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Background: Since late 2019, the development of severe acute respiratory distress syndrome (SARS) occurred, which began as a small cluster of cases in Wuhan, China and subsequently spread across the globe in the shape of a global pandemic. Coronavirus disease 2019 (COVID-19) initiates an immune response over-activity leading to release of pro-inflammatory cytokines, particularly interleukin-6 (IL-6), which leads to overt thyroid dysfunction by disruption of thyroid transport proteins. Level of triiodothyronin (T3) is inversely proportional to IL-6 with a modest decrease of thyroid stimulating hormone (TSH) and thyrotropin (T4). Fatigue is usually expressed by lack of one or more of habits or routines, particularly a lack of exercise. It is also frequently associated with depression. Fatigue might be an indication of various underlying illnesses that necessitate medical attention. COVID-19-related thyroid disorders could biochemically manifest as thyrotoxicosis, hypothyroidism, as well as non-thyroidal illness syndrome. Post-COVID fatigue has become an alarming complication which remains undiagnosed causing more complication at later stage. There are very limited knowledge regarding altered thyroid function in patients who have recovered from COVID-19. Aims of this study were to know about the derangement of thyroid hormones. Methods: This cross-sectional study was conducted in the Department of Biochemistry and Molecular Biology, BSMMU, Dhaka from July, 2020 to June, 2021. A total of 100 post-COVID patients (age 18 – 70 years) with fatigue were enrolled for this study. Among them, 50 were treated at home and 50 were treated in hospital. For this study, serum TSH and FT4 were measured by the automated analyser. The data were expressed as frequency and percentage, mean for normally distributed data. p value d”0.05 was considered statistically significant. Results: The value of TSH and FT4 in home and hospital treated patients were 1.59, 2.96 mIU/L and 9.27, 17.28 pmol/L respectively. There was significant difference of level of serum TSH (p < 0.0001) and FT4 (p < 0.0001) between home and hospital treated post COVID-19 patients with fatigue. Conclusion: Home treated post-COVID patients with fatigue expressed higher level of serum TSH and FT4 than that of hospital treated patients. BIRDEM Med J 2023; 13(1): 34-37

Background:The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread throughout the world causing a serious health issue. After the swine flu pandemic (also known as H1N1) of 2009-10, WHO had declared Coronavirus disease 2019 (COVID-19) as a global pandemic. This pandemic caused huge losses to the entire world. Most of the patients with mild symptoms were treated at home but patients with difficulty in breathing and various complications were treated at the hospital. Naturally produced antibodies or vaccination can only offer protection. The objective was to compare the antibody status after SARS-CoV-2 infection in hometreated and hospital-treated patients. Methods: This cross-sectional study was conducted in the Department of Biochemistry and Molecular Biology, BIRDEM General Hospital, from July, 2020 to June, 2021. A total of 77 patients (age 18 – 70 years) infected by SARS-CoV-2 were enrolled for this study. Among them, 37 were home treated and 40 were treated in hospital. The study subjects were non-vaccinated. For this study, serum IgG level was measured by the automated analyser. For statistical analysis, the Mann Whitney U test was done. Results:The median value of serum IgG was significantly higher in hospital-treated patients than in hometreated patients (p < 0.001). Hospital treated patients with a history of comorbidity developed more amount of antibody in comparison to home treated patients. Conclusion:Hospital treated patients develop higher antibodies in comparison to home treated patients. BIRDEM Med J 2022; 12(1): 11-15

Cryogenic gene banking is a prime necessity for conserving the genetic constitutes of vulnerable, endangered and critically endangered native and exotic fish species. Cryogenic freezing of fish gametes is the first step to develop such a gene bank. In the study, attempts have been taken to develop a cryogenic freezing protocol of spermatozoa of Mohashol, Tor tor as it is considered as a critically endangered fish species by IUCN. Juvenile and brood fish of Tor tor were collected from the Someshwari River of Netrokona district and domesticated in captive condition at Bangladesh Agricultural University campus. During breeding season, sperms were collected from hormone induced males by stripping. The milt was very sticky. The concentration of sperm was 4.47x1010 cells per ml and pH was 8.6±0.5. To evaluate the toxicity of cryoprotectant, sperm was incubated with DMSO and methanol at 5, 10 and 15% concentrations for a period of 5 to 55 min. The motility of sperm decreased with the increase of cryoprotectant concentration (5, 10 and 15%) and 10% DMSO with Alsever’s solution could be the best combination for cryopreservation of T. tor. sperm at 10 min (83.0±2.74).

Mohashol, Tor tor is one of the most beautiful indigenous fish of Bangladesh. It is a globally acclaimed sport and table fish and distributed in many South and Southeast Asian countries. In the past Tor tor was reported to be available in some rivers of different parts of Bangladesh, but at present this species is very rarely found only in Someshwari, one of the transboundary rivers of Bangladesh. Illegal fishing practices, soil erosion and siltation, construction of flood control and drainage structures, excessive human intervention on this river for livelihood as well as climate change have been considered as the main causes to degrade the habitat of mohashol. Moreover, unscientific coal mining in Meghalaya has further aggravated the problem. Consequently, T. tor has been red listed as critically endangered fish in Bangladesh. Though few attempts have been made for conservation of T. putitora, the endangered T. tor did not get such due importance. So, it is the prime time to put our heads together to conserve this lucrative, aristocratic and iconic fish and to design an integrated conservation project under a multilateral agreement among the South Asian countries specially India, Bangladesh and Nepal as the initial step in this regard.

Climate change is a global threat to the world especially for Bangladesh, due to its geographical location. The present study was carried out to the impacts of climate change on livelihood of the fishers at the Meghna, Laukhati and Galachipa river in Bangladesh. The study was assessing the effects of climate change on fishersˊ community in the Meghna, Laukhati and Galachipa rivers near Chandpur and Patuakhali districts. The data on fishersˊ livelihood were collected by using a well-developed questionnaire from the selected areas. The average temperature was recorded as 30.5±0.90°C, 27.1±1.05°C and 27.4±0.60°C and the dissolved oxygen was as 6.37±1.11 mg/L, 5.63±0.33 mg/L and 6.33±0.51 mg/L in the Meghna, Laukhati and Galachipa rivers, respectively. The pH was as 8.3±0.59, 8.03±0.50 and 7.8±0.50 and the salinity was as 0.10±0.10, 0.23±0.13 and 1.2±0.15 ppt in the Meghna, Galachipa and Laukhati rivers, respectively. In the present study, it was found that most of the fishers were belonged to the age groups of 41 to 60 years (45%), represented by 75% muslim and joint family type (61%) was the predominant among the fishers. The highest annual income of fishers was found 20,080 and 24,000 BDT per year at Chandpur and Patuakhali districts, respectively. There has not been conducted much empirical research about the impacts of climate change in the present research areas. Therefore, Government and NGOs should take proper steps by taking various need based projects and providing some sorts of management policy to rescue the vulnerable communities from climate change impacts. Asian J. Med. Biol. Res. March 2020, 6(1): 81-92

Nutritionally balanced diet and selection of appropriate species for culturing environment are important criteria in aquaculture. The present study was conducted to evaluate the effects of polyunsaturated fatty acids (PUFAs) and β-glucan containing diet (PBG) on growth performance, feed utilization, length-weight relationship, and condition factor of Pabdah catfish, Ompok pabda. In this study, squid extracted phospholipid and mushroom powder were used as the source of PUFAs and β-glucan, respectively, and formulated two isonitrogenous diets such as basal or control (CON) diet and PBG diet with maintaining 30% protein levels. During the study period, similar physicochemical conditions of water such as temperature, pH, and dissolved oxygen (DO) were 26.5 ± 2 °C, 7.4 ± 0.2, and 6.7 ± 0.5 ppm, respectively were maintained in each cistern. The results showed that final mean body weight, final mean length gain, food conversion ratio (FCR), specific growth rate (SGR), food conversion efficiency (%), hepato somatic index (HSI), kidney index (KI), and viscerosomatic index (VSI) were significantly (P

Effects of supplementary feeds on growth, survival, and production of red fin mahseer, Tor tor (Hamilton) was assessed in captive condition under a monoculture system. Experiments were conducted for a period of 12 months where two feeds varying in protein contents were used in treatments. One laboratory formulated feed with 36.67% protein and a commercial feed with 28% protein were characterized as treatment-1 (T1) and treatment-2 (T2), respectively. At the same time water quality parameters were measured. The net increment in weight after 12 months was 671.60 g and 509.80 g in T1 and T2 respectively. The feed conversion ratio (FCR) was 4.72 and 5.26, and the specific growth rate (SGR) was 1.39 and 0.10 % day-1 in T1 and T2 respectively. In both treatments 100% fish were survived and provided the net production (kg/ha) 2807.06 and 2557.78 in T1 and T2, respectively. The water quality parameters were within the suitable range for fish culture. Between the feeds evaluated, feed with 36.67% protein (T1) proved best result considering the growth and production performance of the fish. Overall growth performance of T. tor was satisfactory; however, further research is needed. J. Bangladesh Agril. Univ. 16(3): 533–538, December 2018

Sumithion, an organophosphate pesticide, has been used extensively in agriculture as well as in broodfish and nursery ponds in Bangladesh. Although it is being applied for beneficial purposes but eventually it exhibits some short and long term toxic effects to the aquatic ecosystem. Therefore, the present study investigated the toxic effects of sumithion on the breeding performance and subsequent viability of embryos and larvae of Heteropneustes fossilis. A total of 400 adult H. fossilis were equally stocked in two ponds. Sumithion at the dose of 0.24 ppm was applied for four months every 7 days interval in one pond while the rest one was considered as control. No significant (p>0.05) difference was found in growth between the treated and control H. fossilis; however, fertilization and hatching rates of the eggs obtained from the treated group were significantly (p>0.05) lower than that of control. Subsequently, the embryos and larvae produced from the broods of the control pond were exposed to 5 different concentrations of sumithion (0.5, 1.0, 2.0, 4.0, and 8.0 ppm) against a control (0 ppm). Each concentration was assessed in five replicates having 200 eggs. Data obtained from the sumithion acute toxicity tests were evaluated using the Probit Analysis. The mortality of embryos increased with the increasing sumithion concentrations from 0 to 8.0 ppm and the significant (p>0.05) differences were found only among the treated concentrations above 2.0 ppm. The 24 h LC50 value for embryos was estimated to be 7.803 ppm. Dose-response decreased in hatching success and recorded as 90.8, 85.0, 76.2, 73.0, 65.0, and 51.2 % for control and 5 different concentrations of sumithion, respectively (p

Pollutant dispersion in urban areas has been a key concern in densely populated cities because pollutants can negatively impact human health and the environment. Topography and urban obstructions, such as buildings, greatly affect the atmospheric fluid flow, leading to the dispersion process. Street canyons are usually formed in highly populous cities due to the close proximity of buildings to streets to serve commercial purposes. It can also be termed as pollutant traps that exact adverse effects on urban life. Street canyons cause changes in pollutant dispersion, particularly in the case of vehicle exhaust air pollutants, which cannot be transported by the wind owing to the presence of buildings acting as impediments regardless of the wind flow. Hence, it is imperative to completely understand the behavior of pollutants within the confined urban surroundings for further improving the urban air quality. This study explores the effects of street canyons on the busiest street of Dhaka city in Bangladesh. The Reynolds-averaged Navier–Stokes based dispersion model is used to investigate the air quality phenomenon. Building height, width, building distance, and road width have been taken into consideration in the simulation. It is expected that the findings of the current study would be helpful for urban planners and designers of Dhaka city.

The Patharghata Fishery Ghat in Chittagong is one of the largest fish landing centers in Bangladesh. The study aimed to explore different types of gears and crafts used from the landing center, fish species caught by the gears, and certain degree of socio-economic condition of the fishermen. Data were collected from local fishermen through on the spot inspections, Personal Interview (PI), and Focus Group Discussion (FGD). The gears used from the landing center were classified as Large Mesh Drift Gill Nets (DGNs), Marine Set Bag Nets (MSBNs), and Trammel Nets. Mainly 7 types of DGNs having the mesh sizes ranging from 2.5 to 16 inches had been used by the fishermen of which Lakkha Jal, Lal jal and Char Shuta Jal were the most commonly used DGNs to catch Hilsha, Lakhua, Pomfret etc. Hilsha Shad (Tenualosa ilisha) was the most dominant species and about 60% of different nets were used to catch this species. Only single type of artisanal fishing craft (trawlers) was found in the landing center and is propelled by inboard engine. The capacity of the trawlers varied from 8 to 22 metric tons. In case of socio-economic condition, most of the fishermen belonged to the age groups of 21-30 and 31-40 years; each represented 31% of the total fishermen. About 91% of fishermen were found to be Muslim and rest 9% were Hindu. The average members of the nuclear and joint families were 3.78 and 7.83 per household, respectively; however, these groups of people were being deprived in their society. The study also revealed that about 67% of fishermen had no formal education and 27% had primary and rest 6% had secondary level of education. The annual income of the fishermen ranged from BDT 50,000 to 100,000 and the main expenditure of their earnings were for food (80%), followed by physical treatment (10%) of their family members. They had hardly any savings. Lack of knowledge and government support, and illiteracy were the major problems of the fishermen in the landing center.Asian J. Med. Biol. Res. December 2016, 2(4): 712-726

Endangered catfish Rita rita were reared in a cemented raceway to observe the culture potentiality at three different stocking densities (4, 8 and 16 juveniles/m 3) under the three treatments (T1, T2 and T3, respectively) with three replications each. The mean initial length and weight of Rita juveniles were 20.15±1.51 cm and 100.26±6.57 g, respectively. The fish were reared by providing clean poultry viscera (containing 48.56% crude protein) at 3% of biomass once a day. The water quality parameters were measured daily and found them within suitable ranges. The growth parameters such as final mean total length, relative length gain, mean body weight, relative weight gain, SGR and condition factor were significantly (p

A numerical simulation to investigate the Non-Newtonian modeling effects on physiological flows in a three dimensional idealized stenosed carotid artery with 75% severity (by area) is taken from patient specific model. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Where the physiological waveform was performed using a Fourier series with sixteen harmonics. The investigation has a Reynolds number range of 94 to 1120. Low Reynolds number k − ω model is used as governing equation. The investigation has been carried out to characterize two Non-Newtonian constitutive equations of blood, namely, (i) Carreau and (ii) Cross models. The Newtonian model has been investigated also to study the physics of fluid. The results of Newtonian model are compared with the Non-Newtonian models. The numerical results are presented in terms of pressure, wall shear stress distributions and the streamlines contours. At early systole pressure differences between Newtonian and Non-Newtonian models are observed at pre-stenotic, throat and immediately after throat regions. In the case of wall shear stress, some differences between Newtonian and Non-Newtonian models are observed when the flows are the minimum such as at early systole or diastole. It is known that blood is Bingham plastic fluid. So the viscosity of blood will decrease with increase in shear rate and when shear rate will be greater than 100 then viscosity will be constant. The viscosity of Newtonian model is less than that of non-Newtonian model when shear rate is less than 100, but viscosity of all models is equal when shear rate is equal to 100. When Reynolds number is very low then pressure and WSS of Newtonian model will be less than that of non-Newtonian model but opposite scenario will be seen for velocity distribution. Since early systole and diastole there are comparatively low Reynolds numbers, the results of Newtonian and non-Newtonian condition may be different at early systole and diastole. On the other hand maximum Reynolds number is seen at peak systole. So the results of Newtonian and non Newtonian condition follow each other at peak systole. Again the velocity of the throat region is high for any time instant. So the results of Newtonian and non Newtonian condition may be same at the throat region but different at the pre and post stenotic region. The results of pressure, WSS, and velocity distribution are discussed below with respective figure.

Seaweed polysaccharides have been widely used as viscosifier, gelling agents, and stabilizer in the various application fields, e.g., food, pharmaceutical, nutraceutical, and chemical industries. Applications of seaweed polysaccharides are further expanding to versatile directions, e.g., biofuels, bioactive compounds, and functional materials for medical and basic researches. Production of functional oligo- and monosaccharides by the use of specific enzymes is also expected to improve the value of seaweed polysaccharides. The enzymes that depolymerize seaweed polysaccharides are distributed largely among seaweed-associating organisms like marine invertebrates and bacteria. Among them, herbivorous marine gastropods such as abalone and sea hare are the most prominent producers of polysaccharide-degrading enzymes. To date, various kinds of polysaccharide-degrading enzymes have been isolated from the digestive fluid and hepatopancreas of these animals. Among them, alginate lyase, β-1,3-glucanase, mannanase, and cellulase are the major constituents of their digestive fluid. In this chapter, the authors describe the general methods for the preparation and activity assay of the gastropod polysaccharide-degrading enzymes and provide basic knowledge for their primary structures.

A numerical simulation is performed to investigate Newtonian physiological flows behavior on three dimensional idealized carotid artery (CA) and single stenosed (75% by area) carotid artery(SCA). The wall vessel is set as rigid during simulation. Bifurcated blood vessel are simulated by using three-dimensional flow analysis. Physiological and parabolic velocity profiles are set out to fix the conditions of inlet boundaries of artery. In other hand, physiological waveform is an important part of compilation and it is successfully done by utilization of Fourier series having sixteen harmonics. The investigation has a Reynolds number range of 94 to 1120. Low Reynolds number k — ω model has been used as governing equation. The investigation has been carried out to characterize the flow behavior of blood in two geometry, namely, (i) Normal carotid artery (CA) and (ii) Stenosed carotid artery (SCA). The Newtonian model has been used to study the physics of fluid. The findings of the two models are thoroughly co...

The present study was conducted over 4 months during 1 st September to 30 th December 2005 to observe the effects of stocking density on growth and survival of Thai Sharpunti, Barbodes gonionotus in 3 earthen ponds of size of 2.8 decimal each. The stocking densities of 80, 100 and 120 fish/decimal were treated as T 1 , T 2 and T 3 , respectively. All the treatments were subjected to the same feeding regime and fertilization. The range of water quality parameters such as temperature were 30.31, 30.16 and 29.65 0 C, transparency were 29.94, 37.63, and 40.02 cm, water depth were 143.91, 148.67 and 151.54 cm, dissolved oxygen were 4.72, 4.35 and 4.24 mg/l, pH were 7.71, 7.49 and 7.31, plankton biomass were 43.05 x 10 5 /l, 37.97 x 10 5 /l and 36.05 x 10 5 /l in T 1 , T 2 and T 3 , respectively. Among the growth parameters, mean weight gain were 48.87 g, 41.43 g and 34.09 g, percent weight gain were 698.21%, 591.93% and 487%, the average daily gains were 1.65, 1.54 and 1.20 g, the specific growth rate were 1.73, 1.61 and 1.47%, in T1, T2 and T3 respectively. The gross total productions of Barbonymus gonionotus were 1041.96, 1085.71 and 1019.64 kg/ha/120 days while the net productions were 911.60, 929.46 and 846.43 kg/ha/120 days in T 1 , T 2 and T 3 , respectively. The gross and net total productions in T 2 were highest among the treatments. The highest growth and survival rate were obtained in T 1 . DOI: http://dx.doi.org/10.3329/jbau.v9i2.11048 J. Bangladesh Agril. Univ. 9(2): 327–338, 2011

Previously we isolated the major alginate lyase isozyme LbAly35 from a marine snail Littorina brevicula and showed that this enzyme was significantly heat stable in a broad pH range compared with other molluscan alginate lyases (Hata et al., Fish Sci 75:755–763, 2009). LbAly35 showed practically no similarity to other molluscan alginate lyases in the N-terminal amino-acid sequence of 20 residues and no cross-reactivity with anti-abalone alginate lyase antiserum. These led us to consider that the primary structure of LbAly35 is considerably deviated from other molluscan enzymes. Thus, in the present study, we first compared the thermal stability of LbAly35 with an abalone alginate lyase, HdAly, and found that the first order inactivation rate constants for LbAly35 at 40 and 45 °C were 1/20 and 1/45 of those for HdAly, respectively. Then, we cloned cDNAs encoding LbAly35 and characterized its deduced amino-acid sequence comparing with those of other molluscan alginate lyases. The cDNAs were amplified by polymerase chain reaction (PCR) and 5′- and 3′-RACE PCRs from the L. brevicula hepatopancreas cDNA using degenerated primers synthesized on the basis of partial amino-acid sequences of LbAly35. The cDNA covering the entire translational region of LbAly35 comprised 1,093 bp and encoded an amino-acid sequence of 296 residues. The amino-acid sequence consisted of an initiation methionine, a putative signal peptide for secretion (22 residues), a propeptide-like region (10 residues), and a mature LbAly35 domain of 263 residues. Although the N-terminal region of LbAly35 was significantly deviated from those of other molluscan alginate lyases, the catalytic domain of LbAly35 showed ~45 % identity to other molluscan enzymes which had been classified under polysaccharide-lyase-family-14 (PL-14). In addition, the amino-acid residues crucially important for the catalytic actions of PL-14 enzymes were also conserved in LbAly35. Accordingly, LbAly35 was regarded as a member of PL-14 as other molluscan alginate lyases despite the significant deviation of its N-terminal region.

A β-D-mannosidase (EC 3.2.1.25) with a molecular mass of approximately 100 kDa was purified from the digestive fluid of a marine gastropod Aplysia kurodai by ammonium sulfate fractionation followed by column chromatographies on TOYOPEARL Butyl-650 M, TOYOPEARL DEAE-650 M, and Superdex 200 10/300 GL. This enzyme, named AkMnsd in the present study, showed optimal activities at pH 4.5 and 40 °C and was stable at the acidic pH range from 2.0 to 6.7 and the temperature below 38 °C. The Km and Vmax values for AkMnsd determined at pH 6.0 and 30 °C with p-nitrophenyl β- d -mannopyranoside were 0.10 mM and 3.75 μmol/min/mg, respectively. AkMnsd degraded various polymer mannans as well as mannooligosaccharides liberating mannose as a major degradation product. Linear mannan from green alga Codium fragile was completely depolymerized by AkMnsd in the presence of AkMan, an endolytic β-mannanase, which we previously isolated from the same animal (Zahura et al., Comp. Biochem. Physiol. B 157, 137–148 (2010)). A cDNA encoding AkMnsd was amplified from the Aplysia hepatopancreas cDNA by the PCR using degenerated primers designed on the basis of N-terminal and internal amino-acid sequences of AkMnsd. The cloned AkMnsd cDNA consisted of 2985 bp and encoded an amino-acid sequence of 931 residues with the calculated molecular mass of 101,970 Da. The deduced sequence of AkMnsd showed 20–43% amino-acid identity to those of glycoside-hydrolase-family 2 (GHF2) β-mannosidases. The catalytically important amino-acid residues determined in GHF2 enzymes were completely conserved in AkMnsd. Thus, AkMnsd is regarded as a new member of GHF2 mannosidase from marine gastropod.

Alginate lyase (EC 4.2.2.3) is an enzyme that splits glycosyl linkages of alginate chain via β-elimination producing unsaturated oligoalginates. This enzyme is widely distributed in herbivorous marine mollusks, brown algae, and marine and soil bacteria. In the present study, we determined the general properties and partial amino-acid sequences of alginate lyases from three Archeogastropoda, i.e., Haliotis discus hannai, H. iris, and Omphalius rusticus, and one Mesogastropoda, i.e., Littorina brevicula, in order to enrich the information about functional and structural diversity in gastropod alginate lyases. The alginate lyases were extracted from hepatopancreas of these animals and purified by ammonium sulfate fractionation followed by conventional column chromatography. Single alginate lyases with molecular masses of approximately 28 kDa, 34 kDa, and 34 kDa were isolated from H. discus, H. iris, and O. rusticus, respectively. While three alginate lyases with molecular masses of 35 kDa, 32 kDa, and 28 kDa were isolated from L. brevicula. These enzymes were identified as poly(M) lyase (EC 4.2.2.3) since they preferably degraded poly(M)-rich substrate. Western blot analysis using an antiserum raised against H. discus enzyme suggested that H. iris, and O. rusticus enzymes shared similar primary/higher order structure with H. discus enzyme, but the L. brevicula enzymes did not. H. discus, H. iris, and O. rusticus enzymes were classified to polysaccharide-lyase family-14 by the analysis of partial amino-acid sequences, while the L. brevicula enzymes were not.

A numerical simulation to investigate the Non-Newtonian modelling effects on physiological flows in a three dimensional idealized artery with a single stenosis of 85% severity. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Where the physiological waveform is performed using a Fourier series with sixteen harmonics. The investigation has a Reynolds number range of 96 to 800. Low Reynolds number k - ω model is used as governing equation. The investigation has been carried out to characterize two Non-Newtonian constitutive equations of blood, namely, (i) Carreau and (ii) Cross models. The Newtonian model has also been investigated to study the physics of fluid. The results of Newtonian model are compared with the Non-Newtonian models. The numerical results are presented in terms of pressure, wall shear stress distributions and the streamlines contours. At early systole pressure differences between Newtonian an...

The common sea hare Aplysia kurodai is known to be a good source for the enzymes degrading seaweed polysaccharides. Recently four cellulases, i.e., 95 kDa, 66 kDa, 45 kDa and 21 kDa enzymes, were isolated from A. kurodai (Tsuji et al., PLoS ONE, 8, e65418, 2013). The former three cellulases were regarded as glycosyl-hydrolase-family 9 (GHF9) enzymes, while the 21 kDa cellulase was suggested to be a GHF45 enzyme. The 21 kDa cellulase was significantly heat stable, and appeared to be advantageous in performing heterogeneous expression and protein-engineering study. In the present study, we determined some enzymatic properties of the 21 kDa cellulase and cloned its cDNA to provide the basis for the protein engineering study of this cellulase. The purified 21 kDa enzyme, termed AkEG21 in the present study, hydrolyzed carboxymethyl cellulose with an optimal pH and temperature at 4.5 and 40oC, respectively. AkEG21 was considerably heat-stable, i.e., it was not inactivated by the incubation at 55oC for 30 min. AkEG21 degraded phosphoric-acid-swollen cellulose producing cellotriose and cellobiose as major end products but hardly degraded oligosaccharides smaller than tetrasaccharide. This indicated that AkEG21 is an endolytic -1,4-glucanase (EC 3.2.1.4). A cDNA of 1,013 bp encoding AkEG21 was amplified by PCR and the amino-acid sequence of 197 residues was deduced. The sequence comprised the initiation Met, the putative signal peptide of 16 residues for secretion and the catalytic domain of 180 residues, which lined from the N-terminus in this order. The sequence of the catalytic domain showed 47-62% amino-acid identities to those of GHF45 cellulases reported in other mollusks. Both the catalytic residues and the N-glycosylation residues known in other GHF45 cellulases were conserved in AkEG21. Phylogenetic analysis for the amino-acid sequences suggested the close relation between AkEG21 and fungal GHF45 cellulases.

Herbivorous marine snails like Littorina species are known to possess alginate lyases in their digestive tracts. The Littorina enzymes have been identified as endolytic polymannuronate (poly(M)) lyases (EC 4.2.2.3); however, it is still unclear which polysaccharide-lyase family (PL) the Littorina enzymes belong to, since no complete primary structure of Littorina enzymes has been determined. Thus, in the present study, we analyzed the primary structure of LbAly28, a 28 kDa alginate lyase isozyme of Littorina brevicula, by the cDNA method. LbAly28 cDNAs were amplified by PCR followed by 5′- and 3′-RACE PCRs from the L. brevicula hepatopancreas cDNA. A cDNA covering entire coding region of LbAly28 consisted of 1129 bp and encoded an amino-acid sequence of 291 residues. The deduced amino-acid sequence comprised an initiation methionine, a putative signal peptide of 14 residues, a propeptide-like region of 16 residues, and a mature LbAly28 domain of 260 residues. The mature LbAly28 domain showed 43–53% amino-acid identities with other molluscan PL-14 enzymes. The catalytically important residues in PL-14 enzymes, which were identified in the Chlorella virus glucuronate-specific lyase vAL-1 and Aplysia poly(M) lyase AkAly30, were also conserved in LbAly28. Site-directed mutagenesis regarding these residues, that is, replacements of Lys94, Lys97, Thr121, Arg 123, Tyr135, and Tyr137 to Ala, decreased the activity of recombinant LbAly28 to various degrees. From these results we concluded that LbAly28 is a member of PL-14 alginate lyases. Besides the effects of above mutations, we noticed that the replacement of T121 by Ala changed the substrate preference of LbAly28. Namely, the activities toward sodium alginate and poly(MG)-block substrate increased and became comparable with the activity toward poly(M)-block substrate. This suggests that the region including T121 of LbAly28 closely relates to the recognition of poly(MG) region of alginate.

Two alginate lyase isozymes, AkAly28 and AkAly33, with approximate molecular masses of 28 and 33 kDa, respectively, were isolated from the digestive fluid of the common sea hare, Aplysia kurodai. Both of AkAly28 and AkAly33 were regarded as the endolytic polymannuronate (poly(M)) lyase (EC 4.2.2.3) since they preferably degraded poly(M)-rich substrate producing unsaturated tri- and disaccharides and rapidly decreased the viscosity of sodium alginate solution in the initial phase of degradation. Optimal pH and temperature of the two enzymes were similarly observed at pH 6.7 and 40 °C, respectively. Temperature that caused a half inactivation of the two enzymes during 20-min incubation was also similar to each other, i.e., 38 °C. However, NaCl requirement and activity toward oligosaccharide substrates of the two enzymes were significantly different from each other. Namely, AkAly28 showed practically no activity in the absence of NaCl and the maximal activity at NaCl concentrations higher than 0.2 M, whereas AkAly33 showed ~ 20% of maximal activity despite the absence of NaCl and the maximal activity at around 0.1 M NaCl. AkAly28 hardly degraded oligosaccharides smaller than tetrasaccharide, while AkAly33 could degrade oligosaccharides larger than disaccharide producing disaccharide and 2-keto-3-deoxy-gluconaldehyde (an open chain form of unsaturated monosaccharide). Analysis of the N-terminal and internal amino-acid sequences of AkAly28 and AkAly33 indicated that both of the two enzymes belong to polysaccharide lyase family 14.