Effects of acute graded reductions in testicular blood flow on testicular morphology in the adult rat

The effect of moderate reductions in testicular blood flow has not been studied systematically. The aim of this study was, therefore, to examine the effects of different degrees of blood flow reduction on testicular morphology and to determine how much flow can be reduced before damage occurs. The subcapsular testicular artery was partially ligated in the left testes of adult rats. Testicular blood flow was measured before, immediately after, and 5 h after the ligation using laser Doppler flowmetry. After 5 h of partial ligation, the testes were removed, and their morphology was examined and related to the degree of blood flow reduction. The number of in situ end-labeled- or TUNEL-positive (i.e., dying) germ cells and the volume density of intravascular polymorphonuclear (PMN) leukocytes were measured. When flow was reduced to approximately 70% or less of its pretreatment value, a dose-related increase in the number of dying spermatogonia and early spermatocytes was seen. The PMN leukocytes accumulated in testicular blood vessels after partial ligation, and the maximum number was observed in testes where flow was reduced by approximately 50% of the pretreatment value. In conclusion, early stages of spermatogenesis are sensitive to a moderate, acute reduction in blood flow. Discrete reductions in flow may, therefore, have a large impact on sperm production.     

Cloning, analysis, and heterologous expression of a polyketide synthase gene cluster of Streptomyces curacoi.

Streptomyces curacoi produces curamycin, an antibiotic based on a modified orsellinic acid skeleton that is synthesized by the polyketide pathway. We have cloned, characterized, and partly sequenced a polyketide synthase gene cluster of S. curacoi. The sequence data reveal an organization of open reading frames that is similar to those of other polyketide synthetic clusters, although the biosynthetic products differ considerably in size and structure. We propose that one of the predicted open reading frames (curA) encodes polykeptide synthase, on the basis of its homology with other enzymes with similar functions. Expression of the cloned chromosomal fragment in the heterologous host S. lividans leads to the production of a brown pigment in large quantities. The analysis and expression of the cur genes for detailed molecular studies of the mechanism of polyketide biosynthesis is discussed.     

Retinitis pigmentosa: rapid neurodegeneration is governed by slow cell death mechanisms

For most neurodegenerative diseases the precise duration of an individual cell''s death is unknown, which is an obstacle when counteractive measures are being considered. To address this, we used the rd1 mouse model for retinal neurodegeneration, characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cyclic guanosine-mono-phosphate (cGMP) levels. Using cellular data on cGMP accumulation, cell death, and survival, we created mathematical models to simulate the temporal development of the degeneration. We validated model predictions using organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast. Together, photoreceptor data and modeling for the first time delineated three major cell death phases in a complex neuronal tissue: (1) initiation, taking up to 36 h, (2) execution, lasting another 40 h, and finally (3) clearance, lasting about 7 h. Surprisingly, photoreceptor neurodegeneration was noticeably slower than necrosis or apoptosis, suggesting a different mechanism of death for these neurons.     

Differential short-term effects of growth factors on fatty acid synthesis in isolated rat-liver cells

Hepatocytes in suspension, freshly isolated from meal-fed rats, were used to study the acute influence of growth factors on the rate of de novo fatty acid synthesis. Nerve growth factor (2.5 S) and epidermal growth factor caused a substantial increase in the rate of fatty acid synthesis, whereas fibroblast growth factor was inhibitory. Little effect was observed with nerve growth factor (7 S), bombesin or substance P. Transferrin did not affect hepatic fatty acid synthesis. The results are discussed in relation to the effects of insulin and tumor-promoting phorbol esters.     

A comparative study of the reproductive fitness and pathogenicity of a population of Radopholus similis from Davao,Philippines, on banana (Musa spp.)

The in vitro reproductive fitness on carrot discs and the in vivo pathogenicity on selected FHIA (Fundación Hondureña de Investigaciónes Agrícola) banana hybrids of a population of Radopholus similis isolated from banana in Davao, Philippines, were investigated at the Bureau of Plant Industry, Davao City, Philippines. It was shown that on carrot discs following inoculation with 25 females, the Davao population had the highest population density and multiplication rate compared with two other R. similis populations from the Philippines (Los Baños and Quezon) and two exotic populations of R. similis (from Uganda and Indonesia). According to the Gompertz model, the Davao population also had a short lag phase and a high maximum specific growth. Following inoculation with one single female, the Davao population also had the highest multiplication rate and the highest proportion of juveniles and females compared with the other four populations included in the experiments. Nine weeks after inoculation with 1000 vermiforms, the R. similis population from Davao had reduced the plant height of the FHIA hybrids included in the experiment (FHIA-3, FHIA-4, FHIA-5, FHIA-18 and FHIA-23) on average by 37%, plant girth by 5.3–40.9%, shoot weight by 20.1–65.8% and root weight by 31.7–69.7%, indicating the high pathogenicity of this population on banana. FHIA-4 was tolerant to R. similis infection.     

Livestock-Associated MRSA in Household Members of Pig Farmers: Transmission and Dynamics of Carriage,A Prospective Cohort Study

This prospective cohort study describes carriage of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in household members from 49 farrowing pig farms in the Netherlands (2010–2011). Of 171 household members, 4% were persistent MRSA nasal carriers, and the MRSA prevalence on any given sampling moment was 10% (range 7-11%). Working in the stables (of which 98% was MRSA-positive, prevalence ratio (PR) = 2.11 per 10 hours), working with sows (PR=1.97), and living with an MRSA-positive pig farmer (PR=4.63) were significant determinants for MRSA carriage. Significant protective factors were carriage of methicillin-susceptible Staphylococcus aureus (MSSA) (PR=0.50), and wearing a facemask when working in the stables (37% decreased prevalence). All MRSA strains during the study period were known livestock-associated types. The bacteriophage φ3 was not found in household members. Transmission from pigs and the environment appeared to be important determinants; human-to-human transmission could not sufficiently be differentiated. Wearing a facemask when working in the stables and carriage of MSSA are potential interventional targets.