Diabetes, hypertension, and central obesity as cataract risk factors in a black population. The Barbados Eye Study

OBJECTIVE

The increased cataract prevalence of black populations, especially of cortical cataract, remains unexplained. The authors evaluate the relationships of diabetes, hypertension, and obesity patterns to lens opacities, by age, among 4314 black participants in the Barbados Eye Study.

DESIGN AND PARTICIPANTS

Prevalence study of a random sample of the Barbados population, ages 40 to 84 years (84% participation).

MAIN OUTCOME MEASURES

Associations with age-related lens changes (grade > or = 2 in the Lens Opacities Classification System II at the slit lamp) were evaluated in logistic regression analyses by age (persons < 60 years and > or = 60 years). Results are presented as odds ratios (OR) with 95% confidence intervals.

RESULTS

Of the 1800 participants with lens changes, most had cortical opacities. Diabetes history (18% prevalence) was related to all lens changes, especially at younger ages (age < 60 years: OR = 2.23 [1.63, 3.04]; age > or = 60 years: OR = 1.63 [1.22, 2.17]). Diabetes also increased the risk of cortical opacities (age < 60 years: OR = 2.30 [1.63, 3.24]; age > or = 60 years: OR = 1.42 [1.03, 1.96]); additional risk factors were high diastolic blood pressure (age < 60 years: OR = 1.49 [1.00, 2.23]) and higher waist/hip ratio (all ages: OR = 1.36 [1.00, 1.84]). Diabetes was also related to posterior subcapsular opacities. Glycated hemoglobin levels were positively associated with cortical and posterior subcapsular opacities. Overall, 14% of the prevalence of lens changes could be attributed to diabetes.

CONCLUSIONS

The high prevalence of cortical opacities was related to diabetes, hypertension, and abdominal obesity, which also are common in this and other black populations. Interventions to modify these risk factors, especially in populations in which they are highly prevalent, may have implications to control visual loss from cataract, which is the first cause of blindness worldwide.

Immunoaffinity purification and functional characterization of human transcription factor IIH and RNA polymerase II from clonal cell lines that conditionally express epitope-tagged subunits of the multiprotein complexes

Purification of multiprotein complexes such as transcription factor (TF) IIH and RNA polymerase II (pol II) has been a tedious task by conventional chromatography. To facilitate the purification, we have developed an effective scheme that allows human TFIIH and pol II to be isolated from HeLa-derived cell lines that conditionally express the FLAG-tagged p62 subunit of human TFIIH and the RPB9 subunit of human pol II, respectively. An approximate 2000-fold enrichment of FLAG-tagged TFIIH and a 1000-fold enhancement of total pol II are achieved by a one-step immunoaffinity purification. The purified complexes are functional in mediating basal and activated transcription, regardless of whether TATA-binding protein or TFIID is used as the TATA-binding factor. Interestingly, repression of basal transcription by the positive cofactor PC4 is alleviated by increasing amounts of TFIID, TFIIH, and pol II holoenzyme, suggesting that phosphorylation of PC4 by these proteins may cause a conformational change in the structure of PC4 that allows for preinitiation complex formation and initiation of transcription. Furthermore, pol II complexes with different phosphorylation states on the carboxyl-terminal domain of the largest subunit are selectively purified from the inducible pol II cell line, making it possible to dissect the role of carboxyl-terminal domain phosphorylation in the transcription process in a highly defined in vitro transcription system.

Disease progression and cost of insulin dependent diabetes mellitus: development and application of a simulation model

This paper presents the development and application of a Markov model that simulates the onset and progression of insulin dependent diabetes mellitus (IDDM) and its sequelae. The model estimates direct medical costs resulting from different patterns of health states during the course of the disease. The model is user-friendly and allows for changes in the input variables to be specified, thereby providing a frame-work for sensitivity analysis. The Markov process moves a cohort of individuals through six different health states: Healthy, IDDM without chronic microvascular complications, IDDM with retinopathy alone, IDDM with neuropathy alone or with retinopathy, IDDM with nephropathy, and death. Epidemiologic data were obtained from governmental sources as well as the medical literature. Transition probabilities were estimated using data from the Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR). Direct medical costs were estimated from actual charges from a local health maintenance organization in Wisconsin. The validity of the model was tested in several ways including a comparison with an independent cost estimate made by the Wisconsin Department of Health and Family Services. The model appears to be useful in estimating the progression and associated costs of IDDM for any large population over any period of time and in allowing changes in the inputs to evaluate their impact thus providing pertinent information to healthcare decision-makers and health planners.

TAFII-independent activation mediated by human TBP in the presence of the positive cofactor PC4

TFIID is a multiprotein complex comprised of the TATA-binding protein (TBP) and an array of TBP-associated factors (TAFIIs). Whereas TBP is sufficient for basal transcription in conjunction with other general transcription factors and RNA polymerase II, TAFIIs are additionally required for activator-dependent transcription in mammalian cell-free transcription systems. However, recent in vivo studies carried out in yeast suggest that TAFIIs are not globally required for activator function. The discrepancy between in vivo yeast studies and in vitro mammalian cell-free systems remains to be resolved. In this study, we describe a mammalian cell-free transcription system reconstituted with only recombinant proteins and epitope-tagged multiprotein complexes. Transcriptional activation can be recapitulated in this highly purified in vitro transcription system in the absence of TAFIIs. This TBP-mediated activation is not induced by human mediator, another transcriptional coactivator complex potentially implicated in activator response. In contrast, general transcription factors TFIIH and TFIIA play a significant role in TBP-mediated activation, which can be detected in vitro with Gal4 fusion proteins containing various transcriptional activation domains. Our data, therefore, suggest that TFIIH and TFIIA can mediate activator function in the absence of TAFIIs.

Properties of PC4 and an RNA polymerase II complex in directing activated and basal transcription in vitro

A human RNA polymerase II (pol II) complex was isolated from a HeLa-derived cell line that conditionally expresses an epitope-tagged RPB9 subunit of human pol II. The isolated FLAG-tagged pol II complex (f:pol II) contains a subset of general transcription factors but is devoid of TFIID and TFIIA. In conjunction with TATA-binding protein (TBP) or TFIID, f:pol II is able to mediate both basal and activated transcription by Gal4-VP16 when a transcriptional coactivator PC4 is also provided. Interestingly, PC4, in the absence of a transcriptional activator, actually functions as a repressor to inhibit basal transcription. Remarkably, TBP is able to mediate activator function in this transcription system. The presence of TBP-associated factors, however, helps overcome PC4 repression and further enhance the level of activation mediated by TBP. Alleviation of PC4 repression can also be achieved by preincubation of the transcriptional components with the DNA template. Sarkosyl disruption of preinitiation complex formation further illustrates that PC4 can only inhibit transcription prior to the assembly of a functional preinitiation complex. These results suggest that PC4 represses basal transcription by preventing the assembly of a functional preinitiation complex, but it has no effect on the later steps of the transcriptional process.

Urinary compound W in pregnant women is a potential marker for fetal thyroid function

OBJECTIVE

Previously we reported 3,3'-diiodothyronine sulfate-like material (compound W) in maternal serum, and studies suggest that compound W is derived from thyroid hormones of fetal origin. In this study we characterized gestational changes of urinary compound W concentrations to correlate with changes in serum concentrations.

STUDY DESIGN

Urinary samples were collected from 94 women at various gestational ages ranging from 3 to 40 weeks. Urinary compound W was first identified biochemically. The concentrations of compound W (adjusted for creatinine levels) were assessed by a 3,3'-diiodothyronine sulfate radioimmunoassay in ethanol extracts of urine samples.

RESULTS

Compound W increased to 88 +/- 1.4 pmol (of 3,3'-diiodothyronine sulfate equivalent)/mmol creatinine in urinary samples obtained from 26 women in the first trimester of pregnancy compared with 40 +/- 6.9 pmol/mmol creatinine in 10 nonpregnant women. Excretion of compound W increased further during the second and third trimesters: 171 +/- 17 (n = 18) and 434 +/- 26 (n = 50) respectively. In contrast, urinary 3,3',5-triiodothyronine sulfate concentrations measured by radioimmunoassay were similar during pregnancy to values in nonpregnant women.

CONCLUSIONS

Urinary compound W concentrations increase with the progression of normal pregnancy and correlate with the increase in serum levels. Random spot urine compound W concentrations, adjusted for creatinine levels, may be used in place of serum levels in conditions in which obtaining serum samples may be technically difficult, especially during population screening.

Antioxidant vitamins and nuclear opacities: the longitudinal study of cataract

OBJECTIVE

The association of antioxidant nutrients and risk of nuclear opacification was evaluated in the Longitudinal Study of Cataract.

DESIGN

Nutritional data were collected at baseline on the 764 participants, which included assessment of dietary intake, use of vitamin supplements, and plasma levels of vitamin E. Ophthalmologic and other data were collected at baseline and at yearly follow-up visits, including lens photographs, which were graded using the Lens Opacities Classification System III protocol.

MAIN OUTCOME MEASURES

Analyses examined whether the nutritional factors at baseline were related to increases in nuclear opacification at follow-up. The MULCOX2 approach, an extension of the Cox regression model, was used. Results are presented as relative risks (RRs) and 95% confidence intervals.

INTERVENTION

Intervention was not applicable.

RESULTS

The risk of nuclear opacification at follow-up was decreased in regular users of multivitamin supplements (RR = 0.69; 0.48-0.99), vitamin E supplements (RR = 0.43; 0.19-0.99), and in persons with higher plasma levels of vitamin E (RR = 0.58; 0.36-0.94).

CONCLUSIONS

In regular users of multivitamin supplements, the risk of nuclear opacification was reduced by one third; in regular users of vitamin E supplements and persons with higher plasma levels of vitamin E, the risk was reduced by approximately half. These results are similar to those obtained in our earlier case-control study. Because these data are based on observational studies only, the results are suggestive but inconclusive. The possible effect of nutritional supplements on the lens requires confirmation by ongoing clinical trials.

Development and application of a model to estimate the impact of type 1 diabetes on health-related quality of life

OBJECTIVE

To develop a simulation model to assess the impact of type 1 diabetes and its associated complications on health-related quality of life of a population.

RESEARCH DESIGN AND METHODS

The methodology builds upon 1) an existing population model of type 1 diabetes progression, 2) an empirical study designed to measure state- and age-specific health statuses of type 1 diabetes, and 3) existing literature to quantify quality of life of the corresponding health status. Health statuses were measured in a group of type 1 diabetic patients using the Medical Outcomes Study short form 36 (SF-36). A published empirical regression equation was then used to predict corresponding Quality of Well-Being Index (QWB) scores from these assessments. The QWB scores were incorporated into a previously developed type 1 diabetes progression and cost simulation model. Sensitivity analyses on key parameters were performed, and the model was found to be robust.

RESULTS

The augmented model can estimate quality-adjusted life years (QALYs) as well as costs associated with type 1 diabetes on any population of interest over any period of time. The model is used to compare intensive versus conventional treatment strategies using a simplified set of assumptions regarding the relative effects of these alternative treatments. With these assumptions, intensive strategy produces more QALYs than does conventional strategy and is cost-beneficial after 5 years.

CONCLUSIONS

The model enables health planners to perform cost-effectiveness analyses to compare alternative treatment strategies for type 1 diabetes and support subsequent decision making.

Release of nociceptin-like substances from the rat spinal cord dorsal horn

Release of nociceptin-like substances from the dorsal horn of rat spinal cords in situ was measured by the immobilized-antibody microprobe technique. Spinal cords removed from anesthetized 4-6 week-old rats were superfused with oxygenated Krebs solution at room temperature (21+/-1 degrees C). Glass microelectrodes, coated with antibodies to nociceptin, were inserted into the dorsal horn of the lumbar spinal cord (1.9 mm lateral to the midline to a depth 2.5 mm below the surface of the cord) for 15 min periods before, during and after electrical stimulation applied to the dorsal root entry zone of the same segment. There was a basal release of immunoreactive nociceptin-like substance (irNC) from the dorsal horns during the pre-stimulation period. A significant increase in irNC release was detected during the period of electrical stimulation and this increase was maintained for at least 15 min following the cessation of electrical stimulation. These results provide the first evidence on the release of irNC, albeit non-quantitative, from the in situ rat spinal cord dorsal horn and an enhanced release upon electrical stimulation.

GABA- and glycine-mediated inhibitory postsynaptic potentials in neonatal rat rostral ventrolateral medulla neurons in vitro

Whole-cell patch recordings were made from rostral ventrolateral medulla neurons of two in vitro preparations: (i) brainstem spinal cords of two- to five-day-old rats, and (ii) coronal brainstem slices of eight- to 12-day-old rats, and the inhibitory synaptic activities in these neurons have been studied. In brainstem spinal cord preparations, Lucifer Yellow was diffused into the recording neurons at the end of experiments. Medullary neurons were characterized as: (i) spinally projecting by the appearance of an antidromic spike following electrical stimulation of the spinal tract between T2 and T3 segments, and (ii) adrenergic by the detection of phenylethanolamine-N-methyltransferase immunoreactivity in Lucifer Yellow-filled neurons. Of the 13 spinally projecting and phenylethanolamine-N-methyltransferase-positive medullary neurons, focal stimulation elicited in the presence of glutamate receptor antagonists an inhibitory postsynaptic potential in nine neurons. Inhibitory synaptic potentials were reversibly eliminated by the GABA(A) receptor antagonist bicuculline (10-20 microM) in six of nine neurons, by the glycine receptor antagonist strychnine (0.1-1 microM) in two and by a combination of bicuculline and strychnine in one neuron. In brainstem slice preparations, focal stimulation elicited three types of synaptic potential: (i) an excitatory postsynaptic potential, (ii) an inhibitory postsynaptic potential and (iii) a biphasic synaptic potential consisting of an excitatory synaptic potential followed by an inhibitory synaptic potential. Inhibitory synaptic potentials had a reversal potential between -70 and -80 mV, reversed their polarity in a low (6.7 mM) Cl- Krebs' solution, and suppressed or blocked by either bicuculline or strychnine or both. Elimination of inhibitory synaptic potentials unmasked in some cells an excitatory synaptic potential or enhanced the excitatory synaptic potential component in medullary neurons with a biphasic response, indicating a marked convergence of excitatory and inhibitory inputs onto a single neuron. A population of medullary neurons appeared to be pacemaker neurons whereby they discharged spontaneously. When discharges were suppressed by membrane hyperpolarization, focal stimulation elicited inhibitory synaptic potentials in 8/23 neurons tested. Our results suggest that inhibitory synaptic potentials in medullary neurons are mediated by either GABA and/or glycine which open primarily Cl- channels. The prevalence of inhibitory synaptic potentials in medullary neurons indicates an essential role of inhibitory transmission in controlling the input and output ratio of these neurons.

Evaluation of drug usage and expenditure in a hospital diabetes clinic

BACKGROUND

Diabetes mellitus is a major public health problem and often coexists with hypertension and dyslipidaemia. A prescription-based survey was conducted to examine the use of antidiabetic, antihypertensive and lipid lowering drugs in a hospital diabetes clinic. The expenditure incurred was also evaluated.

METHOD

Prescriptions issued from the diabetes clinic were collected for 4 consecutive weeks. Drugs were categorized into three main classes--antidiabetic, antihypertensive and lipid-lowering drugs. The unit cost of each drug and the total amount prescribed were used to estimate the total drug costs.

RESULTS

During the 4-week study period, 534 prescriptions were collected, of which 520 contained antidiabetic drugs. Oral hypoglycaemic agents were prescribed in 379 patients (72.9%). Sulphonylurea was used as a single agent in 119 (22.9%) patients, in combination with metformin in 219 (42%) patients and with insulin in 17 patients (3.3%). Among patients treated with sulphonylureas (n=342), glibenclamide (47.7%) and gliclazide (30.7%) were the main drugs prescribed. Metformin monotherapy was prescribed in only 31 patients (6%). Insulin treatment was prescribed in 141 (27%) patients and in combination with oral drugs in 23 patients (4.5%). Of the 534 prescriptions, 225 (42%) contained antihypertensive drugs. Calcium channel blocking agents and angiotensin converting enzyme inhibitors were the most commonly prescribed drugs in both monotherapy (n=155) and combination therapy (n=70). The antidiabetic and antihypertensive drugs accounted for 45% and 39% of the total drug expenditure, respectively. Lipid-lowering drugs were prescribed in 8% of the diabetic patients. Simvastatin and gemfibrozil were the most common drugs prescribed and accounted for 12% of the total drug expenditure.

CONCLUSION

The use of antidiabetic drugs represents a major burden on the health care system. The high proportions of patients requiring antihypertensive drugs and lipid lowering drugs further increase drug expenditure. Most of these treatments have been shown to improve clinical outcomes and quality of life, if used appropriately. The impacts of these long-term medications on health care financing require careful evaluation to assess their cost-effectiveness.

Risk factors for nuclear opalescence in a longitudinal study. LSC Group. Longitudinal Study of Cataract

This study evaluated risk factors for increases in nuclear opacification of the lens in the Longitudinal Study of Cataract (1989-1993; Boston, Massachusetts), which included 764 participants. Baseline data on demographic, medical, and other risk factors were available from an earlier case-control study; follow-up visits were completed yearly over a 4-year period. The lens photographs taken at baseline and at each follow-up visit were graded using the Lens Opacities Classification System III protocol. Analyses evaluated which risk factors collected at baseline were related to increased nuclear opacification at follow-up. The MULCOX2 method, an extension of Cox regression for nested event-time data, was used to estimate the effects of the risk factors. This method accounted for the correlation between fellow eyes. Results showed that the risk of nuclear opacification increased with each year of age (relative risk (RR) = 1.07), white race (RR = 2.94), lower education (RR = 1.50), use of gout medications (RR = 2.32), current smoking (RR = 1.58), family history of cataract (RR = 1.39), and preexisting posterior subcapsular opacities (RR = 6.67). An association with early use of eyeglasses was also suggested (RR = 1.37). In conclusion, nuclear opacification was related to demographic and other variables, including potentially modifiable factors such as current smoking and use of gout medications. Most risk factors identified by this longitudinal study confirm those found by the original case-control study. The increased risk of nuclear opacities in whites appears to be a new finding.

Electron microscopic observation on a non-occluded baculo-like virus in shrimps

A severe disease of farm-raised shrimp, Penaeus chinensis has spread throughout Chinese coasts since 1993. Recently, a baculo-like virus has been diagnosed as the causative agent for this epidemic disease. The electron microscopic observation of the virus is described. Thin sections of hepatopancreatic and hypodermic tissue of diseased P. chinensis showed many rod-shaped, enveloped, baculo-like virions in hypertrophied nuclei of infected cells. The virion was filled with a highly electron dense core. No occlusion bodies have been found. Negative stained intact virions, purified from infected tissues by centrifugation on sucrose discontinuous gradients, demonstrated that the viral envelops had been broken, but the cylindrical nucleocapside could be observed clearly. The nucleocapsid of average 62 nm x 314 nm was composed of a helix system of capsomers, giving rise to an open stacked ring structure and repeating approximately every third ring. The number of repeating unit was 13 to 15. We propose that the virus described here could be designated as Non-Occluded Shrimp Virus (NOSV) or Penaeus chinensis Baculo-Like Virus (PcBLV).

Nociceptin-like immunoreactivity in the rat dorsal horn and inhibition of substantia gelatinosa neurons

Nociceptin, also referred to as orphanin FQ, is believed to be the endogenous ligand for the ORL1. Nociceptin, when injected intracerebroventricularly to mice, produced hyperalgesia in behavioral tests. Recent studies have demonstrated the presence of ORL1 transcript in the spinal cord, and ORL1-like immunoreactivity has been localized to nerve fibers and somata throughout the spinal cord. Here, we report the localization of nociceptin-like immunoreactivity to fiber-like elements of the superficial layers of the rat dorsal horn by immunohistochemical techniques. Whole-cell recordings from substantia gelatinosa neurons in transverse lumbar spinal cord slices of 22-26-day-old rats showed that exogenous nociceptin at low concentrations (100-300 nM) depressed excitatory postsynaptic potentials evoked by stimulation of dorsal rootlets without causing an appreciable change of resting membrane potentials and glutamate-evoked depolarizations. At a concentration of 1 microM, nociceptin hyperpolarized substantia gelatinosa neurons and suppressed spike discharges. The hyperpolarizing and synaptic depressant action of nociceptin was not reversed by the known opioid receptor antagonist naloxone (1 microM). Our result provides evidence that nociceptin-like peptide is concentrated in nerve fibers of the rat dorsal horn and that it may serve as an inhibitory transmitter within the substantia gelatinosa.

Incidence and progression of cortical and posterior subcapsular opacities: the Longitudinal Study of Cataract. The LSC Group

OBJECTIVE

The purpose of the study is to estimate incidence and progression rates of cortical and posterior subcapsular (PSC) opacities in the Longitudinal Study of Cataract (LSC).

DESIGN

An epidemiologic study of the natural history of lens opacities in a clinic-based population.

PARTICIPANTS

The LSC was based on 764 participants in an earlier case-control study of lens opacities.

MAIN OUTCOME MEASURES

Baseline data, collected until 1988, included color slit and retroillumination photographs. The same data were collected at follow-up visits from 1989 to 1993. The Lens Opacities Classification System III (LOCS III) was used to assess lens changes between baseline and follow-up photographs. The product-limit method was used to estimate the incidence and progression rates.

RESULTS

After 5 years of follow-up, the incidence rates for developing cortical and PSC opacities were 7.7% and 4.3%, respectively. The progression rate of pre-existing cortical opacities was 16.2% after 5 years, and was twice as high as the incidence rate. The progression of pre-existing PSC opacities was much higher, and reached 55.1% after 5 years of follow-up. The incidence of newly developed cortical or PSC opacities increased with age. The incidence of PSC opacities also increased when coexisting opacities were present at baseline.

CONCLUSIONS

After 5 years, 1 in every 13 patients developed new cortical opacities, and 1 in 24 developed new PSC opacities. The 5-year progression rates for cortical and PSC opacities were much higher than the incidence rates. These results can be used to estimate the rate of cortical and PSC changes in similar populations.

Lens opacities, demographic factors and nutritional supplements in the Barbados Eye Study

BACKGROUND

This study evaluated the association of age-related lens opacities with the use of nutritional supplements and demographic factors among 4314 black participants (> or = 40 years) in the population-based Barbados Eye Study.

METHODS

Lenses were classified at the slit lamp by the Lens Opacities Classification System II (LOCS II); a score > or = 2 was used to define the presence of gradable lens opacities, by type. Lens changes also included prior cataract surgery or cataract too advanced to grade. Associations with risk factors were evaluated by logistic regression analyses.

RESULTS

The study identified 1800 individuals with lens changes in at least one eye; 229 had nuclear opacities only; 851 had cortical opacities only. Older age and indicators of lower socioeconomic status (low education and/or non-professional occupation), were positively associated with both nuclear (odds ratio [OR] = 1.90) and cortical (OR = 1.47) opacities. Women had an increased risk of cortical opacities (OR = 1.41). Regular users of nutritional supplements were less likely to have lens changes (OR = 0.78) and, specifically, cortical opacities (OR = 0.77). The association with nutritional supplements was present in those < 70 years, but not at older ages.

CONCLUSIONS

The study supports the association of lower socioeconomic status with lens changes, including nuclear and cortical lens opacities. The findings also suggest that regular users of nutritional supplements have a one-fourth lower risk of lens changes and particularly, of cortical opacities; a result seen at ages under 70 years. The associations with potentially modifiable factors indicate the need for further evaluations, given the high prevalence of lens opacities.

Associations with intraocular pressure in the Barbados Eye Study

OBJECTIVE

To evaluate the demographic, medical, ocular, familial, and other factors possibly associated with intraocular pressure (IOP) in a black population, after excluding persons with any type of glaucoma.

DESIGN

The Barbados Eye Study was a population-based study of a random sample of residents of Barbados, West Indies, aged 40 to 84 years.

PARTICIPANTS

A subset of the Barbados Eye Study population consisting of 3752 black Barbados Eye Study participants without glaucoma.

DATA COLLECTION

A standardized protocol included applanation tonometry and other ocular data, blood pressure measurements, anthropometry, complexion pigmentation gradings, and a comprehensive interview.

MAIN OUTCOME MEASURE

Intraocular pressure was based on the average of 3 measurements at the Barbados Eye Study visit. Multiple linear regression was used to evaluate factors associated with IOP.

RESULTS

Systolic blood pressure (or hypertension), diabetes history, and age were the major factors positively associated with IOP (P<.01). Other positively related factors were female gender, darker complexion, pulse rate, higher body mass, seasonality, family history of glaucoma, current alcohol use, and current smoking. These factors explained 10% of the variation in IOP.

CONCLUSIONS

By identifying risk factors, these results define specific subgroups most likely to have an elevated IOP. The high IOP in this population may be linked to the high prevalence of hypertension and diabetes. Aside from age and a family history of glaucoma, none of the risk factors for high IOP evaluated in this study was similar to those associated with open-angle glaucoma.

High-level expression of bovine beta-lactoglobulin in Pichia pastoris and characterization of its physical properties

Bovine beta-lactoglobulin (BLG) variant A has been expressed in the methylotropic yeast Pichia pastoris by fusion of the cDNA to the sequence coding for the alpha-mating factor prepro-leader peptide from Saccharomyces cerevisiae. P. pastoris Mut+ transformants were obtained by single cross-over integration of the BLG-containing vector into the AOX1 locus. In a fed-batch fermenter, a cell density of approximately 300 mg/ml was achieved by controlled glycerol feeding for a total of 24 h. After 72 h of methanol induction, the secreted BLG reached levels of > 1 g/l. The secreted protein could be purified to homogeneity by ion-exchange chromatography. Amino-terminal sequencing of the secreted BLG revealed that the Glu-Ala spacer repeats inserted between the mature protein and the alpha-factor prepro-leader were still present. The purified protein was characterized by a number of methods, including CD spectroscopy, guanidine-HCl unfolding, crystallization and two-dimensional 1H-NMR spectroscopy. By all of these measures, the physical characteristics of recombinant BLG were indistinguishable from those of the native purified bovine BLG, making it useful as a model for protein folding and other biophysical studies.

Distribution of intraocular pressure. The Barbados Eye Study

OBJECTIVE

To provide data on the distribution of intraocular pressure (IOP) in a predominantly black population, which has a high prevalence of open-angle glaucoma.

DESIGN

Population-based prevalence study.

SETTING AND PARTICIPANTS

Participants (N = 4601) (age range, 40-84 years) who had undergone applanation tonometry measurements in the Barbados Eye Study. Self-reported race was 93% black, 4% mixed (black and white), and 3% white or other.

DATA COLLECTION

A standardized protocol included applanation tonometry and other ocular measurements, fundus photography, demographic data, and an interview.

MAIN OUTCOME MEASURES

The average of 3 IOP measurements at the Barbados Eye Study visit was used to compare IOP by self-reported race. Descriptive data on IOP by age, sex, glaucoma status, and cup-disc ratio were examined in the black population.

RESULTS

The IOP was highest in the population of African origin. The mean (+/-SD) IOP values for black, mixed, and white participants were 18.7 +/- 5.2, 18.2 +/- 3.8, and 16.5 +/- 3.0 mm Hg, respectively. An IOP greater than 21 mm Hg was present in 18.4%, 13.6%, and 4.6% of the black, mixed, and white participants, respectively. In analyses that were adjusted for age, sex, and glaucoma status, such values were 5 times as likely in black than white participants and 3.5 times as likely in mixed race participants (P < .01). Among the black participants, the mean IOP increased approximately 1 mm Hg for every increase in 10 years of age. After excluding persons with any type of glaucoma, suspected glaucoma, or a history of glaucoma treatment, women had significantly (P < .01) higher IOP values; however, no significant IOP trends by sex were evident in the group with glaucoma. The IOP was also positively associated (P < .05) with vertical cup-disc ratios. After 2 visits, the IOP remained 21 mm Hg or less in 21% of the persons with glaucoma vs 64% of those without glaucoma.

CONCLUSIONS

In the black participants, the IOP was higher than in the white participants. The IOP was also associated with age and cup-disc ratios. The results showed that open-angle glaucoma and a high IOP alone have a different distribution by sex; although open-angle glaucoma was more frequent in men, ocular hypertension was more frequent in women. These data have implications for the detection and causation of open-angle glaucoma in this high-risk population.

Increased urinary thyroxine sulfate excretion in thyroxine therapy

Although increased thyroxine sulfate (T4S) levels have recently been detected in fetal serum and amniotic fluid, changes in patients in a high thyroxine (T4) state remain unclarified. This study was conducted to determine the changes in T4S in thyroid hormone regulation in women receiving suppressive T4 therapy. With a highly sensitive and specific radioimmunoassay, we measured the serum and urinary concentrations of T4S in 16 premenopausal women with benign nodular goiter before and after three months administration of T4 (3.2 micrograms/kg/day). Serum levels of other thyroid hormones were also measured. Significant increases in mean serum T4 levels post-treatment (11.1 vs. 6.6 micrograms/dL pre-treatment; P < 0.01) were found, although only low T4S levels were detectable in serum both pre- and post-T4 treatment. The mean urinary or creatinine corrected urinary T4S values post-treatment were significantly increased (20 ng/dL or 396 ng/g creatinine vs. 12 ng/dL or 174 ng/g creatinine pre-treatment, P < 0.01). There was a significant correlation between increased creatinine-corrected urine T4S and increased serum free T4. Our results indicate that the sulfation of T4 may be related to the regulation of thyroid hormone metabolism in T4-treated subjects with relative hyperthyroxinemia.

Potentiation of NMDA currents by pituitary adenylate cyclase activating polypeptide in neonatal rat sympathetic preganglionic neurons

Whole cell patch-clamp recordings were made from sympathetic preganglionic neurons (SPNs) in the intermediolateral cell column of thoracolumbar spinal cord slices of 12- to 16-day-old rats, and the effects of pituitary adenylate cyclase activating polypeptide (PACAP)-38 on N-methyl-D-aspartate (NMDA)- and kainate (KA)-induced inward currents were examined. PACAP, in concentrations (10-30 nM) that caused no significant change of holding currents, reversibly increased NMDA-induced currents but not KA-induced currents. At higher concentrations (>30 nM), the peptide produced a sustained inward current. The potentiating effect of PACAP was nullified by prior incubation of the slices with the adenylate cyclase inhibitor MDL-12,330A (25 microM). Further, superfusing the slices with the membrane-permeable cyclic AMP analogue N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (100-300 microM) in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (700 microM) increased the NMDA currents. This result suggests that PACAP selectively increases NMDA-receptor-mediated responses in the rat SPNs, probably via a cyclic-AMP-dependent mechanism, providing evidence that the peptide may be involved in synaptic plasticity.

Nitric oxide and excitatory postsynaptic currents in immature rat sympathetic preganglionic neurons in vitro

Neuronal nitric oxide synthase immunoreactivity was localized to sympathetic preganglionic neurons of the intermediolateral cell column and cyclic GMP immunoreactivity to nerve fibers projecting into the intermediolateral cell column of 20-25-day-old rats. Whole-cell patch-clamp recordings were made from sympathetic preganglionic neurons in spinal cord slices of immature rats and the role of nitric oxide and cyclic GMP on excitatory postsynaptic currents was studied. Superfusing the slices with the nitric oxide precursor L-arginine (300 microM) increased the amplitude of evoked excitatory postsynaptic currents as well as the frequency of spontaneous miniature excitatory postsynaptic currents in some neurons from minutes to over 1 h. The nitric oxide synthase inhibitor N(W)-nitro-L-arginine (100 microM) and the nitric oxide scavenger hemoglobin (100 microM) antagonized the potentiating effect of L-arginine. The nitric oxide donor sodium nitroprusside (100 microM) potentiated the synaptic currents in a manner similar to that of L-arginine and this effect was blocked by hemoglobin. The membrane-permeable cyclic GMP analogue dibutyryl guanosine 3',5'-cyclic monophosphate (350 microM), in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (750 microM), potentiated the evoked excitatory postsynaptic currents and increased the frequency of miniature excitatory postsynaptic currents; these effects were not prevented by hemoglobin. The results indicate that nitric oxide may facilitate the release of excitatory transmitters, possibly through a presynaptic cyclic GMP-dependent mechanism.

Triiodothyronine (T3) reflects renal graft function after renal transplantation

OBJECTIVE

Abnormalities in thyroid function are observed in patients with end stage renal disease. However, there are no data available evaluating sequential changes of thyroid function after renal transplantation. Therefore, we have studied thyroid hormone function in the immediate post-operative period after renal transplantation in order to determine the relationship between improving renal function and changes in thyroid hormone economy.

DESIGN AND PATIENTS

Thyroid function was evaluated in 22 patients before and on days 1, 3, 7 and 15 after renal transplantation. All patients received prednisone and cyclosporin as immunosuppressive therapy. Twelve patients with normal renal function undergoing comparable surgical procedures served as a control group.

MEASUREMENTS

Serum creatinine and thyroid hormone parameters (total T4, total T3, free T4, free T3, thyroxin binding globulin (TBG), reverse T3, T3 sulphate and TSH) were measured.

RESULTS

According to post-operative kidney function after renal transplantation, patients could be subdivided into three groups: five patients had primary graft function (group I); seven patients had delayed graft function because of acute renal failure (group II); 10 patients had delayed graft function requiring high doses of prednisone and some also of OKT3 because of acute rejection (group III). There was a significant fall in T3 and T4 concentrations with a concomitant rise in reverse T3 in all patients up to 3 days after renal transplantation. However, only patients in group I reached pre-operative values on day 15 after renal transplantation (serum creatinine 167 +/- 52 microM), whereas patients in group II (creatinine 609 +/- 118 microM) and group III (creatinine 839 +/- 71 microM) continued to have T3 concentrations well in the hypothyroid range (group I, 1.68 +/- 0.28 nM) vs 0.87 +/- 0.09 nM in group II and 0.76 +/- 0.10 nM in group III; P < 0.01). Serum T4 concentrations were also low in group III (47.7 nM vs 100.2 nM in group I; P < 0.05) 15 days after renal transplantation. These changes were accompanied by a concomitant fall in T3/TBG ratio and in free T3. Elevated reverse T3 returned to normal values in all groups on the 15th day after renal transplantation. TSH fell significantly on the first post-operative day, but did not return to pre-operative values in renal transplantation patients. In the control group, TSH did not change during the study period. T3 sulphate, known to be elevated in chronic renal failure, remained above normal in all patients irrespective of graft function during this study period.

CONCLUSIONS

T3 concentrations reflect renal graft function after renal transplantation. T3 is below normal in patients with delayed graft function (acute renal failure or acute rejection). The post-operative period (up to 3 days after renal transplantation) is associated with a low T3 syndrome. TSH does not return to pre-operative values even in patients with primary graft function. This might be due to the administration of prednisone. T3-sulphate is elevated before and after renal transplantation irrespective of graft function.

Excitatory action of pituitary adenylate cyclase activating polypeptide on rat sympathetic preganglionic neurons in vivo and in vitro

In vivo and in vitro experiments were undertaken to evaluate the effects of pituitary adenylate cyclase activating polypeptide-38 (PACAP-38) on rat sympathetic preganglionic neurons (SPNs). Intrathecal injection of PACAP-38 (0.1-1 nmol) via an implanted cannula to the T2-T3 segments of urethane-anesthetized adult rats caused a dose-dependent increase of mean arterial blood pressure from minutes to over 1 h. The pressor response was not antagonized by prior injection of the PACAP type II receptor antagonist PACAP6-38 (0.5 nmol), but was significantly attenuated by prior intravenous administration of phentolamine (1 mg/kg). As a positive control, intrathecal injection of glutamate (1 micromol) and substance P (SP, 5 nmol) caused a short- and long-lasting pressor response. Vasoactive intestinal polypeptide (VIP, 1 nmol) had no significant pressor effect. In the second series of experiments, whole-cell patch recordings were made from antidromically identified SPNs of immature (12-16-day-old) rat thoracolumbar spinal cord slices. Applied to the spinal cord slices by superfusion, PACAP-38 (10-30 nM) caused intense neuronal discharges with or without a long-lasting membrane depolarization. The depolarization was not prevented by superfusing the slices with tetrodotoxin (0.3 microM) or low Ca2+ (0.25 mM) solution, indicating that PACAP-38 directly depolarized the SPNs. The depolarization was insensitive to the type II PACAP receptor antagonist PACAP6-38. Collectively, these results provide evidence that PACAP-38 exerts a potent and long-lasting excitatory effect on SPNs, leading to an increase of spinal sympathetic outflow and one of the consequences of which is an elevation of blood pressure.

Characterization of a maize beta-amylase cDNA clone and its expression during seed germination

A maize (Zea mays L.) cDNA clone (pZMB2) encoding beta-amylase was isolated from a cDNA library prepared from the aleurone RNA of germinating kernels. The cDNA encodes a predicted product of 488 amino acids with significant similarity to known beta-amylases from barley (Hordeum vulgare), rye (Secale cereale), and rice (Oryza sativa). Glycine-rich repeats found in the carboxyl terminus of the endosperm-specific beta-amylase of barley and rye are absent from the maize gene product. The N-terminal sequence of the first 20 amino acids of a beta-amylase peptide derived from purified protein is identical to the 5th through 24th amino acids of the predicted cDNA product, indicating the absence of a conventional signal peptide in the maize protein. Recombinant inbred mapping data indicate that the cDNA clone is single-copy gene that maps to chromosome 7L at position 83 centimorgans. Northern blot analysis and in vitro translation-immunoprecipitation data indicate that the maize beta-amylase is synthesized de novo in the aleurone cells but not in the scutellum during seed germination.