Adnexal torsion: MR imaging findings of viable ovary

We report a case of torsed ovarian cystic tumor, in which contrast-enhanced high-resolution MR images accurately contributed to the diagnosis of torsion despite the lack of symptoms and to the preoperative evaluation of viability of the edematous ovary. Accurate preoperative assessment by MR images and prompt conservative surgical approach succeeded in salvaging the involved ovary.

Novel intravascular macromolecular MRI contrast agent with generation-4 polyamidoamine dendrimer core: accelerated renal excretion with coinjection of lysine

One of the major limitations to macromolecular MRI contrast agents (MRI-CAs) is their slow clearance and associated decreased excretion of gadolinium (Gd(III)). The effect of coinjecting lysine to accelerate renal excretion of a macromolecular MRI-CA (generation-4 PAMAM dendrimer (G4D-(1B4M-Gd)64)) was investigated. The biodistribution and urine and fecal excretion in athymic mice was evaluated with and without lysine coinjection. 3D-dynamic-micro-MRI with G4D-(1B4M-Gd)64 was obtained with and without lysine coinjection, and the serial signal intensity (SI) change in the blood and organs was evaluated. When lysine was coinjected, urinary excretion of G4D-(1B4M-Gd)64 increased 5.4-fold compared to that without lysine, resulting in decreased renal accumulation of G4D-(1B4M-Gd)64 from 150% to 40% injected dose per gram (P < 0.001). On dynamic MRI with G4D-(1B4M-Gd)64, when lysine was coinjected, the kidney-to-blood SI ratio was significantly lower than that obtained without lysine (P < 0.001). When lysine was coinjected, the G4D-(1B4M-Gd)64 was excreted from the kidney intact.

3D MR angiography of intratumoral vasculature using a novel macromolecular MR contrast agent

Noninvasive methods to visualize blood flow in the intratumoral vasculature have not previously been studied. In the present study, the use of a novel intravascular MR contrast agent with a generation-6 polyamidoamine dendrimer core (G6-(1B4M-Gd)192; MW: 175kD) was investigated, and the vasculature in experimental tumors was visualized using 3D MR angiography (MRA). Xenografted tumors in nude mice of two different histologies-KT005 (human osteogenic sarcoma) and LS180 (human colon carcinoma)-were used to obtain 3D MRA using G6-(1B4M-Gd)192 and Gd-DTPA. The contrast MR sectional images were correlated with the corresponding histological sections. The intratumoral vasculature in the KT005 tumor was clearly visualized by 3D MRA, which became more evident with the growth of the tumor xenograft. In contrast, the intratumoral vasculature in the LS180 tumor was sparser and much less developed than that in KT005 tumors. Blood vessels with a diameter as small as 100 microm based on histology were visualized using 0.033 mmol Gd/kg of G6-(1B4M-Gd)192. In conclusion, intratumoral vasculature with a 100-microm diameter was visualized better using 3D MRA with G6-(1B4M-Gd)192 than with Gd-DTPA.

Construction of optimum index to maximize overall response across countries in the presence of genotype x environment interaction

Sire effect is partitioned into two parts: constant effect unaffected by environments and interaction effect specific to each environment and responsible for genotype x environment (GE) interaction. Response to selection for constant effect is the same across environments, thus increasing genetic stability, whereas response to selection for interaction effect would vary depending upon environments. The conventional measure of GE interaction based on genetic correlation (gammaG) considers both constant and interaction components even though the constant component plays no role in GE interaction. In contrast, the proposed measure of GE interaction based on interaction correlation (gammaI) deals only with interaction component responsible for GE interaction and thus indicates the intensity of GE interaction generated by responsible genes. Constant and interaction effects with different economic weights were combined into optimum index to improve both genetic stability and overall response across countries (countries represent environments). Optimum index was more efficient than the unpartitioned index which was more efficient than selection in a single country except when economic weights between constant and interaction effects were equal. Optimum index and unpartitioned index were the same when these economic weights were equal. The advantage of optimum index over the other selection methods increases as the intensity of GE interaction increases. When the relative economic weights are equivalent among countries and between constant and interaction effects, selection in a country with a larger sire variance is more effective than selection in a country with a smaller sire variance.

Dynamic micro-magnetic resonance imaging of liver micrometastasis in mice with a novel liver macromolecular magnetic resonance contrast agent DAB-Am64-(1B4M-Gd)(64)

DAB-Am64-(1B4M-Gd)(64) is a newly synthesized macromolecular liver magnetic resonance imaging (MRI) contrast agent with a polypropylenimine diaminobutane (DAB) dendrimer conjugated with a bifunctional diethylenetriaminepentaacetic acid (DTPA) derivative for complexing Gd(III) atoms. The characteristics of DAB-Am64-(1B4M-Gd)(64), which quickly accumulated in the liver, have been reported recently. In the present study, the dynamic micro-MRI with DAB-Am64-(1B4M-Gd)(64) was obtained in the mouse liver metastasis model using colon carcinoma cells to evaluate the ability to visualize the micrometastatic tumors compared with that using Gd-DTPA. The dynamic micro-MRI with DAB-Am64-(1B4M-Gd)(64) was able to homogeneously enhance the normal liver parenchyma and visualize micrometastatic tumors of 0.3-mm diameter in the liver of the mice with better contrast than that with Gd-DTPA. In conclusion, DAB-Am64-(1B4M-Gd)(64) is a new liver MRI contrast agent potentially useful for diagnosis of micrometastasis in the liver.

Avidin-dendrimer-(1B4M-Gd)(254): a tumor-targeting therapeutic agent for gadolinium neutron capture therapy of intraperitoneal disseminated tumor which can be monitored by MRI

Peritoneal carcinomatosis is a late stage in cancer progress, for which no effective therapeutic modality exists. Targeting therapeutic agents to disseminated lesions may be a promising modality for treating peritoneal carcinomatosis. Gadolinium ((157,155)Gd) is known to generate Auger and internal conversion electrons efficiently by irradiation with a neutron beam. Auger electrons from neutron-activated Gd(III) are strongly cytotoxic, but only when Gd(III) atoms have been internalized into the cells. In the present investigation, we have developed a quickly internalizing tumor-targeting system to deliver large quantities of Gd(III) atoms into tumor cells to generate the Auger emission with an external neutron beam. Simultaneously, one would be able to image its biodistribution by MRI with a shortened T1 relaxation time. Avidin-G6-(1B4M-Gd)(254) (Av-G6Gd) was synthesized from generation-6 polyamidoamine dendrimer, biotin, avidin, and 2-(p-isothiocyanatobenzyl)-6-methyl-diethylenetriaminepentaacetic acid (1B4M). The Av-G6Gd was radiolabeled with Gd(III) doped with (153)Gd. All of the 1B4M's on the conjugate were fully saturated with Gd(III) atoms. An in vitro internalization study showed that Av-G6Gd accumulated and was internalized into SHIN3 cells (a human ovarian cancer) 50- and 3.5-fold greater than Gd-DTPA (Magnevist) and G6-(1B4M-Gd)(256) (G6Gd). In addition, accumulation of Gd(III) in the cells was detected by the increased signal on T1-weighted MRI. A biodistribution study was performed in nude mice bearing intraperitoneally disseminated SHIN3 tumors. Av-G6Gd showed specific accumulation in the SHIN3 tumor (103% ID/g) 366- and 3.4-fold greater than Gd-DTPA (0.28% ID/g, p < 0.001) and G6Gd (30% ID/g, p < 0.001) 1 day after i.p. injection. Seventy-eight percent of the tumor-related radioactivity of Av-G6Gd in the SHIN3 tumor was located inside the cells. The SHIN3 tumor-to-normal tissue ratio was greater than 17:1 in all organs and increased up to 638:1 at 1 day after i.p. injection. In conclusion, a sufficient amount (162 ppm) of Av-G6Gd was accumulated and internalized into the SHIN3 cells both in vitro and in vivo to kill the cell using (157/155)Gd with external irradiation with an appropriate neutron beam while monitoring with MRI. Thus, Av-G6Gd may be a promising agent for Gd neutron capture therapy of peritoneal carcinomatosis. This reagent also has the potential to permit monitoring of its pharmacokinetic progress with MRI.

Clinical Value of Positron Emission Tomography with FDG for Recurrent Ovarian Cancer

OBJECTIVE

Recurrence is often a major problem for patients who have undergone surgery for ovarian cancer. This prospective study was undertaken to evaluate the clinical contribution of positron emission tomography (PET) using (18)F-fluorodeoxyglucose (FDG) for recurrent ovarian cancer.

SUBJECTS AND METHODS

Twenty-four women who had undergone surgery or chemoradiotherapy for histopathologically proven ovarian cancer were enrolled in this study. Ovarian cancer was thought to have recurred in 12 of these women because of evidence on conventional imaging modalities or tumor marker measurements (group A). Clinical findings for the remaining 12 women showed them to be disease-free (group B). PET findings for the women were compared with the final diagnoses obtained by histopathology or by clinical follow-up. The clinical contribution of PET was assessed by evaluating whether PET yielded information complementing the findings of conventional modalities and by examining its impact on treatment.

RESULTS

PET gave valuable information for seven of 12 patients in group A in addition to the information obtained from findings on conventional imaging, and treatment was affected in five patients. On the other hand, in group B, additional information was obtained in only three of 12 patients, and treatment of only one patient was affected. Overall sensitivity, specificity, and accuracy of conventional imaging modalities were 72.7%, 75.0%, and 73.3%, respectively, and these rates improved to 92.3%, 100.0%, and 94.4%, respectively, by considering both conventional imaging modalities and PET findings.

CONCLUSION

Our preliminary data suggest that whole-body PET with FDG can be a complementary modality for following up patients who have had ovarian cancer, especially patients believed to be at risk for recurrence.

Anatomy and physiology of the female pelvis: MR imaging revisited

This article reviews the normal anatomy of the female pelvis and focuses on uterine physiology, presenting the kinematics of the uterus that can be identified on ultra-fast MR imaging. It also discusses the many facets of the junctional zone on MR imaging. Ultra-fast MR imaging seems to be a powerful tool for evaluating normal anatomy, physiology, and pathology of the uterus. J. Magn. Reson. Imaging 2001;13:842-849.

Oviposition deterrent by female reproductive gland secretion in Japanese pine sawyer, Monochamus alternatus

Adult females of Monochamus alternatus are known to use palpation to recognize oviposition scars that contain eggs and to be deterred from oviposition. This study investigated the oviposition-deterring activity of a jellylike secretion deposited by the females immediately after oviposition and methanol extracts of female reproductive organs in the laboratory. When females searching for oviposition sites encountered artificial oviposition scars, they stopped walking and drummed the surface and inside of the oviposition scars with their maxillary and labial palpi. When the females encountered the artificial scars plugged with the jellylike secretion, most of them left the scars after palpation. In contrast, when females encountered artificial scars not plugged with the secretion, most of them deposited single eggs through the scars. In another experiment, most females left artificial scars treated with methanol extracts of the spermathecal gland or other reproductive organs after palpation, but most of them oviposited through the scars treated with methanol alone. The results showed that females' recognition of egg-containing scars and departure from such scars were mediated by the chemical(s) produced by their reproductive organs.

Inhibition of telomerase activity by fungus metabolites, CRM646-A and thielavin B

We performed a screening program to identify telomerase inhibitors from our drug source obtained from fungus fermentations, and found that two compounds, CRM646-A and thielavin B, inhibited telomerase activity at doses of 3.2 and 32 microM, respectively. These compounds also inhibited the activity of viral reverse transcriptase at almost the same dose levels which inhibited telomerase activity.

3D-micro-MR angiography of mice using macromolecular MR contrast agents with polyamidoamine dendrimer core with reference to their pharmacokinetic properties

Four novel macromolecular MRI contrast agents, all of which had the same chemical composition but different molecular weights, were prepared using generation-3, -4, -5, and -6 polyamidoamine (PAMAM) dendrimers conjugated with a bifunctional diethylenetriaminepentaacetic acid derivative to change the blood retention, tissue perfusion, and excretion. Size-dependent changes in the pharmacokinetics were observed in the biodistribution study. (153)Gd-labeled generation-6 PAMAM-conjugates remained in the blood significantly longer than all of the other preparations (P < 0.001). The increase in blood-to-organ ratio of the preparations was found to correlate with increasing molecular size (P < 0.001). Additionally, 3D-micro MR images and angiography of mice of high quality and detail were obtained using PAMAM-(1B4M-Gd)x as a macro-molecular MRI contrast agent with a 1.5-T clinical MRI instrument. Numerous fine vessels of approximately 200 microm diameter were visualized on subtracted 3D-MR angiographms with G6D-(1B4M-Gd)(192). The quality of the images was sufficient to estimate the microvasculature of cancerous tissue for anti-angiogenesis therapy and to investigate knockout mice. Magn Reson Med 45:454-460, 2001.

[Development of three-dimensional stereo viewer for high-resolution data]

In order to visualize high-resolution three-dimensional (3D) data as a stereogram, a real-time volume-rendering system using a hardware graphic board and conventional PC was developed. A 256(3) data set could be visualized at a redrawing rate of 12 Hz, and a 512(3) data set at a rate of 2.5 Hz. It was demonstrated that stereogram visualization using volume graphic hardware architecture potentially enables rapid examination of high-resolution 3D data by changing visualization parameters such as level, window, transfer function for opacity, and color map or coordinate direction.

Comparison of the macromolecular MR contrast agents with ethylenediamine-core versus ammonia-core generation-6 polyamidoamine dendrimer

Two novel macromolecular MRI contrast agents based upon generation-6 polyamidoamine dendrimers (G6) of presumed similar molecular size, but of different molecular weight, were compared in terms of their blood retention, tissue distribution, and renal excretion. Two G6s with either ammonia core (G6A) or with ethylenediamine core (G6E), which possessed 192 and 256 exterior primary amino groups, respectively, were used. These dendrimers were reacted with 2-(p-isothiocyanatobenzyl)-6-methyl-diethylenetriaminepentaacetic acid (1B4M). The G6--1B4M conjugates were reacted with (153)Gd for studying biodistribution and blood clearance or Gd(III) for the MRI study. 3D-micro-MR angiography of the mice were taken with injection of 0.033 mmol of Gd/kg of G6A--(1B4M-Gd)(192) or G6E--(1B4M-Gd)(256) using a 1.5-T superconductive MRI unit. Although numerous fine vessels of approximately 100 microm diameter were visualized on subtracted 3D-MR-angiography with both G6A--(1B4M-Gd)(192) and G6E--(1B4M-Gd)(256), (153)Gd-labeled saturated G6E-(1B4M)(256) remained in the blood significantly more than (153)Gd-labeled saturated G6A--(1B4M)(192) at later than 15 min postinjection (p < 0.01). In addition, G6E--(1B4M-Gd)(256) visualized these finer vessels longer than G6A--(1B4M-Gd)(192). The G6A--(1B4M-Gd)(192) showed higher signal intensity in the kidney on the dynamic MR images and brighter kidney images than G6E--(1B4M-Gd)(256). In conclusion, the G6A--(1B4M-Gd)(192) was observed to go through glomerular filtration more efficiently than G6E--(1B4M-Gd)(256) resulting faster clearance from the blood and higher renal accumulation, even though both of G6--1B4M conjugates have almost similar molecular size and same chemical structure. In terms of the ability of intravascular contrast agents, G6E--(1B4M-Gd)(256) was better due to more Gd(III) atoms per molecule and longer retention in the circulation than G6A--(1B4M-Gd)(192).

Role of reducing co-factors in catalytic reactions of 6-hydroxymellein synthase, a multifunctional polyketide biosynthetic enzyme in carrot cells

6-Hydroxymellein (6HM) synthase, a multifunctional polyketide biosynthetic enzyme in carrot cells, is capable of catalyzing the acyl-CoA condensation and the ketoreduction in the presence of the nucleotide reducing co-factors. Although free CoA at high concentrations functioned as the activator of the NADPH-dependent 6HM formation, the compound exhibited an appreciable inhibitory activity toward the reaction mediated by NADH. CoA showed a potent inhibitory activity against substrate entry into the reaction center of the NADH-associated enzyme while, in the presence of NADPH, the compound slightly inhibited the formation of the acylated enzyme. The catalytic rate of the synthase was appreciably decreased when NADPH was replaced by the deuterium-labeled compound, however, the kH/kD value was markedly reduced if NADH and [D]NADH were employed as the reducing co-factors. These results suggest that the phosphate group attached to 2'-position of the adenosyl moiety of NADPH associated with the ketoreducing domain of 6HM synthase plays an important role in the regulation of the enzyme activity.

Predictive factors for detecting colorectal carcinomas in surveillance colonoscopy after colorectal cancer surgery

PURPOSE

The aim of this study was to identify the high-risk groups for metachronous colorectal carcinoma among patients who undergo colorectal cancer surgery.

METHODS

Three hundred forty-one patients undergoing colorectal cancer surgery who had undergone surveillance colonoscopy at least twice during a period of more than three years were analyzed. A metachronous colorectal carcinoma was defined as a new colorectal carcinoma detected by surveillance colonoscopy after surgery.

RESULTS

Surveillance colonoscopy was performed 4.6 times per patient during an average of 6.2 years. Twenty-two metachronous colorectal carcinomas in 19 patients were detected, and 14 (64 percent) of 22 were detected within five years of surgery. The cumulative incidence of developing colorectal carcinomas during a five-year period was 5.3 percent. Seventeen (77 percent) of 22 carcinomas were 10 mm or less in size. Ten (71 percent) of the 14 carcinomas in early stages showed a flat appearance. Univariate analysis showed that extracolonic malignancy, coexistence of adenoma, and synchronous multiple colorectal carcinoma were significant predictive factors for detecting colorectal carcinomas in surveillance colonoscopy and that family history of colorectal carcinoma was a possible predictive factor. Multivariate analysis performed with Cox proportional hazards regression model showed that extracolonic malignancy and the coexistence of adenoma were significant predictive factors.

CONCLUSION

We recommend that patients with the above predictive factors receive surveillance colonoscopy meticulously and regularly.

Monoclonal antibody-dendrimer conjugates enable radiolabeling of antibody with markedly high specific activity with minimal loss of immunoreactivity

For the purpose of radioimmunotherapy, labelling of monoclonal antibody with high specific activity is often necessary, especially when using a radionuclide with a shorter half-life. Polyamine dendrimers (PAMAM) are novel synthetic polymeric molecules with large numbers of amine residues on their spherical surface. In order to bind large numbers of radiometals to single antibody molecules, the generation-4 PAMAM (G4), which has 64 amines, was conjugated with 43 molecules of 2-(p-isothiocyanatobenzyl)-6-methyl-diethylene triamine penta-acetic acid (1B4M), a derivative of DTPA. This product [G4-(1B4M)43] was then conjugated with OST7, a murine monoclonal IgG1. We evaluated the achievable specific activity for 111In labeling, immunoreactivity, biodistribution, and tumor targeting in mice of the 111In- or 153Gd-OST7-G4-(1B4M)43 as compared with radiolabeled OST7-1B4M or 56C-1B4M. The maximum specific activity of 111In-OST7-G4-(1B4M)43 and 111In-OST7-1B4M was 470 and 8.7 GBq/mg (12,700 and 263 mCi/mg), respectively. Immunoreactivity of radiolabeled OST7-G4-(1B4M)43 and OST7-1B4M, as determined by the binding to KT005 cells expressing the antigen, was respectively 91% and 84% of that of 125I-labelled OST7. Biodistribution studies for preparations with maximum specific activity in normal mice 3 h after injection showed that 111In- or 153Gd-OST7-G4-(1B4M)43 cleared faster from the blood and accumulated more in the liver than did 111In- or 153Gd-OST7-1B4M. The dendrimer 1B4M [G4-(1B4M)64] itself showed similar saturation effects with metals. The radioactivity in all the other organs reflected the rapid clearance of radioactivity from the blood. 153Gd-OST7-G4-(1B4M)43 showed specific accumulation in the KT005 tumor. In conclusion, we could successfully bind 49 times as many metal atoms to an antibody molecule as is possible with conventional metal labeling for indium and gadolinium, and did so with minimal loss of immunoreactivity. When we achieved radiolabeling with maximum specific activity, Gd conjugate showed better biodistribution than In conjugate.

Effect of Water-Soaking and Air-Drying on Survival of Aphelenchoides besseyiinOryza sativa Seeds

Several nematicides have been used to disinfest rice seeds contaminated with the white tip nematode, Aphelenchoides besseyi. We measured the efficacy of a standard disinfestation treatment that consists of soaking seeds in an aqueous emulsion of fenitrothion or fenthion and subsequently air-drying the seeds. We also measured the efficacy of the same treatments but without addition of nematicide to the soak water. Viability was monitored at key points during treatment. Our results showed that nematicides alone caused little nematode mortality within seeds. Most mortality occurred while seeds were being air-dried. Mortality caused by air-drying alone was 1.7 times greater than mortality caused by soaking seeds in water for 24 hours.

Unusual arrangement of catalytic domains in head-to-tail associated homodimer of 6-hydroxymellein synthase, a multifunctional polyketide biosynthetic enzyme

6-Hydroxymellein synthase, a multifunctional polyketide synthetic enzyme in carrot, is organized as a homodimer, and the activity of the synthase was appreciably inhibited upon the specific alkylation of cysteine- and cysteamine-SHs at the reaction center with iodoacetoamide and chloroacetyl-CoA, respectively. Dissociation and stoichiometric recombination of the unmodified and the SH-modified enzyme subunits yielded a combination of unmodified-unmodified, unmodified-modified and modified-modified hybrid dimers that together exhibit 50% activity. In contrast, hybrid dimers obtained by reconstruction of the two modified enzymes showed essentially no catalytic activity. These results suggest that the two subunits of 6-hydroxymellein synthase are aligned in head-to-tail orientation to organize two reaction centers which are comprised of a cysteine and a complementary cysteamine SH group, belonging to and contributed from the same subunit in the homodimer structure.

[Recent advances in colorectal cancer surgery]

Recent advances in colorectal cancer surgery have been made in improving the cure rate after surgery, the preservation of postoperative function, and the development of minimally invasive procedures. Indication for wide lymph node dissection in rectal cancer surgery is now limited to a smaller number of cases. Functional outcome is being improved thanks to the introduction of autonomic nerve preserving operations as well as the increasing number of sphincter preserving operations. Laparoscopic colectomy for cancer has been practiced for 7-8 years, and the advantages and disadvantages of this procedure are being clarified. Transanal endoscopic microsurgery (TEM) is a minimally invasive surgery for rectal tumors in early stages. The procedure is now overtaking the posterior surgical approach, which is used less and less in recent years. Future goals in colorectal cancer surgery are further improvements in the cure rate and the functional results. Minimally invasive surgery may become the established procedure after a careful assessment of its cure rate compared to the open surgical procedure.

Yolk sac tumor of the ovary: radiologic-pathologic correlation in four cases

We report the radiologic and pathologic features of yolk sac tumor (endodermal sinus tumor) of the ovary in four patients. Yolk sac tumors were shown as well-enhancing solid tumors on both CT and MR studies and were associated with prominent signal voids on MRI. A hypervascular nature was confirmed on microscopic studies. Areas of hemorrhage were another common characteristic. These imaging findings seem to have an important implication for the diagnosis of this tumor.

[Diagnostic pitfalls in evaluating MR images of the uterus]

The pitfalls in evaluating MR images of the uterus are briefly reviewed. These pitfalls are roughly divided into physiological conditions that simulate organic lesions, benign conditions that simulate malignancy, and malignant diseases that simulate benign conditions. It is important to distinguish these mimicking lesions from real organic lesions.

[Myeloperoxidase-antineutrophil cytoplasmic antibody positive alveolar hemorrhage during propylthiouracil therapy for hyperthyroidism]

A 62-year-old woman had been treated with propylthiouracil(PTU) for hyperthyroidism. Because bloody sputum, dyspnea, and severe hypoxemia developed, the patient was admitted to our hospital. Chest X-ray and chest computed tomographic (CT) films disclosed diffuse infiltrative shadows in both lung fields. Bronchoalveolar lavage revealed abundant hemosiderin-laden macrophages. Alveolar hemorrhage associated with myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) positive vasculitis syndrome was diagnosed because of the high serum level of MPO-ANCA. After the initiation of steroid therapy and termination of PTU, the infiltrative shadows in both lung fields disappeared, PaO2 improved, and MPO-ANCA decreased. There have been some reports of MPO-ANCA positive vasculitis syndrome developing during PTU therapy, but most were concerned with renal disease. We concluded that PTU and similar agents should be given consideration as one of the possible causes of MPO-ANCA-induced alveolar hemorrhage.

Temperature Effects on the Transmission of Bursaphelenchus xylophilus (Nemata: Aphelenchoididae) by Monochamus alternatus (Coleoptera: Cerambycidae)

The object of this research was to investigate the effects of ambient temperature on the transmission of the pinewood nematode, Bursaphelenchus xylophilus, by its vector, Monochamus alternatus. Ninety M. alternatus were reared individually at one of three constant temperatures (16, 20, and 25 degrees C). As the ambient temperature decreased from 25 to 16 degrees C, longevity of vectors decreased, nematode transmission efficiency decreased, and the peak period of nematode transmission was delayed and its peak height decreased. Low temperature may inhibit the transmission process, and this inhibition could be partially responsible for preventing pine wilt disease from devastating pine forests in cool regions.