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Biomedical subjects

M Rendell

Publications and source records attributed to M Rendell.

At least 19 recordsLinked to original sources
PubMed2003

Determination of hemoglobin levels in the finger using near infrared spectroscopy.

We previously demonstrated that near-infrared spectroscopy can be used to measure blood flow. The spectrum of blood is dominated by hemoglobin. Therefore, it should be possible to determine the concentration of hemoglobin in tissue using near-infrared transmittance. We attempted to do this in the finger using a unique handheld multiple wavelength spectrophotometer. We took samples from 73 subjects and performed repeat measurements in several subjects. Hemoglobin level was determined at the time of near-infrared measurement. We performed correlation analysis between the hemoglobin values and the absorbance values. There was a strong correlation between hemoglobin levels and the 14 wavelengths (r = 0.738, n = 121, SEE = 1.7). We categorized the patients by hemoglobin level as either normal (12-16 g/dl), mildly anemic (10-12 g/dl), or moderately anemic (<10 g/dl). There were 21 patients in the low hemoglobin group, 29 in the middle range, and 23 in the normal range. The mean hemoglobin levels were 8.4 +/- 0.3 g/dl for the low group, 10.9 +/- 0.1 g/dl for the mildly anemic group, and 13.8 +/- 0.3 g/dl for the group with normal hemoglobin. There was a clear separation of absorbance values among the three groups. The major differences seen were in the midrange of the spectrum. It is encouraging that this first study of hemoglobin measurement yielded data permitting a discrimination of hemoglobin levels. It is hoped that future refinements will lead eventually to a non-invasive technique for the measurement of blood hemoglobin concentration.

Anemia↗
PubMed2002

Effects of estrogen replacement therapy on abdominal fat compartments as related to glucose and lipid metabolism in early postmenopausal women.

The effects of estrogen replacement therapy on lipid and glucose metabolism as related to abdominal fat distribution were investigated in fifty-one healthy postmenopausal women aged 52-53 years. They were randomized to treatment with either estradiol 2 mg or placebo daily for three months in a double-blind design. Forty-six women continued with estradiol for another nine months in an open design with the addition of medroxyprogesterone for ten days every three months. Intra-abdominal and subcutaneous abdominal fat, and intrapelvic and subcutaneous pelvic fat was estimated by computed tomography before and after one year of estrogen treatment. Euglycemic hyperinsulinemic clamp, oral glucose tolerance test and analyses of blood lipids were performed after 3 and 12 months of treatment. Estrogen replacement therapy decreased body fat mass as well as intra-abdominal and intrapelvic fat, but not the subcutaneous fat compartments. LDL cholesterol decreased and HDL cholesterol increased, whereas triglycerides were not changed by one year of estrogen treatment. Insulin sensitivity and glucose tolerance were not affected by estrogen treatment. In postmenopausal women estrogen treatment for one year decreased intra-abdominal and intrapelvic fat compartments, but this was not related to changes in plasma lipid levels. Insulin sensitivity and plasma triglycerides were not affected by estrogen treatment.

Abdomen↗
PubMed2001

Hormone replacement therapy in healthy postmenopausal women: a randomized, placebo-controlled study of effects on coagulation and fibrinolytic factors.

OBJECTIVES: To evaluate effects of postmenopausal hormone replacement therapy (HRT) on von Willebrand factor, factor (F)VIII, factor (F)VII, fibrinogen, antithrombin (AT) III, prothrombin fragments 1 and 2, protein C, total and free protein S, plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) and resistance to activated protein C. DESIGN: Part 1: double blind randomized trial for 3 months. Part 2: open study for 9 months. SETTING: Department of Endocrinology, University Hospital, Malmö, Sweden. SUBJECTS: Fifty-one postmenopausal women with a history of amenorrhoea of at least 6 months and body mass index > or = 24 kg m-2 participated in part 1 and 46 participated in part 2. INTERVENTION: Randomization for placebo (n=24) or HRT (n=27). HRT was given as 2 mg oestradiol valerate for the first 3 months, with the addition of 10 mg medroxyprogesterone for 10 days every third month thereafter. MEASUREMENTS: At baseline and after 3 and 12 months. RESULTS: During 0-3 months in the HRT group, FVII increased (P < 0.01), whereas fibrinogen, AT III and total protein S all decreased (P < 0.001 for all). Changes in variables were expressed as Delta-values. After 3 months Delta-values differed between groups for fibrinogen (P < 0.05), AT III (P < 0.001), total protein S (P < 0.001), and PAI-1 (P < 0.001). During 0-12 months, fibrinogen, total protein S, tPA (P < 0.01 for all) and AT III (P < 0.05) decreased. In the control group, all variables were unchanged during the study, except for increases (P < 0.05) in total protein S after 3 and 12 months, and a decrease (P < 0.01) in FVIII after 12 months. After 12 months Delta-values differed for fibrinogen (P < 0.05), AT III (P < 0.05) and total protein S (P < 0.001). CONCLUSIONS: Unopposed oestrogen substitution was associated with both potentially beneficial effects, such as decreases in fibrinogen, and potentially thrombogenic effects such as decreasing AT III and protein S and increasing FVII. During prolonged follow-up and addition of progesterone, differences between groups concerning FVII were attenuated. These data suggest that effects of HRT upon coagulation are most pronounced early after institution of unopposed treatment.

Blood Coagulation↗
PubMed2001

Relationship between abdominal fat compartments and glucose and lipid metabolism in early postmenopausal women.

The relationships between abdominal and pelvic fat compartments and glucose and lipid metabolism were investigated in early postmenopausal women. Fifty-five healthy, postmenopausal women aged 52-53 yr participated in the study. Fat distribution (intra-abdominal and sc abdominal fat, and intrapelvic and sc pelvic fat) was estimated by computed tomography. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp. In a multiple regression analysis, the size of the intra-abdominal fat compartment was the only significant predictor of insulin sensitivity (r(2) = 24%; P = 0.0002). Plasma triglycerides were closely related to the size of the intra-abdominal fat compartment (r(2) = 26%; P < 0.0001), whereas plasma free fatty acid concentrations only correlated to the size of the sc abdominal fat compartment (r(2) = 18.5%, P = 0.001). In early postmenopausal women the amount of the intra-abdominal fat strongly influences insulin sensitivity and plasma triglyceride levels, whereas plasma free fatty acids are closely related to the amount of the sc abdominal fat. Accordingly, from a metabolic standpoint it seems most essential to reduce intra-abdominal fat in postmenopausal women.

Abdomen↗
PubMed2001

A randomized trial of rosiglitazone therapy in patients with inadequately controlled insulin-treated type 2 diabetes.

OBJECTIVE: To determine the efficacy and safety of rosiglitazone (RSG) when added to insulin in the treatment of type 2 diabetic patients who are inadequately controlled on insulin monotherapy. RESEARCH DESIGN AND METHODS: After 8 weeks of insulin standardization and placebo (PBO) run-in, 319 type 2 diabetic patients with mean baseline HbA(1c) > or = 7.5% (8.9 +/- 1.1 to 9.1 +/- 1.3) on twice-daily insulin therapy (total daily dose > or = 30 U) were randomized to 26 weeks of additional treatment with RSG (4 or 8 mg daily) or PBO. Insulin dose could be down- titrated only for safety reasons. The primary end point was reduction of HbA(1c) from baseline. RESULTS: RSG 4 and 8 mg daily significantly improved glycemic control, which was unchanged on PBO. By intent-to-treat analysis, treatment with RSG 8 mg plus insulin resulted in a mean reduction from baseline in HbA(1c) of 1.2% (P < 0.0001), despite a 12% mean reduction of insulin dosage. Over 50% of subjects treated daily with RSG 8 mg plus insulin had a reduction of HbA(1c) > or = 1.0%. Neither total:HDL cholesterol nor LDL:HDL cholesterol ratios significantly changed with RSG treatment. Serious adverse events did not differ among groups. CONCLUSIONS: The addition of RSG to insulin treatment results in significant improvement in glycemic control and is generally well tolerated.

Adult↗
PubMed2000

Efficacy and safety of recombinant human nerve growth factor in patients with diabetic polyneuropathy: A randomized controlled trial. rhNGF Clinical Investigator Group.

CONTEXT: Nerve growth factor is a neurotrophic factor that promotes the survival of small fiber sensory neurons and sympathetic neurons in the peripheral nervous system. Recombinant human nerve growth factor (rhNGF) has demonstrated efficacy as treatment for peripheral neuropathy in experimental models and phase 2 clinical trials. OBJECTIVE: To evaluate the efficacy and safety of a 12-month regimen of rhNGF in patients with diabetic polyneuropathy. DESIGN: Randomized, double-blind, placebo-controlled phase 3 trial conducted from July 1997 through May 1999. SETTING: Eighty-four outpatient centers throughout the United States. PATIENTS: A total of 1019 men and women aged 18 to 74 years with either type 1 or type 2 diabetes and a sensory polyneuropathy attributable to diabetes. INTERVENTIONS: Patients were randomly assigned to receive either rhNGF, 0.1 microg/kg (n = 504), or placebo (n = 515) by subcutaneous injection 3 times per week for 48 weeks. Patients were assessed at baseline, 12 weeks, 24 weeks, and 48 weeks. MAIN OUTCOME MEASURES: The primary outcome measure was a change in neuropathy between baseline and week 48, demonstrated by the Neuropathy Impairment Score for the Lower Limbs, compared between the 2 groups. Secondary outcome measures included quantitative sensory tests using the CASE IV System, the Neuropathy Symptom and Change questionnaire, the Patient Benefit Questionnaire (PBQ), and a global symptom assessment, as well as nerve conduction studies and occurrence of new plantar foot ulcers. Patients also were evaluated for presence of adverse events. RESULTS: Among patients who received rhNGF, 418 (83%) completed the regimen compared with 461 (90%) who received placebo. Administration of rhNGF was safe, with few adverse events attributed to treatment apart from injection site pain/hyperalgesia and other pain syndromes. However, neither the primary end point (P =.25) nor most of the secondary end points demonstrated a significant benefit of rhNGF. Exceptions were the global symptom assessment (P =.03) and 2 of 32 comparisons within the PBQ, which showed a modest but significant benefit of rhNGF (P =.05 for severity of pain in the legs and P =.003 for 6-month symptoms in the feet and legs). CONCLUSION: Unlike previous phase 2 trials, this phase 3 clinical trial failed to demonstrate a significant beneficial effect of rhNGF on diabetic polyneuropathy. JAMA. 2000;284:2215-2221.

Activities of Daily Living↗
PubMed2000

Pioglitazone hydrochloride in combination with metformin in the treatment of type 2 diabetes mellitus: a randomized, placebo-controlled study. The Pioglitazone 027 Study Group.

BACKGROUND: Their complimentary mechanisms of action suggest that a combination of pioglitazone hydrochloride and metformin may have clinically beneficial effects in the treatment of patients with type 2 diabetes. OBJECTIVE: This study was undertaken to assess the efficacy and tolerability of pioglitazone in combination with metformin in patients with type 2 diabetes mellitus. METHODS: This was a 16-week, double-blind study with the option of enrollment in a separate open-ended, open-label study. It included patients with poorly controlled diabetes mellitus (glycated hemoglobin [HbA1c] > or =8.0%, fasting C-peptide >1.0 ng/mL) who had been receiving a stable regimen of metformin for > or =30 days. Patients with diabetic retinopathy, nephropathy, or neuropathy; impaired liver or kidney function; or unstable cardiovascular or cerebrovascular conditions were excluded. Patients were randomized to receive once-daily pioglitazone 30 mg + metformin or placebo + metformin. Patients in the open-label extension received pioglitazone 30 mg (with optional titration to 45 mg) + metformin. RESULTS: Three hundred twenty-eight patients were randomized to treatment (168 pioglitazone + metformin, 160 placebo + metformin), and 249 completed the study. Of these, 154 elected to enter the open-label extension study. Patients' mean age was 56 years; most (84%) were white and slightly more than half (57%) were male. Patients receiving piogli- tazone 30 mg + metformin had statistically significant mean decreases in HbA1c (-0.83%) and fasting plasma glucose (FPG) levels (-37.7 mg/dL) compared with placebo + metformin (P < or = 0.05). Decreases in FPG levels occurred as early as the fourth week of therapy, the first time point at which FPG was measured. The pioglitazone + metformin group had significant mean percentage changes in levels of triglycerides (-18.2%) and high-density lipoprotein cholesterol (+8.7%) compared with placebo + metformin (P < or = 0.05). Mean percentage increases were noted in low-density lipoprotein cholesterol levels (7.7%, pioglitazone + metformin; 11.9%, placebo + metformin) and total cholesterol (4.1%, pioglitazone + metformin; 1.1%, placebo + metformin), with no significant differences between groups. In the extension study, patients treated with open-label pioglitazone + metformin for 72 weeks had mean changes from baseline of -1.36% in HbA1c and -63.0 mg/dL in FPG. The incidence of adverse events was similar in both groups. Throughout the study, no patient in either treatment group had an alanine aminotransferase (ALT) value > or =3 times the upper limit of normal, a commonly used marker of potential liver damage. Thus, no evidence of drug-induced hepatotoxicity or drug-induced elevations in serum ALT was observed. CONCLUSIONS: In this study in patients with type 2 diabetes mellitus, pioglitazone + metformin significantly improved HbA1c and FPG levels, with positive effects on serum lipid levels and no evidence of drug-induced hepatotoxicity. These effects were maintained for >1.5 years, including the open-label extension.

Adult↗
PubMed2000

Hormone replacement therapy in healthy postmenopausal women. Effects on intraplatelet cyclic guanosine monophosphate, plasma endothelin-1 and neopterin.

OBJECTIVES: To evaluate beneficial effects of postmenopausal hormone replacement therapy (HRT) on endothelial function, measured as intraplatelet cyclic guanosine monophosphate (cGMP, mediator of nitric oxide), cyclic adenosine monophosphate (cAMP, mediator of prostacyclin) and plasma endothelin-1 (ET-1), and on monocyte activation, measured as plasma neopterin. DESIGN: Part 1: double-blind randomized trial for 3 months; part 2: open study for 9 months. SETTING: The study was performed at the Department of Endocrinology, University Hospital, Malmö, Sweden. SUBJECTS: Fifty-one postmenopausal women participated in part 1 and 46 in part 2. Inclusion criteria included a history of amenorrhoea for at least 6 months before the study and body mass index >/= 24 kg m-2. INTERVENTION: Randomization for either placebo (n = 24) or HRT (n = 27). HRT was given as 2 mg oestradiol valerate for the first 3 months with the addition of 10 mg medroxyprogesterone for 10 days every third month thereafter. MEASUREMENTS: Performed at baseline and after 3 and 12 months of the study. RESULTS: In the HRT group, intraplatelet cGMP increased from 0.56 (0.35-0.94) to 0.61 (0.42-3. 40) and 0.65 (0.43-1.08) pmol (109 platelets)-1 after 3 and 12 months, respectively (P = 0.01), whereas plasma ET-1 decreased from 3.2 (1.1-6.8) to 2.0 (0.8-5.1) and 1.8 (0.4-15.4) pg mL-1 (P < 0. 001). Intraplatelet cAMP and plasma neopterin were unchanged. When smokers (n = 15) and non-smokers (n = 12) in the HRT group were analysed separately, significant effects were seen only amongst smokers. The control group showed unchanged levels of cGMP, cAMP, ET-1 and neopterin. CONCLUSIONS: These data suggest beneficial effects of HRT on endothelial function which may account for anti-atherogenic effects of HRT in postmenopausal women, especially in smokers. No effects of HRT were seen upon monocyte activation.

Blood Platelets↗
PubMed1999

Increasing neopterin and decreasing endothelin-1 in plasma during insulin infusion in women.

Leukocyte-derived inflammatory mediators and endothelial production of vasoconstrictive factors, such as endothelin-1, and vasodilatory and platelet anti-aggregatory factors, such as nitric oxide (NO) and prostacyclin (PGI2), may have a role in the pathogenesis of atherosclerosis. In this study we evaluated whether insulin affects the monocyte-derived inflammatory mediator neopterin and endothelin- in plasma (p), and NO and PGI2 mediators cyclic 3'-5' guanosine monophosphate (cGMP) and cyclic 3'-5' adenosine monophosphate (cAMP) in platelets. P-neopterin was measured by enzyme linked immunosorbent assay (ELISA), and p-endothelin-1, intraplatelet cAMP and cGMP were measured by radioimmunoassay (RIA) before and after euglycaemic hyperinsulinaemic clamping in 51 healthy postmenopausal women aged 53-54 years. "Placebo clamping" with NaCl infusion was performed in a subgroup of 5/51 women. During euglycaemic hyperinsulinaemic clamping, p-endothelin-1 decreased (from 3.3+/-0.2 pg/ml to 2.4+/-0.2 pg/ml; p<0.01), whereas p-neopterin (from 5.0+/-1.1 nmol/l to 6.2+/-1.4 nmol/l; p<0.001) and both intraplatelet cGMP (from 0.61+/-0.03 to 0.68+/-0.03 pmol/10(9) platelets; p<0.05) and cAMP (from 4.00+/-0.14 to 4.76+/-0.20 pmol/10(9) platelets; p<0.001) increased. Increases in cGMP (from 0.79+/-0.05 to 1.07+/-0.15 pmol/10(9) platelets; p = 0.14) and cAMP (from 4.76+/-0.15 to 5.52+/-0.36 pmol/10(9) platelets; p = 0.08) also occurred during NaCl infusion, whereas neopterin and endothelin-1 values were unchanged. In conclusion, insulin administration was associated with decreasing p-endothelin-1 levels and increasing levels of p-neopterin and intraplatelet cyclic nucleotides in accordance with vasodilatation and monocyte activation.

Blood Platelets↗
PubMed1998

Determination of blood flow in the finger using near-infrared spectroscopy.

Wavelengths in the near-infrared range have much better penetrance in organic substances than visible light. We used near-infrared spectroscopy to determine non-invasively blood flow in the fingertip. We used laser Doppler technology to measure skin blood flow as a comparison procedure. We performed several manoeuvres to change blood flow. These included restriction of flow, thermal stimulation and post-occlusion hyperaemia. Near-infrared measurements had coefficients of variation of 10-15% at the various wavelengths, contrasting with variability of 30-40% with laser Doppler measurement. With restriction of blood flow, there was a downward shift in the absorbance curve. With thermal stimulation and with post-occlusion hyperaemia, there was a rise in the curve. The flow-induced shifts in the absorbance curve were particularly pronounced in the range of 850-970 nm. The correlation between absorbance values and laser Doppler-determined blood flow was also highest in this range, averaging about 0.69 (n = 625). Near-infrared spectroscopy can therefore be used to scan the fingertip. The absorbances obtained do reflect changes in blood flow. There is a correlation with skin blood flow, although near-infrared measurements are affected by blood flow in the full breadth of the finger, not just the skin. We can measure this blood flow with significant reproducibility. It may be possible to use near-infrared spectroscopy to measure the concentration of individual blood components.

Fingers↗
PubMed1998

Efficacy and safety of acarbose in insulin-treated patients with type 2 diabetes.

OBJECTIVE: To demonstrate the efficacy, tolerability, and safety of acarbose compared with placebo in patients with type 2 diabetes inadequately controlled with diet and insulin. RESEARCH DESIGN AND METHODS: A multicenter randomized double-blind placebo-controlled parallel-group comparison study was conducted. The trial was 26 weeks with a 2-week screening period and a 24-week period of treatment with acarbose or placebo, with forced titration from 25 mg t.i.d. to 50 mg t.i.d. after 4 weeks, and titration of 50 mg t.i.d. to 100 mg t.i.d. after 12 weeks based on glucose control. The dosage of insulin was to remain stable. The primary efficacy variable was mean change from baseline in HbA1c, and secondary efficacy variables included mean changes in fasting and postprandial plasma glucose and triglyceride levels. RESULTS: The addition of acarbose to the treatment of patients receiving background insulin and diet therapy resulted in a statistically significant reduction in mean HbA1c of 0.69% compared with placebo. There were statistically significant reductions in postprandial plasma glucose and glucose area under the curve, and in postprandial serum triglyceride levels in the acarbose-treated patients. Gastrointestinal side effects were more frequently reported in the acarbose-treated patients. There were no significant differences in hypoglycemic events or liver transaminase elevations between groups. CONCLUSIONS: This study demonstrated that the addition of acarbose to patients with type 2 diabetes who are inadequately controlled with insulin and diet is safe and generally well tolerated and that it significantly lowers HbA1c and postprandial glucose levels.

Acarbose↗
PubMed1995

The effect of aging on skin blood flow in the Wistar-Kyoto rat.

Using laser Doppler techniques in man, we have previously demonstrated that skin blood flow decreases linearly with age. In previous work, we have shown similarities in skin blood flow properties between man and the rat. Our goal was to assess a possible aging effect of skin blood flow in the rat. We determined skin blood flow sequentially in 13 Wistar-Kyoto rats, beginning at 3 months of age, then at 6, 12, 15, and 18 months. We measured flow on the back, the base of the tail, the upper leg, all nutritively (NUTR) perfused sites, and on the plantar paw surface, which is perfused chiefly by arteriovenous anastomotic (AVA) capillaries. We measured flow, microvascular volume and red blood cell velocity at basal temperature and also heated the skin locally to 44 degrees C, to elicit maximal vasodilation. Skin blood flow declined in a linear fashion with increasing age. The decrease was in the order of 15% over 18 months and occurred at both NUTR sites and the paw. The decrease was due to reduced microvascular volume, presumably representing loss of skin capillaries. Red blood cell velocity was not reduced; in fact, it was significantly increased at several NUTR sites. The WKY rat provides an excellent model of aging of the skin microvasculature. The changes we have demonstrated, while not identical to those we have previously demonstrated in man, are sufficiently similar to permit further exploration of the mechanisms of these changes.

Aging↗
PubMed1993

The health care status of the diabetic population as reflected by physician claims to a major insurer.

BACKGROUND: Conventional epidemiologic data suggest that diabetic patients use more health care resources than nondiabetic patients, yet overall health care use by diabetic individuals has never been fully quantitated. We took a new approach to this issue based on the actual economics of the provision of health care to diabetic insured individuals. METHODS: The claims records in the Mutual of Omaha Current Trends database, which contains information on more than 400,000 individuals, were surveyed to identify patients with diabetes and create the contrast population of nondiabetic patients by exclusion. International Classification of Diseases, Ninth Revision, Clinical Modification, codes and Physicians' Current Procedural Terminology, Fourth Edition, codes were used to determine all diagnoses recorded and all physician services rendered to the contrast populations. Age- and sex-adjusted comparisons were performed using Mantel-Haenszel procedures to determine an adjusted odds ratio (AOR). RESULTS: A total of 13,304 diabetic individuals and 388,053 nondiabetic individuals who received health care services from January 1, 1988, to January 1, 1989, were identified. Diabetic insured individuals constituted 3.1% of the overall insured population yet accounted for 8.3% of the charges (P < .01). Inpatient charges accounted for 81% of total diabetic charges but only 61.5% of total nondiabetic charges (P < .001). Diabetic insured individuals had twice as many physician office visits (AOR = 1.87; 95% confidence interval [CI], 1.79 to 1.96), with 2.5 times more physician hospital visits [AOR = 2.50; 95% CI, 2.27 to 2.75). However, the increases in physician care were not uniformly distributed across the diagnostic spectrum. The frequencies of well-established complications of diabetes, such as ischemic heart disease (AOR = 3.32; 95% CI, 3.12 to 3.53), peripheral vascular disease (AOR = 3.14; 95% CI, 2.79 to 3.53), and eye disease (AOR = 3.10; 95% CI, 2.94 to 3.27), were threefold higher in the diabetic group, with parallel increases in related medical services, such as cardiac catheterization (AOR = 3.02; 95% CI, 2.27 to 4.0), vascular surgery (AOR = 2.94; 95% CI, 2.64 to 3.27), and ophthalmologic procedures (AOR = 2.94; 95% CI, 2.72 to 3.18). In contrast, most diagnostic categories showed little or no increase. For example, the frequency of neoplasms (AOR = 1.11; 95% CI, 1.03 to 1.19) was minimally increased, and the associated procedural concomitants of therapeutic radiology (AOR = 0.81; 95% CI, 0.47 to 1.39) and chemotherapy (AOR = 0.98; 95% CI, 0.60 to 1.60) were not increased in the diabetic group. CONCLUSIONS: Our most important new finding is that diabetic patients have neither an elevated risk for a wide spectrum of diseases nor an increase in the receipt of physician services for diagnostic categories without increased risk, despite more frequent physician encounters. We provide real-world risk estimates that help in calculating the effect of offering specific insurance to diabetic individuals or including them in group health plans. The techniques we have developed to analyze computerized claims databases in this way may serve to better quantify the true impact of chronic diseases on the health care system.

Adult↗
PubMed1993

Thermally-induced cutaneous vasodilatation in aging.

A decrease in heat-induced cutaneous vasodilatation has been implicated as the cause of increased heat stress in the elderly. We used laser Doppler techniques to study the skin blood flow response to local heat in 82 healthy volunteers. There were 39 young volunteers, mean age 29 +/- 1, and 43 elderly volunteers, mean age 76 +/- 1. There was minimal difference in skin blood flow at 35 degrees C between the two groups. In contrast, skin blood flow at 44 degrees C was significantly lower in the older subjects at nutritively perfused sites, such as the knee and elbow. However, there was no difference between the young and old groups in skin blood flow at the finger or toe pulp, sites with primarily arteriovenous anastomotic (AVA) flow. In the older subjects, the two components of skin blood flow, microvascular volume (VOL) and red blood cell velocity (VEL), were both decreased at 44 degrees C at nutritive sites, but not at AVA sites. Regression analysis demonstrated a linear fall in blood flow, VOL, and VEL with advancing age at nutritive sites at 44 degrees C. We conclude that thermally-induced cutaneous blood flow is reduced in older persons at nutritive capillary sites, but not at AVA sites.

Adult↗
PubMed1992

Red cell filterability determined using the cell transit time analyzer (CTTA): effects of ATP depletion and changes in calcium concentration.

Cell transit time analysis (CTTA) is a new filtrometric technique for assessing red blood cell deformability by measuring the conductivity change caused by passage of erythrocytes through a polycarbonate filter. Most reported studies to date using CTTA have focused on the transit time (TT), the duration of passage of an individual red cell through a micropore. Bulk flow rate has not been previously measured via CTTA. The use of new enzyme based cleaning solutions make it possible to reduce clogging in micropore filters. Therefore, valid measures of the number of red cell transits per unit time (counts/s: C/S) can now be obtained. We evaluated both parameters, TT and C/S, as indicators of red cell filterability. Our goal was to evaluate the effect of metabolic changes shown by alternative techniques to affect red cell deformability. The two best established factors are changes in intracellular [ATP] and [Ca2+]. ATP depletion produces a very small increase in TT but a very marked decrease in C/S. In contrast, the addition of low concentrations of calcium produces an increase in TT with minimal decrease in C/S. The effects of calcium appear to be complex. The substantial changes in intracellular calcium induced by the ionophore A23187 result in a curvilinear pattern of increase in transit times and reduction in counts per s. Lanthanum, which inhibits egress of intracellular calcium, causes an increase in TT with a drop in C/S. We conclude that CTTA demonstrates the same changes in red cell deformability measurable by alternative filtrometric techniques; however, CTTA furnishes two separate and independent parameters which may be used to evaluate red cell deformability.

Adenosine Triphosphate↗