Ultrastructure of the nephron of the one-humped camel, Camelus dromedarius

The nephron of the one-humped camel Camelus dromedarius was investigated by light and transmission electron microscopy. Besides the many features common to other mammalian kidneys, the nephron of the camel is unique in having an unusually thick basal lamina underlying the epithelial cells of the nephron, the thickest being found in part of the parietal layer of Bowman's capsule and the thin limb of the loop of Henle. In the latter, the membrane usually appears lamellated and contains numerous tiny vesicles. In other parts of the nephron, the basal lamina usually has a homogenous appearance. The possible significance of the thickening of the basal lamina is discussed in relation to the general high renal efficiency of the camel.     

Control of luteolysis in the one-humped camel (Camelus dromedarius)

Blood plasma concentrations of 13,14-dihydro-15-keto PGF2 alpha (PGFM) were measured in groups of mature non-pregnant and pregnant camels to study PGF2 alpha release patterns around the time of luteolysis and the timing of the signal for pregnancy recognition. Injection of each of four camels with 10 and 50 mg of PGF2 alpha showed clearly that five times the dose of exogenous hormone produced five times the amount of PGFM in peripheral plasma, thereby indicating that, as in other animal species, PGFM is the principal metabolite of PGF2 alpha in the camel. Serial sampling of three non-pregnant camels on each of days 8, 10 and 12, and three pregnant camels on day 10, after ovulation for 8 h showed a significant (P < 0.05) rise in mean plasma PGFM concentrations only on day 10 in the non-pregnant, but not the pregnant, animals. A single intravenous injection of 20, 50 or 100 iu oxytocin given to three groups of three non-pregnant camels on day 10 after ovulation did not increase their basal serum PGFM concentrations. However, daily treatment of six non-pregnant camels between days 6 and 15 (n = 3) or 20 (n = 3) after ovulation with 1-2 g of the prostaglandin synthetase inhibitor, meclofenamic acid, inhibited PGF2 alpha release and thereby resulted in continued progesterone secretion throughout the period of meclofenamic acid administration. These results showed that, as in other large domestic animal species, release of PGF2 alpha from, presumably, the endometrium controls luteolysis in the dromedary camel. Furthermore, reduction in the amount of PGF2 alpha released is associated with luteal maintenance and the embryonic signal for maternal recognition of pregnancy must be transmitted before day 10 after ovulation if luteostasis is to be achieved. However, the results also indicate that, in contrast to ruminants, the release of endometrial PGF2 alpha in the non-pregnant camel may not be controlled by the release of oxytocin.     

Responses to dehydration in the one-humped camel and effects of blocking the renin-angiotensin system

Our objectives were to compare the levels of circulating electrolytes, hormones, and renal function during 20 days of dehydration in camels versus the level in non-dehydrated camels and to record the effect of blocking angiotensin II AT1 receptors with losartan during dehydration. Dehydration induced significant increments in serum sodium, creatinine, urea, a substantial fall in body weight, and a doubling in plasma arginine vasopressin (AVP) levels. Plasma aldosterone, however, was unaltered compared with time-matched controls. Losartan significantly enhanced the effect of dehydration to reduce body weight and increase serum levels of creatinine and urea, whilst also impairing the rise in plasma AVP and reducing aldosterone levels. We conclude that dehydration in the camel induces substantial increments in serum sodium, creatinine, urea and AVP levels; that aldosterone levels are altered little by dehydration; that blockade of angiotensin II type 1 receptors enhances the dehydration-induced fall in body weight and increase in serum creatinine and urea levels whilst reducing aldosterone and attenuating the rise in plasma AVP.     

The prenatal development of the skin in the one-humped camel (Camelus dromedarius)

The epidermis of the camel started its development as a single layer of cuboical cells. The second layer occurred at the fetal stage of C RL 5 cm and the intermediate cell layer at the C RL 10 cm-stage. In the C RL 83 cm - fetus the epidermis is differentiated into the Stratum basale, Stratum spinosum, Stratum granulosum and Stratum corneum. In the dermis the collagenic and reticular fibres were observed in the 2 cm - fetus, and the elastic ones at the C RL 20 cm - stage.     

Observations on the distribution of the omentum in the one-humped camel (Camelus dromedarius)

The greater omentum of the camel has been studied for the first time. Although the camel belongs to the suborder Artiodactyla, the greater omentum exhibits a striking similarity to that of Perissodactyla.     

Blood protein polymorphism in the one-humped camel (Camelus dromedarius) in the Sudan

The blood protein polymorphism of serum albumin, haptoglobin, transferrin, ceruloplasmin and haemoglobin have been studied in 135 samples from one-humped Arabian camel (Camelus dromedarius) of the Sudan by starch gel electrophoresis. Only the serum albumin and haptoglobin systems exhibited polymorphism with the estimated frequencies of 0.0222, 0.2227 and 0.7773 for Alb^v, Hp¹Hp⁰respectively. The frequency of Hp was 0.0325. No electrophoretic variant was observed at transferrin, ceruloplasmin and haemoglobin loci in the camel. The activity of the ceruloplasmin of the camel sera was weak.     

Induction of luteal activity and progesterone secretion in the nonpregnant one-humped camel (Camelus dromedarius)

Corpora lutea (n = 20) were detected in 5 one-humped female camels studied during a period of 4 months. Complete mating by a vasectomized male, male introduction into the pen of females without mating, or a progesterone decrease from a previous corpus luteum were followed by a similar progesterone pattern. A maximal plasma concentration of 4.5 +/- 1.5 ng progesterone/ml (2.7-8.8 ng/ml) occurred 8.55 +/- 1.32 days (6-11 days) after the inducing stimulus. Luteal regression, beginning 8.65 +/- 1.18 days after the stimulus, was completed at Day 11.55 +/- 1.05. Morphological development of ovarian structures, detected by rectal palpation, was in synchrony with the progesterone increase, but there was a prolonged period of regression. Females accepted mating up to 7 days after the ovulatory stimulus, when progesterone levels were as high as 3.5 ng/ml. This study establishes the absence of pseudopregnancy in the one-humped female camel, and offers opportunities for improving the management of reproduction. It also shows that ovulatory stimuli other than mating can be effective in these animals.     

The prenatal development of hair follicles and hair in the one-humped camel (Camelus dromedarius)

The development of the hair follicles started in the prescapular region of CRL 15 cm-fetuses as follicular plugs. At CRL 31 cm, they became cylindrical cell cords. In the CRL 45 cm-fetus two types of growing follicles, primary and secondary ones, could be differentiated, while the tertiary follicles were still follicular plugs. The follicles formed groups, and the primary follicles attained their complete structure at CRL 79 cm, while the secondary follicles at CRL 83 cm. The tertiary follicles were present in the full-term fetus. The latter follicles showed the phenomenon of pairing, where two, three, four or five follicles shared in a common hair canal and arose from the epidermis independently.     

Relationship and possible function of the nasal sacs and glands of the one-humped camel, camelus dromedarius.

The relationship between the lateral nasal gland and sacs of the maxillary recesses was investigated. The nasal sacs possess a well-defined aperture communicating with the nasal cavities. It was concluded that the sacs and not the body of the gland produce mucous secretions that moisten the inhaled dry air of the desert and may also act as reservoirs. A possible function of the body of the nasal gland is water economy by excretion of concentrated salts.     

Energy expenditure during level locomotion in large desert ungulates: the one-humped camel and the domestic donkey

This study sought to quantify the rate of energy expenditure (     ), the total cost of transport (COT_tot) and the net cost of transport (COT_net) in camels Camelus dromedaries and donkeys Equus asinus during level locomotion.     of camels and domestic donkeys were measured at exercise speeds between 0 and 4.17 m s⁻¹. Resting     for camels was significantly ( P <0.05) lower than predicted, while donkeys exhibited resting values similar to mammals of the same body mass. In both camels and donkeys     increased in a nearly linear fashion over the range of exercise speeds. The minimum COT_tot of camels in the walking and pacing gaits were not significantly different ( P =0.27). Similarly, donkeys exhibited no significant difference ( P =0.09) in the minimum COT_tot while walking and trotting. In both camels and donkeys, the minimum COT_tot was significantly ( P <0.05) lower than the predicted COT_tot for mammals of the same body mass. The COT_net in both camels and donkeys was determined to be gait dependent and significantly ( P <0.05) lower than the predicted minimum COT_net values for walking and running. The low COT seen in camels and donkeys results in energy and water savings.     

Seasonal plasticity of the pituitary pars intermedia of the one-humped camel (Camelus dromedarius)

The pituitary pars intermedia of Camelus dromedarius is well developed and completely surrounds the pars nervosa. Two major groups of cells are present: endocrine (ec) and glial-like cells (glc). The ec group is composed of three morphologically distinct cell types. Type I, or polyhedral light cells (LC-I) and type II, or polyhedral dark cells (DC-II), have secretory granules of heterogeneous electron density whose size ranges from 170 to 300 nm. Type III cells are elongated with homogeneous electron-dense secretory granules of 80–200 nm. The glc make up an organized network, form follicles in the centrolobular zones and are positive for vimentin and S-100β immunolabelling. The nerve fibres penetrating the lobe are numerous, and can be classified into two types according to the membrane bound vesicles found in their endings (ne). Ultrastructural quantitative analysis revealed significant variations in PI elements between winter and summer seasons (F = 8.014, p = 0.006). DC-II cells characterized by developed biosynthetic machinery and a large pool of secretory granules storage are increased with the ne in winter. However, LC-I cells showing frequent cytoplasmic degranulation are predominant with glc in summer. Thus, important cellular remodelling occurs in the dromedary PI that may depend upon, or perhaps anticipate, external living conditions.     

The development of the sweat and sebaceous glands in the skin of the one-humped camel (Camelus dromedarius)

The sweat gland primordium appeared as a solid bud from the ental side of the epithelial cords of the growing hair follicles in the CRL 36 cm-fetus from the primary hair follicles and in the CRL 64 cm-fetus from the secondary ones. In the CRL 68 cm-fetus the glands were tubular with a slight curving of their lower third, which became convoluted at the CRL 83 cm-stage. At the latter age, clear myoepithelial cells were observed in the secretory portion as also in the duct. The buds of the sebaceous glands could be observed in the CRL 45 cm-fetus from the primary hair follicles and in the CRL 68 cm-fetus from the secondary ones. At the CRL 83 cm-fetal stage, the branched glands were elongated in shape and opened into the follicles by two separated ducts, united at the hair canal. The glands were in function nearly from its early development.     

The existence of extrapineal locations for melatonin synthesis in the one-humped camel (Camelus dromedarius)

We studied the sites of melatonin synthesis which was measured using the radioimmunoassay technique in the eye retina, skin, Harderian gland, liver tissue and jejunal mucosa in the immature and mature (non-rutting and rutting) Camelus dromedarius. For the first time, melatonin hormone was found in extrapineal sources in camel. These sites included the retina, skin, Harderian gland, liver and jejunal mucosa. The levels of melatonin in these sites reached 80.7, 33.5, 84.6, 548.9 and 2024.1 pg/mg, respectively, in the immature camel. In the mature non-rutting camel, during the non-mating season, the level of melatonin was estimated at 73.7, 41.1, 86.3, 1942.6 and 44112.0 pg/mg, respectively, giving a generally high level. In the mating rutting camel during the winter season, the melatonin level exhibited a level of 77.2, 39.5, 82.0, 930.9 and 14644.0 pg/mg, respectively, with an indication of a general decrease with the exception of the retinal melatonin when compared to the non-rutting camel. It should be noted that the finding of the melatonin hormone in the skin has never been recorded before, and has never been estimated before in other animals. The results in the present investigation also revealed that the wild plants upon which camels usually feed contain a significant amount of melatonin (838.2 pg/g in Chloris gayana and 226.6 pg/g in Anabasis setifera). This could be one of the factors causing an increase in the level of melatonin in the blood and consequently influencing testicular regression during the non-rutting season.