Pig epidermis: a cell kinetic study

The basal cell density (BCD), labelling index (LI), duration of DNA synthesis (TS) and cell cycle time (TC) have been calculated for the epidermis of pigs in the age range 4-27 months. The BCD declined progressively from 143.4 +/- 6.5 cells/mm at 4 months to 128.8 +/- 8.3 cells/mm at 15 months, whereafter the values showed little change. There was a small decrease in LI with increasing age, from 7.9 +/- 1.5% at 4 months to 5.9 +/- 1.0% at 27 months. However, the change to housing animals outdoors as compared with indoors had a greater effect on the LI (approximately 10%). Severe weathering in the skin of animals housed outdoors resulted in a very high LI (approximately 20%). Neither TS or TC varied significantly with age. TS was within the range 8.8-9.2 hr and TC 127-161 hr. In animals housed outdoors TC was reduced relative to animals housed indoors. The BCD and TS were not affected by housing conditions. The kinetic parameters investigated in the pig were similar to those reported for man.     

THE EFFECT OF ESTRADIOL ON THE CELL KINETICS IN THE UTERINE AND CERVICAL EPITHELIUM OF NEONATAL MICE

The effect of estradiol-17β on the length of the various phases of the cell cycle was studied in the neonatal mouse uterine, and cervical epithelium. A double labelling method was used, and in addition labelled mitoses were counted. In the uterus proper, estradiol shortens the length of the total cell cycle, T_c, from 17-9 hr to 15-7 hr, and the duration of S phase, T_s, from 6–7 to 5-1 hr 6 hr after estradiol treatment. 12 hr after estradiol treatment, T_c is shortened to 7-4 hr and T_s to 4–5 hr. The shortening of T_c at 12 hr is mainly due to an effect on T_G1, which is shortened from 8–55 hr in untreated animals to 1–8 hr in estradiol treated animals. The T_c of cervix epithelium cells in untreated animals was found to be 21-8 hr. After treating the mice for 6 hr with estradiol the T_c was now increased to 47 hr and further to 61 -2 hr following 12 hr treatment with the hormone. T_s increases from 8-3 hr to 15-2 hr following 6 hr estradiol treatment, and to 15-4 hr after 12 hr treatment. The effect is most pronounced in T_G1, which is lengthened from 10–95 hr in untreated animals to 28-1 hr and 43 hr, respectively, in animals treated for either 6 or 12 hr with estradiol.     

Cell Population Kinetics and Dna Content During Thyroid Carcinogenesis

The proliferation kinetics and DNA content of thyroid follicular cells in rats were studied by autoradiography and cytophotometry. Continuous treatment of animals with methylthiouracil (MTU) results in hyperplasia followed by tumour growth in the thyroid gland. the mitotic index (MI) increases from 0.006 ± 0.002% in controls to 0.13 ± 0.06% in hyperplasia and to 0.09 ± 0.03% in malignant cells. the same is true for the labelling index (LI) which rises from 0.08 ± 0.003% in controls to 1.4 ± 1.1% in hyperplasia and to 1.0 ± 0.6% in follicular adenomas. the S-phase duration (T_s) is shortened from 8.0 ± 1.2 hr in controls to 6.0 ± 1.4 hr in animals treated for 9 months with MTU and prolonged to 15.4 ± 2.1 hr in papillary carcinomas. In all MTU-treated animals a decrease in the value of the potential population doubling time (T_PD) and thyroid weight doubling time (T_D) was observed. the cell loss factor (ø) decreases in animals treated for 3 months with MTU and increases during the stage of tumour growth in the gland (animals treated 12–15 months with MTU). DNA measurements in the nuclei of hyperplastic and neoplastic thyroid tissues reveal cells with values exceeding that in control animals. However, no difference was found in the DNA content between thyroid adenomas and carcinomas, nor between thyroid hyperplasia and neoplasia. During the last decade numerous autoradiographic studies have been performed on the cell population kinetics of benign and malignant tumours in animals and man (Steel, 1977; Tubiana & Malaise, 1977). It has been established that cell proliferation is an important parameter in both the initiation and promotion phases of carcinogenesis (Oehlert, 1973; Berenblum, 1979). Cell kinetic studies during carcinogenesis have predominantly dealt with the liver (Rajewsky, 1967; Chernozemski & Warwick, 1970), skin (Raick, 1974), the mammary gland (Bresciani, 1965; Nagasawa, Yanai & Nagigushi, 1976b), the uterine cervix (Nagasawa, Matsuura & Tojo, 1976a) and intestinal cells (Tutton & Barka, 1966; Pozharisski, Klimashewski & Gushin, 1977). Information on the changes in cell population kinetics during thyroid carcinogenesis is still incomplete. Data reported in the literature are mainly devoted to the short-term effects of goitrogens and radiation factors (Santler, 1957; Sheline, 1969; Philip, Crooks & MacGregor, 1969; Wynford-Stringer & Williams, 1982; Redmond & Tuffery, 1981). The present study was carried out to investigate if changes in the cell population kinetics and DNA content occur during thyroid carcinogenesis, as well as if thyroid adenomas and carcinomas differ in their proliferative potential and DNA content.     

The cell kinetics of the epidermis and follicular epithelium of the rat: variations with age and body site

Abstract The skin from rats of differing age was used to quantify variations in the cell kinetics of the epidermis and the follicular epithelium of different body sites. Four parameters were assessed, namely the basal cell density (BCD), the labelling index (LI), the duration of DNA synthesis (t_s) and the basal cell turnover time (t^T). The BCDs of the epidermis of the dorsum and the upper surface of the foot were similar in rats of 7, 14 and 52 weeks of age, but there was an indication of a progressive decline with increasing age in the BCD of the epidermis of the ear and tail. There were no age-related changes in the length of t_s in any of the four body regions. The rate of cell proliferation, as indicated by the values of the LI and t_T, was relatively rapid in the epidermis of the dorsum, foot and tail of rats aged 7 weeks (LI > 12%; t_T < 80 h). In rats aged 14 weeks this rate of proliferation was maintaned in the epidermis of the dorsum. However, in the foot and tail the rate of cell proliferation was decreased (LI < 10%; t^T > 85 h). A fall in the rate of proliferation of the epidermis of the dorsum was only seen in 52-week-old animals. In these animals the rates of proliferation in the foot and tail were similar to those at the age of 14 weeks. In the epidermis of the ear there was no appreciable change in the rate of cell proliferation with age. The values of the cell kinetic parameters varied in the different body sites. For example, in 52-week-old animals values for t_T were relatively short in the epidermis of the tail and foot and appreciably longer in the epidermis of the dorsum and ear. Considered overall, values for the cell kinetic parameters of the epidermis were comparable with those for the follicular epithelium. The only major differences between the epidermis and the follicular epithelium were in the upper surface of the foot at 7 weeks of age, and in the tail at 7 and 14 weeks of age, where the LI was higher and the t_T shorter in the epidermis than in the follicular epithelium. The relevance of the observed age- and body-site-related variations in the cell kinetics of the epidermis are discussed in relation to previously described differential changes in the radiosensitivity of the skin in this strain of rat.     

CYTOKINETICS OF TUMOUR AND ENDOTHELIAL CELLS AND VASCULARIZATION OF LUNG METASTASES IN C3H/HE MICE

A model of lung metastases was developed using intravenous injection of tumour cell aggregates of spontaneous C3H/He mammary tumours in syngeneic mice. the growth rate of lung tumours decreased with increasing tumour volume, with mean host survival of 46 days. the cytokinetics of individual tumours ranging between 0.004 and 4.2 mm³ in volume were studied. the labelling index (LI) ranged between 12 and 17%, the DNA synthesis time (T_s) being 9–10 hr. the growth fraction (GF) ranged between 26 and 38%. the cell cycle time (T_c) was found to be 18–19 hr. the LI and the GF decreased with increasing tumour volume doubling time (T_d). No correlation was found between the tumour volume and T_c. the LI of endothelial cells within these tumours, ranging between 0.004 and 4.2 mm³ in volume was 14–15% and endothelial cell proliferation was not affected by tumour growth. Vascular parameters were also determined for these tumours as a function of tumour volume. Vascular volume increased with increasing tumour size while the percentage of capillary vessels decreased. the cellular volume to capillary volume ratio increased with increasing tumour volume. Necrosis was observed in 0.27 mm³ tumours and increased with increasing tumour size. The results from these studies suggested that the age-dependent decrease in proliferative activity of tumour cells growing in the lung is related to change in effective vascularity.     

Cell proliferation in the subependymal layer of the adult mouse in vivo and in vitro

Pulse labelling experiments with [³H] thymidine (dT) and double labelling experiments with [³H]dT and bromodeoxyuridine (BrdUrd) were carried out on cells of the subependymal layer in the brain of adult normal mice in vivo, in vivo/in vitro and in vitro. The results should (i) lead to information about cell cycle parameters of these cells in the brain of adult mice, since these cells have been studied mostly in the rat brain up to now and (ii) answer the question whether results concerning cell proliferation obtained in vivo correspond with those from brain slices incubated in vitro with or without prelabelling in vivo. In vivo an LI of 20.2 ± 2.7% (x?± SEM) and T_s= 7.2 ± 0.7h were found. Furthermore, grain count halving experiments led to a surprisingly short cycle time (T_c) of 11.2–14.2 h. The longer T_c values (18–20 h) reported in the literature for subependymal cells in the rat brain seem to be due to evaluations of different areas around the lateral ventricle without considering the migrating behaviour of these cells which is quite different regionally. The in vitro studies (with or without prelabelling in vivo) showed a significantly reduced LI due to the fact that about 20% of the S phase cells, possibly lying in the middle of S, stopped further DNA synthesis after transfer to culture. This was shown by comparing the cell fluxes at the G₁/S and S/G₂ borders of in vivo vs. in vitro studies.     

Vapor–liquid equilibria and thermophysical behavior of the SPC-HW model for heavy water

The vapor–liquid coexistence curve of the simple point charge heavy-water model (SPC-HW), [J. Chem. Phys., 114, 8064–8067 (2001)] is determined by Gibbs Ensemble Monte-Carlo (GEMC) simulation. The estimated critical conditions of the model based on the Wegner-type expansion for the order parameters and the rectilinear diameter are ρ_c = 0.300 g/cc, T _c = 661 K and P _c = 156 bars. The dielectric constant determined by isothermal–isochoric molecular dynamics is underpredicted along the coexistence curve by 29–44% in comparison with the experimental values. The analysis of the orthobaric temperature dependence of the system microstructure, in terms of the three site–site radial distribution functions, indicates that the first coordination numbers for the oxygen–oxygen and the oxygen–deuterium interactions are ～4.3 ± 0.1 and ～1.9 ± 0.1 at T = 300 K, and decrease by 15 and 55%, respectively, at criticality. The dipole–dipole correlation functions show that the orientational order in heavy water is quickly lost beyond the first oxygen–oxygen coordination shell. The model's second virial coefficient is determined by Monte-Carlo integration and used to aid the interpretation of the predicted phase equilibrium results.     

External fluorescence retention of calcein‐marked juvenile brown trout Salmo trutta raised in natural and artificial environments

The fluorescence retention and intensity of juvenile brown trout Salmo trutta marked during their first summer were monitored in a hatchery and in four natural streams. A handheld detector was used for direct examination. In the hatchery, three marking treatments (T) were compared: 3·5 min in a 0·5% calcein solution (T0·5‐3·5), 7 min in a 0·5% calcein solution (T0·5‐7) and 3·5 min in a 1% calcein solution (T1‐3·5). The fish were raised indoors for 11 months and then outdoors until 18 months. The fluorescence retention rate was 100% in all treatments at 11 months, although T1‐3·5 showed the highest mean fluorescence intensity, followed by T0·5‐7 and T0·5‐3·5. The fluorescence intensity was not correlated with the final total length (L_T) of the fish in two treatments, although it significantly decreased with increasing L_T in T1‐3·5. At 18 months, <30% of the fish were still slightly fluorescent, suggesting a negative effect of sunlight exposure. In stream studies, the fluorescence intensity did not significantly differ according to final L_T; an overall mean ± s.d . retention rate of 70·7 ± 26·6% was measured at 12 months with a decrease to 48·6 ± 24·6% at 24 months. Significant differences amongst streams and within reaches of the same stream were observed. Because of a significant positive effect of the shading index on the fluorescence intensity, the use of calcein should be restricted to streams unexposed to direct sunlight. Consequently, the marking method would be reliable for 1 year monitoring studies in shaded streams.     

The influence of natural short photoperiodic and temperature conditions on plasma thyroid hormones and cholesterol in male Syrian hamsters

Adult male Syrian hamsters were subjected to 1, 3, 5, 7 or 11 weeks of either natural winter conditions or rigorously controlled laboratory conditions (LD 1014; 22 ± 2C). Although both groups of hamsters gained weight over the course of the experiment, hamsters housed indoors were significantly heavier after 5 weeks of treatment compared to their outdoors counterparts. Animals housed under natural conditions exhibited a significant decrease in circulating levels of thyroxine (T₄) and a rapid rise in triiodothyronine (T₃) levels; the free T₄ and free T₃ index (FT₄I and FT₃I) mirrored the changes in circulating levels of the respective hormones. Laboratory-housed animals had a slight rise in T₄ and FT₄I at 3 weeks followed by a slow steady decline in these values; T₃ and FT₃I values did not change remarkably in these animals. Plasma cholesterol declined steadily over the course of the experiment in laboratory-maintained animals but increased slightly during the first 5 weeks in animals under natural conditions. Since the photoperiodic conditions were approximately of the same duration in these 2 groups, it is concluded that the major differences in body weight, thyroid hormone values and plasma cholesterol are due to some component (possibly temperature) in the natural environment.     

Roseivivax atlanticus sp. nov., isolated from surface seawater of the Atlantic Ocean

A taxonomic study was carried out on strain 22II-S10s^T, which was isolated from the surface seawater of the Atlantic Ocean. The bacterium was found to be Gram-negative, oxidase and catalase positive, rod shaped and motile by subpolar flagella. The isolate was capable of gelatine hydrolysis but unable to reduce nitrate to nitrite or degrade Tween 80 or aesculin. Growth was observed at salinities of 0.5–18 % (optimum, 2–12 %), at pH of 3–10 (optimum, 7) and at temperatures of 10–41 °C (optimum 28 °C). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 22II-S10s^T belongs to the genus Roseivivax, with highest sequence similarity to Roseivivax halodurans JCM 10272^T (97.2 %), followed by Roseivivax isoporae LMG 25204^T (97.0 %); other species of genus Roseivivax shared 95.2–96.7 % sequence similarity. The DNA–DNA hybridization estimate values between strain 22II-S10s^T and the two type strains (R. halodurans JCM 10272^T and R. isoporae LMG 25204^T) were 22.00 and 21.40 %. The principal fatty acids were identified as Summed Feature 8 (C_18:1 ω7c/ω6c) (67.4 %), C_18:0 (7.2 %), C_19:0 cyclo ω8c (7.1 %), C_18:1 ω7c 11-methyl (6.8 %) and C_16:0 (5.9 %). The respiratory quinone was determined to be Q-10 (100 %). Phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, an aminolipid, a glycolipid and three phospholipids were present. The G+C content of the chromosomal DNA was determined to be 67.5 mol%. The combined genotypic and phenotypic data show that strain 22II-S10s^T represents a novel species within the genus Roseivivax, for which the name Roseivivax atlanticus sp. nov. is proposed, with the type strain 22II-S10s^T (= MCCC 1A09150^T = LMG 27156^T).     

Elimination kinetics and protein binding of theophylline in the rabbit

The detailed elimination kinetics of theophylline were studied in 27 rabbits. Each received a 10 mg/kg intravenous bolus of aminophylline. The theophylline half-life ($\text{T}\text{1}\text{2}$) was 3.8 ± 0.63 hr. The apparent volume of distribution (V_D) and total body clearance (TBC) for theophylline were 439 ± 60 ml/kg and 81.0 ± 17.3 ml/kg·hr respectively. Theophylline protein binding was determined in 10 animals. The mean bound fraction was 74.3 ± 3.9% (range, 68.3–78.0%); the fraction bound was concentration indifferent over a serum concentration range of 5–20 μgm/ml.     

Cell proliferation kinetics of six xenografted human cervix carcinomas: comparison of autoradiography and bromodeoxyuridine labelling methods

Abstract. Cell kinetic and histologic parameters of six xenografted tumours with volume doubling times ranging from 6 to 43 d were investigated in order to obtain kinetic information on a panel of tumours to be used in radiobiological studies. The six tumours covered a range of histologies and their DNA indices varied from 2–7 to 1–4. The length of the cell cycle (T_c), potential doubling time (T_pot) and labelling index (LI) were determined by continuous labelling with [³H]TdR and autoradiography in three tumours. T_c varied from 30 to 40 h. Determinations of the length of the S phase (T_s) were found to be less reliable by this method. Data on T_s and LI were also determined in all six tumours using bromodeoxyuridine (BrdU) labelling and the single sample method; values of T_pot were slightly longer than those obtained via the autoradiographic method. In addition, multiple samples were taken after BrdU labelling. T_c was determined by fitting the data obtained from mid-S, mid-G₂ and mid-G₁ windows to curves described by a damped oscillator. Data obtained via the mid-S window were found to be most reliable. Generally, cell cycle times obtained by the BrdU method were longer than those observed with the autoradiographic method. Differences between the two methods could be explained by inaccuracies in the determination of T_s, LI and T_c and differences in the experimental approach. We consider the BrdU labelling method to be a suitable alternative for the time-consuming autoradiography, if data on T_s or T_pot are sufficient. Due to difficulties in the reproducibility of the immunofluorescence staining and asynchronization of cells approximately 10 h after labelling, the method of windows analysis was affected by similar problems to those observed in interpretation of percentage labelled mitosis (PLM) curves. However, the method may serve as an alternative to determine cell cycle times in vitro and, if improved technically, in vivo. Careful comparison of the data obtained from mid-S, mid-G₁ and mid-G₂ windows may increase the reliability of the determination of cell kinetic parameters.     

Resting metabolic rate and lung function in fasted and fed rough-toothed dolphins,Steno bredanensis

We measured resting metabolic rate (RMR), tidal volume (V_T), breathing frequency (f_R), respiratory flow, and end-expired gases in rough-toothed dolphins (Steno bredanensis) housed in managed care after an overnight fast and 1–2 hr following a meal. The measured average (± standard deviation) V_T (4.0 ± 1.3 L) and f_R (1.9 ± 1.0 breaths/min) were higher and lower, respectively, as compared with estimated values from both terrestrial and aquatic mammals, and the average V_T was 43% of the estimated total lung capacity. The end-expired gas levels suggested that this species keep alveolar O₂ (10.6% or 80 mmHg) and CO₂ (7.6% or 57 mmHg), and likely arterial gas tensions, low and high, respectively, to maximize efficiency of gas exchange. We show that following an overnight fast, the RMR (566 ± 158 ml O₂/min) was 1.8 times the estimated value predicted by Kleiber for terrestrial mammals of the same size. We also show that between 1 and 2 hr after ingestion of a meal, the metabolic rate increases an average of 29% (709 ± 126 ml O₂/min). Both body mass (M_b) and f_R significantly altered the measured RMR and we propose that both these variables should be measured when estimating energy use in cetaceans.     

THE CELL CYCLE TIME IN THE RAT JEJUNAL MUCOSA

The regional variation of the duration of cell cycle parameters was studied by constructing fraction of labelled mitoses curves at several levels in the jejunal crypt column of male Wistar rats. Prolonged T_c and T_s values were apparent only in the bottom eight cell positions, and these differences were shown to be significant compared with the remaining cell positions by analysing the data by the method of Gilbert (1972). Above cell position 8 the proliferating crypt cells showed effectively the same phase durations. For the whole crypt column T_c was 11.32 ± 0.14 (SE) and T_s 6.49 ± 0.10. Although variation in phase durations was confined to the basal portion of the crypt, the results essentially confirm the findings of Cairnie, Lamerton & Steel (1965a), and may be interpreted in terms of the slow cut-off model. The demonstration of prolonged T_c values in basal cell positions confirms the presence of a longer cycling subpopulation of cells at the bottom of the crypt.     

Melatonin and porphyrin in the harderian glands of the Syrian hamster: circadian patterns and response to autumnal conditions

1. Adult male Syrian hamsters were killed at nine intervals during a 24 hr period in the autumn, after 2 months either indoors in controlled conditions or in natural outdoor conditions. 2. Harderian glands were taken for determination of N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) activities and melatonin and porphyrin concentrations. 3. Mean 24 hr Harderian NAT and melatonin values were lower outside than inside. 4. Twenty-four hour melatonin rhythms were detected with similar daytime (afternoon) acrophases in both environmental conditions. 5. An NAT rhythm was seen only in animals kept inside, with a circadian maximum in the late dark phase. 6. Mean 24 hr HIOMT activity was slightly higher outdoors than indoors, and 24 hr rhythms were not detected in either condition. 7. Mean porphyrin concentrations were higher outdoors, with 24 hr rhythms detected in both conditions and a significantly earlier nocturnal circadian maximum outdoors.     

Rat C-6 Glioma Cells Maintained In an Organ Culture System: A Study of Kinetic Parameters

Rat C-6 glioma cells were grown on a sponge foam matrix in an organ culture system and the cell cycle parameters, including the growth fraction (GF), were assessed after autoradiography. the zones of growth consisted of a compact upper layer (UL) at the gaseous interface, a central necrotic layer and a deeper lower layer (LL) which invaded the matrix. the fraction of continuously labeled mitoses (FCLM) was similar in both the UL and LL cells. the derivatives of the FCLM curves obtained in three experiments gave an average modal T_G2 of 5 hr. A mathematical model relating GF, T_G2, T_C and labeling index as a function of time, LI(t), was devised for cells in a steady state exposed continuously to tritiated thymidine and was applied to data obtained from UL cells. A mean GF of 9% (range: 8–10%) and a mean cell cycle time (T_C') of 27 hr (range: 13–47 hr) were obtained. the mean T_S was calculated to be 11 hr (range: 8–16 hr) by the method of grain counts per mitotic figure or grain index (GI). Knowledge of T_S permitted alternative calculation of the cell cycle time from the equation T_S/T_C= LI(0)/GF: this gave a mean cell cycle time (T_C) of 29 hr (range: 20–45 hr). Except for the GF, the cell kinetics were comparable to those of the same cell line grown in monolayer culture. the GF in the in vitro system described is in the lower range reported in some human malignant gliomas in vivo.     

Animal Housing and Welfare: Effects of Housing Conditions on Body Weight and Cortisol in a Medium-Sized Rodent (Cavia aperea)

Rodents are the most abundant experimental nonhuman animals and are commonly studied under standard laboratory housing conditions. As housing conditions affect animals' physiology and behavior, this study investigated the effects of indoor and outdoor housing conditions on body weight and cortisol level of wild cavies, Cavia aperea. The changing housing condition strongly influenced both parameters, which are commonly used as indicators for animal welfare. The transfer from outdoor to indoor enclosures resulted in a body-weight loss of about 8%. In contrast, animals kept indoors showed a substantial weight gain of about 12% when they were transferred outdoors. These effects were reversible. To substantiate a connection between body-weight changes and the health states of the animals, blood basal cortisol concentrations were measured. Animals kept outdoors had significantly lower cortisol levels than did animals kept indoors. These results imply that indoor conditions have a direct effect on the animals' states. The physiological and metabolic consequences as well as potential welfare aspects should be taken into account when planning experimental work, especially on nondomestic animals.     

ANALYSIS OF INTESTINAL CELL PROLIFERATION AFTER GUANETHIDINE-INDUCED SYMPATHECTOMY

Rats were treated with guanethidine-sulphate every 48 hr from birth until 15 days and then maintained until young adulthood. Sympathectomy was verified by dissection and light microscopic preparation of the superior cervical and coeliac ganglia which showed at least a 78% reduction in the number of perikarya. The effect of the chemical sympathectomy was a decrease in the amplitude of the circadian mitotic rhythm from 44·7 to 27·1%, 67·0 to 25·3% and 54·9 to 24·7%, in the duodenum, jejunum, and ileum, respectively. The shape of the mitotic index curve was altered and the mean mitotic index was significantly decreased (P < 0·01) in all three segments of the small intestine. The mean mitotic index of control intestinal epithelium was 3·2 ± 0·1%, 3·6 ± 0·1% and 4·0 ± 0·1% in the duodenum, jejunum, and ileum, respectively, and 2·3 ± 0·1%, 2·4 ± 0·1%, and 2·5 ± 0·1% in guanethidine-treated rats. Stathmokinetic estimates of cycle time were obtained by use of the metaphase arrest agent, colchicine. The longest cell generation cycle time (T_c) and lowest mitotic index occurred between 12.00 and 16.00 hours and the shortest T_c and highest mitotic index occurred between 00.00 and 04.00 hours, in all three segments of the small intestine. Guanethidine-treatment lengthens T_c throughout the small intestinal epithelium and reduces the range of variation in T_c over a 24-hr period. It is suggested that norepinephrine depletion induced by guanethidine may be the cause of the inhibition in circadian periodicity and that norepinephrine and the sympathetic nervous system may be essential for the maintenance of circadian rhythms in mitotic activity.     

Effects of housing differences upon activity budgets in captive sifakas (Propithecus verreauxi)

Activity budgets of captive sifakas (Propithecus verreauxi coquereli and Propithecus verreauxi verreauxi) were assessed from 500 hours of observational data obtained at the Duke University Primate Center (Durham, NC). Data were examined for behavioral differences according to gender, availability of intergroup contact, subspecies, indoor/outdoor housing, and enclosure size. Results showed few differences between the activity budgets of males and females. Several differences found in conjunction with availability of intergroup contact appeared to relate more to subspecific, than to contact, differences. Sifakas housed outdoors were more active, spending less time resting and more time in locomotion, feeding, and playing than sifakas housed indoors. The findings of this study implicate outdoor housing as a primary factor in stimulating activity in these rare prosimian primates.     

<Emphasis Type="Italic">Nibribacter flagellatus</Emphasis> sp. nov., isolated from rhizosphere of <Emphasis Type="Italic">Hibiscus syriacus</Emphasis> and emended description of the genus <Emphasis Type="Italic">Nibribacter</Emphasis>

A Gram-stain negative, aerobic, motile by flagella, rod-shaped strain (THG-T16^T) was isolated from rhizosphere of Hibiscus syriacus. Growth occurred at 10–40 °C (optimum 28–30 °C), at pH 6.0–8.0 (optimum 7.0) and at 0–1.0% NaCl (optimum 0%). Based on 16S rRNA gene sequence analysis, the near phylogenetic neighbours of strain THG-T16^T were identified as Nibribacter koreensis KACC 16450^T (98.6%), Rufibacter roseus KCTC 42217^T (94.7%), Rufibacter immobilis CCTCC AB 2013351^T (94.5%) and Rufibacter tibetensis CCTCC AB 208084^T (94.4%). The DNA G+C content of strain THG-T16^T was determined to be 46.7 mol%. DNA–DNA hybridization values between strain THG-T16^T and N. koreensis KACC 16450^T, R. roseus KCTC 42217^T, R. immobilis CCTCC AB 2013351^T, R.tibetensis CCTCC AB 208084^T were 33.5?±?0.5% (31.7?±?0.7% reciprocal analysis), 28.1?±?0.2% (25.2?±?0.2%), 17.1?±?0.9% (10.2?±?0.6%) and 8.1?±?0.3% (5.2?±?0.1%). The polar lipids were identified as phosphatidylethanolamine, two unidentified aminophospholipids, an unidentified aminolipid and three unidentified lipids. The quinone was identified as MK-7 and the polyamine as sym-homospermidine. The major fatty acids were identified as C_16:1 ω5c, C_17:1 ω6c, iso-C_15:0, summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c) and summed feature 4 (iso-C_17:1 I and/or anteiso-C_17:1 B). On the basis of the phylogenetic analysis, chemotaxonomic data, physiological characteristics, and DNA–DNA hybridization data, strain THG-T16^T represents a novel species of the genus Nibribacter, for which the name Nibribacter flagellatus sp. nov. is proposed. The type strain is THG-T16^T(=?KACC 19188^T?=?CCTCC AB 2016246^T).