The B-lymphocyte differentiation from committed B-cell progenitors to antibody-secreting cells was discussed. B-cell progenitors derived from hematopoietic stem cells undergo the rearrangement of immunoglobulin(Ig) gene. The earliest cells as B-cell precursors have cytoplasmic Is(${\mu}$ chain). The entire Is molecule is expressed on the surface after synthesis of L chain. The resting B cells(Go stage) stimulated by binding antigen via Ig-receptors are activated(G$_1$ stage) and followed by proliferation(S stage), coupled with further selection(affinity maturation. class switch). The production of antibody against a particular antigen depends on the activation of B cells with surface Is capable of reacting with that antigen. This process does not occur in isolation but is controlled by helper and suppressor T cells and antigen presenting cells(APC). The mechanism of T cell-dependent B-cell response for production of antibody is largely explained by the cell to cell cooperation and soluble helper factors of T cells. 1) The antigen specific B cells and helper T cells are linked by Is-receptors, leading to the delivery of helper signals to the B cells. 2) Helper T cells recognize the processed antigen-derived peptides with the MHC class II molecules(la antigen) and is stimulated to secrete B-cell proliferation and differentiation factors which activate B cells of different antigenic specificity. The two models are shown currently 1) At low antigen concentration, only the antigen-specific B cell binds antigen and presents antigen-derived peptides with la molecules to helper T cells, which are stimulated to secrete cytokines(IL-4, IL-5, etc.) and 2) At high antigen concentration, antigen-derived peptides are presented by specific B cells, by B cells that endocytose the antigens, as well as by APC Cytokines secreted from helper T cells also lead to the activation of B cells and even bystander B cells in the on- vironmment and differentiate them into antibody-secreting plasma cells.

The effects of intra-articula. sodium hyaluronate(SH) and polysulfated glycosaminoglycan(PSGAG) on degenerative joint disease of the carpus were compared each other In 20 racehorses. Ten horses were dosed with intra-articula. injection of 20mg SH(2 times/2 weeks interval) and ten horses were dosed with intra-articular injection of 250mg of PSGAG(4 times/1 week into.val). Synovial fluid analysis and clinical examination were made to evaluate the effects of the drugs on degenerative joint disease at before injection and 2 weeks after the last injection, respectively. Appearance and mucinous precipitate quality oi synovial fluids of the group injected with 58 and PSGAG were improved by 40～50% and 60～80%, respectively. The chemical values of alkaline phosphatase, lactic dehydrogenase, aspartate aminotransferase, total protein, A/G ratio and glucose of synovial fluid in the group injected with PSGAG were more clearly returned to the normal values than those of the group injected with SH. Relative viscosity and total white blood cells of synovial fluid were returned to the normal walues after the treatments in both groups. Clinical symptoms(swelling, heat and pain on carpal joint, and lameness) of the horses in the group injected with SH and PSGAG were disappeard by 56～67% and 67～80%, respectivelty. Conclusively, the PSGAG was superior to SH in the effects on treatment of the degenerative joint disease in the horses.

Transferrin type of stallions and their foals in total of 56 was analysed. Phenotype showed 8 types(AA, AB, AC, AD, AE, BB, BC, BD), while gene frequencies A ; 0.410, B ; 0.455, C : 0.063, D ; 0.063, E ; 0.09 There were not negative factors in the result of idenification of real paternity but showed AC type that is abscent in their parents.

Present experiment was performed in order to establish the optimal reaction conditions for determination of urinary AAP and GRS activities and to investigate the applicability of urinary AAP and GRS in nephrotoxicity test in rat. The results were as follows ; 1. The optimal pH of phosphate buffer for determination of urinary AAP activity was 7.8. 2. The Michaelis constant of urinary AAP ranged from 0.8 to 1.0mmol/$\ell$ 3. The optimal wave length for determination of urinary GRS activity was 405nm. 4. The optimal pH of acetate buffer for determination of urinary GRS activity was 5.6. 5. The Michaelis constant of urinary GRS ranged from 0.65~0.79mmo1/$\ell$. 6. The AAP activities in gel-filtered samples were significantly higher than those in crude samples. Mean values of AAP activities in gel-filtered samples and crude samples were 29$\pm$20 and 20$\pm$13U/$\ell$, respectively. 7. There was not significant difference between gel-filtered samples and crude samples in urinary GRS activities. Mean values of GRS activities in gel-filtered samples and crude samples were 57$\pm$40 and 56$\pm$39U/$\ell$, respectively. 8. Limits of linearity of urinary AAP and GRS activities were 2.0 and 3.6U/$\ell$, respectively. 9. Within-run imprecisions of the assays, were acceptable, as the coefficients of the AAP activities ranged from 5.5 to 6.3% and those of GRS activities ranged from 1.4 to 6.2%, respectively. 10. Urinary AAP excretion was 675$\pm$227mu/24hrs.kg before administration of potassium dichromate, and increased significantly to 4246$\pm$2567mU/24hrs.kg within 24 hours after administration of potassium dichromate. 11. Urinary GRS excretion did not increase significantly after administration of potassim dichromate. 12. From these findings it is concluded that urinary AAP excretion is early and sensitive Indicator to detect kidney damage in nephrotoxicity experiment.

A total of 2,024 quarters of 515 dairy cattle in Kangweon area were examined for incidence of subclinical mastitis. Milk samples from cattle infected with subclinical mastitis were studied bacteriologically and the bacterial strains isolated were further examined for sensitivity to 12 antibacterial agents. And the status of carrying out the mastitis control program in 28 dairy farms was examined. The results obtained were summerized as follows ; 1. A total of 308(59.8%) of 515 cattle and 656(32.4%) of 2,024 quarters were found to be infected with subclinical mastitis. 2. The 277 strains of etiological agents were isolated from 358 subclinical quarters. These were identified as Staphylococcus aureus(14.4%), other staphylococci(36.5%), Streptoccus agalatiae(8.7%), other streptococci(30.7%), Bacillus spp.(1.8%), Corynebacterium spp.(1.4%) and coliform(0.7%). 3. The 109 strains of streptococci and 141 strains of staphylococci were examined for sensitivity to 12 antibacterial agents. All the strains of streptococci were sensitive to penicillin, ampicillin and cephalothin, and they were also sensitive to erythromycin(88.1%), clindamycin(83.5%), enrofloxacin(75.2%), trimethoprim＋sulfamethoxazole(67.9%), The strains of staphylococci were sensitive to cephalothin(97.2%), gentamicin(83.0%). enroflozacin(80.9%), trimethoprim＋sulfamethoxazole(78.0%), erythromycin(71.6%) and clindamycin(71.6%). But all the strains resisted to colistin. 4. In the 28 dairy farms examined, condition of udder before washing was dirty in most of the farms (89.7%). Hygiene of milking equipment was only good in the 5 farms(17.9%). Teat preparation before milking was good in the 6 farms(21.4%). The farms in which teat dipping after milking was conducted were 46.4%. Dry cow treatment for the complete herd was carried out in most of the farms(89.3%) but mastitis checking was only carried out in the 8 farms(28.6%) irregularly.

항생물질과 부신피질홀몬을 장기간 투여한 7세의 홀스타인종 암소에 있어서 Candida 에 의한 유방의 기회성진균감염율 보고하였다. C. tropicalis는 섭씨 30도의 단순한 해바라기씨 배지에서 반복하여 분리되었다. 이 병원체는 PHOL 기법에 의해 감염된 우유에서 직접 검출되었다. 우유침전물을 그람염색하여 현미경하에서 검사한 결과 Candida spp. 와 일치하는 다수의 효모세포와 균사가 관찰되었다. 실험 실내 약물감수성을 조사한 결과 nystatin에 감수성을 나타내었다. 임상적 및 진균학적 검사결과 nystatin에 의한 유방내 화학요법은 성공적이었다. 수의학에 있어서 C. tropicalis와 기타 기회성진균의 점증하는 중요성이 강조되었다.

돼지의 이유자돈 설사병을 효과적으로 치료, 예방하고자 Enrofloxacin(Baytril premix)을 사료에 혼합투여하여 설사 발생여부, 증체량, 사료요구율, 돈분내 대장균수의 변화, 분리한 대장균의 항균물질에 대한 감수성을 조사하여 다음과 같은 결과를 얻었다. 1. 이유자돈에 Baytril premix를 급여하였던 바 대조구보다 62일령에서 체중은 3.2kg의 통계적 유의차이를 보여(p<0.01) 현저한 증체효과 나타내었으며, 사료요구율도 계선되었고 설사발생도 예방할 수 있었다. 2. Baytril Premix를 급여한 자돈의 분변내 대장균수는 3.14$\times$$10^{8}$에서 5일후 2$\times$$10^{7}$ 개/g 10일후 1$\times$$10^{5}$개/g으로 현저히 감소하였다. 3. 공시농장에서 분리한 E. coli 10중의 항균물질에 대한 감수성은 baytril, gentamicin 및 trimeoprim＋sulfamethoxazole에 감수성이 우수하였다.다.

The sudden death syndrome has been encountered in Korean native cattle in a small island village of Yeochun, Chonnam since 1984. In an effort to diagnose the causes of the condition, 10 calves were purchased and shipped to the village to be reared conventionally. During the period of April 1988 through March 1989 the animals were clinically examined every month, samples of blood and feces collected and examined. Soils, plants and water samples were analysed, and necropsy was performed on two calves which died during the period. No abnormalities were found by clinical examination. Soil, plant and water analysis did not reveal any abnormalities which could be related to sudden death. One of the 2 dead calves was fallen and suffocated to death after the right hock was tied by rein. The other had a torsion In jejunum after plowing. Epidemiological examination revealed that two calves of one farmer died in one day from bloat. Authors explained the results and asked the people in the island to improve management of the animals, and no more sudden death occurred for 2 years.

Clinical signs, serum chemical values and histological findings of hepatic tissue after partial and complete obstruction of common bile duct in Korean goats were investigated. Abnormal clinical signs were not observed in partial obstruction of common bile duct, but in complete obstruction clinical signs such as jaundice, urine color change, were observed. Serum total bilirubin, total cholesterol, aspartate aminotransferase, sorbitol dehydrogenase, gamma glutamyltranspeptidase, and total protein values increased on the 1-4th day and then gradually decreased to normal level in partial obstruction. However, they tend to increase persistently by the 24th day in complete obstruction of common bileduct. Histologic features of hepatic tissue in partial obstruction were not changed as compared with normal hepatic tissue. On the other hand, in complete obstruction of common bite duct there were moderate bile duct proliferation in a portal area, rupture of bile canaliculi, phagocytosis of bile pigment by Kupffer cells, periportal fibrosis, intrahepatic bile stasis and hepatic cell necrosis.

This study was carried out to investigate the effects of intravenous drip with ketamine hydrochloride and its application for control depth and maintenance of anesthesia in dogs. Changes of blood pressure, vital signs, blood gas and anesthetic state were observed in this study. The obtained were summerized as follows ; 1. Changes of blood pressure and heart rate after intravenous drip anesthesia with ketamine hydrochloride were observed with significant increase in all group ; group II (0.135m81k9/min), group III (0.269mg/kg/min) and group IV(0.538mg/kg/min). These conditions were maintained unchangeably until 160 minutes after administration in all group. This may be indicated that there were no side effects on account of ketamine accumulation. 2. There were irregular respiration, pain reflex, Jaw tone reflex and vomition probability in the anesthetic conditions of group II The anesthetic conditions of group III were rarely shown as mentioned above. Awakening time and recovery time of group H were more prolonged 21 minutes and 27 minutes respectively than those of group III. These experimental data suggested that the optimal dosage of intravenous drip anesthesia of ketamine Hcl was 0.269mg/kg/min.

Experimental obstruction of urethra was induced for 66 hours on 5 male dogs to determine the diagnostic value of ECG and blood chemical values. The results obtained in the examination were summarized as follows ; 1. Changes of ECG, blood chemical values and clinical sings were observed from 30 hours after urethral obstruction. 2. In ECG, the peaked and amplitude of T wave were increased remarkably. p wave were decreased, and intervals of PR(Q) and QRS complex were prolonged after urethral obstruction. 3. The levels of BUN, potassium, creatinine in serum after urethral obstruction were increased remarkably and correlation between these levels and the increase of amplitude in T wave were recognized to be significant.

It was carried out to investigate the effect of the kind of medium, the concentration of serum added and the temperature of storage on the survival of mouse and bovine embryos preserved In vitro. The survival of frozen-thawed mouse embryos after cooling at 4$^{\circ}C$ was also investigated. It was possible to preserve the embryos of mouse until 4 days and of cattle in a day without significant decrease of the survival rates. The survival rates of frozen-thawed mouse embryos after cooling at 4$^{\circ}C$ over 3 days were below 20%.

This experiment was carrid out to investigate whether Aloe arborescens had a radioprotective effect in cobalt-60 gamma irradiated(600 and 700ra4s) mice. The survival ratio of mice for 30 days and blood pictures were investigated. 1. The survival ratios of 600ra4s gamma Irradiated(dose rate 50rads/min.) in pre-irradiation aloe administered group(A), post-irradiation aloe administered group(B) and control group were 73.3%, 72.3% and 63.3%, and those of 700ra4s groups were 63.3%, 60.0% and 51.7%, respectively. 2. The total leucocyte counts of aloe administered groups were less decreased and more rapidly recovery to normal level than those of control group. 3. The lymphocyte counts were rapidly decreased on the 1st day after irradiation in all experimental groups than those of control group. 4. The recovery effects of total leucocyte counts of pre-irradiation aloe administered groups were superior to those of post-irradiation aloe groups and control group.

Hypervitaminosis A occurred in about 30% of foxes of five farms in Choongcheongbukdo-province from October 1989 to February 1990. Clinical signs were loss of appetite, retarded growth, lameness. Radiological changes were decreased density of the long bones, especially fibula, and osteophytes developed either on the lateral condyle of humerus or ulnar just below the semilunar notch. Pathological change was the development of exotosis as is evidenced by radiological examination. Pig liver and lung consisted 30∼55% of feeds from March 1989 to February 1990. The serum concentrations of vitamin A in 2 affected foxes were 45,900 and 47,300 IU/d$\ell$ and the concentrations of vitamin A in the liver were 8,760 and 10,842 IU/gm respectively. It is concluded that the high level of vitamin A in the pig liver and the large amount of pig liver in the feed composition are the etiology of the disease.