Glucose metabolism in splenocytes from the BB rat was studied for the presence of abnormalities in [‘“C] 2-deoxy-~-glucose (2-dGlc) uptake, [U-’4C]glucose conversion to “COZ, and the production of lactate and pyruvate. Cells were studied freshly isolated (“resting”), and following culture both unstimulated (control) and stimulated with concanavalin A (ConA) or phorbol myristate acetate (PMA) + ionomycin. Both resting and control cells from diabetic (BBd) and diabetes-prone (BBdp) rats transported more ( p < 0.05) 2-dGlc than did cells from nondiabetes-prone (BBn) rats. Consistent with prior in vivo activation, sustained in vitro, lactate production was higher ( p < 0.05) under control conditions in BBd and BBdp than in BBn cells. Lactate production increased less with ConA and PMA + ionomycin in both BBd and BBdp than in BBn cells. PMA + ionomycin increased 2-dGlc uptake as much in BBd and BBdp cells as in BBn cells. Elevated rates of pyruvate production were observed in BBd cells under resting, control, and (especially) ConA conditions, suggesting an abnormality in pyruvate conversion to lactate. Few changes were observed in 14C02 production. The presence of similar abnormalities in BBdp cells to those of the BBd cells suggests that the diabetic state is not causal, and the absence of an in vitro effect of 15 mmol/liter glucose in BBn cells further tends to exclude hyperglycemia as a cause of these alterations.

The high-density lipoproteins LPI and LPII were isolated from the hemolymph of the crayfish Cherax quadricarinatus by gradient ultracentrifugation and high-performance liquid chromatography (HPLC). Both lipoproteins contained a carotenoid moiety. LPI is comprised of a single polypeptide with an approximate molecular mass of 96 kDa. LPII was composed of two similar native components, LPIIa and LPIIb, both having polypeptides of 80 and 177 kDa. Both under natural conditions and after endocrine manipulations, LPI was present in males and in females, regardless of the female reproductive stage. LPII was present only in secondary-vitellogenic females, but not during the winter reproductive arrest period. LPII was also absent from young females that had received androgenic gland implants. LPII also appeared in the hemolymph of intersex individuals from which the androgenic gland had been removed. It is therefore suggested that LPII serves as a marker indicating the onset of secondary vitellogenesis in C. quadricarinatus females.

The present study investigated the effects of the red microalga Porphyridium sp. on gastrointestinal physiology and lipid metabolism in male Sprague-Dawley rats. Diets containing dietary fibre from pelleted red microalgal cells (biomass) or their sulfated polysaccharide, pectin or cellulose (control) were fed to rats for a period of 30 d. All three fibre-supplemented diets increased the length of both the small intestine and colon, with a significantly greater effect in rats fed the algal polysaccharide. The polysaccharide also increased mucosa and muscularis cross-sectional area of the jejunum, and caused hypertrophy in the muscularis layer. The algal biomass significantly lowered gastrointestinal transit time by 44% in comparison with the control rats. Serum and mucosal cholecystokinin levels were lower in rats on the pectin and polysaccharide diets, while cholecystokinin levels in rats fed algal biomass were not different from those in the control animals. In comparison with the control diet, all the experimental diets significantly lowered serum cholesterol levels (22-29%). Feeding of non-fermentable algal polysaccharide or biomass significantly increased faecal weight and bile acid excretion compared with pectin-fed or control rats. The algal polysaccharide and biomass were thus shown to be potent hypocholesterolaemic agents active at low concentrations in the diet. Both metabolic and morphological changes were observed following consumption of algae, suggesting several possible mechanisms by which the alga affects lipid metabolism. The results presented in the present study encourage the use of red microalga as a functional food.

Research Article| November 01 1999 Hands-On Method for Teaching the Concept of the Ratio between Surface Area & Volume Annette Cohen, Annette Cohen Search for other works by this author on: This Site PubMed Google Scholar Anat Ben Moreh, Anat Ben Moreh Search for other works by this author on: This Site PubMed Google Scholar Reuben Chayoth Reuben Chayoth Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1999) 61 (9): 691–695. https://doi.org/10.2307/4450805 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Annette Cohen, Anat Ben Moreh, Reuben Chayoth; Hands-On Method for Teaching the Concept of the Ratio between Surface Area & Volume. The American Biology Teacher 1 November 1999; 61 (9): 691–695. doi: https://doi.org/10.2307/4450805 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright The National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

We compared the effects of prostaglandin E-2 (PGE(2)) in vitro, as reflected by cAMP levels, on ovaries and testes of the giant prawn Macrobrachium rosenbergii (Decapoda, Caridea) and the red-claw crayfish Cherax quadricarinatus (Decapoda, Astacidea). These decapods differ in their reproductive physiology, representing distinct reproductive strategies. In both ovaries and testes of M. rosenbergii, PGE(2) (10 mu g/ml) significantly stimulated cAMP synthesis, the reaction being aug mented by IBMX. In contrast, in both ovaries and testes of C. quadricarinatus, PGE(2) had no effect on cAMP levels. In muscular tissue, which served as the control for both species, cAMP levels were unaffected by PGE(2). This comparative study suggests a case of different responses to PGE(2) in the gonads of 2 decapod species that have distinctly different reproductive biologies.

We have developed a method for the administration of juvenile hormone-like compounds into crustacean larvae through a live food vector, the brine shrimp Artemia, commonly used in prawn aquaculture. In crustaceans, the only juvenile hormone-like compound found to date is methyl farnesoate (MF), the unepoxidated form of insect juvenile hormone III. Since MF is hydrophobic, its administration to crustacean larvae in aqueous culture media is problematic. Accumulation of the compound in Artemia cultured in a lipid medium enriched with MF was verified by HPLC, which demonstrated the stability of the compound within the vector. Artemis that were cultured in media containing [H-3]MF accumulated 7.27% of the total radioactivity added. About 0.065% of the total radioactivity added was found in 20 M. rosenbergii larvae fed on the enriched Artemia. MF freshly administered daily to M. rosenbergii larvae caused a retardation of larval growth, manifested by carapace length. In addition, MF altered larval development by retarding the stage specific morphological features between larval stages 5 and 9. This new method for administering MF may facilitate further studies examining the regulatory role of MF in crustacean larval development and metamorphosis. It may also be instrumental in the administration of other hydrophobic drugs into crustacean larvae.

Research Article| March 01 1996 A Simulation Game for the Study of Enzyme Kinetics & Inhibition Reuben Chayoth, Reuben Chayoth Search for other works by this author on: This Site PubMed Google Scholar Annette Cohen Annette Cohen Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1996) 58 (3): 175–177. https://doi.org/10.2307/4450110 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Reuben Chayoth, Annette Cohen; A Simulation Game for the Study of Enzyme Kinetics & Inhibition. The American Biology Teacher 1 March 1996; 58 (3): 175–177. doi: https://doi.org/10.2307/4450110 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright 1996 The National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

Elcosanoids are thought to play a role in the regulation of invertebrate reproduction, as they do in vertebrate systems. This was investigated using the previtellogenic ovary of the freshwater prawn Macyobrachium rosenbergii as a biological model. Concentrations of prostaglandin E2 (PGE2), assessed by means of radioimmunoassay, in the previtellogenic ovary (oocyte diameter 20-40 μm) were 32.4 ± 14.1 pg/mg ovary. Preincubation of the ovary with indomethacin (10 μM) inhibited PGE2 synthesis by 43%. In addition, if indomethacin was added to the culture medium. cAMP levels decreased by 48%. When previtellogenic ovaries were incubated in vitro with PGE2 (0.05 μg/ml medium and up), cAMP levels in the tissue homogenate sharply increased. The levels of cAMP rose most significantly (up to 10-fold) when 1-10 μg PGE2/ml medium was applied. These results suggest that PGE2, and possibly other prostaglandins, may play a role in the endocrine regulation of crustacean reproduction.

Glucose metabolism in splenocytes from the BB rat was studied for the presence of abnormalities in [14C] 2-deoxy-D-glucose (2-dGlc) uptake, [U-14C]glucose conversion to 14CO2, and the production of lactate and pyruvate. Cells were studied freshly isolated (resting), and following culture both unstimulated (control) and stimulated with concanavalin A (ConA) or phorbol myristate acetate (PMA) + ionomycin. Both resting and control cells from diabetic (BBd) and diabetes-prone (BBdp) rats transported more (p less than 0.05) 2-dGlc than did cells from nondiabetes-prone (BBn) rats. Consistent with prior in vivo activation, sustained in vitro, lactate production was higher (p less than 0.05) under control conditions in BBd and BBdp than in BBn cells. Lactate production increased less with ConA and PMA + ionomycin in both BBd and BBdp than in BBn cells. PMA + ionomycin increased 2-dGlc uptake as much in BBd and BBdp cells as in BBn cells. Elevated rates of pyruvate production were observed in BBd cells under resting, control, and (especially) ConA conditions, suggesting an abnormality in pyruvate conversion to lactate. Few changes were observed in 14CO2 production. The presence of similar abnormalities in BBdp cells to those of the BBd cells suggests that the diabetic state is not causal, and the absence of an in vitro effect of 15 mmol/liter glucose in BBn cells further tends to exclude hyperglycemia as a cause of these alterations.

The reproductive capacity of mature rats at the age of 8 days was studied following neonatal exposure to 0.06 Gy dose of gamma-radiation. Decreased litter size and reduced body weight of the pups on weaning day, but not at parturition, were observed in female rats. The reduced litter size was not associated with impaired ovulation, impaired uterine implantation or mortality in utero, but resulted from increased death rate or at near parturition. Of the neonatally irradiated males 29% were found to be sterile and had degenerated or necrotic testes. The testicular damage and the reduced growth rate of the offspring of the irradiated females demonstrate the extreme sensitivity of the immature reproductive system to ionizing radiation, even at very low doses.

Adult male rats were treated with a single, whole body exposure to a dose of 0.001, 0.01 or 0.1 Gy (1 Gy = 100 rad). The animals were sacrificed 1, 7, 30, 100 or 180 days following exposure. Serum testosterone, serum and hypophyseal LH, FSH and prolactin as well as hypothalamic LHRH were measured. In the 0.1 Gy irradiated rats, serum LH and FSH were 100% higher and serum prolactin was 30% lower as compared to controls, 30 days after irradiation. The concentrations of these hormones remained significantly different from control values even after 180 days after exposure. On the other hand, the hypophyseal content of LH, FSH and prolactin decreased in the 0.1 Gy treated rats, 100 days after irradiation. In the group of the 0.01 Gy irradiated rats, serum FSH increased by 70% and hypophyseal FSH decreased. No changes were observed in serum testosterone and hypothalamic LHRH in any of the irradiated groups and no changes were observed in the group exposed to 0.001 Gy. It may be concluded that a long term damage to the reproductive system of the male rat was induced by a single, whole body exposure to 0.1 Gy of gamma radiation.

In this research an educational programme was developed to teach the topic 'From DNA to Protein' with the aid of didactic games. Three games were designed, viz., (1) 'The Structure of the DNA Molecule'; (2) 'Replication and Transcription of the DNA Molecule'; and (3) 'From DNA to Protein'. 217 students from eight 9th and 10th grade classes in the southern district of Israel participated in the study. The students were divided into two groups‐‐'players' and 'non‐players'. The players studied the topics using the above three games in the appropriate context of the biology unit, while the non‐players learnt the same topics by the usual frontal teaching method. The evaluation showed the following: (1) Students who played received higher grades on the subject examination than students who did not play. (2) Students, with lower levels of abstract reasoning ability were more influenced by the use of the games than students of higher ability. (3) When comparing anxiety levels of both groups before and after the research, it was found that students who played reported a significant decrease in anxiety towards biology lessons, while students who did not play reported a slight but insignificant increase in anxiety.

Adult male rats were injected s.c. once a week for 3 weeks with DBCP, 20 mg/kg B.W. Animals were sacrificed 5, 9, 13, 17, 25 and 50 weeks after last injection. Body weight was recorded once a week. Prior to sacrifice each male was presented with proestral females in order to determine the male's mating behaviour and fertility. Testes were removed, weighed and taken for standard histological examination. DBCP treatment caused a reduction of body weight which reverted back to control levels some 17 weeks post injection. Testes weights were reduced and remained low despite the recovery of body weight. Generally, all males showed normal mating behaviour but most of them were infertile. Testicular histology showed a correlation between decreasing testicular weight and increasing percentage of degenerated seminiferous tubules, which was on the other hand correlated with decreasing tubular diameter. Serum levels of FSH and LH were significantly increased in the infertile DBCP treated males while values for the fertile ones were similar to those of controls. There were no differences in serum testosterone levels between DBCP treated and control animals. It is concluded that in DBCP treated rats testicular degenerative damages are associated with increased circulating gonadotrophin levels and with normal testosterone levels. Although mating behaviour is unaffected fertility is depressed and does not recover for at least 50 weeks post injection. It is suggested that DBCP treatment affects mainly the activity of the Sertoli cells while the Leydig cells are affected to a much lesser degree.

Immunological variables were studied in rats chronically exposed to high environmental temperature (35 degrees C). Responses were compared with those of rats at 25 degrees C both fed ad libitum and pair fed to the decreased intake found in heat-exposed rats. Heat-exposed rats showed slower delayed-type hypersensitivity responses to keyhole limpet hemocyanin. They showed lower counts of peripheral blood total T cells (OX19+) as well as helper T cells (W3/25+) and smaller numbers of splenic T cells. The thymus was decreased in size. Increased levels of serum IgG antitetanus toxoid antibodies were found in heat-exposed rats. [3H]-thymidine incorporation into Concanavalin A (ConA)-stimulated splenic lymphocytes was decreased in pair-fed rats but not significantly altered in heat-exposed rats compared with controls. Heat exposure alters some aspects of both cellular and humoral immune function in a manner different from that induced by comparable food restriction without heat exposure.

Adult male rats were injected s.c. once a week for 3 weeks with DBCP, 20 mg/kg BW. Animals were sacrified 20 weeks after last injection. Body and testes weights were recorded and testes were taken for standard histological preparation and for in vitro experiments. The in vitro experiments were carried out on testes slices (90-110 mg) incubated for 3 h with or without the addition of hCG to the incubation medium. Cyclic AMP content of the tissue as well as testosterone released into the incubation medium were determined. Testes weights of DBCP treated animals were 68% lower than that of controls. All semiferous tubules were damaged and shrunken, thus, their number per microscope field was 2.6 times that of controls. Cyclic AMP levels in testes slices were similar in both DBCP treated and controls. The addition of hCG stimulated cyclic AMP accumulation to a much higher level in the DBCP treated than in controls. When calculated per one pair of testes the content in unstimulated pair was more than twice that of DBCP treated. Stimulation of hCG increased both DBCP treated and controls to similar levels. Testosterone release into the medium by slices was higher in DBCP treated than in controls and so was also the increment due to hCG stimulation. Similar results were obtained when testosterone release was calculated per one pair of testes. It is suggested that since the major testicular compartment damaged by DBCP is the tubular one, the proportion of the interstitium per testicular unit weight is larger than in controls, thus, cyclic AMP content increment due to hCG stimulation is much higher.(ABSTRACT TRUNCATED AT 250 WORDS)

The neonatal streptozocin (STZ)-injected rat (NSIR) model of diabetes mellitus resembles human non-insulin-dependent diabetes mellitus (NIDDM) with respect to abnormalities in insulin secretory responses. The suggestion that insulin deficiency leads to insulin resistance, a prominent feature of human NIDDM, led us to examine insulin binding and glucose transport in the NSIR during the development of hyperglycemia. Male Wistar rats were injected at 2 days of age with STZ (90 mg/kg i.p.) or vehicle alone. Mild insulin deficiency, reflected by minimally decreased fed plasma insulin concentrations, was apparent at 4 wk (mean +/- SE, control vs. NSIR, 2.32 +/- 0.19 vs. 1.75 +/- 0.21 ng/ml) and at 8 wk. Pancreatic insulin content was dramatically reduced in NSIR to 12 and 5% of control values at 4 and 8 wk, respectively (P less than .001). Fed plasma glucose concentrations increased in the NSIR between 4 and 5 wk and were significantly elevated at 8 wk (251 +/- 25 vs. 527 +/- 52 mg/dl, P less than .001). 125l-labeled insulin binding showed a progressive increase as a function of adipocyte volume in control and NSIR. Epididymal fat pad weights and adipocyte volumes were significantly decreased in the NSIR. Thus, insulin binding did not differ when expressed per cell number but was increased in NSIR when corrected for cell size (percent specific binding X 10(2), 8.49 +/- 0.96 vs. 11.56 +/- 1.08/microliter cell vol; P less than .05, all ages combined).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of isobutyl 1-methyl xanthine (IBMX) upon cyclic AMP level and DNA synthesis was determined in vivo in Ehrlich ascites tumor (EAT) cells. Cyclic AMP was found to be elevated by IBMX while 3H-thymidine incorporation into the cells was inhibited when the phosphodiesterase inhibitor was injected in the mice bearing the tumor cells. The effect upon cyclic AMP level and H thymidine incorporation was more pronounced in cells obtained 4 days after the implantation compared to the effect found 8 days after cells implantation. Following 12 days of implantation, a weaker effect was found upon cyclic AMP level and no effect was found on 3H-thymidine incorporation.