During normal development of the vertebrate nervous system, large numbers of neurons in the central and peripheral nervous system undergo naturally occurring cell death. For example, about half of all spinal motor neurons die over a period of a few days in developing avian, rat and mouse embryos. Previous studies have shown that extracts from muscle and brain, secreted factors from glia, as well as several growth factors and neurotrophic agents, including muscle-derived factors, can promote the survival of developing motor neurons in vitro and in vivo. But because neurotrophins and other known trophic agents administered alone or in combination are insufficient to rescue all developing motor neurons from cell death, other neurotrophic molecules are probably essential for the survival and differentiation of motor neurons. Here we report that glial-cell-line-derived neurotrophic factor (GDNF), a potent neurotrophic factor that enhances survival of mammalian midbrain dopaminergic neurons, rescues developing avian motor neurons from natural programmed cell death in vivo and promotes the survival of enriched populations of cultured motor neurons. Furthermore, treatment with this agent in vivo also prevents the induced death and atrophy of both avian and mouse spinal motor neurons following peripheral axotomy.

Glial cell line-derived neurotrophic factor (GDNF) has been shown to rescue developing motoneurons in vivo and in vitro from both naturally occurring and axotomyinduced cell death. To test whether GDNF has trophic effects on adult motoneurons, we used a mouse model of injuryinduced adult motoneuron degeneration. Injuring adult motoneuron axons at the exit point of the nerve from the spinal cord (avulsion) resulted in a 70% loss of motoneurons by 3 weeks following surgery and a complete loss by 6 weeks. Half of the loss was prevented by GDNF treatment. GDNF also induced an increase (hypertrophy) in the size of surviving motoneurons. These data provide strong evidence that the survival of injured adult mammalian motoneurons can be promoted by a known neurotrophic factor, suggesting the potential use of GDNF in therapeutic approaches to adultonset motoneuron diseases such as amyotrophic lateral sclerosis.Factors that promote motoneuron survival have potential as therapeutic agents for the treatment of human neurodegenerative diseases (1). It has been shown that several neurotrophic factors, including brain-derived neurotrophic factor (BDNF) (2-4), insulin-like growth factor (I.GF) (5), ciliary neurotrophic factor (6), and glial cell line-derived neurotrophic factor (GDNF) (7-10), can rescue developing motoneurons from both naturally occurring and axotomy-induced cell death. However, whether these trophic factors also play a role in adult motoneuron survival is not known. Because many motoneuron diseases, such as amyotrophic lateral sclerosis, have a late (i.e., adult) onset, it is important to determine whether neurotrophic factors are effective on injured adult motoneurons.Interactions between motoneurons and their target muscles have been extensively investigated. For example, it is known that transection of axons of motoneurons or removal of their target during embryonic and early postnatal development results in massive motoneuron cell loss, whereas axotomy of adult peripheral nerve induces little if any neuronal death (11)(12)(13)(14)(15)(16)(17)(18)(19). A plausible explanation for this difference is that trophic support derived from mature nonneuronal cells (e.g., Schwann cells) associated with the peripheral nerve maintains the survival of adult motoneurons.A different type of lesion, ventral root avulsion, which involves pulling the root out of the spinal cord, induces the death of virtually all motoneurons in the adult rat and provides a good model to examine the response of adult motoneurons to trophic factors (20,21). The expression of nitric oxide synthase (NOS), an enzyme for synthesis of the free radical nitric oxide (NO), can be induced in adult rat motoneurons following both spinal root avulsion (20,22) and cranial nerve axotomy (23), and it has been suggested that the cell death following these lesions may be induced by oxidative stress and reactive oxygen species such as [20][21][22].Although the target dependency of motoneuron survival is diminished in adult animals (15, 18), adult rat m...

Adult Leydig cells (ALCs) are the steroidogenic cells in the testes that produce testosterone. ALCs develop postnatally from a pool of stem cells, referred to as stem Leydig cells (SLCs). SLCs are spindle-shaped cells that lack steroidogenic cell markers, including luteinizing hormone (LH) receptor and 3β-hydroxysteroid dehydrogenase. The commitment of SLCs into the progenitor Leydig cells (PLCs), the first stage in the lineage, requires growth factors, including Dessert Hedgehog (DHH) and platelet-derived growth factor-AA. PLCs are still spindle-shaped, but become steroidogenic and produce mainly androsterone. The next transition in the lineage is from PLC to the immature Leydig cell (ILC). This transition requires LH, DHH, and androgen. ILCs are ovoid cells that are competent for producing a different form of androgen, androstanediol. The final stage in the developmental lineage is ALC. The transition to ALC involves the reduced expression of 5α-reductase 1, a step that is necessary to make the cells to produce testosterone as the final product. The transitions along the Leydig cell lineage are associated with the progressive down-regulation of the proliferative activity, and the up-regulation of steroidogenic capacity, with each step requiring unique regulatory signaling.

We have examined the ability of different neurotrophic and growth factors to prevent axotomy-induced motoneuron cell death in the developing mouse spinal cord. After postnatal unilateral section of the mouse sciatic nerve, most motoneuron (MN) loss occurs in the lateral motor column of the fourth lumbar segment (L4). Significant axotomy-induced cell death occurred after surgery performed on or before postnatal day (PN) 5. In contrast, no significant cell loss was found when axotomy was performed after PN10. Axotomy on PN2 or PN5 resulted in a 44% loss of L4 motoneurons by 7 days, and a 66% loss of motoneurons by 10 days postsurgery. Implantation of gelfoam presoaked in various neurotrophic factors at the lesion site rescued axotomized motoneurons. Nerve growth factor (NGF), neurotrophin-4/5 (NT-4/5) and ciliary neurotrophic factor (CNTF) rescued 20%-30% of motoneurons, whereas brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and insulin-like growth factor 1 (IGF-1) rescued virtually all motoneurons from axotomy-induced death. By contrast, platelet-derived growth factor (PDGF)-AA, PDGF-AB, basic fibroblast growth factor (bFGF), and interleukin (IL-6) were ineffective on motoneuron survival following axotomy. NGF, BDNF, NT-3, IGF-1, and CNTF also prevented axotomy-induced atrophy of surviving motoneurons. These data show that mouse lumbar motoneurons continue to be vulnerable to axotomy up to about 1 week after birth and that a number of trophic agents, including the neurotrophins, CNTF, and IGF-1, can prevent the death of these neurons following axotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

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Phage-coded lysin is an enzyme that destroys the cell walls of bacteria. Phage lysin could be an alternative to conventional antibiotic therapy against pathogens that are resistant to multiple antibiotics. In this study, a novel staphylococcal phage, GH15, was isolated, and the endogenous lytic enzyme (LysGH15) was expressed and purified. The lysin LysGH15 displayed a broad lytic spectrum; in vitro treatment killed a number of Staphylococcus aureus strains rapidly and completely, including methicillinresistant S. aureus (MRSA). In animal experiments, a single intraperitoneal injection of LysGH15 (50 g) administered 1 h after MRSA injections at double the minimum lethal dose was sufficient to protect mice (P < 0.01). Bacteremia in unprotected mice reached colony counts of about 10 7 CFU/ml within 3.5 h after challenge, whereas the mean colony count in lysin-protected mice was less than 10 4 CFU/ml (and ultimately became undetectable). These results indicate that LysGH15 can kill S. aureus in vitro and can protect mice efficiently from bacteremia in vivo. The phage lysin LysGH15 might be an alternative treatment strategy for infections caused by MRSA.Staphylococcus aureus is a common and dangerous pathogen that causes various infectious diseases, including skin abscesses, wound infections, endocarditis, osteomyelitis, pneumonia, and toxic shock syndrome (2, 23). Treatment of these infections has become ever more difficult due to the emergence of multidrug-resistant strains, especially methicillin-resistant S. aureus (MRSA) (15,25,26,36,37). Vancomycin was effective against MRSA, but certain MRSA strains have already acquired resistance to vancomycin as well (vancomycin-resistant S. aureus [VRSA]), raising serious concerns within the medical community (17,18,37). Therefore, there is an urgent need for novel therapeutic agents directed against this formidable pathogen (2, 9).The phage lysin is encoded by the bacteriophage genome and is synthesized at the end of the phage lytic life cycle to lyse the host cell (30). Lysins belong to the family of mureolytic enzymes that directly destroy peptidoglycans in the bacterial cell wall. Previous studies have suggested that lysins from certain phages were highly efficient in lysing bacteria, especially when applied exogenously (11,14,21,22,29,35). As a potential antibacterial agent, lysins possess several promising features, namely, a distinct mode of action, species or type specificity, and bactericidal activity independent of the antibiotic susceptibility pattern (1). Indeed, there is a low probability that bacteria will develop resistance against lysin (12, 21).Some Staphylococcus phage lysins have been isolated and studied, including LysK, ClyS, MV-L, LysWMY, and ⌽H5; however, only MV-L and ClyS have been studied in in vivo assays (6, 33). In this study, a novel myovirus phage infecting S. aureus was isolated. The lysin derived from this phage, LysGH15, was expressed and refined. The lysin LysGH15 demonstrated a very broad host range and strong lytic activity. We evaluate...

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