (p < 0.01). This PET-18F-FUdR study succeeded in differentiating high and low grade gliomas from the view point of nucleic acid metabolism.

Trabecular texture analysis of CT images in the relationship with spinal fracture

PURPOSE

To evaluate age-related changes in trabecular texture and bone mineral density (BMD) and to determine the usefulness of texture analysis in the assessment of the risk of fracture.

MATERIALS AND METHODS

The vertebral trabecular BMD was measured in 209 women aged 18-86 years. Run length analysis was applied to computed tomographic images obtained with 2-mm section thickness. The width of the trabecula (T-texture) and the width of the intertrabecular space (I-texture) were calculated.

RESULTS

I-texture significantly increased with age in women 50 years of age or older (P < .0001). Women with fracture had significantly lower BMD (P < .0001 at 60-69 years, P < .05 at 70-79 years) and significantly higher I-texture (P < .05 at 60-69 years, P < .01 at 70-79 years). For fracture risk, BMD had the highest sensitivity and I-texture had the highest specificity in women aged 60-69 years; I-texture had the highest sensitivity and specificity in women aged 70-79 years.

CONCLUSION

Texture analysis was helpful in the assessment of fracture risk, especially in elderly women.

Influence of a cold front upon the onset of Meniére's disease in Toyama, Japan

In order to clarify the influence of a cold front (CF) upon the onset of Meniére's disease (MD), major CFs were defined by meteorological observations, and the influence of CFs on MD was evaluated by using the time n method. From our preliminary study it was seen that the onset of MD had its highest incidence exactly on days where a CF passed by. Out of the patients with MD, sudden deafness (SD) and Bell's palsy (BP) who visited our neurotological clinic of the Toyama Medical and Pharmaceutical University from 1987 to 1992, 67 MD patients, 70 SD patients and 70 BP patients could clearly define the date of the onset of their disease, and were therefore selected for this epidemiological study. Thirty-six our of the 67 MD patients had the first attack on the day when a CF passed by or on the next day. The results obtained from these studies were as follows. i) The onset of MD was influenced by the passing of a CF, and this influence was more specific in MD than in SD or BP. ii) In the 36 CF influence MD patients, the majority were over the forty years, and their hearing level was worse than that of the other 31 MD patients during the observation periods.

Isolation of methicillin-resistant staphylococci in the dental operatory

The state of contamination by methicillin-resistant Staphylococci, including methicillin-resistant Staphylococcus aureus (MRSA) at the conservative dentistry section of the School of Dentistry, Aichi-Gakuin University, was investigated. Methicillin-resistant coagulase-negative Staphylococci (MRCNS) were detected in 8 (20.5%) of 39 dental staff (28 dentists, 8 dental hygienists, and 3 dental assistants), but MRSA was not detected. MRCNS was also detected in locations such as the dental chair, dental bracket, dental cabinet, and floor, as well as in airborne samples. The presence of the same strain in both the oral cavity of staff persons and the dental chair/floor locations was determined by biochemical properties, antibiotic sensitivity tests, and electrophoretic patterns.

Size and position invariance of neuronal responses in monkey inferotemporal cortex

1. Object vision is largely invariant to changes of retinal images of objects in size and position. To reveal neuronal mechanisms of this invariance, we recorded activities from single cells in the anterior part of the inferotemporal cortex (anterior IT), determined the critical features for the activation of individual cells, and examined the effects of changes in stimulus size and position on the responses. 2. Twenty-one percent of the anterior IT cells studied here responded to ranges of size > 4 octaves, whereas 43% responded to size ranges < 2 octaves. The optimal stimulus size, measured by the distance between the outer edges along the longest axis of the stimulus, ranged from 1.7 to 30 degrees. 3. The selectivity for shape was mostly preserved over the entire range of effective size and over the receptive field, whereas some subtle but statistically significant changes were observed in one half of the cells studied here. 4. The size-specific responses observed in 43% of the cells are consistent with recent psychophysical data that suggest that images of objects are stored in a size-specific manner in the long-term memory. Both size-dependent and -independent processing of images may occur in anterior IT.

[Comparative study on frequency-doubled Nd: YAG laser, krypton laser and diode laser photocoagulation for diabetic maculopathy]

Twenty six eyes of thirteen patients with diabetic maculopathy (Fukuda's classification AI, AII, BI) were treated with frequency-doubled Nd:YAG laser (6 eyes) or krypton laser (7 eyes) in one eye and diode laser (13 eyes) in the other eye. Group A was treated with frequency-doubled Nd: YAG laser and diode laser, and group B was treated with krypton laser and diode laser. The visual acuity, visual field (Octopus program 31) and fundus were examined at one month, 3 months, and 6 months after photocoagulation. Visual acuity was stable in all eyes. The central 30 degree visual sensitivity decreased more after diode laser treatment than after that of the other lasers. Krypton laser photocoagulation maintained the better visual function and was easy to use followed by frequency-doubled Nd: YAG laser. Because the appearance immediately after diode laser lesion was weaker than one hour after coagulation, it was difficult to get the proper power setting.

Cloning of tropomodulin cDNA and localization of gene transcripts during mouse embryogenesis

Tropomodulin (Tmod) is a tropomyosin-binding protein involved in the structuring of actin filaments. This report describes Tmod expression in distinct patterns during embryonic development in a wider variety of adult and embryonic vertebrate tissues than previously reported. Identical Tmod cDNAs were cloned from mouse brain, skeletal muscle, heart, and hematopoeitic cells. Genomic blotting demonstrates that Tmod is encoded by a single gene, which has a 1077-bp open reading frame that is highly homologous to that of the human erythrocyte. The spatial and temporal expression of the Tmod gene was examined during mouse embryogenesis using in situ hybridization. Tmod mRNA is present by 9.5 days postcoitum (p.c.) in the developing rostral somites, coincident with expression of contractile protein genes in myotomes, suggesting that Tmod may play an important role in sarcomeric thin filament organization in skeletal muscle. While the expression of Tmod mRNA in cardiac muscle is earlier than that in skeletal muscle, its appearance in the heart also coincides with the expression of genes for thin filament proteins and correlates with initial myocardial contractions at 8.0 days p.c. Tmod mRNA is not detected in developing smooth muscle of the gut, but Tmod mRNA is expressed in hematopoeitic cells in yolk sac and developing liver. The sensory ganglia and epithelia of the inner ear express Tmod mRNA as do other sensory neurons such as those in the olfactory epithelium. Expression levels in the brain are much lower prenatally than postnatally. These findings show that Tmod expression in many cell types is developmentally regulated, suggesting that the interaction of actin filaments with this tropomyosin binding protein is an important process in tissue and cell differentiation.