Adrenal steroids act as inhibitory modulators of thyrofollicular cell morphology and proliferation in neonatal chicks (Gallus domesticus)

In the present study the effects of adrenal corticoids, both natural and synthetic, namely cortisol and dexamethasone respectively, was observed on the thyroid gland cell morphology and proliferation in neonatal male chicks (Gallus domesticus). Cortisol was injected at a dose of 4 mg/100 g body weight and dexamethasone at a dose of 1 mg/100 g b.w. subcutaneously daily for fifteen consecutive days. The control birds were similarly injected with normal saline at a daily dose of 0.2 ml per bird for the same time period. The results indicated that both cortisol and dexamethasone caused a significant decrease in thyrofollicular cell height. On the contrary, a significant increase in the ratio of the follicular diameter to the number of nuclei per follicle i.e. D/N value was observed in both cortisol and dexamethasone treated chicks. It was also observed that both cortisol and dexamethasone induced suppression of mitotic activity, as evidenced from a significant decrease in mitotic percentage compared with the control chicks. The present authors' studies thus indicate that adrenal corticoids act as inhibitory modulators of thyroid follicular activity as regards karyomorphology and cell proliferation.

Rho-kinase activation is involved in hypoxia-induced pulmonary vasoconstriction

Rho-associated serine/threonine kinase (Rho-kinase) is a downstream effector of small GTPase RhoA that has recently been shown to play an important role in regulating smooth muscle contraction. The present study investigated the role of Rho/ Rho-kinase in hypoxia-induced pulmonary vasoconstriction (HPV). Small pulmonary resistance vessels and cultured pulmonary arterial smooth muscle cells (PASMCs) from the rat were used. PASMCs exposed to hypoxia (PO(2) = 26 +/- 2 mm Hg) showed a significant increase in Rho-kinase activity. Exposure to hypoxia for 20, 40, 60, 90, and 120 min also resulted in a significant increase in myosin light chain (MLC) phosphorylation at all time points in PASMCs. Hypoxia-induced MLC phosphorylation was inhibited by Y-27632 (a Rho-kinase inhibitor), exoenzyme C3 (a specific Rho inhibitor), or toxin B (an inhibitor for Rho proteins). In addition, hypoxia-induced Rho-kinase activation was blocked by C3 and toxin B. Small rat intrapulmonary arterial rings, which were made hypoxic (PO(2) = 30 +/- 3 mm Hg), showed a slow sustained contraction, and Y-27632 caused a significant relaxation during the sustained phase of HPV in a concentration-dependent manner. In summary, the data show that Rho-kinase is activated by hypoxia in PASMCs, and Rho/Rho-kinase is functionally linked to hypoxia-induced MLC phosphorylation and plays a role in the sustained phase of HPV.

Features of primary care associated with variations in process and outcome of care of people with diabetes

BACKGROUND

There is now clear evidence that tight control of blood glucose and blood pressure significantly lowers the risk of complications in both type I and type II diabetes. Although there is evidence that primary care can be as effective as secondary care in delivering care for people with diabetes, standards in primary care are variable. Previous studies have shown that practice, patient or organisational factors may influence the level of care of patients with diabetes. However, these studies have been conducted in single geographical areas and involved only small numbers of practices.

AIM

To determine the standard of diabetes care in general practice and to determine which features of practices are associated with delivering good quality care.

DESIGN OF STUDY

A questionnaire survey and analysis of multi-practice audit data.

SETTING

Three health authorities in England, comprising 169 general practices.

METHOD

This study was conducted with a total population of 1,182,872 patients and 18,642 people with diabetes. Linkage analysis was carried out on data collected by a questionnaire, routinely collected health authority data, and multi-practice audit data collected by primary care audit groups. Practice annual compliance was measured with process and outcome measures of care, including the proportion of patients who had an examination of their fundi, feet, blood pressure, urine, glycated haemoglobin, and the proportion who had a normal glycated haemoglobin.

RESULTS

Median compliance with process and outcome measures of care varied widely between practices: fundi were checked for 64.6% of patients (interquartile range [IQR] = 45.3-77.8%), urine was checked for 71.4% (IQR = 49.7-84.3%), feet were checked for 70.4% (IQR = 51.0-84.4%), blood pressure for 83.6% (IQR = 66.7-91.5%), and glycated haemoglobin was checked for 83.0% of patients (IQR = 69.4-92.0%). The glycated haemoglobin was normal in 42.9% of patients (IQR = 33.0-51.2%). In multiple regression analysis, compliance with measures of process of care were significantly associated with smaller practices, fundholding practices, and practices with a recall system. Practices with more socioeconomically deprived patients were associated with lower compliance with most process measures. Practices with a greater proportion of patients attending hospital clinics had lower compliance with process and outcome measures. Being a training practice, having a diabetes mini-clinic, having more nurses, personal care, and general practitioner or nurse interest in diabetes were not associated with compliance of process or outcome of care.

CONCLUSIONS

Despite recent evidence that complications of diabetes may be delayed or prevented, this study has highlighted a number of deficiencies in the provision of diabetes care and variations in care between general practices. Provision of high quality diabetes care in the United Kingdom will present an organisational challenge to primary care groups and trusts, especially those in deprived areas.

Inequalities in provision of systematic care for patients with diabetes

BACKGROUND

GPs are now playing a greater role in the care of people with diabetes; however, the level of performance in primary care is variable. Practices with a recall system and diabetes mini-clinic have been shown to achieve better outcome of care of patients with diabetes. Systematic care also requires effective community-based diabetes services and access to primary care diabetes teams including dieticians, chiropodists, and optometrists and ophthalmologists.

OBJECTIVES

The aims of this study were to determine how services for people with diabetes are organized in primary care and whether there are inequalities in systematic care of people with diabetes.

METHODS

A piloted postal questionnaire was sent to all 327 general practices in three health authorities in England serving a population of >2 million people. The three health authorities provided practice-based routine data relating to all general practices.

RESULTS

A total of 264 (80.7%) practices replied; 236 (89.4%) employed a diabetes recall system and 196 (74.2%) reviewed their patients in a diabetes mini-clinic. Multiple regression showed that having a recall system was associated independently with a GP [odds ratio (OR) 6.2; 95% confidence interval (CI) 2.6-14.9] or a practice nurse (OR 3.5; 1.4-8.7) with an interest in diabetes. Having a diabetes mini-clinic was associated independently with a GP with an interest in diabetes (OR 4.1; 2.1-7.8), a practice nurse having attended a diabetes course (OR 2.8, 1.3-6.2), practices with more partners (OR 1.2 per additional partner; 1.0-1.4) and fundholding practices (OR 2.6; 1.2-5.5). One hundred and sixteen (43.9%) practices had a chiropodist present in the practice, and 90 (34.1%) had a practice-based dietician. A chiropodist and a dietician were significantly more likely to be attached in training practices and in less deprived areas. A practice-based dietician was significantly associated with larger practices.

CONCLUSIONS

Providing high quality primary care is essential to meeting the government's agenda of reducing inequalities. This study shows high levels of structured diabetes care which are not related to deprivation. However, practices in more deprived areas still lag behind practices in more affluent areas in terms of access to members of the diabetes team. To improve care of people with diabetes in primary care, deficiencies and inequalities highlighted in our survey must be addressed. The results of this survey will be valuable to primary care groups and organizations responsible for commissioning diabetes services.

Structural insights into the amino-terminus of the secretin receptor: I. Status of cysteine and cystine residues

The secretin receptor is prototypic of the class II family of G protein-coupled receptors, with a long extracellular amino-terminal domain containing six highly conserved Cys residues and one Cys residue (Cys(11)) that is present only in the most closely related family members. This domain is critical for function, with some component Cys residues believed to be involved in key disulfide bonds, although these have never been directly demonstrated. Here, we examine the functional importance of each of these residues and determine their involvement in disulfide bonds. Secretin binding was markedly diminished after treating cells with cell-impermeant reducing reagents, supporting the presence of important extracellular disulfide bonds. To determine whether the amino-terminal domain was covalently attached to the receptor body by disulfide linkage, a strategy was implemented that involved introduction of an acid-labile Asp-Pro sequence to enable specific cleavage at the boundary of these domains. Under nonreducing conditions, the amino terminus was released from the receptor body, supporting the absence of covalent association between these domains. Quantitative [(14)C]iodoacetamide incorporation into the isolated amino-terminal domain of the receptor in the absence and presence of chemical reduction established the ratio of free to total Cys residues as 1:7, consistent with three disulfide bonds. Mutagenesis of each of the amino-terminal Cys residues to Ala was tolerated only for Cys(11), suggesting that these bonds linked the conserved Cys residues. This was further supported by treatment of intact cells expressing wild-type or C11A mutant secretin receptor with a cell-impermeant sulfhydryl-reactive reagent. Thus, the functionally important amino terminus of the secretin receptor represents a structurally independent, highly folded, and disulfide-bonded domain, with a pattern that is likely critical and conserved throughout this receptor family.

Who looks after people with diabetes: primary or secondary care?

Because the prevalence of type 2 diabetes has increased greatly over the past decade, UK general practitioners have been encouraged to develop services for people with diabetes and to offer structured diabetes care. The resultant shift from secondary care can place considerable demands on primary health care teams. Data were obtained from 108 practices in two English health districts followed up in primary and secondary care. Nearly two-thirds of the people with diabetes were being followed up only in general practice, the remainder in hospital or both. The proportion managed in primary care varied from 5.6% to 94.6%. The settings where diabetes care was most likely to be offered were training practices, practices with good nursing support, practices with a high prevalence of diabetes, and practices in which a high proportion of diabetic patients were controlled by diet or hypoglycaemic agents. Tight control of glycaemia and blood pressure is now seen as important in diabetes, and is best achieved in general practice. This survey revealed large variations in delivery of general-practice diabetes care that need to be addressed by better organization and funding.

Role of polyphenol oxidase and peroxidase in the generation of black tea theaflavins

It has been reported earlier that when macerated tea leaf is fermented at lower pH, the resultant black tea contains increased levels of theaflavin, an important quality marker in black tea. In an attempt to investigate the biochemistry and chemistry underlying this observation, in vitro oxidation experiments using polyphenol oxidase (PPO) from fresh tea leaves, horseradish peroxidase (POD), and tea catechins, precursors for theaflavins, were carried out. In vitro oxidation experiments using crude tea PPO resulted in higher content of theaflavins at pH 4.5 in comparison with pH 5.5, the normal pH of the macerated tea leaf. When purified PPO was used in the in vitro system, surprisingly a reversal of this trend was observed, with more theaflavins being formed at the higher pH. A combination of pure tea PPO and POD led to an observation similar to that with the crude enzyme preparation, suggesting a possible role for POD in the formation or degradation of theaflavin. POD was observed to oxidize theaflavins in the presence of H(2)O(2), leading to the formation of thearubigin, another black tea pigment. This paper demonstrates that tea PPO, while oxidizing catechins, generates H(2)O(2). The amount of H(2)O(2) produced is greater at pH 5.5, the optimum pH for PPO activity, than at pH 4.5. Hence, an observed increase of theaflavins in black teas fermented at pH 4.5 appears to be due to lower turnover of formed theaflavins into thearubigins.

The cellular intake kinetics and acute biological effects of various oxovanadium species: a comparative study

It is well known that different oxovanadium species can have significantly different biopotencies, including hypoglycemic actions. The basis for the observed differences in the biopotency of different oxovanadium species: vanadate, vanadyl, 1,10-phenanthroline bisperoxovanadate (phen-bpv), 4-methyl 1,10-phenanthroline bisperoxovanadate (mpv) and 4,7-dimethyl 1,10-phenanthroline bisperoxovanadate (dpv), was examined in this study. The cellular uptake kinetics for these oxovanadium species was measured. Phen-bpv and vandyl had the most rapid cellular uptake. Mpv, dpv and vanadate exhibited a much slower uptake kinetics. Stimulation of protein tyrosine phosphorylation (PTP), both the time dependency and the dose dependency, was used as an index for biopotency. Although phen-bpv and vanadyl had the same cellular uptake kinetics, they differed markedly in their ability to stimulate PTP. Structurally similar oxovanadium species, phen-bpv, mpv and dpv demonstrated different uptake kinetics and effects on stimulating PTP. Bioavailability, both in term of cellular uptake and migration or transport to the active site, has been shown to be an important factor, in addition to intrinsic activity of the oxovanadium species, in determining the overall biopotency. Finally, this study demonstrates that variation of the chelating ligand has a profound effect on the physiochemical properties and biological effects of the oxovanadium species.

Differential acute effects of oxovanadiums and insulin on glucose and lactate metabolism under in vivo and in vitro conditions

Oxovanadium compounds such as vanadate and peroxovanadiums have been shown to have insulin-mimetic effects on various metabolic pathways, including glucose metabolism. A differential effect of various oxovanadium species on glucose metabolism in different tissues has been reported. The results from our present in vivo studies using rats show that peroxovanadiums and insulin have similar acute effects on decreasing blood glucose levels, but dissimilar effects on blood lactate levels. Furthermore, when bisperoxovanadate (BPV) was administered acutely to intact animals immediately before a bolus insulin challenge, it blunted the effectiveness of insulin in decreasing the blood lactate level, but at the same time demonstrated a synergistic effect on the hypoglycemic action of insulin. It was also observed in in vitro studies using normal 3T3-L1 adipocytes (not serum-deprived) that 1,10-phenanthroline bisperoxovanadate (PHEN-BPV) attenuates the incorporation of carbon from lactate but not from glucose, into lipid in both the absence and presence of insulin. Additionally, it was observed that PHEN-BPV had no effect on lactate dehydrogenase (LDH) activity. Thus, one may speculate that PHEN-BPV interferes with carrier-mediated lactate transport. These observations demonstrate that insulin and oxovanadiums differ in the handling of different metabolic substrates. Thus, even though oxovanadiums mimic many of the metabolic actions of insulin, their metabolic effects are by no means identical. Moreover, since vanadate had no acute effect on glucose metabolism under in vivo conditions, this may suggest that to be effective as a hypoglycemic agent vanadate needs to be converted to some other biologically active oxovanadium species. Finally, the observed interference by PHEN-BPV in the metabolism of lactate may predispose subjects using oral vanadate, as a part of the therapeutic regimen for management of diabetic hyperglycemia, to lactic acidosis.

Multiple extracellular loop domains contribute critical determinants for agonist binding and activation of the secretin receptor

Distinct themes exist for ligand-binding domains of G protein-coupled receptors. The secretin receptor is prototypic of a recently described family in this superfamily which binds moderate-sized peptides possessing a diffuse pharmacophore. We recently demonstrated the importance of the N terminus and first loop of this receptor for secretin binding (Holtmann, M. H., Hadac, E. M., and Miller, L. J. (1995) J. Biol. Chem. 270:14394-14398). Here, we extend those findings to define another receptor domain important for agonist recognition and to focus on critical determinants within each of these domains. Extending the secretin-vasoactive intestinal polypeptide (VIP) chimeric receptor approach, we confirmed and refined the critical importance of the N terminus and the need to complement this with other domains of the secretin receptor. There was redundancy in the complementary determinants required, with the second extracellular loop able to compensate for the absence of the first loop. The first 10 residues of the N terminus of the secretin receptor were critical. Sequential segmental and site replacements permitted focusing on the His189-Lys190 sequence at the C terminus of the first extracellular loop, and on four residues (Phe257, Leu258, Asn260, and Thr261) in the N-terminal half of the second loop as providing critical determinants. All receptor constructs which expressed sensitive cAMP responses to secretin (EC50 <5 nM) bound this peptide with high affinity. Of note, one construct dissociated high affinity binding of secretin from its biological responsiveness, providing a clue to the conformational "switch" that activates this receptor.

Neuropharmacological studies on Fusarium toxins-III: Neurochemical investigations on total toxin extracts from F. moniliforme and F. oxysporum

Neurochemical effects of different fusarial toxins elaborated from F. moniliforme (FM) and F. oxysporum (FO) were investigated. FM showed significant nonspecific and irreversible monoamine oxidase (MAO) inhibition which was qualitatively comparable to that induced by nialamide, a nonselective MAO inhibitor. FO did not exhibit any significant MAO inhibitory effect. FM produced a dose related increase in monoamine concentrations (dopamine, noradrenaline and 5-hydroxytryptamine) in different rat brain areas namely, diencephalon-midbrain, caudate nucleus and pons-medulla. FO, on the contrary, produced marked increase in dopamine concentration in the caudate nucleus with concomitant reduction in noradrenaline levels in diencephalon-midbrain and pons-medulla with little effect on 5-HT concentration. The neurochemical effects of FM and FO are consonant with the earlier reports on the neuropharmacological profile of these toxins. Thus, FM was reported to have nialamide like activity, whereas FO actions were dopaminergic in nature.

Neuropharmacological studies on Fusarium toxins--II: Total toxin extract from F. oxysporum

The neuropharmacological activity profile of total fungal extract of F. oxysporum (FO) was investigated. FO enhanced spontaneous locomotor activity, exploratory behaviour and reduced pentobarbitone hypnosis. It had per se anticonvulsant action against maximal electroshock seizure (MES) and potentiated phenobarbitone and phenytoin in MES and also potentiated pentylenetetrazol (PTZ) convulsion. It antagonised morphine, tetrabenazine and haloperidol catalepsy. FO did not show per se analgesia or potentiation of morphine antinociception in mice, while both effects were present in rats. The effect of FO on body temperature was complex. It produced per se reduction in rectal temperature and potentiated the hypothermic responses of reserpine, apomorphine, PEA and I-dopa, and also the hyperthermic response of 5-HTP. The hyperthermic response of haloperidol was reversed by FO. It potentiated amphetamine and morphine lethality, amphetamine, PEA and apomorphine stereotypy, 5-HTP headtwitch response and post-swim grooming response. On swim-stress immobility, while the time of onset of immobility was reduced, FO did not modify the duration of immobility. On foot-shock induced aggression in paired rats, FO produced a decrease in the latency to onset of fighting behaviour and increased the total contact period and the cumulative aggressive score. FO potentiated clonidine automutilation. It has, thus, facilitated aggressive behaviour. The effects are likely to be due to the presence of fusaric acid in FO, which inhibits dopamine beta-hydroxylase and is known to have dopaminergic effects. This investigation has practical implications. since F. oxysporum is a common food contaminant.

Nuclear accumulation of multiple protein kinases during prolactin-induced proliferation of Nb2 rat lymphoma cells

Intracellular kinases play important roles in signal transduction and are involved in the surface receptor-mediated regulation of cellular functions, including mitogenesis. In the present study, we examined the possible involvement of various protein kinases in the passage of a mitogenic signal from the cell surface to the nucleus of Nb2 cells, a rat nodal lymphoma cell line in which prolactin is a mitogen. Following a prolactin challenge, various kinase activities were monitored at short intervals in different cellular fractions over a 60 min period. Protein kinase C (PKC) activity in the cytosolic fraction rapidly declined to 50% of its original activity within the first 30 min, while PKC activity in the nuclear fractions increased sharply, reaching its highest level by 30 min following a prolactin challenge. There were also increases in both casein kinase and protein tyrosine kinase (PTK) activities in the nuclear fractions during the first 30 min following a prolactin challenge that paralleled PKC activity. The activities of all three kinases declined thereafter, reaching levels close to their respective basal values by 60 min following initiation of prolactin treatment. These observations suggest the possibility that multiple protein kinases may be involved in mitogenic signal transduction for prolactin in Nb2 cells.