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Biomedical subjects

M Zeman

Publications and source records attributed to M Zeman.

At least 19 recordsLinked to original sources

[Fatty acid composition and parameters of VLDL and LDL in persons with dyslipidemia].

BACKGROUND: Oxidatively modified LDL play an important role in the pathogenesis of endothelial dysfunction, initiation and development of atherosclerosis and stability of the atheromatous plaque. The increased oxidative stress is apparent from a number of deviations, which are part of the insulin resistance syndrome (hypertension, hypoalphacholesterolaemia, diabetes and hyperlipoproteinaemia). The objective of the work was to examine the degree of oxidation and oxidability of LDL and VDL in subjects with dyslipidaemia. METHODS AND RESULTS: In 40 subjects with dyslipidaemia, defined as a triglyceride concentration above 2.30 mmol/l and a drop of HDL cholesterol below 0.90 mmol/l, the authors assessed the fatty acid profile in plasma lipid classes and LDL by capillary gas chromatography. Lipoperoxidation in VLDL and LDL was examined by the method of kinetics of conjugated dienes according to Esterbauser. The results were compared with a group of healthy controls. The group of dyslipidaemic subjects had higher concentrations of NEFA, IRI, blood sugar and uric acid. In these subjects the concentration of conjugated dienes in VLDL was significantly higher and the lag stage in VLDL and LDL was reduced. Both groups differed as to the composition of VLDD and LDL. The group of dyslipidaemic subjects had a higher concentration of cholesterol, phospholipids, triglycerides and apolipoprotein B. A constant finding in the fatty acid profile of all lipid classes was a raised concentration of palmitoleic acid and reduced linoleic acid concentration. CONCLUSIONS: Dyslipidaemic subjects have, as compared with a control group, higher NEFA, IRI and uric acid concentrations. Furthermore they differed not only by the composition of VLDL and LDL but also by a higher degree of VLDL oxidation and reduced resistance to lipoperoxidation of VLDL and LDL particles. A consistent finding in the fatty acid profile was an increased level of palmitoleic acid in all plasma lipid classes and LDL and a drop of linoleic acid in phosphatidylcholine LDL and plasma cholesterolesters.

Adult↗

Duplications and defects in the CYP2A6 gene: identification, genotyping, and in vivo effects on smoking.

In humans, 80% of nicotine is metabolized to the inactive metabolite cotinine by the enzyme CYP2A6, which can also activate tobacco smoke procarcinogens (e.g., 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone). Previously, we demonstrated that individuals who are nicotine-dependent and have defective CYP2A6 alleles (*2, *3) smoked fewer cigarettes; however, we recognize that the genotyping method used for the CYP2A6*3 allele gave a high false-positive rate. In the current study we used improved genotyping methods to examine the effects of the defective CYP2A6*2 and CYP2A6*4 alleles on smoking behavior. We found that those with the defective alleles (N = 14) smoked fewer cigarettes per day than those homozygous (N = 277) for wild-type alleles (19 versus 28 cigarettes per day, P <.001). In addition, we identified a duplicated form of the CYP2A6 gene, corresponding to the gene deletion CYP2A6*4 allele, developed a genotyping assay, assessed the gene copy number, and examined its prevalence in Caucasian smokers (N = 296). We observed an ascending rank order for plasma cotinine and breath carbon monoxide levels (an index of smoke inhalation) in individuals with null (CYP2A6*2 and CYP2A6*4) alleles (N = 14), those homozygous for wild-type (CYP2A6*1/*1) alleles (N = 277), and those with our newly identified CYP2A6 gene duplication (N = 5). The phenotype, as determined by plasma nicotine/cotinine ratios, had a descending rank order for these three genotype groups that did not reach significance. Although further characterization is required for the duplication gene variant, these results extend our previous findings and suggest a substantial influence of CYP2A6 genotype and phenotype on smoking behavior.

Adolescent↗

[Effect of fat distribution on lipoprotein composition and parameters of lipoperoxidation].

Fat distribution, not overweight and obesity per se, are supposed to be associated with hemodynamic, hemostatic and other metabolic disturbances (insulin resistance, hyperuricemia and dyslipidemia). Moreover, obesity increases the total risk of cardiovascular disease. Oxidative modification of lipoproteins, especially of LDL, is supposed to play a key role in the initiation and progression of atherosclerosis. Therefore we analysed VLDL a LDL composition and Cu(2+)-catalyzed conjugated diene formation in both lipoprotein fractions in patients with intraabdominal fat accumulation and in control group. Patients (33, 12 M/21 F) with intraabdominal fat accumulation (WHCR 1.00 for men, 0.85 for women) revealed, in comparison with control group (72, 47 M/25 F), after adjustment for the same age, increased plasma total cholesterol, apolipoprotein B, non-esterified fatty acid concentrations, and systolic blood pressure as well. In the group of patients increased levels of cholesterol, triglycerides, phospholipids, proteins and apolipoprotein B (only in the fraction of VLDL) were found in the both VLDL and LDL fractions. In this group of patients increased concentrations of conjugated dienes in VLDL and decreased length of lag phase of VLDL were found. Parameters of conjugated diene formation of LDL (basal absorbance, length of lag phase, propagation phase) did not differ significantly from controls. Concomitantly, persons with intraabdominal fat distribution showed decreased titres of antibodies against oxidative modified LDL. The results indicated that the patients with intraabdominal fat accumulation revealed not only adverse composition of VLDL and LDL particles, but also increased VLDL oxidation and oxidability.

Abdomen↗

[Insulinemia, fatty acids in plasma lipids and lipoproteins and oxidation of VLDL and LDL in hyperlipidemia].

Both insulin resistance and hyperlipidaemia are connected with an increased oxidative stress, playing a significant role in the development of atherosclerosis. A significant event in the process being the oxidative modification of the lipoproteins, especially LDL. Aim of the study was to analyse relationships between the fatty acid composition of the plasma cholesteryl esters (CE), triglycerides (TG) and phosphatidylcholine (PC) and of the separated LDL, insulinaemia and oxidability of both VLDL and LDL particles. We have observed the group of 75 patients with hyperlipidaemia (52 men and 23 women), which was divided in the two subgroups after the basal insulinaemia (more resp. less than 13 mU/l). Fasting hyperinsulinaemia of the probands with normal glucose tolerance served as a marker of an insulin resistance. Patients with both hyperlipidaemia and basal hyperinsulinaemia were characterized by a significantly higher concentration of TG, apolipoprotein B in LDL, and lower concentration of cholesterol in HDL, especially in HDL3. We have observed only marginally significant elevation of concentration of the dihomo-gammalinolenic acid (DGLA) in plasma PC and also higher concentrations of alpha-linolenic and lower of arachidonic acid (AA) and in LDL-CE in the hyperinsulinaemic group. We have also found significantly positive correlations between the stearic acid in plasma PC, alpha-linolenic acid in plasma TG on one hand and the basal insulinaemia on the other hand. Significant positive correlation was also found between the ratio docosahexaenoic/docosapentaenic acid and insulinaemia in 120 min of oral glucose tolerance test. Significant negative correlation was observed between the ratio AA/DGLA and basal insulinaemia. Analysing the lipoperoxidation of VLDL and LDL using the method of conjugated diene kinetics we have found statistically non-significant decrease of lag phase duration of LDL and VLDL (their oxidability).

Fatty Acids, Nonesterified↗

Role of melatonin in the control of growth and growth hormone secretion in poultry.

The pineal hormone melatonin controls reproduction of photoperiodic mammals and is an integral part of the circadian organization in birds. Recent findings indicate an involvement of this hormone also in more basic physiological processes, including growth, development, and aging. Melatonin may modulate growth in poultry through interaction with transcriptional factors, through interaction with hormones involved in growth control, and by modulation of energy metabolism and decreasing physical activity. Our studies showed that a single melatonin injection increased plasma growth hormone (GH) concentrations in the Japanese quail. Specific serotonin receptor blocker ketanserin did not preclude a stimulatory action of melatonin on GH synthesis. Serotonin agonist quipazine increased GH levels but failed to enhance the stimulatory effect of melatonin. Pretreatment with melatonin in drinking water did not affect the magnitude of the GH response to subcutaneous (s.c.) administration of thyrotropin releasing hormone (TRH) that considerably stimulated GH secretion. Present data suggest that melatonin modulates rather central neural pathways involved in the control of GH synthesis at the hypothalamic level than the sensitivity of the pituitary gland.

Animals↗

Perinatal development of circadian melatonin production in domestic chicks.

In contrast to the situation in mammals, in which circadian melatonin production by the pineal gland does not begin until some time after birth, the development of pineal gland rhythmicity is an embryonic event in the precocial domestic fowl. A distinct melatonin rhythm was found in 19-d-old chick embryos maintained under light:dark (LD) 16:8. No significant variation in melatonin levels was detected in embryos exposed to LD 8:16. The melatonin rhythm in the pineal gland and plasma of chick embryos incubated for 18 d in LD 12:12 persisted for 2 d in constant darkness indicating that melatonin production is under circadian control at least from the end of embryonic life. A 1-d exposure to a LD cycle during the first postembryonic day was sufficient to entrain the melatonin rhythm, and previous embryonic exposure to either LD or constant darkness (DD) neither modified this rapid synchronization nor did it affect the melatonin pattern during the two subsequent days in DD. It is suggested that, in contrast to the situation in mammals, the avian embryo has evolved its own early circadian melatonin-producing system because, as a consequence of its extrauterine development, it cannot use the system of its mother.

Animals↗

Melatonin content in plasma and large intestine of patients with colorectal carcinoma before and after surgery.

The distinct melatonin rhythm with higher concentrations during the darktime was found in plasma of both control patients and patients with colorectal carcinoma. Moderate surgery did not induce any changes in plasma melatonin levels, but a pronounced increase in both the day- and nighttime melatonin concentrations was found after surgical treatment for colon cancer. The melatonin content in the tumor tissue did not differ from that in the proximal and the distal parts of the resected gut, which were without signs of malignant changes. Neither concentrations of serotonin nor 5-hydroxyindole acetic acid differed among analyzed parts of the gut. Daytime melatonin concentrations in gut tissue (314.7 +/- 87.8 pg/g of wet tissue) were more than ten times higher than the daytime levels in circulation. It was hypothesized that increased levels of this hormone in the gastrointestinal tract may play an important protective role against the development of colorectal cancer via stimulation of the immune system, protection against free radicals, and interaction with fatty acid uptake and metabolism.

Aged↗

[Fatty acid composition of plasma phosphatidylcholine and levels of lipids and lipoproteins in hyperlipoproteinemia. II. Relation with B lipoproteins].

BACKGROUND: Epidemiological trials provided evidence that the cholesterol concentration in lipoproteins B, i.e. VDL, IDL and LDL, correlate significantly with the incidence of ischaemic heart disease (IHD). The objective of the present study was to assess how the fatty acid composition in plasma phosphatidyl choline affects the total and LDL cholesterol, triglyceride and apolipoprotein B concentrations in subjects with primary hyperlipoproteinaemia and dyslipidaemia. METHODS AND RESULTS: In a group of 142 subjects with primary hyperlipoproteinaemia and dyslipidaemia the concentrations of plasma lipids, lipoproteins apolipoproteins and fatty acids in plasma phosphatidyl choline (PC) were assessed. The authors provided evidence by discriminant analysis where the dependent variables were the lower quintiles (Q1 + Q2) and the upper quintiles (Q4 + Q5) of concentrations of total cholesterol, triglycerides, LDL-cholesterol and apolipoprotein B and the independent variables were FA concentrations in plasma PC, that the total cholesterol concentration was inversely associated with the concentration of docosahexaenic acid (22:6n-3). The concentration of LDL-cholesterol correlated inversely with the concentration of palmitoleic acid (16:1n-7). Triglyceridaemia was inversely associated with the linoleic acid concentration (18:2n-6). The concentration of apolipoprotein B correlated positively with myristic acid (14:0) and negatively with concentrations of oleic acid (18:1n-9) and linoleic acid (18:2n-6). CONCLUSIONS: The submitted results indicate that the fatty acid concentrations of PC in plasma are significantly and markedly correlated with concentrations of total cholesterol, triglycerides, LDL-cholesterol and apolipoprotein B. It is possible that atherogenic lipoproteins may be favourably influenced not only by the amount of fat but also by a suitable fatty acid composition.

Apolipoproteins B↗

[Fatty acid composition of phosphatidylcholine and levels of lipids and lipoproteins in hyperlipoproteinemia. I. Relation to HDL lipoprotein].

BACKGROUND: Epidemiological trials revealed a significant inverse relationship between the cholesterol concentration in high density lipoproteins (HDL-C), apolipoprotein A-I and the incidence of ischaemic heart disease (IHD). It is assumed that the protective effects of HDL against the development of IHD are due to its important function during the reverse cholesterol transport. The HDL-C and apo A-I concentration are influenced by a number of genetic, racial, sexual, hormonal, metabolic and nutritional factors. The objective of the present investigation was to assess how the fatty acid (FA) composition in phosphatidyl choline in plasma affects the HDL-C and A-I concentration in subjects with primary hyperlipoproteinaemia and dyslipidaemia. METHODS AND RESULTS: In a group of 142 subjects with primary hyperlipoproteinaemia and dyslipidaemia the plasma concentrations of lipids, lipoproteins, apolipoproteins and fatty acids in plasma phosphatidyl choline (PC) were assessed. Using discriminant analysis where the dependent variables were the lower quintiles (Q1 + Q2) and upper quintiles (Q4 + Q5) of HDL-C and A-I concentrations and the independent variables FA concentrations in plasma PC, the authors provided evidence that low HDL-C concentrations are associated with 18:0 and conversely a rise of Apo-I is associated with concentrations of 18:1n-9, 18:2n-6, 18:3n-6 and 22:6n-3 in plasma phosphatidylcholine. CONCLUSIONS: The submitted results indicate that FA concentrations in plasma PC are significantly and markedly associated with HDL-C and A-I concentrations in subjects with hyperlipoproteinaemia and dyslipidaemia. This opens the opportunity to influence favourably the concentration of these parameters by changing the dietary fatty acid composition.

Adult↗

Regulation of rhythmic melatonin production in pineal cells of chick embryo by cyclic AMP.

The pineal cells of chick embryos incubated in vitro exhibited a daily rhythm of melatonin synthesis under a 12:12 light:dark (LD) cycle at the embryonic days 16 and 19. In order to elucidate whether cyclic adenosine monophosphate (cAMP)--a component of the melatonin generating system--is already at work in the embryonic period, we measured the effects of forskolin and isobuthylmethylxantine (IBMX) on melatonin production, cAMP efflux and accumulation. Forskolin (after 10, 20, 30, 45, 60 and 90 min of administration) and IBMX (6 h), when applied during the light phase of LD cycle, stimulated melatonin production and cAMP efflux and accumulation during the embryonic period (at days 16 and 19 fo development). Our results suggest that the biochemical pathway involving cAMP, which controls melatonin production in the postnatal period, is developed before hatching and already on embryonic day 19 works in a way similar to that in post-hatched chicks. Differences in response to cAMP stimulation between 16- and 19-day-old pinealocytes seem to be mostly quantitative.

1-Methyl-3-isobutylxanthine↗

Chromium levels in patients with internal diseases.

Chromium (Cr), an essential element, mainly affects saccharide (potentiated insulin action via interaction with insulin receptor on the cell surface) and lipid metabolism (inhibition of hydroxymethylglutaryl-CoA reductase with a hypolipidemic effect). The aim of the study was to describe Cr serum levels in different diseases (malignant, metabolic, renal) using an advanced analytical technique with correlation to other biochemical parameters. The concentration was measured using atomic absorption spectrometry with electrothermal atomization. The Cr levels were increased in hemodialysis patients-HD (3.67 +/- 0.35 micrograms/L) compared to controls-C (0.40 +/- 0.12 microgram/L), in significantly changed in diabetic patients-DM (0.29 +/- 0.08 microgram/L) and patients with lymphoproliferative disease-LP (0.24 +/- 0.07 microgram/L), and decreased in hyperlipidemic patients-HL (0.15 +/- 0.03 microgram/L). There were no differences in Cr concentration between DM treated by diet or peroral antidiabetic drugs; likewise hypolipidemic drugs in HL did not change the Cr concentration. The biochemical parameters-total protein, transferrin in LP group, glucose in DM group, total cholesterol, triacylglycerols, LDL-cholesterol, apolipoprotein B and A-I did not correlate with serum Cr concentration. However, the HDL-cholesterol concentration marginally significantly (p < 0.07) correlated with it. The role of Cr in humans has not yet been fully characterized. To prevent some complications in patients, it may be important to monitor the Cr levels. Chromium supplementation may be indicated in some diseases with no controversy concerning the importance of decreased serum and/or tissue levels and documented positive effects of Cr supplementation on the quality of life (e.g. hyperlipidemia).

Adult↗

Influence of melatonin on chick skeletal muscle cell growth.

Melatonin as a highly lipophilic compound readily enters all subcellular compartments and acts by various mechanisms. In the present study, we investigated the effects of different concentrations of melatonin in medium (physiological and supraphysiological doses) at two treatment times (48 and 120 hr) on growth and changes of growth parameters of cultured chick embryonic skeletal muscle cells. The physiological doses of melatonin (100 pg to 10 ng/ml of medium) stimulated proliferation of cells and raised DNA, RNA protein contents and an incorporation of [3H]leucine into cell protein after 48 hr of treatment. The prolongation of exposure to melatonin in the physiological dose to 120 hr or an increase of melatonin dose to a supraphysiological one evoked the inhibition of cell growth and proliferation by decreasing the number of cells and the amount of labeled leucine incorporated into cell protein. Results demonstrate that melatonin's action in these cells is time and dose dependent.

Animals↗

Synchronization by low-amplitude light-dark cycles of 24-hour pineal and plasma melatonin rhythms of hatchling European starlings (Sturnus vulgaris).

In young European starlings, as in other avian species, high-amplitude 24-hr rhythms in plasma and pineal melatonin are already present around the time of hatching. In chickens this rhythmicity results at least partly from the light sensitivity of the melatonin-producing and -secreting system. In contrast to the chicken, the starling is a hole-nesting bird, and it seemed questionable whether the low light intensities in the nest are sufficient to synchronize perinatal melatonin rhythms. We therefore exposed starling eggs to light cycles roughly simulating those measured in nest-boxes, i.e., an 11-hr phase of complete darkness and a 13-hr phase consisting of 15 min of dim light (10 lux) alternating with 30 min of darkness. For one group the photophase lasted from 0600 to 1900 hr; for the other group the photophase lasted from 1800 to 0700 hr. In approximately 10-hr-old hatchlings of both groups, plasma and pineal melatonin concentrations were high during the dark phase and low during the light phase. We conclude that perinatal low-amplitude light intensity changes of the kind experienced by hatching starlings in the field are sufficient for synchronizing the melatonin-producing and -secreting system in the pineal and possibly other organs.

Animals↗

[Effect of fish oils on plasma lipid risk factors and esterified fatty acids in primary hyperlipoproteinemia].

BACKGROUND: Some epidemiological, clinical and experimental studies have shown that intake of n-3 fatty acids (FA) lowers the incidence of coronary heart disease (CHD). The effects of fish oil and n-3 FA on the development of atherosclerosis include several factors such as the platelet-vascular wall interaction, modulation of eicosanoid metabolism as well as platelet aggregation and its survival time. There were also changes in the fibrinolytic system and cardiovascular reactivity observed. Effects of n-3 FA on lipid and lipoprotein metabolism exert antiatheromatous action as well. The aim of the study was to evaluate changes in plasma lipid risk factors for CHD in subjects with primary hyperlipoproteinemia (HLP) after the administration of fish oil rich in n-3 FA. METHODS AND RESULTS: A total of 82 patients (61 men and 21 women) were administered fish oil (3.5 g n-3 FA daily) for a period of 3 weeks. The group of hyperlipidemics included 9 patients with HLP IIA, 29 with HLP IIB, and 35 with HLP IV. Seven patients had HLP type V while two had HLP type III. Intake of fish oil led to a mild decrease in total plasma cholesterol which was significant in the whole group and in HLP type V. Triglyceride levels declined significantly in all HLP phenotypes, with the changes being most marked in HLP types IIB, IV, and V. We also observed a significant increase in cholesterol concentration in HDL and in the both HDL2 and HDL3 subfractions in the whole group and all HLP phenotypes as well. On the other hand no statistical significant changes were observed in LDL-cholesterol levels. The levels of apo B rose significantly only in HLP type V. A statistically significant increase was found in apo A-1 levels in the whole group and in the HLP IIB subgroup. Fish oil administration led to a mild reduction in diastolic pressure and uricemia. In part of patients fish oil induced decrease in lipoprotein(a) concentration was observed.

Adult↗

[The effect of fish oil on metabolic parameters in patients with type 2 diabetes mellitus associated with dyslipidemia].

BACKGROUND: The authors discuss the effect of administration of fish oils rich in n-3 fatty acids in diabetic patients type 2 and draw attention to the possible deterioration of glucose homeostasis. The objective of the investigation was to assess changes of the lipid and carbohydrate metabolism in type 2 diabetics with associated dyslipidaemia after enrichment of the diet with n-3 fatty acids. METHODS AND RESULTS: To 17 patients with type 2 diabetes and dyslipidaemia fish oil containing 5.5 g n-3 fatty acids per day was administered. After six weeks a decline of triglycerides was recorded (-47%, P < 0.01), free fatty acids (-27%, P < 0.01) and a rise of HDL2-cholesterol (25%, P < 0.05). The concentration of apo B, apo A-1, LDL- and HDL cholesterol did not change significantly. There were no significant changes of the blood sugar level, glycosylated haemoglobin and fructosamine. The insulin and C-peptide concentration on fasting (and after glucagon stimulation) did not change significantly. With regard to the HDL2-cholesterol and 18:0 fatty acid concentration in serum the group can be divided into responders (with a decline of glycosylated haemoglobin) and non-responders. The two groups have a reverse trend of blood sugar levels and insulinaemia and differ as to the metabolism of 18:1 n-7 acid. CONCLUSIONS: Enrichment of the diet with n-3 fatty acids in diabetics with dyslipidaemia has a favourable effect on the plasma lipid spectrum without causing deterioration of parameters of diabetes compensation. Among the group of patients some can be found where fish oil administration improves also glucose homeostasis.

Blood Glucose↗

Plasma thyroid hormone and growth hormone patterns in precocial Japanese quail and altricial European starlings during postnatal development.

Plasma concentrations of thyroid hormones (TH) and growth hormone (GH) during postnatal development in the precocial Japanese quail (Coturnix japonica), and the altricial European starling (Sturnus vulgaris) were measured. Developmental changes in plasma TH found in the starling, differ considerably from those detected in quail. In quail rather high triiodothyronine (T3) values were measured during the first few days after hatching. Subsequently a steady decrease of plasma T3, to adult levels, was observed. Thyroxine (T4) concentrations did not change significantly during the period studied. In starlings, on day 1, plasma T3 was low and T4 was at or below the assay detection limit. An increase in concentrations of both hormones occurred between day 1 and day 5 after hatching. A gradual increase of T4 occurred afterwards, while plasma T3 levels remained nearly constant during this growing period. Plasma GH concentrations showed a similar pattern in both species. There was an increase during first days after hatching and GH concentrations peaked at day 7 in quail and day 5 in starlings. A subsequent decrease was observed in both species. Although the GH profiles in species studied were comparable, there were noticeable differences in their growth rates. Thus different developmental strategies have been reflected in different developmental patterns of TH in precocial Japanese quail and altricial European starling whereas developmental changes of GH levels were similar in both species.

Aging↗

Effect of recombinant human insulin-like growth factor-II on weight gain and body composition of broiler chickens.

Osmotic minipumps containing either saline or recombinant human insulin-like growth factor-II (IGF-II) were implanted into 4-wk-old female broiler chickens such that the treated chickens received 0.5 mg IGF-II/kg body weight per d. At the end of the trial, no differences in body weight gain or bone length were detected between the treated and control groups. Similarly, there were no differences between the two treatments with respect to heart, spleen, liver, or bursa of Fabricius weight. The relative weight of the abdominal fat pads was greater (P < 0.05) in the birds treated with IGF-II than in the controls, whereas the weight of breast muscle was reduced (P = 0.06) in the birds treated with IGF-II. There was no effect of IGF-II treatment on feed intake or feed conversion efficiency. Plasma growth hormone (GH) levels were acutely depressed by 15 min after IGF-II administration; and also after 2 wk of IGF-II treatment. Plasma triiodothyronine (T3) concentrations were significantly depressed by IGF-II treatment. These results suggest that IGF-II may not stimulate growth in chickens, but can act as a nutrient partitioning agent, either directly or indirectly through altering plasma GH or T3 concentrations.

Adipose Tissue↗