[Stress-associated hypertension in the work place: results of the STARLET project]. / Stressassoziierte Hypertonie am Arbeitsplatz--Ergebnisse des STARLET-Projekts.

BACKGROUND AND OBJECTIVE: To assess the influence of work stress and initial blood pressure on the prognosis of hypertension. SUBJECTS AND METHODS: In a prospective, controlled, multicentre, observational study, ambulatory 24-hour blood pressure measurements (ABPM) of employees from different work places were recorded at the work place on working days. Recurrent ABPM were performed for up to 5 years on 3448 subjects (mean age 44.6 years) who gave consent for follow-up. Subjects with hypertension were told to consult their family doctor so that they could receive antihypertensive treatment (the angiotensin receptor blocker eprosartan, an ACE-inhibitor or a beta-blocker were recommended for initial treatment). Subjects were classified as being in mental strain (stress-positive [stress+]/ stress-negative [stress-]), using standardized questionnaires. RESULTS: Only 1242 (36.0%) of the 3448 employees (69.% males) were normotensives. Only 166 (7.5%) of the 2206 hypertensives had normal ABPMs (<135/85 mmHg) and received antihypertensive treatment at the time of inclusion into the trial. During follow-up 57.8% of patients were treated with eprosartan or ACE-inhibitors, 34.6% with beta-blockers. By the time of the final visit 80.5% of hypertensives had achieved improvement of systolic and/or diastolic blood pressures (29.1% normotensive). Patients with hypertensive ABPM at baseline had more cardiovascular events than normotensives (normotensives 3.0%; grade 1 7.8%, grade 2-3 9.8%). Hypertensive ABPMs at the last follow up or an increase in blood pressure grade were associated with higher event rates than normotensives (stable normotensives 1.8% events vs. stable hypertensives 7.9%, vs. worsening or grade 2-3: 9.1%) More hypertensives were classified as stress+ than normotensives. Persons classified as stress- (or changing to stress-) had fewer events (6.2%) than those regarded as stress+ or changing to stress+ (7.1%). Persons regarded as stable stress- had lower mean blood pressures than those who were stable stress+. Change to another stress group was associated with an increase or decrease of mean blood pressure. CONCLUSIONS: Many employed people are hypertensive at work and are not treated adequately. ABPM control and antihypertensive treatment based on eprosartan, ACE-inhibitors or beta-blockers resulted in a significant increase in the number of patients with lower blood-pressure levels and a reduction in cardiovascular events. Patients under mental strain were more likely to be hypertensive. Mental strain was associated with changes in blood pressure.

Diagnosis of impaired glucose tolerance in hypertensive patients in daily clinical practice.

Many patients with hypertension suffer from impaired glucose tolerance or type 2 diabetes mellitus. Although these diagnoses are generally simple and reliable, it is more difficult to diagnose impaired glucose tolerance. As the gold standard (oral glucose tolerance test (OGTT)) is complicated to perform, a simpler alternative would be useful. The aims of the Pre-Diabetes Score study are to correlate demographic and/or laboratory parameters that are clinically simple to determine with the results of the OGTT and to determine the diagnostic significance of the combinations of parameters with regard to impaired glucose tolerance. A total of 260 patients were included in the evaluation; 39% had impaired glucose tolerance and 12% had diabetes mellitus. A combination of HbA1c of > or =6%, a venous fasting glucose of > or =110 mg/dl, an age of > or =55 years, a systolic blood pressure of > or =140 mmHg and an enlarged waist size is highly predictive of impaired glucose tolerance.

[Recurrent hemispheric symptoms without proof of ischemia]. / Rezidivierende Hemisymptomatik ohne Ischämienachweis.

ANAMNESIS AND CLINICAL FINDINGS: Over the last 6 years, a 48-year-old patient recurrently experienced passing neurological left hemispheric symptoms of varying strength. Because of the patient's distinctive cardiovascular risk profile, these symptoms were diagnosed as transitory ischaemic episodes. On inquiry, the patient now reported frequent headaches in close temporal connection to the events. EXAMINATIONS: Repeated imaging of the neocranium using various techniques (CCT, cMRT, MRT-angiography) revealed no conspicuous features. Duplex sonography of the brain feeding arteries, echocardiography, EEG and 24h-ECG also gave findings within the normal range for the patient's age group. Clinical chemistry showed increased values for cholesterol and triglycerides. Incidentally, a moderate upper airway resistance syndrome was identified during polysomnography. DIAGNOSIS: Suspected migraine with aura in terms of a sporadic hemiplegic migraine. TREATMENT AND COURSE: On administration of ASS and rizatriptane, the neurological hemispheric symptoms disappeared completely over the course of a few hours. Under prophylactic treatment with metoprolol and acetazolamide over two months, no further events have been observed up to now. CONCLUSION: Recurrent, temporary neurological deficits, together with the presence of several cardiovascular risk factors, can easily be misinterpreted to be the result of an underlying cerebral ischemia. Even in cases with typical cardiovascular risk profile, a migraine with aura must be considered as one of the possible causes for hemispheric neurological symptoms.

Histogenesis and ultrastructure of pancreatic islet graft microvasculature. Evidence for graft revascularization by endothelial cells of host origin.

In previous studies we have demonstrated that syngeneic and xenogeneic pancreatic islet grafts are revascularized within a 10 to 14-day period after transplantation. With the combined use of intravital and electron microscopy, as well as immunohistochemistry using a set of species-specific or -crossreacting antibodies to endothelial cell antigens, we investigated 1) the origin of the endothelium of the newly formed capillaries in free pancreatic islet isografts (hamster-->hamster) and xenografts (rat-->hamster), and 2) the ultrastructural characteristics of these microvessels. Intravital microscopy demonstrated that newly formed microvessels grow from the vascular bed of the host muscle tissue into the islet grafts. Immunohistochemical analysis of host tissue and transplanted islets with antibodies against factor VIII (recognizing both hamster and rat factor VIII), bovine PECAM-1 (CD31; endoCAM, crossreacting with hamster but not rat PECAM-1), and rat ICAM-1 (CD54, non-crossreacting with hamster ICAM-1) showed that the transplanted rat islets were revascularized by endothelium of hamster (host) origin. At an ultrastructural level, the endothelial lining of the newly formed microvessels showed diaphragmatic fenestration, a characteristic feature of endothelial cells of pancreatic islets in situ. On the basis of these findings we suggest that pancreatic islet transplantation may take a unique position in the field of organ transplantation, since the generally proposed mechanisms of endothelial cell-dependent antigen recognition as a trigger of graft rejection may not be transferred to islet grafts, containing microvessels lined by endothelial cells of host origin.

Dextran vs. hydroxyethylstarch in inhibition of postischemic leukocyte adherence in striated muscle.

Microvascular injury associated with ischemia/reperfusion (I/R) is characterized by both "no reflow" and "reflow paradox." Prophylactic isovolemic hemodilution with dextran 60 to a hematocrit of 30% has been shown to prevent I/R-induced capillary no reflow in striated muscle. The objective of the present study was to analyze whether hemodilution prior to ischemia has the potential to reduce postischemic leukocyte-endothelium interaction, which is known to be one of the major components of I/R-induced reflow paradox. Syrian golden hamsters (n = 21) were fitted with a dorsal skinfold chamber, which contains striated muscle and subcutaneous tissue and allows for repetitive analyses of the microcirculation by means of intravital fluorescence microscopy. Four hr of pressure-induced ischemia and 30 min of subsequent reperfusion (controls, n = 7) resulted in a significant (P < 0.05) increase of microvascular leukocyte accumulation (40,630 +/- 12,731 mm-3) and adherence to the endothelial lining of postcapillary venules (74.2% +/- 11.5%) when compared to preischemic baseline (7,502 +/- 1,700 mm-3 and 3.4% +/- 1.0%, respectively). Recovery was not complete after an observation period of 24 hr reperfusion [13,735 +/- 2,666 mm-3 (P < 0.05) and 18.5% +/- 6.0% (P < 0.05)]. Prophylactic isovolemic hemodilution with 6% dextran 60 (Dx60) to a hematocrit of 30% (Dx60, n = 7) significantly attenuated postischemic leukocyte accumulation (23,402 +/- 13,837 mm-3; P < 0.05 vs. controls) and adherence (22.6% +/- 6.4%; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo assessment of neovascularization and incorporation of prosthetic vascular biografts.

Neovascularization plays a major role in prosthetic vascular graft healing. New developments in manufacturing biomaterials have encouraged the use of biological and biosynthetic materials for both arterial replacement and bypass procedures. We have analyzed in vivo the process of neovascularization and incorporation of biolized bovine carotid artery (Solco P), a biological material, and the composite of ovine collagen and polyester mesh (Omniflow), a biosynthetic material. The synthetic fabric polytetrafluorethylene (e-PTFE), which is widely used in cardiovascular surgery, served as control. Using the dorsal skinfold chamber of the Syrian golden hamster as site for implantation (n = 15), angiogenesis and neovascularization were analyzed quantitatively by means of intravital fluorescence microscopy. In each chamber a piece (approximately 1 mm2) of each of the three vascular grafts was implanted. Five days after implantation neovascularization was ascertained in 90% of the Omniflow grafts, while only 40% of the PTFE and 20% of the Solco P implants revealed new ingrowing microvessels. On day 10 the density of newly formed microvessels was significantly higher (p less than 0.01) in Omniflow grafts (263.5 +/- 24.1 cm-1) as compared to PTFE (134.2 +/- 20.8 cm-1) and Solco P (153.2 +/- 32.0 cm-1). In addition, the biosynthetic composite revealed a larger extension of neovascularization into the perigraft tissue, and 12 days after implantation these grafts were most tightly incorporated.(ABSTRACT TRUNCATED AT 250 WORDS)

Increase in skin-flap survival by the vasoactive drug buflomedil.

The effect of buflomedil to protect skin tissue from ischemia and necrosis was studied in random cutaneous flaps. Measurements were performed by intravital microscopy on the microcirculatory level of capillary perfusion in a flap model in the hairless mouse. In 30 hairless mice, single-pedicle flaps measuring 6 x 16 mm were raised perpendicular to the spine of the animal. This flap develops a reliable amount of necrosis at its distal edge over a period of 7 days. A group of 10 mice received intravenous injections of buflomedil in doses of 3 mg/kg per day diluted in 0.1 ml normal saline beginning 4 hours before flap elevation and for 6 consecutive days postoperatively. In addition, 10 further animals received the same treatment except that it was started 5 minutes after flap elevation. In 10 mice serving as controls, normal saline in equal volumes as in the experimental groups was applied. By means of intravital microscopy, functional vessel density (FVD) was determined in 2.5-mm increments from the flap's base to its distal edge at 1, 6, and 24 hours after elevation. Skin-flap survival was quantified by measuring the necrotic area on day 7 by means of digital planimetry. Functional vessel density was preserved in the distal flap of animals pretreated with buflomedil, revealing a higher functional vessel density at 10.0 mm (p less than 0.01), 12.5 mm (p less than 0.05), and 15.0 mm (p less than 0.001) from the flap's base as compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

A new model for studying microcirculatory changes during dermal wound healing.

Intact blood supply by microcirculation to a wounded site is an indispensable prerequisite for normal tissue regeneration. However, microvascular changes taking place in the healing process of skin wounds are not understood due to the fact that only few models allow chronic in vivo studies on skin microcirculation. Therefore, we have modified the hairless mouse ear model with the purpose of a quantitative in vivo study of microhemodynamic changes throughout the healing process. Following the creation of a standardized skin wound on the ear of the homozygous hairless mouse (hr/hr), microvessel diameters, red blood cell velocities, wet weight, and leucocyte content of the ear tissue were determined. Surface area of the wound was assessed until complete closure was achieved. By repeated measurements at identical sites over the entire healing period, a distinct pattern of microvascular changes could be observed: microvessel diameters increased to a maximum a few days after wound creation, whereas red blood cell velocities reached their highest values at a later point in time and were still elevated after complete reepithelization of the wounds. Edema and leucocyte content of the ear tissue was most prominent in the early healing phase and gradually decreased to normal values thereafter. These results demonstrate changes of the microvasculature of the hairless mouse ear to injury, which are in accordance to other more indirect studies on this topic. Therefore, we conclude that the model presented is suitable for prolonged quantitative analysis of microcirculation during normal wound healing and may be used to assess microvascular changes taking place during wound healing in pathologically altered tissue.

Redistribution of intraorgan blood flow in acute, hyperdynamic porcine endotoxemia.

In a standardized porcine model of acute, hyperdynamic endotoxemia the distribution of intraorgan blood flow within heart, kidney and brain was analyzed. Twelve pigs received either short-term (23 min) or long-term (205 min) continuous intravenous infusion of endotoxin (Salmonella abortus equi). A high cardiac output/low peripheral resistance state was maintained throughout the 3.5 h observation period. Total organ blood flow in heart, kidney and brain remained high; however, already small amounts of endotoxin provoked a significant redistribution of intraorgan blood flow within the left ventricle and the kidney. These characteristic alterations were absent in a control group of 5 animals subjected to the same protocol, but receiving 0.9% saline instead of endotoxin. Deterioration of respiratory function developed exclusively after continuous intravenous endotoxin infusion over 205 min, indicating incipient organ failure. Using electron microscopy, endothelial cells swelling and entrapment of blood cells in capillaries of the midmyocardium as well as severe ultrastructural damage in the kidney could be demonstrated already after 90 min of endotoxemia in two additional animals. It is concluded that already in the initial phase of acute endotoxemia, in the presence of high cardiac output and high global organ blood flow microcirculatory deterioration and organ failure develops. As small amounts of endotoxin are capable of inducing these alterations, earliest possible diagnosis of endotoxemia should be achieved in critically ill patients.

Direct monitoring of capillary perfusion following normovolemic hemodilution in an experimental skin-flap model.

The effects of normovolemic hemodilution on skin flap survival are studied in a recently developed skin-flap model (homozygous hairless mouse ear) in which nutritional capillary flow is monitored directly by means of intravital microscopy from the time of flap creation throughout the establishment of necrosis. Two diluting agents (dextran 60 and hydroxyethyl starch 200) are utilized. Our quantitative findings demonstrate that the amount of nonperfused tissue following flap creation in both the dextran (n = 23) and starch (n = 13) groups was significantly decreased as compared with controls (n = 19). Our qualitative observations suggest that improved hemorrheologic properties at the microcirculatory level are responsible for the observed decreased necrosis. Various mechanisms by which hemodilution may act to prevent necrosis are discussed.

Neovascularization of prosthetic vascular grafts. Quantitative analysis of angiogenesis and microhemodynamics by means of intravital microscopy.

Neovascularization of prosthetic vascular grafts seems to play an important role in the prevention of early graft failure due to infection of thrombotic occlusion. The process of angiogenesis and neovascularization was analyzed for three different prosthetic vascular grafts (PTFE, Dacron double microvelour and gelatin-coated Dacron double microvelour) in vivo by means of fluorescence microscopy. Under Nembutal anesthesia (50 mg/kg BW) Syrian golden hamsters were fitted with a dorsal skinfold chamber, which contains the cutaneous skeletal muscle as well as subcutaneous tissue, and allows for quantitative analysis of the microcirculation for a prolonged period of time. In each chamber one piece (1mm2) of all three vascular grafts was implanted. Five days after implantation neovascularization was ascertained in 9/11 (coated) and 8/11 (non-coated) Dacron grafts, while only 4/11 PTFE implants revealed new microvessels. On day 10 the density of newly-formed microvessels was significantly higher (p less than 0.001) in Dacron grafts (234.3 +/- 31.2 cm-1 and 238.9 +/- 41.3 cm-1 respectively) as compared to PTFE implants (154.9 +/- 30.4 cm-1). In addition, Dacron grafts revealed a larger neovascularization zone extending into the perigraft tissue. 12 days after implantation non-coated Dacron grafts were most tightly integrated into the perigraft tissue. The better neovascularization of Dacron might be due to the high porosity of the graft compared to low porous PTFE, which revealed insufficient neovascularization.

A novel technique for studies on the microvasculature of transplanted islets of Langerhans in vivo.

Transplantation of isolated islets of Langerhans in diabetic patients is frequently followed by an early loss of function due to acute rejection. Since the primary target of host-vs-graft reaction is the endothelium of the microvessels, it is of great importance to analyze the microcirculation of freely grafted pancreatic islets. For this purpose we present a new model, allowing for intravital microscopy of the microvasculature of transplanted islets of Langerhans. The islets are isolated from Syrian golden hamsters and DA-rats, respectively, by a modified collagenase digestion technique. Subsequently, the islets are transplanted into a hamster dorsal skinfold chamber. Using intravital fluorescence microscopy and video techniques, the microcirculation of the islet grafts can be observed repeatedly over a time period of up to four weeks. Quantitative analysis of the microhemodynamics, i.e. functional capillary density, capillary RBC-velocity and microvascular diameters, can be performed by means of a computer assisted image analysis system. In addition, the model allows for investigation of the flow behaviour of white blood cells and their interaction with the endothelium of the microvascular segments. For the first time a model is presented, enabling for in vivo analysis of the revascularization process and microcirculatory function of transplanted islets of Langerhans. Furthermore, the model allows to assess microvascular phenomena during host-vs-graft reaction as well as effects of immunosuppressive regimens.

On the fine structure of arc-capillaries: true a.v. anastomoses or sphincter capillaries?

The arc-capillaries represent vessels of the terminal bed: they are not true arterio-venous anastomoses. They exhibit a typical capillary structure of their wall. The existence of smooth muscle cells and modified smooth muscle cells, such as epithelioid cells, cannot be demonstrated. Likewise, a specific activation by nerves does not exist. The arc-capillaries differ from the net-capillaries neither in the structure of their wall nor in diameter. At the origin of the arc-capillaries from the final arteriole there are no smooth muscle cells, only pericytes (adventitial cells). The arc-capillaries branch off where the final arteriole no longer possesses smooth muscle cells. The electron microscopic studies showed that arc-capillaries do not represent sphincter capillaries.

Microvascular ultrastructure in non-freezing cold injuries.

The effects of repeated local exposure to cold on the integrity of the subcutaneous microcirculation were studied in a model using a transparent tissue chamber implanted into a dorsal skin fold of Syrian hamsters. A detailed study of the vascular ultrastructure within the chamber revealed the following features: Endothelial damage was prominent in true capillaries and venous vessels, while arterioles remained unaffected. The endothelial lining appeared extremely attenuated around the entire vascular perimeter causing the development of "gaps", some of which contained leukocytes or platelets. Smaller vessels were often completely filled with blood cells with leukocytes integrated into the endothelial wall. Fibrin was never observed within these occluded vessels. Finally, only veil-like remnants of the endothelium persisted, and compressed erythrocytes were still mimicking the original vascular outline. It is concluded that the ultrastructural changes observed after a repeated non-freezing cold injury closely resemble those observed during ischemia/reperfusion injury.

Quantitative analysis of neovascularization of different PTFE-implants.

The process of neovascularization was analyzed in vivo in different expanded polytetrafluoroethylene (e-PTFE) implants which are frequently used in cardio-thoracic and vascular surgery. We have used the model of the hamster dorsal skinfold chamber which allows quantitative analysis of the microcirculation by means of intravital fluorescence microscopy. Pieces of approximately 1 mm2 of the cardiovascular patch (CVP, fibril length: 30 microns; n = 21), surgical membrane (SM, fibril length: 1 micron; n = 16), and soft tissue patch (STP, fibril length: 22 microns; n = 12) were implanted into the skinfold chambers. On day 10 after implantation, the functional density of newly formed microvessels was significantly (P less than 0.05) higher in CVP (145.0 +/- 10.9 cm-1) as compared to SM (688 +/- 13.9 cm-1) and STP (86.9 +/- 21.2 cm-1). In addition, CVP revealed a larger zone of neovascularization (311.6 +/- 19.4 microns) and the tightest integration (dynamic breaking strength: 17.9 +/- 3.0 cN/mm2) into the perigraft tissue, while SM demonstrated only few microvessels and no integration (6.0 +/- 1.9 cN/mm2) into the perigraft. None of the three different PTFE-implants revealed transmural ingrowth of capillaries. The internodal distance of PTFE implants seems to be the most important factor for neovascularization. Surgical membrane used for the replacement of passive biological membranes demonstrated, as is its purpose, little neovascularization and no integration into the perigraft tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct monitoring of nutritive blood flow in a failing skin flap: the hairless mouse ear skin-flap model.

A new experimental skin-flap model is presented in which direct observations of blood flow in individual capillaries can be made from the time of flap creation throughout the entire evolution of the establishment of necrosis. After flap creation, one observes through the microscope that at 1 hour a large area of tissue is nonperfused as a result of the surgical trauma. This is followed by vasodilatation at 6 hours, resulting in an increase in the area of perfused tissue. At 24 hours, the vasodilatation persists, and the red cells that have entered the tissue during the vasodilatation (6 hours) accumulate in the capillaries, this being reflected by an increased area of nonperfused tissue. This increase continues to 72 hours, at which time the perfusion-nonperfusion interface becomes well defined and remains so throughout the 5-day experiment. Analyses of the relationship between early postoperative capillary perfusion and eventual necrosis are presented. Advantages and disadvantages of this model are listed.

The hairless mouse ear for in vivo studies of skin microcirculation.

The homozygous (hr/hr) hairless mouse ear was introduced in 1980 by Eriksson and coworkers as a model for in vivo studies of the skin microcirculation. Herein we expand on this work, presenting results of in vivo microvascular parameter measurements and morphologic studies in the intact ear. The in vivo measurements include microvascular diameter, RBC velocity, capillary density, and the frequency and amplitude of arteriolar vasomotion. In connection with the in vivo studies, a detailed anatomic description of the overall and vascular anatomy is given. Additionally, the preparation techniques for carrying out these in vivo and morphologic studies in the mouse ear are presented in detail.

Angiogenesis and hemodynamics of microvasculature of transplanted islets of Langerhans.

Transplantation of isolated islets of Langerhans is frequently followed by early loss of islet function. Because whether this is caused by insufficient vascularization or graft rejection is unknown, angiogenesis and microvascularization of islet grafts were studied in vivo by means of intravital microscopy. After transplantation of syngeneic islets in hamster dorsal skin-fold chambers, 97% (n = 66) of the islets exhibited the first signs of angiogenesis at days 2-4, characterized by sinusoidal sacculations and capillary sprouts. After 10 days, angiogenesis was completed, consisting of a microvascular network similar to those of islets in situ: arterial supply, afferent and efferent capillary loops, and venular drainage. Functional density of microvessels was 700.1 +/- 127.0 cm-1, and erythrocyte velocity was 0.58 +/- 0.35 mm/s. Intracellular insulin was demonstrated immunohistochemically. Electron-microscopic studies revealed normal fine structure of the capillary wall. The model allows in vivo analysis of microvascular phenomena occurring in host-vs.-graft reaction after allogeneic and xenogeneic islet transplantation. Furthermore, it may be used to quantitatively assess immunosuppressive regimens.