Differential retinal angiogenic response to sustained intravitreal release of VEGF and bFGF in different pigmented rabbit breeds

PURPOSE

To determine if two different breeds of pigmented rabbits can demonstrate differences in the degree of inducible angiogenesis within the retina.

METHODS

Non-biodegradable Hydron pellets approximately 1.5 mm in diameter containing both vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were implanted intravitreally over the optic disk of either Dutch belt rabbits or New Zealand White/Black satin cross rabbits. Control animals from both groups were implanted with blank Hydron pellets. Animals were examined periodically over a 30-day period following implantation. Results were documented by fundus photography and flourescein angiography. Stages of neovascularization (NV) were graded between +1 (preproliferative) and +4 (total NV) with +5 for NV complicated by hemorrhage and/or retinal detachment.

RESULTS

The angiogenic response in the retinas of pigmented NZW/Black satin cross rabbits (N = 5) following implantation of VEGF/bFGF-containing pellets varied extensively from the Dutch belt animals (N = 7). In the Dutch belt rabbits, grading of the angiogenic response demonstrated either +4 or +5 between day 20 and day 30 after implantation. In contrast, the NZW/Black satin cross animals gave a more muted response with a maximum grade of +2 following exposure to the same amount of VEGF and bFGF. Control eyes that received only blank pellets showed no evidence of retinal NV in either the Dutch belts (N = 5) or the NZW/Black satin cross rabbits (N = 5). Statistical analysis showed a significant interaction effect for breed and pellet type (F = 44.85 with 1 df, p < 0.00005), indicating a difference between the breeds in the angiogenic response to the pellet. Moreover, both the NZW/BSC and Dutch belt rabbits displayed a significant increase in angiogenesis with the VEGF/bFGF pellet in comparison to the blank pellet (p = 0.037 and p < 0.00005, respectively).

CONCLUSIONS

These studies indicate that two different breeds of pigmented rabbits exhibit different angiogenic responses to the same amount of both VEGF and bFGF. Florid retinal NV leading to hemorrhage, fibrovascular membrane formation, and traction retinal detachment occurred in the Dutch belt rabbits while tortuosity and dilatation of existing blood vessels with subsequent regression occurred in the NZW/Black satin cross animals. Such differences in the angio-genic response may be due to differences in the genetic background of these animals. If genetic heteriogeneity exists for angiogenic responses, then understanding the genetic role in the regulation of angiogenesis will lead to the design of more effective anti-angiogenic agents and can provide predictive outcomes of individual responses to therapy.

Prospective study of 125 cases of Staphylococcus aureus bacteremia in children in New Zealand

BACKGROUND

Staphylococcus aureus bacteremia is a common complication of S. aureus infection. There are few pediatric studies defining the incidence and associated morbidity and mortality of S. aureus bacteremia and no such New Zealand studies. We conducted a prospective study of S. aureus bacteremia in children in New Zealand.

METHODS

From July 1, 1996 to December 31, 1998, we included all children < 16 years of age with S. aureus bacteremia in Auckland and Christchurch. Relevant information regarding patient demographics, clinical course and outcome and laboratory results was recorded.

RESULTS

One hundred twenty-five cases of true S. aureus bacteremia were identified. There were 4 deaths within 30 days of the onset of bacteremia. Fourteen (11%) of the children were < 1 month of age. Maori children (relative risk, 2.0; 95% confidence interval, 1.3 to 3.2) were twice as likely and Pacific Island children (relative risk, 2.5; 95% confidence interval, 1.6 to 3.8) 2.5 times as likely as white children to acquire S. aureus bacteremia. The peak incidence of S. aureus bacteremia was observed in Pacific Island children < 1 year of age (105 cases/100,000 children/year). Twenty-seven percent of cases were related to intravenous catheters. Seventy percent of cases were community-acquired. Ninety-eight percent of non-catheter-related cases in children > 1 month of age were community-acquired. There was a low rate of methicillin resistance (6%).

CONCLUSIONS

S. aureus bacteremia is largely community-acquired in children in New Zealand and is more common in Pacific Island and Maori populations. Although there is a low associated mortality, a significant number are potentially preventable cases secondary to intravenous catheters.

Pneumococcal bacteraemia and opportunities for prevention

AIMS

Despite availability of active antimicrobial agents for its treatment, the mortality from pneumococcal bacteraemia (PB) may reach 30% to 40% in high-risk groups. Greater vaccine use may reduce the incidence of PB. The aim of this study was to determine the proportion of patients with PB who had indications for, but had not received, pneumococcal vaccination.

METHODS

From December 1998 to March 2000, all episodes of PB in adults in four Auckland hospitals were followed prospectively. Underlying disease, outcome, and pneumococcal vaccination history were recorded.

RESULTS

96 patients had PB: the median age was 63 years, range 16 to 93 years. 42 (44%) were > or = 65 years. The relative risk (RR) of acquiring PB for Maori and Pacific Island people was more than two times that of both European and other ethnic groups: RR 2.3 (95% CI 1.5 - 3.6) and 2.4 (1.6 - 3.8), respectively. The most common presentation was pneumonia; 84 (88%), of which 74 (88%) were community acquired. Five (5%) patients had meningitis. The overall mortality was 18%. Eleven (11%) pneumococcal isolates had intermediate susceptibility to penicillin and six (6%) were resistant. 69 (72%) patients had one or more condition for which pneumococcal vaccination is recommended but only two (2%) patients had received it. 82 (85%) patients were infected with serotypes included in the current pneumococcal vaccine.

CONCLUSIONS

Most adult patients with PB have underlying medical conditions for which vaccination is recommended but only rare patients get vaccinated. Emerging antimicrobial resistance is a further incentive to increase the use of pneumococcal vaccination. Greater use of pneumococcal vaccine will probably require a change in its funding status, similar to the current policy for influenza vaccine. It may also be appropriate to consider targeted use of the vaccine in Maori and Pacific Island people given their higher rates of disease.

Prospective study of 424 cases of Staphylococcus aureus bacteraemia: determination of factors affecting incidence and mortality

BACKGROUND

Staphylococcus aureus bacteraemia (SAB) is a common complication of S. aureus infection and is associated with a high mortality.

AIMS

To document prospectively the pattern of illness associated with SAB in New Zealand and, by recording patient demographic factors and clinical features, to identify risk factors associated with a poor outcome.

METHODS

From 1 July 1996 to 31 December 1997, adults with SAB were prospectively studied in six tertiary care hospitals. All information obtained from patients' records was recorded on worksheets and transferred to a computerized spreadsheet for analysis.

RESULTS

There were 424 patients with SAB. Maori (relative risk (RR)= 1.8, 95% confidence interval (CI) = 1.3-2.6) and Pacific Island people (RR = 4.0, 95% CI = 3.1-5.3) were significantly more likely than people of European descent to acquire SAB, but not to die from the infection. Fifty per cent of cases were community acquired. A source was identified for 85%: intravenous catheter (31%), primarily hospital acquired, and skin/soft tissue (22%), primarily community acquired, were the most common foci. The 30-day mortality was 19%, 83% of whom died within 2 weeks. Risk factors for a poor outcome were: increasing age above 60, female sex (RR = 1.4, 95% CI = 1.0-2.1), diabetes mellitus (RR = 1.5, 95% CI = 1.0-2.4), immunosuppression (RR = 1.5, 95% CI = 1.0-2.4), pre-existing renal impairment (RR = 1.8, 95% CI = 1.2-2.7), malignancy (RR= 2.2, 95% CI = 1.4-3.5), lung as a source (RR = 2.8, 95% CI = 1.9-4.2) and unknown source (RR = 2.3, 95% CI = 1.5-3.3). Mortality was also accurately predicted by two multifactor scoring systems. There was a low rate of methicillin resistance (5%).

CONCLUSIONS

Staphylococcus aureus bacteraemia is more likely to occur in certain ethnic groups, while mortality is associated with other identifiable risk factors and continues to be high. Intravenous catheters remain the most common and most preventable cause of SAB.

Localization of the human mGluR4 gene within an epilepsy susceptibility locus(1)

The family of metabotropic glutamate receptors (mGluRs) consists of eight homologous G-protein coupled receptors. Several of the mGluRs, including the mGluR4 receptor subtype, are localized presynaptically; activation of this receptor induces an inhibition of neurotransmitter release from nerve terminals. Disruption of the mGluR4 gene in mice results in impaired motor and spatial learning, and alterations in seizure susceptibility. In this study, we have determined the structure of the human mGluR4 gene, as well as its chromosomal localization. A comparison of the gene structure of mGluR4 with the highly homologous mGluR6 receptor subtype reveals that both of the genes contain ten exons with similar exon/intron boundaries. A refined localization of mGluR4 was carried out by constructing a bacterial artificial chromosome clone contig of the region surrounding the gene. Thirteen sequence tagged sites (STSs) were identified within this contig. The gene was localized to chromosome 6 band p21.3 by fluorescence in situ hybridization (FISH). The mapping of the mGluR4 gene indicates that it is approximately 1 megabases centromeric of the major histocompatibility complex and 5 megabase from the GABA(B)R1 gene. The mGluR4 gene also falls within a susceptibility locus for juvenile myoclonic epilepsy suggesting a potential link to this form of epilepsy.

Intravitreal VEGF and bFGF produce florid retinal neovascularization and hemorrhage in the rabbit

PURPOSE

Vascular endothelial growth factor (VEGF) causes widespread retinal vascular dilation, produces breakdown of the blood-retinal barrier, and is implicated in ocular neovascularization (NV). Basic fibroblast growth factor (bFGF) also has been implicated in the production of ocular NV. This study was performed to investigate the ability of simultaneous sustained intravitreal release of both VEGF and bFGF to induce robust retinal NV in the rabbit.

METHODS

Intravitreal implantation of sustained-release Hydron polymeric pellets containing both 20 microg of VEGF and 20 microg of bFGF was performed on adult male Dutch belted rabbits. In other animals either 20 microg or 50 microg bFGF-containing pellets was implanted intravitreally; also, either 20 microg VEGF or 50 microg VEGF-containing pellets was implanted. Control rabbits received either blank polymeric pellets or a pellet containing 30 microg bovine serum albumin. Eyes were examined by indirect ophthalmoscopy after surgery at 24 hrs, 48 hrs, 4 days, 7 days, 14 days, 21 days, and 28 days. Findings were documented by color fundus photography and fluorescein angiography (FA). Eyes were enucleated and prepared for histologic analysis at 28 days following intravitreal implantation of the VEGF/bFGF-containing pellets.

RESULTS

In all eyes implanted with VEGF/bFGF pellets, dilation and tortuosity of existing blood vessels were observed within 48 hrs after pellet implantation. The progression of retinal vascular changes was rapid and occurred over the entire optic disk and medullary rays between 4 and 7 days. Hemorrhage occurred as early as 14 days after VEGF/bFGF pellet implantation. In eyes with massive hemorrhage, total traction retinal detachment developed after the second week. The presence of abnormal tissues at the vitreo-retinal interface within 28 days was demonstrated by light microscopy while FA showed profuse leakage of dye from anomalous vessels within the first week. Neither bFGF-exposed eyes nor control eyes showed any vascular changes. Eyes that received only VEGF-containing pellets exhibited tortuosity of existing vessels, but neither hemorrhaging nor retinal detachment occurred.

CONCLUSIONS

These results demonstrate that retinal vascular changes leading to hemorrhaging is produced rapidly in the rabbit by simultaneous intravitreal release of both VEGF and bFGF. Understanding how these growth factors induce retinal NV may suggest novel therapeutic treatment strategies.

Surveillance for antimicrobial resistance in enterococci

AIM

To describe antimicrobial resistance patterns of Enterococcus species in Auckland.

BACKGROUND

Antimicrobial resistant enterococci have emerged as major nosocomial pathogens in overseas hospitals. It is recommended that hospitals perform periodic surveys to determine local enterococcal resistance patterns.

METHODS

Enterococcal isolates from four patient groups were tested: group I were recovered from routine clinical specimens; group II were stool isolates from patients at risk of having vancomycin resistant enterococci, eg, intensive care unit patients, patients receiving vancomycin, and immunocompromised patients receiving antibiotics; group III were enterococci from stool specimens sent for Clostridium difficile toxin testing; group IV were isolates from stool specimens submitted to a community laboratory for enteric pathogen testing. All enterococci isolated were tested for the presence of beta-lactamase, susceptibility to amoxycillin, teicoplanin, vancomycin, and for high level gentamicin and streptomycin resistance.

RESULTS

There were 121 group I enterococcal isolates. 628 stool specimens were cultured. Enterococci were isolated from: 76/148 (51%) group II specimens; 166/279 (60%) group III specimens; and 70/201 (35%) of group IV specimens. Antimicrobial susceptibility testing was performed on 433 isolates; 74% were E faecalis, 12% E faecium, 6% E gallinarum/casseliflavus group and 8% other enterococcal species. No isolate produced beta-lactamase. All E faecalis were susceptible to amoxycillin. Two E faecium and one enterococcus species were resistant to amoxycillin (MICs all 16 mg/L). All isolates were susceptible to teicoplanin. Fourteen E gallinarum/casseliflavus group isolates had intermediate susceptibility to vancomycin (MICs of 8 mg/L). One E faecium had intermediate susceptibility to vancomycin (MIC 8 mg/L). High level gentamicin and streptomycin resistance occurred in 64 (15%) and 50 (12%) isolates respectively.

CONCLUSION

Vancomycin resistance is rare and is essentially restricted to species that are rarely clinical pathogens, i.e., E casseliflavus and E gallinarum. Our results have established the local susceptibility profile for enterococcal isolates. This allows comparison with other locations and the detection of emerging trends of resistance.

Chronic inhalation exposure to ozone and nitric acid elevates stress-inducible heat shock protein 70 in the rat lung

The ability of urban oxidant and acid air pollutants to induce heat shock proteins (HSPs) in the mammalian lung is not known. Such proteins are known to be correlated with environmental stress and pathophysiological conditions. In this study, stress-inducible HSP 70 was assessed by slot-blotting in rat lungs (N=10 per group) following inhalation exposures for 4 h per day, 3 days per week for 40 weeks to the following pollutants: (a) purified air;(b) 0.15 ppm ozone (O3);(c)50 micrograms/m3 nitric acid (HNO3); or(d) a combination of both 0.15 ppm O3 and 50 micrograms/m3 HNO3. At 24 h following the last exposure, samples from the right apical lobe of the lung were obtained for either slot-blotting or gel electrophoretic separation, subsequent protein immunoblotting, and chemiluminescence detection of HSP 70 levels. Experiments demonstrate that stress-inducible HSP 70 was present constitutively in the control lungs and was separable from the constitutive form of HSP 70. Slot-blotting analysis demonstrate that the O3 and HNO3 exposures alone produced significant elevations of HSP70. Specifically, either O3 or HNO3 alone significantly elevated lung stress-inducible HSP 70 levels by 277% and 221% respectively, above control levels. The group exposed to combined O3 and HNO3 showed a 177% elevation in lung stress-inducible HSP 70 that was significantly greater that the group inhaling purified air, but this effect was less than the effects of either pollutant component alone. Moreover, all exposure groups were significantly different from one another. These results indicate that stress-inducible HSP 70 in the rat lung is highly elevated after chronic inhalation exposures to both O3 and HNO3 when administered either alone or in combination within the range of urban ambient concentrations.

Melatonin inhibits the proliferation of retinal pigment epithelial (RPE) cells in vitro

The possible antiproliferative effect of melatonin on retinal pigment epithelial (RPE) cells in vitro was investigated. Bovine RPE cells cultured in Ham's F12 medium supplemented with 10% fetal bovine serum had a nuclear density of 73.6 +/- 6.1 nuclei/mm2 at 72 h after seeding. The nuclear density at this time-point was doubled if either 50 or 100 ng/ml human epidermal growth factors (hEGF) was added to the culture medium. When these hEGF-stimulated cells were treated with melatonin from 10 to 500 pg/ml, the proliferation was suppressed with a dose-response relationship. At 250 and 500 pg/ml melatonin, the nuclear densities of the melatonin-treated cells were similar to those of the control cells. Using mitotically active SV-40 transformed human fetal RPE cells cultured in a serum-free medium, melatonin was also shown to be antiproliferative. In the presence of 500 pg/ml melatonin, the proliferation of these cells was inhibited to 77% as compared to the control. These results were further supported by the reduced [H3]thymidine uptake in the melatonin-treated cells. We propose that melatonin, at physiologic concentrations, has an antiproliferative effect, and that cultured RPE cells stimulated to proliferate by either hEGF treatment or SV-40 transfection are responsive to melatonin. Melatonin may either inhibit mitosis in actively dividing cells or modulate hEGF action.

Induction of stress proteins in SV-40 transformed human RPE-derived cells by organic oxidants

The expression and induction of heat shock proteins (HSPs) were examined in cultured SV-40-transformed human retinal pigment epithelial (RPE)-derived cells following exposure to chemical oxidants. Concentrations of hydrogen peroxide and the organic oxidants tert-butyl hydroperoxide, cumene hydroperoxide and linoleic acid hydroperoxide were used under conditions where cell viability was between 75% and 90% as determined by the trypan blue exclusion tests. The types of HSPs that are either induced and/or elevated from constitutive levels in cultured transformed cells were separated both by SDS-PAGE and by two-dimensional gel electrophoresis. Subsequent immunoblotting was performed with both a monoclonal antibody (MAb C92) specific for only the stress-inducible form of HSP 70, namely HSP 72, and with a monoclonal antibody (MAb N27) specific for both the stress-inducible HSP 72 and its constitutive form, HSP 73. As positive controls for comparison, other types of stressing agents were used that included heat shock at 41 degrees C for various times and exposure to the proline analogue, azetidine-2-carboxylic acid (AzC). Protein immunoblotting analysis demonstrate that: (a) Stress-inducible HSP 72 is present at low levels in non-stressed cultured transformed RPE-derived cells and in fresh bovine retina and RPE, but is not detectable in non-stressed cultured lung fibroblasts until induction with heat shock; and (b) Stress-inducible HSP 72 is elevated from constitutive levels in RPE-derived cultured cells after exposure to various oxidants. After cellular exposure to both organic oxidants and to AzC in the presence of L-[35-S]-methionine, two-dimensional gel electrophoresis confirmed the elevation of newly synthesized HSP 72. Thus, these results indicate that cultured human SV-40-transformed RPE-derived cells are capable of elevated HSP 72 biosynthesis under conditions of oxidative stress produced by organic oxidants.

Induction of stress proteins in cultured human RPE-derived cells

The expression and induction of stress protein families were examined in cultured human fetal retinal pigment epithelial (RPE)-derived cells. These stress proteins (SPs) include the heat-shock proteins (HSPs) that have been shown to be highly inducible following treatment by heat, amino acid analogues, and various chemical oxidants. Three sets of proteins with molecular weights of 70, 84, and 110 kilodaltons were elevated simultaneously from constitutive levels after treatment with azetidine-2-carboxylic acid (AzC), an amino acid analogue of proline. Further experiments demonstrated that incubation of cultured human fetal RPE-derived cells with hydrogen peroxide (H2O2) at concentrations ranging from 10(-5) M to 10(-3) M for 30 minutes to 60 minutes did not elevate the levels of the common families of HSPs as with AzC. These results indicate that cultured human fetal RPE-derived cells are capable of elevated HSP biosynthesis after AzC exposure but appear resistant to H2O2 treatment.

Applicability of the Chinese Beck Depression Inventory

Using a sample of 329 currently depressed patients from 24 hospitals across China, this study assesses the reliability and validity of the Chinese version of Beck Depression Inventory (CBDI). Even though the internal reliability and the concurrent validity were good (Cronbach alpha = 0.846; r = 0.566), the results showed that the item of Loss of Libido was most weakly correlated with the CBDI's total score; the items of Sense of Punishment, Sense of Hate, Self Accusations, Crying Spells, Irritability, and Somatic Preoccupation were poorly associated with the intensity of depression measured by the total score of the Chinese version of Hamilton Depression Rating Scale (CHDS). The CBDI's construct validity was rather poor by principal component analysis: three of six factors were unexplainable in terms of clinical features of depression. The results demonstrated that CBDI, even though it was semantically translated into Chinese language, still could not be effectively applied in clinic and research settings in China. Using the theory and methods of psychometrics to develop China's own culturally sensitive self-report inventory is the correct way to eliminate cultural bias and make cross-cultural research more valid. This is the most rigorous scientific approach to cross-cultural comparisons.

Ornithine decarboxylase activity in rabbit retina following treatment with alpha-difluoromethylornithine

The rabbit retina has been utilized as a model for the study of abnormal cellular proliferation on the retinal surface and into the vitreous, a process commonly initiated by trauma and generally leading to retinal detachment. This study characterizes the ability of alpha-difluoromethylornithine (alpha-DFMO), a suicide inactivator of L-ornithine decarboxylase (EC 4.1.1.17) to inactivate normal retinal ornithine decarboxylase (ODC) activity in the crude supernatant fraction after incubation with different concentrations of alpha-DFMO and at various times after intraocular administration. Partial inactivation of ODC activity occurred following preincubation of crude retinal supernatant fraction with 10(-5) M alpha-DFMO (N = 3; 34 +/- 6.9% of control), whereas preincubation with 10(-8) M alpha-DFMO did not alter ODC activity significantly (N = 3; 94 +/- 2% of control). Different concentrations of alpha-DFMO administered intraocularly inactivated retinal ODC activity to varying degrees with different rates of recovery. No gross toxicity occurred with ocular tissues following intravitreal administration of alpha-DFMO as determined by electrophysiologic measurements, by indirect examination of the retina, and by measurement of intraocular pressure. These results suggest that alpha-DFMO may be a useful tool in which to define the physiologic role of ODC and polyamines in intraocular cellular proliferative diseases.

Intranuclear rodlets in the rabbit retina following treatment with MPTP

Retinas from pigmented rabbits treated with N-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP, a chemical inducer of Parkinsonism in man and monkeys) were studied using light- and electron microscopy. The nuclei of many cells in the inner nuclear layer and the ganglion cell layer of the treated retinas contained crystalloids (intranuclear rodlets) of varying length (0.5-8 microns) which were composed of bundles of 12 nm filaments and which were seen only rarely in untreated retinas. The induced rodlets are oval to round cylinders, 15-20 filaments across (although they are smaller in untreated retinas). Similar intranuclear inclusions have been described under varying conditions in neurons and glia in the central nervous system of several animal species. In rabbits injected acutely with MPTP, most of the affected cells are in the inner nuclear layer in the position of bipolar cells, while in the chronically injected animals, clearly identifiable amacrine cells, and the nuclei of some cells in the ganglion cell layer also contained the inclusions. Evidence is presented that the rodlet-containing cells in the ganglion cell layer include both ganglion cells and displaced amacrine cells. These anatomic findings are relevant to understanding the physiological and biochemical effects of the drug on the retina which we reported previously (Wong, Ishibashi, Tucker and Hamasaki, 1985).

Ornithine decarboxylase activity during formation of experimental epiretinal membranes

This study demonstrates in a rabbit model of epiretinal membrane formation that retinal-associated ODC activity increases during this pathological process. These changes in retinal-associated ODC activity most likely occur in relationship to the proliferative lesion itself, since the retina consists primarily of nonproliferative tissues. Further knowledge of intraocular polyamine metabolism during epiretinal membrane formation which can result in retinal detachment may lead to the development of an effective pharmacological treatment.

Consequences of ornithine decarboxylase inactivation by alpha-difluoromethylornithine and 5-fluorouracil on the growth of rabbit fibroblasts

The role of ornithine decarboxylase and polyamines in proliferative vitreoretinopathy (PVR) is ill-defined. An increase in the activity of this enzyme concurrent with an increase in polyamine levels may be essential in the process of intraocular cellular proliferation. Therefore, in this study, cultured rabbit fibroblasts were exposed to DL-alpha-difluoromethylornithine (alpha-DFMO), a mechanism-based irreversible inactivator of ornithine decarboxylase, alone and in combination with 5-fluorouracil (5-FU). Concentrations of 0.1mM alpha-DFMO and 0.125mM 5-FU decreased rabbit fibroblast cell number by 60% and 65%, respectively, after three days, while with either 5.0mM alpha-DFMO or 0.25mM 5-FU, cell number is decreased by 95%. The effectiveness of inhibitory concentrations of 5-FU and alpha-DFMO together in reducing cell number is additive.

Inhibitors of inosinic acid dehydrogenase. 2-Substituted inosinic acids

A series of 2-substituted inosine monophosphate (IMP) and inosine derivatives were synthesized and tested for inhibitory activity against IMP dehydrogenase from Escherichia coli. All of the IMP analogues that possessed electron-withdrawing substituents on the phenyl ring of a benzylthio group placed at the 2-position of IMP showed strong inhibition, which was competitive with IMP. No evidence of hydrophobic interactions of the 2-substituent with the enzyme was observed.

Specific reaction of 9-cis-retinoyl fluoride with bovine opsin

Opsin readily undergoes Schiff base formation between an active site lysine and 9-cis- or 11-cis-retinaldehyde to form the visual pigments isorhodopsin (lambda max = 487 nm) and rhodopsin (lambda max = 500 nm), respectively (Dratz, 1977). It would be predicted that 9-cis-retinoyl fluoride (1), an isostere of 9-cis-retinal, should be an active site directed, mechanism-based labeling agent of opsin, since a stable peptide bond should be formed instead of a Schiff base. It is shown here that 9-cis-retinoyl fluoride (1) reacts with opsin in a time-dependent fashion (t1/2 = 9 min at 25 microM 1) to form a new, nonbleachable pigment with a lambda max of approximately 365 nm. beta-Ionone competitively slows down the rate of the reaction. The absorbance of the new pigment at approximately 365 nm is similar to that of model amide compounds. This result is consistent in a general and qualitative way with the Nakanishi-Honig point-charge model for visual pigments which requires that the chromophore be charged, a situation not possible when the retinoid is linked to opsin via a peptide bond rather than a protonated Schiff base [Honig, B., Dinur, U., Nakanishi, K., Balogh-Nair, V., Gawinowicz, M.A., Arnabaldi, M., & Motto, M.G. (1979) J. Am. Chem. Soc. 101, 7084-7086]. 9-cis-Retinoyl fluoride (1) is approximately 4-fold more potent than all-trans-retinoyl fluoride (2) as an inactivator of bovine opsin. Importantly, 13-cis-retinoyl fluoride (3) is inactive, and no new absorption band at 365 nm is observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatic ganglioside abnormalities in a patient with familial erythrophagocytic lymphohistiocytosis

Familial erythrophagocytic lymphohistiocytosis (FEL) is an autosomal recessive disease of unknown pathogenesis. Because of evidence of increased circulating and hepatic lipids in FEL, we performed a comprehensive analysis of the hepatic lipids of a patient with this disease. In contrast to normal qualitative characteristics and to normal or only mildly elevated concentrations of total lipids, neutral lipids, phospholipids, and neutral glycosphingolipids, this study reports a significant elevation of acidic glycosphingolipids, gangliosides (387 versus 147 nmole lipid-bound sialic acid/g wet weight, patient versus control). This quantitative abnormality was unusual in that it included disproportionately increased concentrations of most of the minor hepatic ganglioside species rather than either a marked increase in one single or a generalized nonspecific increase in all gangliosides, which is characteristic of known disorders exhibiting hepatic ganglioside storage. Activities of the hepatic lysosomal glycosylhydrolases which are important in ganglioside metabolism were therefore assessed by using artificial substrates. Of the enzymes tested, beta-galactosidase activity alone was remarkable, being moderately reduced (33% of that of the normal liver); no biochemical explanation for the reduction was found. The findings suggest FEL may be associated with a unique quantitative and qualitative abnormality in hepatic gangliosides, the cause of which remains to be elucidated.

Retention of gangliosides in serum delipidated by diisopropyl ether-1-butanol extraction

Extraction with diisopropyl ether-1-butanol is a rapid method for the delipidation of serum without protein denaturation. We sought to confirm that this solvent system would also extract the highly polar acidic glycosphingolipids, gangliosides. In fact, however, both endogenous serum gangliosides and radiolabeled rat brain gangliosides added to serum were nearly quantitatively retained (87.5% and 98.7%, respectively) in the aqueous phase after two extractions. Therefore, while useful for the extraction of most lipids, this delipidation procedure cannot be used to remove gangliosides from serum or plasma.

Pharmacokinetics of 5-fluorouracil: inter-relationship with biochemical kinetics in monitoring therapy

The major difficulty in using pharmacokinetic concepts for monitoring individual therapy with 5-fluorouracil is based on the mostly intracellular location of the active nucleotide metabolites of 5-fluorouracil with no clear correlation of plasma levels of the drug. In addition, the basic biochemical mechanism of 'thymine-less cell death' following inhibition of de novo thymidylate synthesis by 2'-deoxy-5-flurouridine 5'-monophosphate (FdUMP) is poorly understood, and only some of the biochemical determinants of therapeutic response to 5-fluorouracil are known. Individualised therapy with 5-fluorouracil requires an intergrated approach which should include methods of pharmacokinetics and biochemical kinetics. 5-Fluorouracil stands as an example for most of the pyrimidine and purine metabolites to which similar consideration apply in monitoring of cancer chemotherapy.

Hydrolysis of lithocholate sulfate by Pseudomonas aeruginosa

Pseudomonas aeruginosa was found to be able to hydrolyze bile sulfate. This property was observed when lithocholate sulfate was substituted for the sulfur source in the culture medium. The addition of MgSO4 to the medium inhibited the hydrolysis of the bile sulfate.