Secular trend and associated factors of twinning in Taiwan

Delivery records of public hospitals and local health centers were analyzed to investigate the secular trend of multiple births from 1955 to 1990 in Taiwan. Twinning rates decreased gradually from the late 1950s to 1973, slightly increased and remained stable from 1974 to 1980, and then increased strikingly from 1981 to 1990. During the study period, MZ rates were consistently higher than DZ rates except in 1986 when a higher DZ rate was observed. The highest MZ rate of 7.7 per 1,000 deliveries was observed in 1985, while the highest DZ rate of 4.6 per 1,000 deliveries was observed in 1986. The triplet incidence rate also declined from the early 1960s to 1973 and then increased markedly from 1974 to 1990. A case-control study including 482 MZ and 252 DZ twin pairs and 1,496 singletons was carried out in four teaching hospitals in Taipei City between October 1985 and June 1989 to examine factors related to twinning. The zygosity of twin pairs was determined by sex, placentation and red blood cell antigens. Multiple logistic regression analysis showed that the higher the maternal age, the lower the MZ and DZ rates, while the higher the parity, the higher the rates. There was no association of paternal age or of maternal educational level with twinning rates.

Modification of cardiovascular response of adenosine A2 receptor agonist by adenylate cyclase in the spinal cord of rats

This study was performed to investigate the influence of spinal adenosine A2 receptors on the central regulation of blood pressure (BP) and heart rate (HR), and to define whether its mechanism is mediated by adenylate cyclase or guanylate cyclase. Intrathecal (i.t.) administration of drugs at the thoracic level were performed in anesthetized, artificially ventilated male Sprague-Dawley rats. Injection (i.t.) of adenosine A2 receptor agonist, 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA; 1, 2 and 3 nmol) produced a dose dependent decrease of BP and HR. Pretreatment with adenylate cyclase inhibitor, MDL-12,330, attenuated the depressor and bradycardiac effects of CPCA (2 nmol), but not with guanylate cyclase inhibitor, LY-83,583. These results suggest that adenosine A2 receptor in the spinal cord plays an inhibitory role in the central cardiovascular regulation and that the depressor and bradycardiac actions are mediated by adenylate cyclase.

Is health care different? Popular support of federal health and social policies

Over the past several years there has been a striking increase in policymakers' attention to health care reform. This paper explores whether there has been a corresponding shift in popular attitudes and identifies factors that may have changed these attitudes. The first part of the analysis relies on survey data collected between 1975 and 1989 to estimate a set of regression models, relating support for federal involvement in health care, antipoverty programs, and general domestic policies to a set of sociodemographic characteristics. Relative to other federal policies, support for health initiatives grew over this period. During the same period, long-standing differences in support between rich and poor, old and young, educated and uneducated, all narrowed for health care, though they did not for other types of federal policies. The second part of this study explores motivations that might account for these patterns. We identify a half dozen ways in which health care may be viewed as "different," that is, more or less appropriate for federal action. Analysis of survey data from 1987 suggests that there are relatively small differences in the attitudes and perceptions that motivate support for federal health initiatives, relative to federal domestic policies in general. However, there are more striking differences between health programs and more overtly redistributive policies. Compared to redistributive federal programs, support for federal health initiatives are (a) less identified with racial minorities or economically disadvantaged groups, (b) less constrained by notions of individual responsibility, (c) more closely associated with concerns about equal opportunity in American society, and (d) somewhat more constrained by choices between federal and local government. These patterns persist whether or not respondents are politically active and whether they report themselves to be liberal or conservative. We suggest that the growing support for federal intervention in health care, relative to other social policies, is in part an inadvertent by-product of ideological positions popularized during the Reagan and Bush administrations. We draw from these results some predictions about the course of the ongoing debate over federal health policies.

Expression of nitric oxide synthase isoforms in the testes of pigs

This study examined the expression of three isoforms of nitric oxide synthase (NOS) in the testes of pigs. Immunohistochemical studies demonstrated the presence of nNOS, eNOS and iNOS in interstitial cells, primary spermatocytes and spermatids. Positive immunoreactions for eNOS and iNOS were detected in peritubular myoid cells. Some vascular endothelial cells were positive for nNOS and eNOS. The expression of nitrotyrosine was detected in interstitial cells. In addition, the histochemical study revealed that all the interstitial cells were stained positively for NADPH-diaphorase, although some spermatids and vascular endothelial cells displayed moderate enzymatic activity. These findings suggest that three isoforms of NOS are expressed in the testis of pig and that they play important roles in the biology of interstitial cells that produce testosterone, as well as in spermatogenesis in the seminiferous tubules.

Natural history of deep vein thrombosis in children

OBJECTIVE

To determine the natural history of deep vein thrombosis in children presented with a first episode in the lower extremity veins.

METHODS

Children with objective diagnosis of acute deep vein thrombosis were followed up with ultrasound and clinical examination. Risk factors and clinical presentation were prospectively collected. The prevalence of recurrent deep vein thrombosis and the development of signs and symptoms of chronic venous disease were recorded.

RESULTS

There were 27 children, 15 males and 12 females, with acute deep vein thrombosis, with a mean age of 4 years, range 0.1-16 years. The median follow-up was 23 months, range 8-62 months. The location of thrombosis involved the iliac and common femoral vein in 18 patients and the femoral and popliteal veins in 9. Only one vein was affected in 7 children, two veins in 14 and more than two veins in 6. Recurrent deep vein thrombosis occurred in two patients, while no patient had a clinically significant pulmonary embolism. Signs and symptoms of chronic venous disease were present at last follow-up in 11 patients. There were nine patients with vein collaterals, but no patient developed varicose veins. Reflux was found in 18 veins of 11 patients. Failure of recanalization was seen in 7 patients and partial recanalization in 11. Iliofemoral thrombosis (p = 0.012) and failure to recanalize (p = 0.036) increased significantly the risk for developing signs and symptoms.

CONCLUSIONS

Children with acute proximal deep vein thrombosis develop mild chronic venous disease signs and symptoms at mid-term follow-up and are closely related with iliofemoral thrombosis and failure to recanalization.

Effectiveness of low-dose ASA in prevention of secondary ischemic stroke, the ASA Study Group in Taiwan

This randomized double-blind controlled study was carried out to investigate the effect of 100 mg acetylsalicylic acid (ASA) per day on the secondary prevention of ischemic stroke. Patients who suffered a first ischemic stroke from 13 participating hospitals were enrolled. They were independent or only partially dependent in activities of daily living and all had received brain CT for diagnosis. Eligible patients were randomly allocated to the 100 mg ASA or the nicametate citrate (a vasodilator) groups, and trial medications were started within three to six weeks after the onset of stroke. The primary end point was cerebral reinfarction, and intracranial hemorrhage was classified as an adverse event. Four hundred and sixty-six patients participated in this study; and 222 cases (136 males and 86 females) were allocated to the ASA group while 244 cases (150 males and 94 females) were assigned to the nicametate group. No significant difference in baseline characteristics between the two groups was observed. Cerebral reinfarction developed 6.3% (14/222) in the ASA group and 11.9% (29/244) in the nicametate group. According to the Cox's proportional hazards model, the estimated risk ratio (ASA group vs. nicametate group) was 0.538, with a 95% confidence interval of 0.284-1.019. The result was of borderline statistical significance. The risk for cerebral reinfarction was reduced by almost 50% among those who took 100 mg ASA versus those who took nicametate.

Comparison of the effect of acetylsalicylic acid on platelet function in male and female patients with ischemic stroke

The aim of this study was to observe whether acetylsalicylic acid (ASA) had different effects in both sexes. Out of the ischemic stroke patients who were admitted to the National Taiwan University Hospital (NTUH), those who had not taken ASA or ASA-like drugs for more than 2 weeks were selected for this study. For the diagnosis of ischemic stroke, computed tomography (CT) of the brain was performed in all cases, and for differential diagnosis, other necessary procedures were employed in a few cases. The serum salicylate (SA) level was measured by Trinder's method, thromboxane B2 (TXB2) and 6-keto-PGF1 alpha by radioimmunoassay, threshold concentration of adenosine diphosphate (ADP) by Born's method, and circulating platelet aggregates (CPA) by Wu and Hoak's method. The present study showed that the means of serum SA levels after administration of the same dose of ASA were not significantly different between the two sexes. After ingestion of ASA, a single dose of 75 mg, 300 mg or 600 mg, or 300 mg 4 times a day, mean plasma TXB2 levels were significantly suppressed and mean threshold concentrations of ADP were significantly elevated in the two sexes. After administration of above-mentioned various doses of ASA, the abnormally high plasma TXB2 levels and abnormally low threshold concentrations of ADP and CPA ratios were significantly normalized in both male and female patients. Plasma 6-keto-PGF1 alpha levels were not influenced by ingestion of ASA 75 mg, but significantly depressed by administration of ASA 300 mg in both sexes. There were no sex differences in the antiplatelet effect of ASA in this experiment.

Factors influencing the preservation of the facial nerve during acoustic surgery

We reviewed the last 30 acoustic neuromas excised in our department and attempted to find out the factors associated with preservation of the facial and cochlear nerves. While the size of the tumour was the most important factor, vascularity and consistency were both important. Facial and cochlear nerves were preserved in 63% and 10% of the patients respectively. The importance of early diagnosis cannot be overemphasized.

Factors affecting the first recurrence of noncardioembolic ischemic stroke

Studies of the factors affecting the first recurrence of ischemic stroke have reported inconsistent findings. Types of initial stroke and the racial differences in study samples are among the explanations that may account for this inconsistency. The aims of this study were to estimate the cumulative recurrence rates of noncardioembolic ischemic stroke and identify the factors that influence the first recurrence of noncardioembolic ischemic stroke in the Taiwanese Chinese population. Four hundred and sixty-six patients with noncardioembolic ischemic stroke from thirteen hospitals in Taiwan were followed up in this study to ascertain first recurrence of noncardioembolic ischemic stroke between October 1992 and April 1995. The Kaplan-Meier method was used to estimate the cumulative recurrence rate. The Cox regression model was used to ascertain the significant factors affecting the first recurrence of noncardioembolic ischemic stroke. The overall cumulative recurrence rate was 10.5% (49/466) from the follow-up period of 30 months. After adjustment for age, sex, treatment modes, and variables pertinent to blood pressure, the site of brain lesion remained a significant factor. The relative risk of first recurrence for the basal ganglion vs. the region of middle cerebral artery was 3.06 (95% CI: 1.29-7.26). The brain lesion site was demonstrated to be an independent predictor of risk for the first recurrence of noncardioembolic ischemic stroke among the Taiwanese Chinese population. Whether this finding was also seen in other populations should be corroborated in future research.

Regional cerebral blood flow changes in patients with intractable obsessive compulsive disorders treated by limbic leukotomy

The object of this study is to assess the changes in regional cerebral blood flow (rCBF) following stereotactic limbic leukotomy in patients with medically intractable Obsessive-Compulsive Disorder (OCD). Technetium-99-Hexa Methyl Propylene Amine Oxime (99mTc-HMPAO) Single Photon Emission Computed Tomography (SPECT) data obtained before and after limbic leukotomy were subjected to image fusion with MRI images. Eight samples were obtained from healthy voluteers. After localization of the ROI (Region Of Interest) in anatomical area, rCBF measurements were obtained by METLAB. The results of this study show a change of rCBF following limbic leukotomy in intractable OCD. Postoperative 99mTc-HMPAO SPECT findings implicate the medial frontal cortex, cingulate and striatum, which culd be linked to limbic leukotomy that blocks the functional connection of corticolimbic loop.

Indolent glioma: a cause of epilepsy

We studied eight patients with indolent gliomas. In all eight cases, despite characteristic radiological features, there was a delay in diagnosis because of misinterpretation of the initial computed tomogram. These tumours are an important cause of epilepsy of childhood, and surgery may well alleviate the epilepsy and possibly achieve a long term 'cure'. Therefore it is important that a diagnosis is made early and the lesion completely excised.

Postoperative selective bowel decontamination prevents gram-negative bacterial translocation in small-bowel graft recipients

Gram-negative septic episodes are a potential risk of small-bowel transplantation; bacterial translocation through the graft is considered the mechanism. As a measure to prevent this complication, we evaluated postoperative selective bowel decontamination (SBD) in the rat model of orthotopic small-bowel transplantation [Lewis (LEW) and Brown-Norway (BN) rats as donors and recipients]. For 4 days after transplantation we gave FK 506, 2 mg/kg, which prevents rejection and results in indefinite recipient survival. For SBD, 24 mg/kg/day polymyxin E and 20 mg/kg/day tobramycin were administered via orogastric gavage to allograft recipients, both with and without FK 506 therapy. On Day 9, all rats were sacrificed, the peritoneal cavity was swabbed, and mesenteric lymph nodes (MLN), spleen, liver, and ileum were harvested for microbial qualitative and quantitative analysis. Animals with positive peritoneal swab cultures were excluded. SBD resulted in a significant reduction of the quantitative gram-negative bacterial flora in the ileum and cecum and of bacterial translocation to the MLN [0% versus 50% (no FK 506 therapy) and 8% versus 50% (FK 506 treated)]. In the allograft groups not treated with FK 506, SBD failed to significantly prolong survival, suggesting that acute rejection is not hastened by infection (bacterial translocation). We conclude that SBD in small-bowel-graft recipients prevents bacterial translocation by reducing intestinal gram-negative bacterial flora; this may reduce local and systemic infections by gut-derived organisms.

Mongolian spots with involvement of the temporal area

A Chinese baby girl was born after an uncomplicated pregnancy and a normal spontaneous vaginal delivery to a gravida 2, para 1, 32-year-old mother at 37 weeks' gestation. Neither parent had a history of alcohol or drug ingestion. There was no history of consanguinity. The Apgar scores were 7 at 1 min and 9 at 5 min. Her birth weight was 5 lb 14 oz and her length was 46 cm. At birth, she was noted to have grayish areas on the face and lower back. The infant was seen at 3 months of age because of persistent regurgitations. On average, she regurgitated 7-8 times a day. Physical examination showed that the infant was not in distress. Her weight was 6 lb 4 oz and length 47 cm. She had a Mongolian spot measuring 0.8 x 1.2 cm in the left temporal area (Fig. 1) and another Mongolian spot measuring 4 cm in diameter in the lumbar area. The Mongolian spots were grayish in color and the pigmentation was uniform in intensity. The rest of the examination was essentially normal. The infant was diagnosed to have Mongolian spots and gastroesophageal reflux. The latter was treated with postural therapy, thickened feedings, and metoclopramide 0.35 mg q.i.d. The infant was seen again at 4 months of age for a reassessment. There was no noticeable change in shape, size, or color of the Mongolian spots.

Evaluation of finger blood flow with Tc-99m MDP (methylene diphosphonate)

BACKGROUND

A variety of methods were used to establish objective diagnostic criteria of Raynaud's phenomenon. We intended to introduce another method, using radionuclide (Tc-99m methylene diphosphonate) scintigraphy, which is more objective, simple and economical than the past methods.

METHODS

The finger blood flow with radionuclide scintigraphy was evaluated in 10 patients of Raynaud's syndrome, 12 patients of connective disease without Raynaud's symptoms, and 20 normal persons. After immersing one hand in ice water (4 degrees C) for 30 seconds, the hand was exposed to 22 degrees C room air for 15 minutes, and then the patients received the intravenous (IV) bolus of 20 microCi of Tc-99m methylene diphosphonate (MDP). At the same time, scintigraphic image of both hands started with the region of interest, including the second, third, fourth and fifth fingers distal to the metacarpophalangeal (MCP) joints. Computer recording of the counts in the region of interest every 2 seconds for 310 seconds was started on IV bolus injection.

RESULTS

The 310 seconds cumulative digital blood flow ratio of cold exposed hand to room air exposed hand was significantly lower in Raynaud's group (p < 0.001), and the ratio of initial slope of activity curve was also lower in the Raynaud's group (p < 0.001). Of the 8 patients showing Raynaud's syndrome, 4 patients of scleroderma and 1 patient of multiple myeloma showed no improvement of finger blood flow in the cold exposed hand after 2 weeks of pharmacological therapy, but 1 patient of mixed connective tissue disease, 1 patient of Behcet's syndrome and 1 patient of SLE showed much improved finger blood flow after combined administration of vasodilator, calcium channel blockers and antiplatelet drugs.

CONCLUSIONS

The evaluation of finger blood flow with 99mTc-MDP could be considered to be one of the simple, economical and new methods that can be used in the follow-up, objective assessment of therapeutic effect, and giving an aid in the study of the pathophysiology of the Raynaud's phenomenon.

Prevalence of cardiovascular diseases in elderly Chinese people in Taiwan

In order to study the health status and prevalence of diseases in elderly Chinese people in Taiwan, a hospital-based, physician-conducted epidemiological survey was undertaken. Study subjects were people aged > or = 65 years who were randomly selected from four regions of Taiwan. A total of 2600 subjects were studied. Most of the study subjects visited the hospitals for detailed history taking, physical examination and laboratory tests, including urinalysis, blood chemistry, electrocardiography, and chest and lumbar spine radiography. The cardiovascular data of 2518 subjects (males 1283) comprised this report. The prevalence of hypertension in the aged Chinese in Taiwan was high in both males and females (males 33.2%, females 40.9%, combined 37%). Coronary artery disease was also common (11.4%), but the prevalence was relatively low compared with Western people. Other cardiovascular diseases such as aortic aneurysm and valvular heart disease were rare. About 70% of the electrocardiograms were found abnormal. This well-organized, large-scale epidemiological survey not only presents useful information for local medical care for the elderly but also provides important data for comparison between different people in the world.

Comparison of rabies humoral antibody titers in rabbits and humans by indirect radioimmunoassay, rapid-fluorescent-focus-inhibition technique, and indirect fluorescent-antibody assay

Rabies humoral antibodies were induced in eight New Zealand rabbits by a single intramuscular injection of inactivated suckling mouse brain rabies vaccine. The primary response to immunization was measured in blood samples taken at selected intervals for 6 months. The anamnestic response was measured in blood samples obtained 2 weeks after the rabbits received a booster immunization. The humoral antibody concentrations were measured by the rapid-fluorescent-focus-inhibition technique (RFFIT), indirect fluorescent-antibody assay (IFA), and indirect radioimmunoassay (RIA). The maximal neutralizing antibody titers as measured by RFFIT were attained by the 4th week and persisted into the 24th week. After booster immunization the antibody response was almost 10-fold higher than the highest level attained in the primary response. The antibody levels as measured by IFA and RIA were similar, but the titers as measured by either procedure were almost 10-fold lower than those determined by RFFIT. After booster immunizations the antibody levels, as measured by IFA and RIA, were three- and sixfold higher, respectively, than the maximal levels attained in the primary response. Twenty-two human serum specimens were tested by the same serological procedures, with disparate results. Both RIA and RFFIT effectively differentiated antirabies-positive sera from antirabies-negative sera.

Molecular Cloning and Expression of an Endo-β-1,4-D-glucanase I (Avicelase I) Gene from Bacillus cellulyticus K-12 and Characterization of the Recombinant Enzyme

Bacillus cellulyticus K-12 Avicelase (Avicelase I; EC 3.2.1.4) gene (ace A) has been cloned in Escherichia coli by using the vector pT7T3U19 and HindIII- HindIII libraries of the chromosomal inserts. The libraries were screened for the expression of avicelase by monitoring the immunoreaction of the antiavicelase (immunoscreening). Positive clones (Ac-3, Ac-5, and Ac-7) contained the identical 3.5-kb HindIII fragment as determined by restriction mapping and Southern hybridization, and expressed avicelase efficiently and constitutively using its own promoter in the heterologous host. From the immunoblotting analysis, a polypeptide that showed a carboxymethylcellulase (CMCase) activity with an Mr of 64,000 was detected. The recombinant endo 1,4-beta-D-glucanase I was purified to homogeneity from an intracellular fraction of E. coli by DEAE-Toyopearl M650, Phenyl Toyoperal M650, and TSK gel HW50S chromatography. The enzyme had a monomeric structure, its relative molecular mass being 65 kDa by gel filtration and 64 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pI was 5.3 and the optimal pH was 4.6, and the enzyme was stable at pH 4.0-10.5. The enzyme had a temperature optimum of 50 degrees C and was stable at 55 degrees C for 48 h, and retained approx 20% of its activity after 30 min at 70 degrees C. It showed high activity toward carboxymethylcellulose (CMC) as well as p-nitrophenyl-beta-D-cellobioside, 4-methylumbelliferyl cellobioside, Avicel, filter paper, and some cellooligosaccharides. Km values for CMC and Avicel were 7.6 and 85.2 mg/mL, respectively, whereas Vmax values were 201 and 9.2 micromol x min(-1) x mg(-1), respectively. Cellotetraose (G4) was preferentially cleaved into cellobiose (G2) and cellopentaose (G5) was cleaved into G2 + cellotriose (G3), whereas cellohexaose (G6) was cleaved into G4 + G2 and, to a lesser extent, into G3 + G3. G3 was not cleaved at all. G2 was the main product of Avicel hydrolysis. G2 inhibited whereas Mg++ stimulated the activity of CMCase and Avicelase. Hydrolysis of CMC took place with a rapid decrease in viscosity but a slow liberation of reducing sugars. Based on these results, it appeared that the cellulase should be regarded as endo type, although it hydrolyzed Avicel.

Enhancement of pairing correlation by t' in the two-dimensional extended t-J model

We investigate the effects of the next-nearest-neighbor (t') and the third-nearest-neighbor (t") hopping terms on superconductivity correlation in the 2D hole-doped extended t-J model based on the variational Monte Carlo, mean-field calculation and exact diagonalization method. Despite the diversity of the methods employed, the results all point to a consistent conclusion: While the d-wave superconductivity correlation is slightly suppressed by t' and t" in underdoped regions, it is greatly enhanced in the optimal and overdoped regions. The optimal Tc is a result of the balance of these two opposite trends.

Inhibitory effect of acetylsalicylic acid on platelet function in patients with completed stroke or reversible ischemic neurologic deficit

The purpose of our study was to investigate the effects of different doses of acetylsalicylic acid on platelet aggregation. Among inpatients of the National Taiwan University Hospital, 236 cases of completed stroke and seven cases of reversible ischemic neurologic deficit that were diagnosed by computed tomography of the brain and that had not ingested acetylsalicylic acid or acetylsalicylic acidlike drugs for greater than 2 weeks before admission were selected for this study. Thromboxane B2 and 6-keto-PGF1 alpha were measured by radioimmunoassay, threshold concentration of adenosine diphosphate was measured by Born's method, and circulating platelet aggregates were measured by the method of Wu and Hoak. Various single doses of acetylsalicylic acid (75, 300, or 600 mg) or 300 mg acetylsalicylic acid every 6 hours for four doses or one dose of 300 mg acetylsalicylic acid with 75 mg dipyridamole significantly suppressed the mean plasma thromboxane B2 concentrations and elevated the mean adenosine diphosphate threshold concentrations. Abnormal plasma thromboxane B2 concentrations, adenosine diphosphate threshold concentrations, or circulating platelet aggregate ratios were significantly normalized after administration of these regimens. The effects were not significantly different among treatment groups. Forty milligrams of acetylsalicylic acid seemed to have less platelet-inhibitory effect. A single dose of 75 mg acetylsalicylic acid significantly inhibited platelet hyperfunction and effectively corrected the abnormal plasma thromboxane B2 concentrations, adenosine diphosphate threshold concentrations, and circulating platelet aggregate ratios. Higher doses did not enhance the inhibitory effect. In addition, this single dose of acetylsalicylic acid did not significantly suppress plasma 6-keto-PGF1 alpha. We conclude that 75 mg acetylsalicylic acid per day is adequate to inhibit platelet hyperfunction.

Molecular characterization and an infectious clone construction of sweet potato leaf curl virus (SPLCV) isolated from Korea

Sweet potato leaf curl disease (SPLCD) was primarily identified in sweet potato fields in Korea in 2003, and the complete genomic sequence of sweet potato leaf curl virus (SPLCV) has been cloned. The genome of the Korean SPLCV isolate (SPLCV-KR) comprises 2,828 nucleotides with six open reading frames in DNA-A, similar to a monopartite begomovirus. Additionally, neither the genome B genomic component nor the DNA beta sequence was detected. The results of phylogenetic analysis using the maximum parsimony method showed that SPLCV-KR is more closely related to SPLCV-US (US) than SPLCV-CN (China) and SPLCV-JP (Japan). A tandem repeat dimer of SPLCV-KR was cloned and found to be infectious in sweet potatoes (Ipomoea batatas) via biolistic inoculation. The SPLCV-infected sweet potatoes exhibited mild leaf curl symptoms of SPLCD, and the newly-replicated viral DNA was detected via Southern blot analysis. Results of biotic, molecular, and phylogenetic characterization suggest that SPLCV-KR is a new strain of SPLCV and is importantly placed in the evolutionary progression from curtoviruses to begomoviruses.

KEYWORDS

sweet potato leaf curl virus; sweet potato leaf curl disease; phylogenetic analysis; infectious clone; biolistic infection.

Use of concanavalin A as a topographical probe for protein-protein interaction. Application to lactose synthase

Galactosyltransferase (EC 2.4.1.38) has been shown to bind to Con A-Sepharose. Concentrations of methyl-alpha-mannoside greater than 0.7 M were required to release the enzyme from the immobilized lectin. Molecular weight determination by gel filtration revealed that galactosyltransferase formed a 1:1 complex with concanavalin A. Preincubation of the enzyme with excess concanavalin A did not affect its catalytic activity either in the presence or absence of alpha-lactalbumin. The galactosyltransferase-concanavalin A complex was retained on an alpha-lactalbumin-Sepharose column in the presence of N-acetylglucosamine and manganese chloride and was eluted from the column in their absence. Galactosyltransferase immobilized onto a Con A-Sepharose was still active either in the presence or absence of alpha-lactalbumin. Lactose synthase activity was also observed when the galactosyltransferase-concanavalin A complex was assayed with alpha-lactalbumin immobilized on Sepharose. These data indicate that the carbohydrate moiety of galactosyltransferase is involved in neither the catalytic process nor the binding of alpha-lactalbumin and must be linked to the enzyme at a location where it does not present any steric hindrance on the binding of concanavalin A, either free or immobilized on Sepharose.