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Background: Acute hamstring strains are common injuries in different sports. They are often serious, causing long rehabilitation times and a proneness for re-injury. Preliminary observations indicate that the injuries can be of at least two types, one occurring during high-speed running and the other during motions where the hamstring muscles reach extreme lengths. Aims: To investigate the possible existence of different types of acute hamstring strains in two specific athletic groups, namely sprinters and dancers, as well as the generality of these findings in other sports. Methods: In the first project, 18 sprinters and 15 dancers with acute first time hamstring strains were prospectively included. All subjects were examined, clinically and with magnetic resonance imaging (MRI), on 4 occasions after injury: at day 2-4, 10, 21 and 42. The follow-up period was 2 years. In the second project, 30 subjects from 21 different sports were prospectively included. All subjects were examined clinically and with MRI. The follow-up period lasted until the subjects returned to sport or finished their sport activity due to the injury. Results: All sprinters sustained their injuries during competitive high-speed running. In contrast, all dancers encountered their injuries during slow-speed stretching type of exercises. The initial loss of strength and flexibility was significantly greater in sprinters than in dancers. At 42 days after injury, both groups could perform more than 90% of the test values of the uninjured leg. All the sprinters’ injuries were primarily located in biceps femoris long head, whereas the dancers’ injuries were mainly (87%) involving the proximal free tendon of semimembranosus. For the sprinters, involvement of the proximal free tendon, as estimated by MRI, and proximity to the ischial tuberosity, as estimated both by palpation and MRI, were associated with significantly longer time to return to pre-injury level. In the dancers, there were no significant correlations between clinical or MRI parameters and time to return to per-injury level. The time to pre-injury level was significantly longer (median 50 weeks, range 30-76) for the dancers compared to the sprinters (16, 6-50). In the second project, all injuries occurred during movements reaching a position with combined extensive hip flexion and knee extension. They were all located close to the ischial tuberosity and 83% involved the proximal free tendon of semimembranosus. Fourteen subjects (47%) decided to end their sport activity and for the remaining 16 subjects the median time back to sport was 31 (range 9-104) weeks. There were no significant correlations between clinical and MRI parameters and time to return to sport. Conclusions: There seems to be a link between the injury situation and the two types of acute hamstring strain in sprinters and dancers with respect to clinical findings, injury location, muscles and tissues involved, and time to return to pre-injury level. Proximity of the injury to the ischial tuberosity, as estimated both by palpation and MRI, is associated with longer recovery time. Also in other sports, an injury situation where the hamstrings reach extensive lengths caused a specific injury to the proximal posterior thigh similar to that described in dancers. Due to the prolonged recovery time associated with this type of injury, correct diagnosis based on history, clinical and MRI investigation, and adequate information to the athletes are essential. / <p>För att beställa tryckta exemplar av avhandlingen kontakta Carl Askling, carl.askling@gih.se</p>

It is widely believed that vascular smooth muscle in spontaneously hypertensive rats (SHR) is prone to a greater genetically determined propensity to growth because antihypertensive drugs typically do not completely normalise the structural development of SHR resistance arteries. In order to investigate this further, the blood pressure rise in one hindlimb of SHR and normotensive Wistar Kyoto (WKY) control rats was attenuated by a partially constricting ligature around one external iliac artery at 5 weeks. Therefore blood pressure reduction was mediated by non-therapeutic means. At 12 and 24 weeks the femoral mean arterial pressure distal to the ligature was reduced in both strains, and the low pressure hindlimb in the SHR was subject to perfusion pressures similar to normally perfused WKY hindlimbs. Femoral resistance arteries were mounted in a myograph to permit measurements of morphology and reactivity. The smooth muscle content of arteries distal to the ligature was reduced in both strains and SHR arteries from the low pressure hindlimb were structurally indistinguishable from those of normally perfused WKY hindlimbs, suggesting that blood pressure was the major determinant of vascular structure and SHR femoral vascular smooth muscle is not subject to greater pressure independent influences. The reduced noradrenaline sensitivity in SHR arteries at 12 and 24 weeks was normalised distal to the ligature in 12 week rats. Noradrenaline-stimulated calcium sensitivity was increased only at 12 weeks but the ligature increased this sensitivity at both ages in SHR. The ligature did not influence noradrenaline or noradrenaline-stimulated calcium sensitivity in WKY rats. Additional studies revealed that vasopressin sensitivity is normal in SHR mesenteric resistance arteries but vasopressin-stimulated calcium sensitivity is increased. Also, mesenteric resistance arteries from Wistar rats made hypertensive by 2-bromoethylamine-induced chemical renal medullectomy have reduced noradrenaline sensitivities - a possible mechanism for reduced pressor responses to noradrenaline in vivo.

Changes in intracellular pH (pHi) in vascular smooth muscle cells influence growth and contraction. It has been proposed that both processes are critically dependent on cell alkalinisation due to increased Na+/H+ exchange; therefore pHi may be an important mediator of the vascular hypertrophy resulting in an increased peripheral resistance which characterises established hypertension. Resistance artery morphology followed by simultaneous recording of isometric contraction and pH were measured using a myograph in conjunction with a pH sensitive fluorescent probe and microscope capable of exciting the intracellular trapped dye at appropriate wavebands and recording the fluorescence. Mesenteric resistance arteries from the genetically hypertension prone spontaneously hypertensive rat were more alkaline than the normotensive Wistar Kyoto control. However secondary hypertension due to aortic coarctation did not result in mesenteric artery alkalinisation, although pHi regulation was altered. In contrast pHi and its regulation were unchanged in subcutaneous resistance arteries from the gluteal region from untreated hypertensive patients and first degree offspring of hypertensive patients compared to matched controls. Mesenteric arteries displayed anticipated pHi changes to manoeuvres which directly cause alkalinisation and acidification. On the other hand contraction induced intracellular acidification rather than alkalinisation as observed in cells grown in tissue culture conditions. These measurements of pHi carried out for the first time in human resistance arteries highlight the limitations of using animal models or surrogate cells when studying this potentially crippling vascular disorder.

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Corn oil (CO) and Sterculic foetida oil (SFO) fed rats were injected with [9, 10-methylene-¹⁴C]sterculic acid. Less than 1% of the label was expired as carbon dioxide. The majority of the label was excreted in the urine as short-chain dicarboxylic acids with an intact cyclopropane ring. The major metabolites for both CO and SFO fed rats were cis-3, 4-methylene adipic acid and cis-3, 4- methylene suberic acid. Sterculic acid must undergo β- and [Greek w]-oxidation to form these urinary metabolites, α-oxidation played a minor role in the formation of cis- and trans-3, 4-methylene pimelic acid. Rats on the SFO diet could metabolize sterculic acid faster than fats on the CO diet. However, both CO and SFO fed rats produced the same urinary metabolites. CO fed rats incorporated more label from sterculic acid into protein and acid soluble liver fractions than SFO fed rats. Less than 0.01% of the label from either group was found in liver lipid sterol or glycerol fractions. There was a tendency for SFO fed rats to metabolize n-[1-¹⁴C] octadecane faster than CO fed rats. This suggests that sterculic acid may induce [Greek w]-hydroxylation of n-octadecane. / Graduation date: 1977

The experiments in this dissertation were undertaken to purify a humoral natriuretic substance from human urine and to investigate its possible role in hypertension by examining its effect on smooth muscle at various stages of purification. Activity of the natriuretic substance was monitored by its ability to cause sodium excretion in conscious rats and by its effect on Na-KATPase which mediates sodium transport in epithelial tissues including renal tubules. The natriuretic substance was purified from human urine by successive purifications on sephadex G-25 anf G-10 gels. Further purification was attempted with cation exchange resin AG-50W x8. The NF (natriuretic fraction) of sephadex G-25 contracted smooth muscle and the contracting activity of the NF positively correlated with its naturiuretic activity. Also both the contracting and the natriuretic activities were excreted in higher concentrations in hypertensive subjects. These findings, taken in isolation, support the hypotheses of Haddy <i>et al</i> (1976) and Balustein (1977). However, further purification of the NF on sephadex G-10 revealed the presence of two smooth muscle contracting substances and one natriuretic substance in the NF of sephadex G-25. The two contracting substances were not natriuretic and they stimulated Na-KATPase. The natriuretic substance did not contract smooth muscle although it inhibited Na-KATPase. Thus the natriuretic substance of human urine (extracted by sephadex G-10) is most unlikely to be the sodium transport inhibitor postulated (Haddy <i>et al</i> , 1976; Blaustein, 1977) to have a role in the genesis of hypertension. It is known that a subgroup of hypertensive subjects has raised plasma catecholamine levels. The contracting activity of sephadex G-25 extracted NF was found to be excreted in higher concentrations in hypertensive subjects. Further purification of NF on sephadex G-10 showed that the contracting activity of NF was due to two contracting substances, one of which was a catecholamine and the other could be a derivative of catecholamines. Further studies and purification would be necessary to establish the identity of these catecholamines and to ascertain which or whether both of these two catecholamines are excreted in higher concentrations in hypertension and what role they could play in the pathogenesis of hypertension. Similarly, the natriuretic substance was also excreted in higher concentration in hypertension. Additional studies would be necessary to delineate the possible role of the natriuretic substance in the impaired ability of the kidney to handle sodium in hypertension. The NF of sephadex G-25 contained both stimulators and inhibitors of Na-KATPase. With continued use of the same sephadex G-25 column, more Na-KATPase inhibitory and less stimulatory activity tend to elute. Purification of the NF of sephadex G-25 on sephadex G-10 showed the presence of multiple Na-KATPase stimulators in the NF. An intense stimulator of Na-KATPase was found in both sephadex G-25 and G-10 stages of purification. Purification on sephadex G-10 revealed that this intense stimulator of Na-KATPase caused significant antinatriuresis. Purification on sephadex G-10 also showed that there were two Na-KATPase inhibitors in the NF of sephadex G-25 but only the pre-salt Na-KATPase inhibitor caused natriuresis. Thus the antinatriuretic intense stimulator of Na-KATPase with the natriuretic inhibitor of Na-KATPase could form the physiological regulatory system for Na-KATPase. Sephadex G-10 was a useful purification medium as shown by 8-fold increase in the specific activity of the natriuretic substance. However, cation exchange resin was not a useful medium for further purification as evidenced by the lack of increase of the specific activity of the natriuretic substance and by the elution pattern of the natriuretic substance. The natriuretic substance is likely to have a molecular weight of less than 700 daltons since it eluted in pre-salt fraction of sephadex G-10.

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No description available.