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Biomedical subjects

D Gerber

Publications and source records attributed to D Gerber.

At least 19 recordsLinked to original sources
PubMed1999

Phosphorylation by CK2 and MAPK enhances calnexin association with ribosomes.

Calnexin was initially identified as an endoplasmic reticulum (ER) type I integral membrane protein, phosphorylated on its cytosolic domain by ER-associated protein kinases. Although the role of the ER luminal domain of calnexin has been established as a constituent of the molecular chaperone machinery of the ER, less is known about the role of the cytosolic phosphorylation of calnexin. Analysis by two-dimensional phosphopeptide maps revealed that calnexin was in vitro phosphorylated in isolated microsomes by casein kinase 2 (CK2) and extracellular-signal regulated kinase-1 (ERK-1) at sites corresponding to those for in vivo phosphorylation. In canine pancreatic microsomes, synergistic phosphorylation by CK2 and ERK-1 led to increased association of calnexin with membrane-bound ribosomes. In vivo, calnexin-associated ERK-1 activity was identified by co-immunoprecipitation. This activity was abolished in cells expressing a dominant-negative MEK-1. Activation of ERK-1 in cells by addition of serum led to a 4-fold increase in ribosome-associated calnexin over unstimulated cells. Taken together with studies revealing calnexin association with CK2 and ERK-1, a model is proposed whereby phosphorylation of calnexin leads to a potential increase in glycoprotein folding close to the translocon.

Animals↗
PubMed1999

Novel bioartificial liver support system: preclinical evaluation.

Preclinical safety and efficacy evaluation of a novel bioartificial liver support system (BLSS) was conducted using a D-galactosamine canine liver failure model. The BLSS houses a suspension of porcine hepatocytes in a hollow fiber cartridge with the hepatocytes on one side of the membrane and whole blood flowing on the other. Porcine hepatocytes harvested by a collagenase digestion technique were infused into the hollow fiber cartridge and incubated for 16 to 24 hours prior to use. Fifteen purpose-bred male hounds, 1-3 years old, 25-30 kg, were administered a lethal dose, 1.5 g/kg, of D-galactosamine. The animals were divided into three treatment groups: (1b) no BLSS treatment (n = 6); (2b) BLSS treatment starting at 24-26 h post D-galactosamine (n = 5); and (2c) BLSS treatment starting at 16-18 h post D-galactosamine (n = 4). While maintained under isoflurane anesthesia, canine supportive care was guided by electrolyte and invasive physiologic monitoring consisting of arterial pressure, central venous pressure, extradural intracranial pressure (ICP), pulmonary artery pressure, urinary catheter, and end-tidal CO2. All animals were treated until death or death-equivalent (inability to sustain systolic blood pressure > 80 mmHg for 20 minutes despite massive fluid resuscitation and/or dopamine administration), or euthanized at 60 hours. All animals developed evidence of liver failure at 12-24 hours as evidenced by blood pressure lability, elevated ICP, marked hepatocellular enzyme elevation with microscopic massive hepatocyte necrosis and cerebral edema, elevated prothrombin time, and metabolic acidosis. Groups 2b and 2c marginally prolong survival compared with Group 1b (pairwise log rank censored survival time analysis, p = 0.096 and p = 0.064, respectively). Since survival times for Groups 2b and 2c are not significantly different (p = 0.694), the groups were combined for further statistical analysis. Survival times for the combined active treatment Groups 2b and 2c are significantly prolonged versus Group 1b (p = 0.047). These results suggest the novel BLSS reported here can have a significant impact on the course of liver failure in the D-galactosamine canine liver failure model. The BLSS is ready for Phase I safety evaluation in a clinical setting.

Animals↗
PubMed1999

Characterisation of a potentially abortigenic strain of feline calicivirus isolated from a domestic cat.

Feline calicivirus (FCV) was isolated from one of four dead fetuses delivered by ovariohysterectomy from a queen with an acute FCV infection. The most prominent lesions in the fetuses were petechial haemorrhages in the skin. The virus isolated was characterised as FCV by antigenic analysis and cDNA sequence analysis. This is the second report of abortion associated with acute FCV infection.

Abortion, Veterinary↗
PubMed1999

Management of portal hypertension-related bleeding.

Although endoscopic sclerotherapy and TIPS remain the primary therapeutic tools in management of acute variceal bleeding, surgical shunts must be considered for low-risk patients with bleeding. OLTx is the only definitive treatment for patients with end-stage liver disease and vascular decompensation. Furthermore, the current prospective multicenter randomized study, funded by the National Institutes of Health and Human Services, will help determine the role of DSRS versus TIPS in cirrhotic patients with good hepatic reserve. This is a necessity in a time in which organ shortages are ever-increasing because of a growing disparity between the number of patients listed for transplantation each year versus the number of suitable organ donors. The various surgical techniques should be applied in different situations based on patients' clinical status at the time of the bleed and whether they are considered candidates for liver transplantation.

Acute Disease↗
PubMed1998

Impact energy measurement in time-of-flight mass spectrometry with cryogenic microcalorimeters.

Time-of-flight mass spectrometry-most notably matrix-assisted laser-desorption-ionization time-of-flight (MALDI-TOF) spectrometry-is an important class of techniques for the study of proteins and other biomolecules. Although these techniques provide excellent performance for masses up to about 20,000 daltons, there has been limited success in achieving good mass resolution at higher masses. This is because the sensitivity of the microchannel plate (MCP) detectors used in most systems decreases rapidly with increasing particle mass, limiting the utility of MCP detectors for very large masses. It has recently been proposed that cryogenic particle detectors may provide a solution to these difficulties. Cryogenic detectors measure the thermal energy deposited by the particle impact, and thus have a sensitivity that is largely independent of particle mass. Recent experiments have demonstrated the sensitivity of cryogenic particle detectors to single biomolecules, a quantum efficiency several orders of magnitude larger than the MCP detectors, and sensitivity to masses as large as 750,000 daltons. Here we present results demonstrating an order of magnitude better energy resolution than previous measurements, allowing direct determination of particle charge state during acceleration. Although application of these detectors to practical mass spectrometry will require further development of the detectors and cryogenics, these detectors can be used to elucidate the performance-limiting processes that occur in such systems.

Animals↗
PubMed1998

Persistent interactions of core histone tails with nucleosomal DNA following acetylation and transcription factor binding.

In this study, we examined the effect of acetylation of the NH2 tails of core histones on their binding to nucleosomal DNA in the absence or presence of bound transcription factors. To do this, we used a novel UV laser-induced protein-DNA cross-linking technique, combined with immunochemical and molecular biology approaches. Nucleosomes containing one or five GAL4 binding sites were reconstituted with hypoacetylated or hyperacetylated core histones. Within these reconstituted particles, UV laser-induced histone-DNA cross-linking was found to occur only via the nonstructured histone tails and thus presented a unique tool for studying histone tail interactions with nucleosomal DNA. Importantly, these studies demonstrated that the NH2 tails were not released from nucleosomal DNA upon histone acetylation, although some weakening of their interactions was observed at elevated ionic strengths. Moreover, the binding of up to five GAL4-AH dimers to nucleosomes occupying the central 90 bp occurred without displacement of the histone NH2 tails from DNA. GAL4-AH binding perturbed the interaction of each histone tail with nucleosomal DNA to different degrees. However, in all cases, greater than 50% of the interactions between the histone tails and DNA was retained upon GAL4-AH binding, even if the tails were highly acetylated. These data illustrate an interaction of acetylated or nonacetylated histone tails with DNA that persists in the presence of simultaneously bound transcription factors.

Acetylation↗
PubMed1997

The T cell receptor repertoire of intestinal intraepithelial gammadelta T lymphocytes is influenced by genes linked to the major histocompatibility complex and to the T cell receptor loci.

Most of the gammadelta T cells in the intestinal epithelium of normal mice use the Vgamma1 or the Vgamma7 gene segments. However, the relative proportions of gammadelta intraepithelial lymphocytes expressing either the Vgamma1 or the Vgamma7 chain vary among different strains of mice whereas they are quite constant between different individuals of the same strain, suggesting that genetic factors, rather than environmental factors, are responsible for the observed differences. To analyze the genetic factors influencing the representation of different gammadelta T cell subsets in the intestinal epithelium, we used available anti-T cell antigen receptor (TCR) V region-specific mAbs against Vgamma1, Vgamma4, Vgamma7, and Vdelta4 to examine the TCR repertoire of intraepithelial gammadelta lymphocytes in a set of (C57BL/6 x DBA/2) recombinant inbred strains. Our results show that the representation of different Vgamma and Vdelta gene products among gammadelta intestinal intraepithelial lymphocytes is under a complex genetic control with a marked influence by genes closely linked to the TCRgamma, TCRdelta, and major histocompatibility complex loci.

Animals↗
PubMed1996

Subregion- and cell type-restricted gene knockout in mouse brain.

Using the phage P1-derived Cre/loxP recombination system, we have developed a method to create mice in which the deletion (knockout) of virtually any gene of interest is restricted to a subregion or a specific cell type in the brain such as the pyramidal cells of the hippocampal CA1 region. The Cre/loxP recombination-based gene deletion appears to require a certain level of Cre protein expression. The brain subregional restricted gene knockout should allow a more precise analysis of the impact of a gene mutation on animal behaviors.

Animals↗
PubMed1996

Increased pituitary activation following metyrapone administration in post-traumatic stress disorder.

Our previous findings have demonstrated that individuals with post-traumatic stress disorder (PTSD) show lower basal cortisol levels, a larger number of lymphocyte glucocorticoid receptors, and an enhanced suppression of cortisol following the administration of dexamethasone compared to normals and patients with major depression. We have previously suggested that these alterations reflect an enhanced negative feedback inhibition of the hypothalamic-pituitary-adrenal (HPA) axis in PTSD. However, in the absence of direct knowledge of pituitary capability in this disorder, it has been equally likely that the alterations observed reflected either pituitary or adrenal insufficiency. In the present study, we examined ACTH release from the pituitary gland in PTSD following the administration of metyrapone. Metyrapone resulted in a significantly greater increase of ACTH and 11-deoxycortisol in combat veterans with PTSD (n = 11) compared with normal male volunteers (n = 8). When seen in the context of other abnormalities observed in PTSD, the present demonstration of increased pituitary activity in the absence of negative feedback provides unequivocal support for the hypothesis of enhanced negative feedback.

Adrenocorticotropic Hormone↗
PubMed1996

Rearrangement and expression of Vzeta1, Vzeta2 and Vzeta3 TCR zeta genes in C57BL/6 mice.

We have recently described a mAb (2.11) that recognizes the Vgamma1-Jgamma4-Cgamma4 chain. With this mAb and an anti-delta mAb we separated gammadelta+ 2.11(+) and gammadelta+ 2.11(-) intraepithelial lymphocytes (i-IEL) by FACS. Transcripts of rearranged TCR Vgamma1 and Vdelta2 genes in both i-IEL populations were analyzed by PCR followed by sequence analysis of cDNA spanning the junction of variable (V) and joining (J) genes. Roughly the same number of Vgamma1 and Vgamma2 transcripts were found in the 2.11(+) population while >90% of the transcripts in the 2.11(-)population contained a Vgamma gene sequence. Furthermore, gamma transcripts in the 2.11+ population were functional, while only 30-40% of the Vgamma transcripts in either population contained an in-frame sequence. The observed frequency of transcripts is what would be expected from cell populations that have not gone through cellular selection mediated by the RCR. Expression of Vgamma mRNA in RCRalphabeta and TCRgammadelta thymocytes was studied by a technique that analyzed populations of transcripts of rearranged genes. In both T cell population similar levels of Vgamma transcripts were found and about two out of three transcripts were out-of-frame. During the cloning and sequence analysis, we indentified a clone that expresses the Vgamma segment rearranged to the Jgamma3-Cgamma region in C57BL/6 mice. Together with the PCR cloning and sequencing of the complete Cgamma region in C57BL/6 mice these data demonstrate that the Jgamma-Cgamma gene is functional in this strain. Taken together, these studies revealed that: (i) cells expressing the Vgamma1 chain are an important subset of the gammadelta i-IEL population and that they show extensive junctional diversity; (ii) there is no correlation between expression of in-frame Vgamma transcripts and expression of Vgamma2 chains at the cell surface; and (iii) cells expressing the Vgamma3 chain might be a minor subset of the gammadelta T cell population in C57BL/6 mice.

Amino Acid Sequence↗
PubMed1995

Ontogenic development and tissue distribution of V gamma 1-expressing gamma/delta T lymphocytes in normal mice.

A hamster monoclonal antibody (mAb) recognizing an epitope in the V gamma 1-J gamma 4-C gamma 4 chain of the gamma/delta T cell receptor has been generated. Using this mAb, we have quantitated the occurrence of V gamma 1-bearing gamma/delta T cells in the developing thymus and in the lymphoid organs and several epithelia of adult mice. The V gamma 1-expressing cells constitute a minor gamma/delta T cell subpopulation during fetal and early postnatal life, but they constitute a major population of gamma/delta T cells in the thymus and in the peripheral lymphoid organs in adult mice. In addition, we found that V gamma 1-bearing cells comprise a large proportion (15-60%) of the gamma/delta T cells present in the intestinal epithelium (i-IEL) in all strains of mice tested. V gamma 1+ i-IEL are present in athymic (nude) mice and in antigen-free mice, demonstrating that they can develop extrathymically and that their presence in the intestinal epithelium is independent of the antigenic load of the gut. Our results show that V gamma 1-bearing lymphocytes account for the largest population of gamma/delta T cells in the mouse. This population includes a thymus-dependent component that homes to the secondary lymphoid organs and a thymus-independent component that constitutes a major fraction of the gamma/delta i-IELs.

Animals↗
PubMed1995

Tonegawa defended.

Explore the source record for details and available documents.

Competitive Behavior↗
PubMed1995

Interactions of polyamines with Mg(2+)-sensitive macroelectrodes and Mg2+ buffers.

The polyamines spermine, spermidine and putrescine interact with Mg(2+)-sensitive macroelectrodes based on the neutral carrier ETH 7025; the interaction in decreasing order being spermine, spermidine and putrescine. The effect is small and dependent on the ionized magnesium concentration ([Mg2+]free), only resulting in a significant increase in the measured [Mg2+]free with spermine and spermidine at [Mg2+]free less than 0.5 mM. The polyamines compete with Mg2+ for common binding sites on Mg2+ buffers such as ATP, ADP and citrate, releasing bound Mg2+ and increasing the [Mg2+]free. This effect is most prominent with Mg ATP and the action of the polyamines in decreasing order is spermine, spermidine and putrescine. Increases in polyamines which occur in cell proliferation and cancer could thus secondarily increase the [Mg2+]free resulting in an activation of Mg(2+)-dependent metabolic pathways.

Adenosine Diphosphate↗
PubMed1994

Influence of age, breed, and stage of pregnancy on hepatic ultrasonographic findings in cows.

Influence of age, breed, and stage of pregnancy on hepatic ultrasonographic findings of cows was determined. In addition, the relation between body weight, height at the withers, milk production, and the measurements determined via ultrasonography was investigated. The liver of 186 cows was examined ultrasonographically. The cows comprised Swiss Braunvieh, Simmental, and Holstein breeds, and age ranged from 2.5 to 11.5 years. The ultrasonographic findings of the liver, gallbladder, caudal vena cava, and portal vein were described, and the position, size, thickness, and distal angle of the liver were determined. In addition, the position and diameter of the caudal vena cava and portal vein were determined. There was no significant difference between any of the variables determined and breed or age. Therefore, measurements for the 3 breeds and for the various ages were summarized into 1 group. There were significant correlations between body weight, milk production, and size and thickness of the liver. In 3 pregnant cows, the liver was examined ultrasonographically 8 times during the course of pregnancy. Positive correlation was detected between stage of pregnancy and diameter of the caudal vena cava. There was a negative correlation between stage of pregnancy and diameter of the portal vein. In 23 cows, the ultrasonographically determined measurements of the liver were compared with those determined at slaughter. Weight of the liver correlated well to thickness of the liver determined via ultrasonography.

Aging↗
PubMed1992

Ultrasonography of the urinary tract of female sheep.

We determined the position, dimensions, and structure of the kidneys, ureters, bladder, and urethra of 62 female sheep by use of ultrasonography. A 5.0-MHz convex transducer was placed over the right flank to examine the kidneys, and a 5.0 MHz-linear transducer was used to examine the bladder and urethra transrectally. All examinations were performed on sheep in standing position. The left kidney was 7.1 to 8.9 cm long, 3.4 to 5.5 cm wide, and 3.3 to 4.7 cm deep. Diameter of the parenchyma and renal sinus of the left kidney ranged between 1.1 and 1.9 cm and 1.1 and 2.0 cm, respectively. Circumference of the medullary pyramids varied between 2.1 and 3.3 cm. Similar ultrasonographic measurements were obtained for the right kidney. The diameter of the bladder varied between 0.3 and 6.9 cm in 96.8% of the sheep. The diameter of the bladder could not be determined in 32% of the sheep because it was > 10 cm, and, therefore, was beyond the penetration depth of the scanner. The only part of the urethra that could be ultrasonographically visualized was the internal urethral orifice. It had diameter between 0.1 and 0.2 cm. The ureters could not be ultrasonographically visualized in any of the sheep examined. The urinary tract of 8 sheep was examined 10 times within 2 weeks to examine whether measurements were reproducible. The interassay variation coefficient determined ranged from 3.1 to 31.8%, although for most variables, it ranged between 5 and 11%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1992

Percutaneous ultrasound-guided cholecystocentesis in cows.

A method was developed for percutaneous ultrasound-guided cholecystocentesis in cattle. The procedure was performed on the right side in the 9th, 10th, or 11th intercostal space of 30 cows. Of the 30 cows, 20 were slaughtered 24 hours after cholecystocentesis and the remaining 10 cows were slaughtered after a 10-day observation period. Changes in the peritoneum and gallbladder wall, observed at slaughter, were minimal. During the 10-day observation period, general behavior, attitude, and appetite of the 10 cows were normal. A transient, slight increase in rectal temperature was observed in 6 cows at 4, 5, or 8 days after cholecystocentesis. Total and differential WBC counts and total protein and fibrinogen concentrations, determined daily, were all within normal ranges. Bile samples from 20 cows were examined microscopically and biochemically. Fasciola hepatica and Dicrocoelium dendriticum eggs were observed in bile from 7 and 12 cows, respectively. Fecal examination revealed F hepatica eggs in 4 cows; D dendriticum eggs were not identified in any of the fecal samples. In 1 cow, F hepatica eggs were observed in the feces, but not in the bile. Bile acids concentration in bile varied from 12.5 to 68.5 mmol/L (mean +/- SD, 45.3 +/- 3.05 mmol/L) and in serum from 3.8 to 281.0 mumol/L (41.6 +/- 17.24 mumol/L). Negative correlation was obtained between bile acids concentration in bile and that in serum (r = -0.60, P less than 0.01). It was concluded that percutaneous ultrasound-guided cholecystocentesis in cows is a safe procedure and that microscopic and biochemical examinations of obtained bile can be useful diagnostic aids.

Animals↗