Murine xenotropic type C viruses I. Distribution and further characterization of the virus in NZB mice.

The xenotropic mouse type C virus, originally detected in cultured embryo cells from New Zealand Black (NZB) mice, has been recovered from over 50 adult NZB animals and 15 NZB embryos. Its presence is best detected by measuring its ability to rescue a murine sarcoma virus (MSV) genome from a non-virus-producing MSV-transformed rat cell. The virus can serve as a helper for replication of MSV. It has a distinct type-specific coat and is a prototype for a third serotype of mouse type C viruses, NZB. The xenotropic virus may have an evolutionary role since it has a wide host range, including the ability to infect avian cells. It is produced spontaneously by all cells cultivated from NZB tissues and accounts for the high concentration of viral antigens associated with NZB tissues. The extent of virus production is similar in both male and female mice. All cell clones established from embryos also produce the virus. A variability in the intracellular regulation of virus replication is suggested since tissue cells from the same animal differ quantitatively in their ability to produce xenotropic viruses. Since enhanced spontaneous virus production is associated with cells from NZB mice, the virus may play a role in the autoimmune disease of this mouse strain.     

Quantitative characterization of a biological membrane by means of its spatial autocovariance.

Profiles for the exoplasmic face (EF) of the freeze-fractured plasma membrane from the root storage tissue of red beets are reconstructed by microdensitometry of micrographs of surface-shadowed-platinum carbon replicas. Autocovariance functions (ACFs) are computed from those profiles. The initial portions of the ACFs have a Gaussian form whose parameters (root mean square surface roughness and autocovariance length) are estimated. The parameter estimates are used to show that the pits on the EF faces are in good complementarity with the intramembrane particles seen on the complementary protoplasmic fracture faces.     

Effect of infusing branched-chain amino acid during incremental exercise with reduced muscle glycogen content

The aim of this study was to investigate whether, when muscle glycogen is reduced, a pre-exercise infusion of branched-chain amino acids (BCAA) modifies exercise performance or the metabolic and respiratory responses to incremental exercise. Six moderately trained volunteers took part in the following protocol on two occasions. On day 1, at 9 a.m. in the postabsorptive state, they performed a graded incremental exercise (increases of 35 W every 4 min) to exhaustion (Ex-1). A meal of 1,000 kcal (4,200 kJ; 60% protein, 40% fat) was consumed at 12 p.m. No food was then allowed until the end of the experiment (20–21 h later). A 90-min period of exercise at alternating high and moderate intensities, designed to deplete muscle glycogen, was performed between 6 p.m. and 7.30 p.m. The morning after (day 2), the subjects randomly received either a mixed solution of BCAA (260 mg × kg^–1 × h^–1 for 70 min), or saline. They then repeated the graded incremental exercise to exhaustion (Ex-2). Metabolic and respiratory measurements suggested a muscle glycogen-depleted state had been achieved. No significant differences were observed in total work performed, maximal oxygen uptake or plasma ammonia, alanine, and blood pyruvate concentrations in the two treatments. After BCAA infusion, higher blood lactate concentrations were observed at maximal power output in comparison with those during saline [BCAA 4.97 (SEM 0.41) mmol × l^–1, Saline 3.88 (SEM 0.47) mmol × l^–1,P < 0.05]. In summary, in conditions of reduced muscle glycogen content, after a short period of fasting, BCAA infusion had no significant effect on the total work that could be performed during a graded incremental exercise.     

Benzodiazepine-sensitive GABA(A) receptors limit the activity of the NMDA/NO/cyclic GMP pathway: a microdialysis study in the cerebellum of freely moving rats

In the cerebellum, infusion of NMDA (200 microM) for 20 min evoked a marked (200%) increase of extracellular cyclic GMP (cGMP) levels. The selective GABA(A) receptor agonist muscimol (0.01-100 microM) was able to counteract the NMDA effect with an EC(50) of 0.65 microM; the inhibitory effect of muscimol (10 microM) was prevented by bicuculline (50 microM). Diazepam (10 microM) significantly potentiated the muscimol (1 microM) inhibition; furthermore, when coinfused with 0.1 microM muscimol (a concentration not affecting, on its own, the cGMP response to NMDA), diazepam (10 microM) reduced the NMDA effect. Similar results were obtained with zolpidem (0.1-1 microM). Finally, local infusion of the benzodiazepine site antagonist flumazenil (10 microM), together with muscimol and diazepam, almost completely restored the effect of NMDA on extracellular cGMP levels. It is concluded that GABA(A) receptors potently control the NMDA/nitric oxide/cGMP pathway in the cerebellum in vivo. In terms of the alpha subunit composition, we can deduce that the cerebellar GABA(A) receptor does not contain alpha(6) or beta(4) subunits because it is diazepam-sensitive. Moreover, the observation that zolpidem is active at a rather low concentration, in combination with localization studies present in the literature, tend to exclude the presence of alpha(5) subunits in the receptor composition and suggest the involvement of an alpha(1) subunit.     

Programmed cell death progressively models the development of anther sporophytic tissues from the tapetum and is triggered in pollen grains during maturation

To characterize the spatial and temporal occurrence of programmed cell death (PCD) in Lilium anther tissues, we used both microscopical and molecular markers of apoptosis for developmental stages from meiosis to pollen release. The first hallmarks of PCD include cell condensation and shrinkage of the cytoplasm, separation of chromatin into delineated masses, and DNA fragmentation in the tapetum as early as the premeiosis stage. PCD then extended to other anther sporophytic tissues, leading to anther dehiscence. Although the PCD clearly affected the endothecium and the epidermis, these two cell layers remained alive until anther dehiscence. In pollen, no sign of PCD was found until pollen mitosis I, after what apoptotic features developed progressively in the vegetative cell. In addition, DNA ladders were detected in all sporophytic tissues and cell types throughout pollen development, whereas in the male gametophyte DNA ladders were only detected during pollen maturation. Our data suggest that PCD is a progressive and active process affecting all the anther tissues, first being triggered in the tapetum.     

A Simple Method for the Reconstitution of Membrane Proteins into Giant Unilamellar Vesicles

A simple method for the reconstitution of membrane protein from submicron proteoliposomes into giant unilamellar vesicles (GUVs) is presented here: This method does not require detergents, fusion peptides or a dehydration step of the membrane protein solution. In a first step, GUVs of lipids were formed by electroformation, purified and concentrated; and in a second step, the concentrated GUV solution was added to a small volume of vesicles or proteoliposomes. Material transfer from submicron vesicles and proteoliposomes to GUVs occurred spontaneously and was characterized with fluorescent microscopy and patch-clamp recordings. As a functional test, the voltage-dependent, anion-selective channel protein was reconstituted into GUVs, and its electrophysiological activity was monitored with the patch clamp. This method is versatile since it is independent of the presence of the protein, as demonstrated by the fusion of fluorescently labeled submicron vesicles and proteoliposomes with GUVs.     

Global transcriptional response of pig brain and lung to natural infection by Pseudorabies virus

Background  

Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult.     

Epidemiology and psycho-social aspects of onchocercal skin diseases in northeastern Nigeria

Background

Observations were made on the prevalence of onchocerciasis and Onchocercal Skin Diseases (OSD); frequency of occurrence and anatomical distribution of OSD in the Hawal River Valley, an established onchocerciasis endemic focus in north-eastern Nigeria.

Methods

Symptoms of OSD were diagnosed in 5 844 subjects using Rapid Assessment Method (RAM) while 1 479 of the subjects chosen from alternate households had their skin biopsies examined for active microfilariae of Onchocerca volvulus. Also, Focal Group Discussions (FGD) were conducted at the Health District levels.

Results

O. volvulus was recorded in (19.0%) and OSD in (43.8%) of the subjects. The Mantel-Haenszel test for linear association showed a close agreement between onchocerciasis prevalence and the rate of OSD (χ² = 3.93; p < 0.05). The various forms of OSD occurred in the order: CPOD (17.7%), APOD (9.9%), DPM (9.0%), LOD (7.0%) and ATR (3.1%). The overall frequency of occurrence of various symptoms of OSD on different anatomical locations showed the locations in descending order of occurrence as lower limbs (24.6%), upper limbs (21.3%), buttocks (19.9%), shoulder & neck (19.1%), abdomen and trunk (11.3%), backside (10.6), and 'other' sites (7.5%). The Focal Group Discussion (FGD) revealed the most worrisome consequences of OSD as social isolation of victims (31.3%), shame and low self esteem (22.7%) and high cost of medication (15.6%).

Conclusion

It is recommended that Onchocerciasis control programmes in the Hawal River Valley and any other focus with high incidence of OSD should incorporate an aspect that would address the anxiety and depression caused by various OSD lesions since they carry lots of psycho-social implications. This would increase acceptance and compliance of the target population. The classification criteria of onchocerciasis endemicity should be based on either or both of the O. volvulus and onchocercal skin disease burden of any community and no longer on O. volvulus parasitic infection rate alone.