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Pamela Vig

Publications and source records attributed to Pamela Vig.

7 recordsLinked to original sources
PubMed2025

Smith-Lemli-Opitz syndrome: Clinical, biochemical, and genetic insights with emerging treatment opportunities.

Smith-Lemli-Opitz syndrome (SLOS), also known as RSH syndrome, is an inborn error of cholesterol biosynthesis first described in 1964. Since then, significant advances have been made in understanding its pathophysiology, both during fetal development and postnatally. Cholesterol is a crucial lipid in the body, especially in the central nervous system, which accounts for nearly 25% of the body's total cholesterol. Cholesterol deficiency in SLOS can lead to congenital malformations and severe neurodevelopmental disabilities. The biochemical and genetic bases of SLOS have been elucidated. Reduced or absent 7-dehydrocholesterol reductase enzymatic activity results not only in cholesterol deficiency but also in accumulation of 7-dehydrocholesterol, 8-dehydrocholesterol, and toxic oxysterol metabolites, which contribute to the pathophysiology of SLOS and correlate variably with the severity of its clinical symptoms. Despite decades of research, the clinical recognition of SLOS remains challenging because of the condition's multisystemic nature and noteworthy phenotypic variability. This review provides an up-to-date summary of major research advances in the study of SLOS with a focus on clinical manifestations and biochemical and genetic findings, which, taken together, facilitate recognition and diagnostic confirmation. Additionally, we recap past and current efforts in therapeutic development and offer guidance for disease management.

Humans↗
PubMed2006

The sources of parenchymal regeneration after chronic hepatocellular liver injury in mice.

After liver injury, parenchymal regeneration occurs through hepatocyte replication. However, during regenerative stress, oval cells (OCs) and small hepatocyte like progenitor cells (SHPCs) contribute to the process. We systematically studied the intra-hepatic and extra-hepatic sources of liver cell replacement in the hepatitis B surface antigen (HBsAg-tg) mouse model of chronic liver injury. Female HBsAg-tg mice received a bone marrow (BM) transplant from male HBsAg-negative mice, and half of these animals received retrorsine to block indigenous hepatocyte proliferation. Livers were examined 3 and 6 months post-BM transplantation for evidence of BM-derived hepatocytes, OCs, and SHPCs. In animals that did not receive retrorsine, parenchymal regeneration occurred through hepatocyte replication, and the BM very rarely contributed to hepatocyte regeneration. In mice receiving retrorsine, 4.8% of hepatocytes were Y chromosome positive at 3 months, but this was frequently attributable to cell fusion between indigenous hepatocytes and donor BM, and their frequency decreased to 1.6% by 6 months, as florid OC reactions and nodules of SHPCs developed. By analyzing serial sections and reconstructing a 3-dimensional map, continuous streams of OCs could be seen that surrounded and entered deep into the nodules of SHPCs, connecting directly with SHPCs, suggesting a conversion of OCs into SHPCs. In conclusion, during regenerative stress, the contribution to parenchymal regeneration from the BM is minor and frequently attributable to cell fusion. OCs and SHPCs are of intrinsic hepatic origin, and OCs can form SHPC nodules.

Animals↗
PubMed2005

Safety and efficacy of adefovir dipivoxil in patients infected with lamivudine-resistant hepatitis B and HIV-1.

BACKGROUND/AIMS: Adefovir dipivoxil (10 mg once-daily) was added to antiretroviral therapy including lamivudine in 35 HIV/HBV co-infected patients. METHODS: Parameters evaluated included alanine aminotransferase (ALT), HBV DNA and serological markers, HIV-1 RNA, and CD4+ cell count. RESULTS: Twenty-nine patients (83%) completed 144 weeks. Serum HBV DNA declined from a baseline 9.76 log10 copies/mL (median) to 4.68, 5.24, and 5.90 log10 copies/mL at weeks 48, 96, and 144, respectively (P<0.0001 at all time points). Seven patients (25%) achieved HBV DNA<2.3 log10 copies/mL. No adefovir-associated resistance mutations in HBV DNA polymerase or HIV-1 reverse transcriptase were detected. ALT declined from 81 IU/L (median) at baseline by -16.0, -44.5, and -46.0 IU/L at week 48, 96 and 144, respectively (P=<0.05, respectively), and normalized in 71% of patients (20 of 28) by week 144. Two patients developed antibodies against HB 'e' antigen by week 48. No serious adverse events related to adefovir dipivoxil occurred during the study, and HIV-1 RNA and CD4+ cell counts were stable. CONCLUSIONS: Treatment with adefovir dipivoxil for 144 weeks was well tolerated and resulted in significant and sustained reductions in HBV DNA and ALT in HIV/HBV co-infected patients. Efficacy increased with treatment duration, with no loss of viral suppression.

AIDS-Related Opportunistic Infections↗
PubMed2003

Plastic adult stem cells: will they graduate from the school of hard knocks?

Notwithstanding the fact that adult bone marrow cell engraftment to epithelial organs seems a somewhat uncommon event, there is no doubt it does occur, and under appropriate conditions of a strong and positive selection pressure these cells will expand clonally and make a significant contribution to tissue replacement. Likewise, bone-marrow-derived cells can be amplified in vitro and differentiated into a multitude of tissues. These in essence are the goals of regenerative medicine using any source of stem cells, be it embryonic or adult. Despite such irrefutable evidence of what is possible, a veritable chorus of detractors of adult stem cell plasticity has emerged, some doubting its very existence, motivated perhaps by more than a little self-interest. The issues that have led to this state of affairs have included the inability to reproduce certain widely quoted data, one case where the apparent transdifferentiation was due to contamination of the donor tissue with haematopoietic cells and, most notoriously, extrapolating from the behaviour of embryonic stem cells to suggest that adult bone marrow cells simply fuse with other cells and adopt their phenotype. While these issues need resolving, slamming this whole new field because not everything is crystal clear is not good science. The fact that a phenomenon is quite rare in no way mitigates against its very existence: asteroid collisions with the Earth are rare, but try telling the dinosaurs they do not occur! When such events do occur (transdifferentiation or collision), they certainly can make an impact.

Animals↗
PubMed2002

Hepatic stem cells.

The liver in an adult healthy body maintains a balance between cell gain and cell loss. Though normally proliferatively quiescent, hepatocyte loss such as that caused by partial hepatectomy, uncomplicated by virus infection or inflammation, invokes a rapid regenerative response to restore liver mass. This restoration of moderate cell loss and 'wear and tear' renewal is largely achieved by hepatocyte self-replication. Furthermore, hepatocyte transplants in animals have shown that a certain proportion of hepatocytes can undergo significant clonal expansion, suggesting that hepatocytes themselves are the functional stem cells of the liver. More severe liver injury can activate a potential stem cell compartment located within the intrahepatic biliary tree, giving rise to cords of bipotential so-called oval cells within the lobules that can differentiate into hepatocytes and biliary epithelial cells. A third population of stem cells with hepatic potential resides in the bone marrow; these haematopoietic stem cells can contribute to the albeit low renewal rate of hepatocytes, make a more significant contribution to regeneration, and even completely restore normal function in a murine model of hereditary tyrosinaemia. How these three stem cell populations integrate together to achieve a homeostatic balance is not known. This review focuses on two major aspects of liver stem cell biology: firstly, the identity of the liver stem cells, and secondly, their potential value in the treatment of major liver disease.

Animals↗
PubMed2002

Adult stem cell plasticity: new pathways of tissue regeneration become visible.

There has recently been a significant change in the way we think about organ regeneration. In the adult, organ formation and regeneration was thought to occur through the action of organ-or tissue-restricted stem cells (i.e. haematopoietic stem cells making blood; gut stem cells making gut, etc.). However, there is a large body of recent work that has extended this model. Thanks to lineage tracking techniques, we now believe that stem cells from one organ system, for example the haematopoietic compartment, can develop into the differentiated cells within another organ system, such as liver, brain or kidney. This cellular plasticity not only occurs under experimental conditions, but has also been shown to take place in humans following bone marrow and organ transplants. This trafficking is potentially bi-directional, and even differentiated cells from different organ systems can interchange, with pancreatic cells able to form hepatocytes, for example. In this review we will detail some of these findings and attempt to explain their biological significance.

Adult↗